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Crucial to the development and refinement of organic electronics is a fundamental understanding of how deposition processes affect the active material's resulting microstructure in the thin film. Meniscus-guided coating (MGC) methods are attractive because of their amenability to high-throughput, industrially relevant continuous processes like roll-to-roll deposition, but the mechanism of solid film formation has not been elucidated and is valuable for the precise control of thin-film morphology and thus ultimate device performance. In this work, we investigate the microstructural evolution of thin films of a diketopyrrolopyrrole-terthiophene donor-acceptor polymer semiconductor using both in situ and ex situ X-ray diffraction methods. On the basis of a comparison of disorder between the film bulk and the top surface and a depth profiling of the out-of-plane orientation of crystallites, we find that faster coating speeds introduce more disorder into the resulting films because the stochastic nucleation of disordered crystallites at the meniscus air-liquid interface becomes more dominant than substrate-mediated nucleation. Our results suggest that there exist three separate deposition regimes--namely the shear-dominate, disorder-dominate, and Landau-Levich-Derjaguin regimes--revealed by observing both polymer alignment via dry film thickness and optical dichroism, a property sensitive to the flow and shear fields. At low coating speeds, the shear strain imparted upon the solution directly induces polymer alignment, causing an increase in dichroism as a function of coating speed. When solvent evaporation becomes too rapid as coating speeds increase, a decrease in the dichroic ratio is observed before the classical Landau-Levich-Derjaguin regime occurs at the highest coating speeds, resulting in isotropic films. The preservation of out-of-plane crystalline texture throughout the thickness of the films is seen only for lower coating speeds, and a study of different deposition temperatures similarly indicates that the lower overall solvent evaporation is conducive to this process. Increased paracrystalline disorder (i.e., peak broadening) is observed by grazing-incidence wide-angle X-ray diffraction at the top interface of the dry films and at higher coating speeds. Together, these results indicate that more rapid solvent evaporation at higher coating speeds causes increased disorder, which can cause the nucleation of misaligned crystallites, affect the dichroic ratio, and may frustrate the alignment of polymer molecules in the amorphous regions of the film. Because the polymer studied and the deposition technique used are representative models, these results are likely general for aggregating, semicrystalline donor-acceptor polymers deposited with MGC. [ABSTRACT FROM AUTHOR]

Despite the several decades study of the confinement effect of the polymeric nanomaterials, how the confinement influences 1D polymeric fiber nanomaterials is little understood. Here, we report that confinement can render ultrathin polymeric fibers rigid. By observing the changes in the crystalline and amorphous morphologies of electrospun nylon-6 nanofibers with variations in diameter and shape, we reveal that their crystalline phase changes into highly packed, stable a phase when the diameter is smaller than 120 nm. In addition, the molecular motion of the amorphous chains is severely suppressed with decrease in nanofiber diameter, indicating that the amorphous chains are also closely packed, forming a rigid structure. Indeed, the change in chain topology by confinement suppressed the release of rhodamine B from the ultrathin nanofibers. These findings allow us new insights for the design and development of advanced 1D polymer nanomaterials. [ABSTRACT FROM AUTHOR]

Fabrication of regularly porous films by the breath-figure method has attracted much attention. The simple, low-cost technique uses the condensation of water droplets to produce these structures, but the phenomenon itself is complex, requiring control over many interacting parameters that change throughout the process. Developing a unified understanding for the molecular design of polymers to prepare ordered porous films is challenging, but required for further advancements. In this article, the effects of the chemical structure of polymers in the breath-figure technique were systematically explored using side-chain-type liquid-crystalline star polymers. The formation of porous films was affected by the structure of the polymers. Although the entire film surface of poly(11-[4-(4-cyanobiphenyl)oxy]undecyl methacrylate) (P11CB) had a hexagonal ordered porous structure over a certain Mn value, regularly arranged holes did not easily form in poly(methyl methacrylate) (PMMA), even though the main chain of PMMA is similar to that of P11CB. A comparison of P11CB and poly(11-[(1,1'-biphenyl)-4-yloxy]undecyl methacrylate) (P11B) (P11CB without cyano groups) showed that the local polar groups in hydrophobic polymers promoted the formation of ordered porous films. No holes were formed in poly(4-cyanobiphenyl methacrylate) (P0CB) (P11CB without alkyl spacers) films due to its hydrophilicity. The introduction of alkyl chains in P0CB allowed the preparation of honeycomb-structured films by increasing the internal tension. However, alkyl chains in the side chain alone did not result in a porous structure, as in the case of poly(undecyl methacrylate) (P11). Aromatic rings are also required to increase the Tg and improve film formability. In the present study, suitable molecular designs of polymers were found, specifically hydrophobic polymers with local polar groups, to form a regularly porous structure. Development of clear guidelines for the molecular design of polymers is the subject of our current research, which will enable the fabrication of porous films using various functional polymers. [ABSTRACT FROM AUTHOR]

The physical properties of glassy polymer films change as they become confined. These changes are often attributed to increased average molecular mobility and reduction in entanglement density. Both are known to alter mechanical behavior, including the formation of strain localizations, e.g., crazing and shear deformation zones. Here, we determine how the entanglement density and surface mobility change the mechanical behavior of a glassy polymer film when it becomes confined. We utilize a custom-built uniaxial tensile tester for ultrathin films and dark-field optical microscopy to characterize the complete stress-strain response and the associated strain localizations for ultrathin polystyrene films of varying thickness (hF = 20-360 nm). These experiments provide direct measurement of the stress in a craze as well as the stresses involved through the transition from crazing to shear deformation zones. Most significantly, we observe a transition in strain localization from crazing to shear deformation zones as film thickness changes from 30 to 20 nm, providing new insights into how the surfaces alter the mechanical behavior in confined polymer films. [ABSTRACT FROM AUTHOR]

Ultrathin polymer films exhibit a liquidlike mobile surface layer near the free surface, which plays an important role in the size-dependent physical properties of polymer nanomaterials. Most research has focused on the thickness of the surface layer related to segmental relaxation, while few studies have focused on that related to large-scale segmental rearrangement, such as crystallization and diffusion. In this paper, a simple measurement of the surface mobile layer thickness with accelerated crystallization kinetics in a poly(ethylene terephthalate) film was performed by examining the stepwise crystallization behavior. The thickness of the surface crystallization layer (hscry) was determined by ellipsometry or X-ray reflection and was taken as the surface mobile layer thickness. hscry was observed to increase from 4 to 13 nm when the temperature increased from 343 to 373 K without any dependence on the molecular weight or film thickness, which fits well with the theoretical prediction by the cooperative strings model. [ABSTRACT FROM AUTHOR]

Geometrical confinement can profoundly affect the dynamics of glass-forming polymers. In this context intense research has been mostly devoted to the understanding of how polymers subjected to 1-D confinement, that is, thin films, vitrify when cooled from the supercooled melt or recover equilibrium while in the glassy state. With the aim of extending our knowledge to other kinds of confinement, here we consider polystyrene (PS) nanospheres, that is, systems subjected to 3-D confinement. We investigate the physical aging following the enthalpy recovery in the glassy state employing fast scanning calorimetry, allowing heating/cooling rates as large as ~1000 K/s. These systems have been previously shown to exhibit suppressed glass transition temperature in comparison to bulk PS. We find accelerated recovery toward equilibrium, in line with previous findings on other confined polymer glasses exhibiting weak interactions with the substrate. Furthermore, the time evolution of the enthalpy exhibits two mechanisms of equilibration. Apart from a slow one, normally observed in proximity of the glass transition, a fast, mildly activated mechanism of equilibration is observed. We emphasize the analogy with bulk glasses, also exhibiting this behavior though on considerably larger time scales. [ABSTRACT FROM AUTHOR]

Within the current study, a novel approach for the detailed determination of the scratch healing efficiency in mussel-inspired polymer films is presented. For this purpose, a sensor molecule was incorporated into a self-healing polymer network based on reversible zinc-histidine interactions. The fluorescence of the sensor molecule was monitored enabling a detailed depth- and time-resolved determination of the healing efficiency by means of confocal laser scanning microscopy (CLSM). Finally, this concept represents an efficient and detailed approach for the determination of the scratch self-healing efficiency in polymer films and can also be applied for other scratch self-healing systems, which are based on reversible dynamic bonds. [ABSTRACT FROM AUTHOR]

We report a simple and efficient laser-writing strategy to fabricate hierarchical nested wrinkling microstructures on conductive polypyrrole (PPy) films, which enables us to develop advanced functional surfaces with diverse applications. The present strategy adopts the photothermal effect of PPy films to mimick the formation of hierarchical nested wrinkles observed in nature and design controlled microscale wrinkling patterns. Here, the PPy film is grown on a poly(dimethylsiloxane) (PDMS) substrate via oxidation polymerization of pyrrole in an acidic solution, accompanied by in situ self-wrinkling with wavelengths of two different scales (i.e., λ1 and λ2). Subsequent laser exposure of the PPy/PDMS bilayer induces a new surface wrinkling with a larger wavelength (i.e., λ3). Owing to the retention of the initial λ1 wrinkles, we obtain hierarchical nested wrinkles with the smaller λ1 wrinkles nested in the larger λ3 ones. Importantly, we realize the large-scale path-determinative fabrication of complex oriented wrinkling microstructures by controlling the relative motion between the bilayer and the laser. Combined with the induced changes in surface color, surface-wrinkling microstructures, and conductivity in the PPy films, the laser-writing strategy can find broad applications, for example, in modulation of surface wetting properties and fabrication of microcircuits, as demonstrated in this work. [ABSTRACT FROM AUTHOR]

Adhesion of nanoparticles to polymer films plays a key role in various polymer technologies. Here we report experiments that reveal how silica nanoparticles adhere to a viscoelastic PMMA film above the glass transition temperature. The polymer was swollen with CO2, closely matching the conditions of nanoparticle-nucleated polymer foaming. It is found that the degree by which the particles sink into the viscoelastic substrate is strongly size dependent and can even lead to complete engulfment for particles of diameter below 12 nm. These findings are explained quantitatively by a thermodynamic analysis, combining elasticity, capillary adhesion, and line tension. We argue that line tension, here proposed for the first time in elastic media, is responsible for the nanoparticle engulfment. [ABSTRACT FROM AUTHOR]

A new and highly transparent multilayer coating on poly(lactic acid) (PLA) film has been designed and constructed based on the layer-by-layer assembly of green and renewable hydroxypropyl methylcellulose (HPMC) and tannic acid (TA). The surface chemical structure, thickness, and morphology analyses of the multilayer coating confirm that HPMC and TA are successfully incorporated based on the hydrogen-bonding interaction. The resultant coated PLA film presents excellent UV-shielding and antifogging properties, which shows strong dependency on the number of assembly cycles. Although the tensile mechanical property of coated PLA film shows a decrease, the thermal property of the PLA substrate remained. This work provides a simple but effective pathway to design and fabricate highly transparent and environmentally friendly coating for the UV-shielding and antifogging applications. [ABSTRACT FROM AUTHOR]

This paper explores whether the photochromic reaction of a molecule embedded in a polymer film can affect its surface adhesion properties, as measured by shear strength and delamination in water. The adherence of polystyrene (PS) to glass was chosen as a model system. Two commercially available photochromes--a spiropyran derivative 1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole]) (SP) and a diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene (DAE)--are studied in detail. Both photochromic reactions can significantly enhance the adhesion of PS to a glass surface. The most dramatic results were obtained for PS/SP films, whose shear strength increased by a factor of 7 while the delamination rate was suppressed by at least 2 orders of magnitude after exposure to UV light. The enhanced polymer adhesion could only be partially reversed, even after extended exposure to visible light completely regenerated the UV-absorbing isomer. Nanoindentation and heating experiments suggest that the limited reversibility results from changes in polymer internal structure. We hypothesize that the adhesion changes arise from localized polymer and molecular motions that eliminate void spaces and surface gaps at the polymer-glass interface. The results show that adhesive forces between a prototypical polymer and an inorganic substrate can be modulated by photochromic reactions of embedded molecules. [ABSTRACT FROM AUTHOR]

The process of open-porous structure development in high-density polyethylene (HDPE) films during uniaxial deformation in supercritical carbon dioxide (SC-CO2) fluid at 35 °C and 10 MPa has been studied and visualized by means of atomic force microscopy. We suggest that the supercritical fluid act as adsorption-active medium, and the porous structure is developed via the crazing mechanism due to the increasing the distance between of lamellae and the formation of oriented separate fibrils in the intercrystallite space. Effective bulk porosity of the films has been up to 40%. Small-angle X-ray scattering studies and ethanol permeability measurements have revealed that the pores and fibrils are about 10 nm in diameter. The prepared nanoporous materials exhibit good vapor permeability. Structural and mechanical behavior of the prepared porous films has been investigated. Large reversible deformation (up to 80%) of HDPE in the SC-CO2 has been observed. Repeated drawing of the shrunk films in air under ambient conditions has led to the open-porous structure recovery. [ABSTRACT FROM AUTHOR]

To achieve adhesion between two arbitrary substrates, a sub-minute curable dry nanoadhesive was devised in a one-step manner. The dry adhesive is composed of a copolymer film containing poly(glycidyl methacrylate) (pGMA) and poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) segments, where the tertiary amine moiety in pDMAEMA acts as an initiator that triggers the ring-opening reaction of the epoxy ring in pGMA, leading to a self-cross-linking of the epoxide groups in pGMA. Optimization of curing condition resulted in dramatic enhancement of the adhesion strength to values exceeding 250 N/cm2 of shear strength and 32.5 N/25 mm of peel strength. Also, strong bonds are observed in various types of substrate materials including glass, latex rubber, Si wafer, and many polymeric films to each other. Moreover, it maintained excellent adhesion against harsh mechanical, thermal, and chemical stresses. The copolymer-based nanoadhesive developed in this study will be highly advantageous for emerging flexible and foldable device applications. [ABSTRACT FROM AUTHOR]

We investigate the pressure-driven transport of particles 200 or 300 nm in diameter in shallow microfluidic channels ∼1 μm in height with a bottom wall characterized by a high roughness amplitude of ∼100 nm. This study starts with the description of an assay to generate cracks in hydrophilic thin polymer films together with a structural characterization of these corrugations. Microfluidic chips of variable height are then assembled on top of these rough surfaces, and the transport of particles is assessed by measuring the velocity distribution function for a set of pressure drops. We specifically detect anomalous transport properties for rough surfaces. The maximum particle velocity at the centerline of the channel is comparable to that obtained with smooth surfaces, but the average particle velocity increases nonlinearly with the flow rate. We suggest that the change in the boundary condition at the rough wall is not sufficient to account for our data and that the occurrence of contacts between the particle and the surface transports the particle away from the wall and speeds up its motion. We finally draw perspectives for the separation by field-flow fractionation. [ABSTRACT FROM AUTHOR]

The control of structure and thermal stability in semicrystalline polymer films remains an important challenge in applications ranging from solar energy devices to packaging films. Here, we demonstrate the ability to dramatically alter the morphology and melting temperature (Tm) of low-molecular-weight linear polyethylene (PE) by employing an innovative vapor-assisted deposition process termed matrix assisted pulsed laser evaporation (MAPLE). We report the ability to tune Tm of PE films by 20 °C by simply adjusting the deposition temperature during MAPLE processing. This unique capability stems from the ability of MAPLE to exploit confined crystallization during thin film growth. In addition, we demonstrate the ability to exploit MAPLE to design PE films that exhibit the same Tm as their melt-crystallized analogues but have an ~25% higher degree of crystallinity. Our investigation offers new insights into how confinement effects in polymer crystallization can be utilized in the emerging field of polymer film fabrication by MAPLE to control structure and key material properties of semicrystalline polymer films. [ABSTRACT FROM AUTHOR]

This work introduces photoactivated molecular layer deposition (pMLD) as a route to deposit organic nanoscale polymer films with molecular-level control. Surface-tethered acrylate polymers are obtained through a radical step-growth polymerization where a diene and a diiodo monomer, ethylene glycol dimethacrylate (EGM) and 1,3-diiodopropane (DIP), respectively, are sequentially dosed in the vapor-phase under pulsed UV irradiation. pMLD occurs with a constant growth rate of 3.7 Å/cycle, and both monomers display self-limiting saturation. Films deposited by pMLD exhibit excellent stability in organic solvents. Furthermore, annealing studies with in situ X-ray photoelectron spectroscopy (XPS) reveals thermal stability up to 350 °C in vacuum. The mechanism behind pMLD of EGM and DIP is proposed based on detailed characterization of the polymer films by XPS and Fourier transform infrared spectroscopy, growth modeling, and comparison with control studies of pMLD involving monofunctional precursors. The coupling chemistry of pMLD presented herein provides future possibilities to create apolar linkages in the formation of nanoscale organic films. [ABSTRACT FROM AUTHOR]

The physical structure of polymer films is important for understanding the observed macroscopic properties. In crystalline-crystalline block copolymers, the hierarchical nature of assembly is even more influential. Controlling this assembly process is crucial for tailoring film properties. In materials where crystallization of each block occurs nearly simultaneously, the ability to manipulate crystallization order is desirable. Poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) films were monitored via ATR-FTIR to determine the crystallization order during drying from varying solvents. PCL crystallized first from most solvents except toluene and ethyl acetate, where PEO nucleation occurred first. Moreover, after melting the sample to remove solvent-polymer interaction effects, PCL was first to crystallize from the melt, as has been previously reported. Differences in the films' morphologies based on crystallization order were observed using polarized optical microscopy. These results demonstrate that the order of crystallization and the assembly within the film were controllable when casting symmetric diblock PEO-b-PCL films from different solvents. [ABSTRACT FROM AUTHOR]

Surface properties such as topography and chemistry affect the motion of the three-phase contact line (solid/liquid/air), which in turn affects the contact angle of a liquid moving on a solid surface. In this work, the motion of the receding water contact line was studied on chemically and topographically patterned surfaces obtained from the dewetting of thin polymer films. The patterned surfaces consisted of hydrophilic poly(4-vinylpyridine) (P4VP) bumps, which were either microsized and sparse or nanosized and dense, on top of a hydrophobic polystyrene (PS) background layer. These patterns are designed for atmospheric water capture, for which the easy roll off of water droplets is crucial to their efficient performance. The dynamic receding water contact angle and contact line height of the patterned surfaces were measured by vertically withdrawing the surfaces from a water bath and compared to those of a flat P4VP substrate. For both the micropatterned and nanopatterned surfaces, the height of the dynamic contact lines normalized by the capillary length was characterized by the equilibrium limit that was predicted from static states. The nanopatterned surface had a faster increase in the normalized height as the capillary number increased. The dynamic receding contact angles on all surfaces studied decreased with increasing withdrawing velocity. Surprisingly, even for these patterned surfaces with high hysteresis, the dynamic receding contact angle followed the Cox-Voinov relation at capillary numbers of between 1 × 10-5 and 5 × 10-5. [ABSTRACT FROM AUTHOR]

The emergence of polymer-free water surface in a Langmuir polymer film at conditions where a homogeneous coverage has been expected previously is explained on the basis of the surface tensions of polymer and water, Υpv and Υwv, respectively, as well as the interfacial tension between the two materials, Υpw. The polymer molecules considered are 22-residue poly(Υ-benzyl-l-glutamate) (PBLG) peptides in α-helical conformation. Values for Υpv and Υpw derived from MD simulations are consistent with values inferred from experiments considering the emergence of polymer-free surface area for ultrathin films studied using the surface forces apparatus in earlier work. Based on these surface properties, the behavior of individual PBLG peptides at the air-water interface, the dimerization of PBLG peptides, the equilibrium height and width of fibers with given cross section, and the lateral fusion of fibers are described. We show that a prerequisite for the emergence of multilayer structures, which appear locally in domains of sizes of tens to hundreds of micrometers in the considered Langmuir polymer film, is that the condition Υpv + Υpw - Υwv > 0 holds true. [ABSTRACT FROM AUTHOR]

Plasma polymer films that contain amine groups (NH2-PPFs) are known to degrade over time, particularly in aqueous environments. To reduce such aging effects, a vertical chemical gradient regarding the amine group density was explored ranging over a few nanometers at the coating surface. The gradient-containing nanofilms were formed in low-pressure plasma by tuning plasma conditions while keeping the plasma "switched on". The coating process started with a more cross-linked NH2-PPF (70 W, 4:7 NH3/C2H4), followed by the deposition of a few nanometers of a less cross-linked yet more functional NH2-PPF (50 W, 7:7 NH3/C2H4). Characterization of the prepared gradient coatings showed that the chemical composition depends on the NH3/C2H4 gas flow ratio, as observed by different analytical methods: plasma diagnostics during deposition and depth profiling analyses of the deposited coating. Finally, surface chemistry was analyzed during air and water aging, showing a similar aging process of the NH2-PPF single layer and NH2-PPF with a vertical chemical gradient in air, while the stability of the gradient coating was found to be enhanced under aqueous conditions maintaining an [NH2]/[C] amount of ~1%. [ABSTRACT FROM AUTHOR]

Fouling has been a persistent issue within applications ranging from membrane separation to biomedical implantation. Research to date focuses on fouling-resistant coatings, where electrical conductivity is unnecessary. In this study, we report the synthesis of multifunctional thin films with both fouling resistance and electrical conductivity for their potential applications in the electrolysis-based self-cleaning of separation membranes and in the field of bioelectronics. This unique combination of properties results in multifunctional coatings that are a zwitterionic derivative of intrinsically conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) synthesized via oxidative chemical vapor deposition (oCVD). Their fouling resistance is shown to be comparable to that of known dielectric fouling-resistant surfaces, such as a poly(4-vinylpyridine)-co-divinylbenzene (p4VP-DVB)-derived zwitterionic coating, an amphiphilic poly(1H,1H,2H,2H-perfluorodecyl acrylate-co-2-hydroxyethyl methacrylate) (pPFDA-HEMA) coating, and a glass surface, and are far superior to the fouling resistance of gold or polydimethylsiloxane (PDMS) surfaces. The fouling resistances of seven surfaces are quantitatively characterized by molecular force probe (MFP) analysis. In addition, four-point probe electrical measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), variable-angle spectroscopic ellipsometry (VASE), profilometry, water contact angle (WCA) measurements, surface ζ-potential measurements, and atomic force microscopy (AFM) were employed to characterize the physiochemical properties and morphology of the different surfaces. [ABSTRACT FROM AUTHOR]

Incorporating nanoparticles (NPs) within a polymer host to create polymer nanocomposites (PNCs) while having the effect of increasing the functionality (e.g., sensing, energy conversion) of these materials influences other properties. One challenge is to understand the effects of nanoparticles on the viscosity of nanoscale thick polymer films. A new mechanism that contributes to an enhancement of the viscosity of nanoscale thick polymer/nanoparticle films is identified. We show that while the viscosities of neat homopolymer poly(2-vinylpyridine) (P2VP) films as thin as 50 nm remained the same as the bulk, polymer/nanoparticle films containing P2VP brush-coated gold NPs, spaced 50 nm apart, exhibited unprecedented increases in viscosities of over an order of magnitude. For thicker films or more widely separated NPs, the chain dynamics and viscosities were comparable to the bulk values. These results--NP proximities and suppression of their dynamics--suggest a new mechanism by which the viscosities of polymeric liquids could be controlled for nanoscale applications. [ABSTRACT FROM AUTHOR]

Using Monte Carlo simulations combined with a geometric primitive path analysis method (Z1 algorithm), we investigate the effect of bidispersity on the structure and entanglement of polymer films which consist of short (the molecular length is below the characteristic entanglement molecular length) and long (the molecular length is above the characteristic entanglement molecular length) chains between two neutral walls. Our results demonstrate the length-based migrations of chains in bidisperse films (the longer chains reside away from the walls and the shorter chains are close to the walls), which becomes more obvious with the decrease in the weight fraction of long chains. With decreasing the weight fraction of long chains, the number of short-long entanglements exhibits a dramatic increase, whereas the number of long-long entanglements exhibits a slight decrease, which indicates that short chains can significantly affect the local situations of entanglements of bidisperse polymer films. On the basis of the constraint release mechanism, our simulations imply that for the lower weight fraction of long chains, the local degree of confinement instead of the long-long entanglements has a marked effect on the relaxation of long chains, due to the fast relaxation of short chains dilating the tube diameter of long chains. However, for the higher weight fraction of long chains, after the relaxation of short chains, the long-long entanglements are in sufficient quantities to restrict long chains within a tube, which implies that the relaxation of long chains is hardly affected by the number of short-long entanglements. Our work can be helpful for understanding the microscopic structure and entanglement of bidisperse polymer films, which can provide computational support for their various technological applications. [ABSTRACT FROM AUTHOR]

The effect of solvent quality on the slip flow penetration of polymer films was evaluated by monitoring small-molecule mass transport under varying laminar flow rates using Förster resonance energy transfer in combination with total internal reflectance fluorescence microscopy (FRET-TIRFM). For thin films of poly(N-isopropylacrylamide) (pNIPAM), solvents with solvent quality ranging from good to poor were studied. The solvents used were composed of varying mole ratios of methanol and water in order to take advantage of the unique cononsolvency phenomenon of pNIPAM such that differences in the physicochemical properties of these solvents were insignificant for fluorescence detection. FRET quenching of a donor fluorophore covalently tethered on the substrate surface at the bottom of the pNIPAM film by a solution-confined acceptor was monitored as a function of time. Quenching curves were fit to a combined Taylor-Aris-Fickian mass transport model for the acceptor, rhodamine B (RhB) or 2-nitrobenzylaclohol (2-NBA), allowing apparent diffusion coefficients to be determined and used to assess slip flow penetration into the polymer film. An increase in the apparent diffusion coefficient of tracer molecules was observed with increasing laminar flow rate for all solvents, indicating that mass transport processes in the pNIPAM film are significantly perturbed by laminar slip flow penetration. In going from poor solvents, 31 mol % MeOH/H2O and 20 mol % MeOH/H2O, to the theta solvent, 13 mol % MeOH/H2O, and finally to a good solvent, 100% methanol, the slip length increases from 25 to 37 to 70 to 128 nm, with the corresponding percentage of the film penetrated by slip flow increasing from 19 to 27 to 42 to 57%, respectively. The apparent diffusion coefficients of the two acceptors, RhB and 2-NBA, which differ substantially in size and charge, in pNIPAM films under identical conditions were found to be of the same order of magnitude, albeit with a small difference (~10%) due to inherently different diffusive properties. Therefore, the dominant mechanism for the mass transport of small molecules in densely grafted thin pNIPAM brush films is suggested to be linear Fickian diffusion under the chosen laminar flow conditions with linear flow velocities ranging from 192 to 2952 μm/s. High-quality fits to a Taylor-Aris-Fickian diffusion model of the experimental breakthrough curves obtained with both acceptor molecules further substantiate the proper use of this model and the validity of the FRET-TIRFM method. [ABSTRACT FROM AUTHOR]

Drug delivery systems based on stimuli-responsive porous polymer films (PPFs) have been extensively investigated because of their many advantages. However, the ability to adjust the drug release from PPFs is not always perfect, and at times, it cannot satisfy real-world requirements. In this paper, supramolecular host-guest interactions were harnessed to overcome the difficulties associated with adjustable release from these systems by incorporating host molecules into the pore walls of thermoresponsive PPFs. β-Cyclodextrin-functionalized porous amphiphilic block copolymer films (β-CD-PBCPFs) with controllable pore parameters, high homogeneity, and large areas were prepared by combining the self-assembly and breath-figure methods. Drug-loaded β-CD-PBCPFs displayed thermoresponsive release behavior, which could be tuned by increasing the β-CD content in phosphate-buffered saline. The release was governed by the host-guest interactions of the β-CD moieties and drug molecules. The concept of host-guest interaction-enhanced adjustable release could be applied to different drug molecules, such as doxorubicin and metronidazole. [ABSTRACT FROM AUTHOR]

Suppression of the glass transition temperature, T g, in polymer thin films is of great practical importance and theoretical significance. It is widely believed that such T g suppression results from enhanced segmental mobility at the free surface. To investigate these effects, we carry out united-atom molecular dynamics simulations on free-standing polystyrene thin films. Care has been taken to ensure consistent behavior between thin films and the bulk. The dilatometric T g inferred from the density versus temperature shows substantial reduction in thin films compared to the bulk even at high cooling rates. Furthermore, we find that dynamical T g shifts, obtained by collapsing temperature-dependent short-time dynamical properties onto a master curve, vary with film thickness just like the dilatometric T g. We apply the same data collapse procedure to dynamics of segments within a given distance from the free surface to obtain the local T g(z), which reveals a mobile surface layer of about 4 nm. [ABSTRACT FROM AUTHOR]

Fabrication of films with plasmonic nanoparticles (NPs) arrays arranged in chiral configurations of prescribed handedness is highly attractive for the design of new functional materials; however, this remains a formidable challenge in nanotechnology. In this study, we demonstrated the controlled arrangements of gold (Au) NPs into helical structures templated by helical pores created in cross-linked block copolymer (BCP) films. d- and l-tartaric acid (TA) were used to direct the self-assembly of achiral poly(1,4-butadiene)-b-poly(ethylene oxide) BCPs into helical cylindrical morphologies with prescribed handedness, i.e., D or L. Helical pores were generated by BCP cross-linking followed by TA extraction. Helical Au NP arrays, subsequently arranged within the helical pores, exhibited the chiral optical response. The helical structures of NPs arrays and the resulting optical handedness were tunable simply by using either D- or L-porous templates. This simple strategy offers a straightforward pathway for the fabrication of chiral porous BCP films and helical NPs arrays with chiral optical properties. [ABSTRACT FROM AUTHOR]

Dynamic covalent networks are polymer networks that contain a dynamic covalent bond which allows them to be reprocessable, remoldable, and recyclable as well as exhibit crack healing or stress-relaxation properties. A key component of these materials is the nature of the dynamic covalent bond, which in addition to chemical composition and architecture can be used to dramatically alter the physical properties of these networks. The aim of this study is to understand the impact of steric hindrance of N-alkyl substituents and network connectivity in poly(alkylurea-urethane) dynamic network films. In these materials, the dynamic bond is the hindered alkyl urea moiety, whose dynamic behavior is dictated by the sterics of the alkyl substituent. Networks were prepared by the noncatalyzed curing reaction of aminoethanol compounds of varying substituents with a trifunctional isocyanate cross-linker and varying amounts of a monofunctional capping agent. Thermomechanical properties and FTIR studies show the impact of hindered urea bond sterics on the reaction conversion, network connectivity, and therefore the relaxation of the dynamic networks. Stress relaxation analysis show the vitrimer-like behavior of these dynamic networks only when the degree of cross-linking is maintained by high reaction conversion (high equilibrium constant of the dynamic bond). These results give some insights into the design and properties of dynamic covalent networks and how the nature of dynamic bonds can be used to impact their properties. [ABSTRACT FROM AUTHOR]

We investigated the orientation of gyroid structures in thin films of high-molecular-weight (HMW) polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) upon a solvent vapor annealing (SVA) process with tetrahydrofuran nonselective to the PS and PMMA blocks. During the SVA process, the swollen PS-b-PMMA films produced the gyroid structures that were developed through a cylindrical morphology from a poorly ordered structure. The interfacial interactions exerted by the substrates significantly influenced the orientation of cylinders, like the parallel and perpendicular orientations on the selective and neutral substrates, respectively, while the solvent vapor generated perpendicular cylinders at the surface. In the final formation of gyroid structures, we identified the two distinct [211] and [111] planes on the surface throughout the interior of the films, which were directed from cylinders on the selective and neutral substrates, respectively. To provide the insight of the molecular mechanisms taking place during the order-order transition, we further performed coarse-grained simulations of a block copolymer model. Our results based on experiments and simulations suggest a simple route for the directed orientation of well-defined gyroid structures. [ABSTRACT FROM AUTHOR]

Organic nanoparticles (ONPs) in the form of star polymers and single chain nanoparticles (SCNPs) are used as fillers in block copolymer (BCP)/ONP nanocomposite thin films to induce perpendicular microdomains without any substrate treatment. The nonselective ONPs for both blocks of BCP neutralize the substrate and the free surface via an entropy-driven boundary surface segregation process, which differs markedly from the conventional neutralization process relying on surface chemistry. To examine the architectural effect of ONPs for surface segregation, neutral star polymers with ~30, 21, and 6 arms and single-chain nanoparticles (SCNPs) are used as fillers in PS-b-PMMA thin films in an attempt to produce perpendicular microdomains. Consequently, it was observed that ~30- and 21-arm star polymers and SCNPs, which may behave like hard particles having excluded volume interactions with host BCPs, effectively induced perpendicular microdomains, while soft particle-like 6-arm stars led to morphological compatibilization with BCPs. [ABSTRACT FROM AUTHOR]

A face-on oriented thin film of poly(3-hexylthiophene) (P3HT) is suitable for an organic semiconductor layer in a photovoltaic device, and thus analysis of the film structure in terms of molecular orientation is crucial. Although the face-on film often has a poor crystallinity, diffraction techniques have long been employed for the structural analysis, and only very minor crystal parts have been discussed. In our previous study, P3HT was revealed to have a uniquely oriented structure even in an amorphous film by using p-polarized multiple-angle incidence resolution spectrometry (pMAIRS), which is powerful to analyze the molecular orientation, crystallinity, and the conjugation length of P3HT. With the best use of the potential of pMAIRS, in the present study, the controlling mechanism of the molecular orientation of P3HT correlated with the crystallinity in a spin-coated thin film is revealed. As a result, by employing a high-spin speed at 8000 rpm, a highly face-on oriented thin film having a very low crystallinity is obtained, which readily reveals that the face-on component has a strong correlation with the amorphous aggregates. [ABSTRACT FROM AUTHOR]

Over the past few decades, anisotropic polymer particles are of significant interest because of their unique properties which can be applied in various areas, such as drug delivery, biotechnology, and electronics. Most approaches to synthesize anisotropic polymer particles, however, are complicated, and the three-dimensional shapes of the anisotropic particles are usually difficult to be controlled. In this work, we develop a solvent on-film annealing (SOFA) method to fabricate anisotropic polymer particles by studying the morphological evolution of polystyrene (PS) microspheres on poly(methyl methacrylate) (PMMA) films annealed in toluene vapor. At different annealing stages, the isotropic PS microspheres gradually transform to anisotropic PS particles with different morphologies, such as UFO-, cymbal-, peanut-, and bowl-shaped particles. The morphology evolution is driven by the surface and interfacial tensions during the annealing processes and can be confirmed by a selective removal technique. Acetic acid, a selective solvent for PMMA, and cyclohexane, a selective solvent for PS, are also used as the annealing solvents to further investigate the effect of the annealing solvent. [ABSTRACT FROM AUTHOR]

We report herein the first examples of organoboron-based photochromic polymers. The synthesis of a series of blue fluorescent random copolymers bearing photochromic boron repeating units, poly[(6-B(ppy)Mes2)oxyhexyl methacrylate)m-r-(tert-butyl methacrylate)n], ppy = 2-phenylpyridyl and Mes = mesityl, via atom transfer free radical polymerization (ATRP) has been accomplished. These new polymers display thermally reversible photochromism, switching color from colorless to deep blue, and fluorescence from bright sky blue to deep blue. By controlling the monomer ratio, the photoisomerization quantum efficiencies of the polymers can be tuned effectively. In addition, the number of boron units in the polymer has been found to have a significant impact on fluorescence quenching efficiency. The new organoboron-based polymers can be used effectively as a switchable/erasable ink on glass or paper substrate or for creating switchable/erasable patterns as neat polymer films. [ABSTRACT FROM AUTHOR]

We propose that chemically inert polymeric films can enhance van der Waals (vdW) forces in the same way as nanofabrication of biomimetic adhesive materials. For the vdW adhesion of an ethylene-chlorotrifluoroethylene (ECTFE) film on rough metal and dielectric substrates, we present a model that combines microscopic quantum-chemistry simulations of the polymer response functions and the equilibrium monomer-substrate distance with a macroscopic quantum-electrodynamics calculation of the Casimir force between the polymer film and the substrate. We predict adhesive forces up to 2.22 kN/mm², where the effect is reduced by substrate roughness and for dielectric surfaces. [ABSTRACT FROM AUTHOR]

An experimental study was carried out to investigate the existence of a critical layer thickness in nanolayer coextrusion, under which no continuous layer is observed. Polymer films containing thousands of layers of alternating polymers with individual layer thicknesses below 100 nm have been prepared by coextrusion through a series of layer multiplying elements. Different films composed of alternating layers of poly(methyl methacrylate) (PMMA) and polystyrene (PS) were fabricated with the aim to reach individual layer thicknesses as small as possible, varying the number of layers, the mass composition of both components, and the final total thickness of the film. Films were characterized by atomic force microscopy (AFM), and a statistical analysis was used to determine the distribution in layer thicknesses and the continuity of layers. For the PS/PMMA nanolayered systems, results point out the existence of a critical layer thickness around 10 nm, below which the layers break up. This critical layer thickness is reached regardless of the processing route, suggesting it might be dependent only on material characteristics but not on process parameters. We propose this breakup phenomenon is due to small interfacial perturbations that are amplified by (van der Waals) disjoining forces. [ABSTRACT FROM AUTHOR]

Acenes comprise an important class of organic semiconducting materials. As graphene nanoribbons of ultimate width, they are valuable atom-precise model systems for studying the properties of this form of nanoscale carbon materials. Heptacene is the smallest member of the acene series that could only be studied under matrix isolation conditions. Its existence in bulk had never been positively confirmed, despite efforts dating back more than 70 years. We report that the reduction of 7,16-heptacenequinone produces a mixture of two diheptacene molecules. The diheptacenes undergo thermal cleavage to heptacene at high temperatures in the solid state. Monitoring this cycloreversion by solid state 13C cross-polarized magic angle spinning NMR reveals that solid heptacene has a half-life time of several weeks at room temperature. The diheptacenes are valuable precursors for generating films of heptacene by vapor phase deposition that can be studied below or at room temperature. [ABSTRACT FROM AUTHOR]

To understand the rate determining processes during the equilibration of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-based (PEDOT(PSS)-based) solid contact (SC) ion-selective electrodes (ISEs), the surfaces of Pt, Au, and GC electrodes were coated with 0.1, 1.0, 2.0, and 4.0 µm thick galvanostatically deposited PEDOT(PSS) films. Next, potential vs time transients were recorded with these electrodes, with and without an additional potassium ion-selective membrane (ISM) coating, following their first contact with 0.1 M KCl solutions. The transients were significantly different when the multilayered sensor structures were assembled on Au or GC compared to Pt. The differences in the rate of equilibration were interpreted as a consequence of differences in the hydrophilicity of PEDOT(PSS) in contact with the substrate electrode surfaces based on X-ray photoelectron spectroscopy (XPS) and synchrotron radiation-XPS (SR-XPS) analysis of 10-100 nm thick PEDOT(PSS) films. The influence of the layer thickness of the electrochemically deposited PEDOT(PSS)-films on the hydrophilicity of these films has been documented by contact angle measurements over PEDOT(PSS)-coated Au, GC, and Pt electrode surfaces. This study demonstrates that it is possible to minimize the equilibration (conditioning) time of SC ISEs with aqueous solutions before usage by optimizing the thickness of the SC layer with a controlled ISM thickness. PEDOT(PSS)-coated Au and GC electrodes exhibit a significant negative potential drift during their equilibration in an aqueous solution. By coating the PEDOT(PSS) surface with an ISM, the negative potential drift is compensated by a positive potential drift related to the hydration of the ISM and activity changes at the PEDOT(PSS)|ISM interface. The potential drifts related to activity changes in the ISM have been determined by a novel adaptation of the "sandwich membrane" method. [ABSTRACT FROM AUTHOR]

Thin amorphous poly(ethylene terephthalate) (PET) films covered with/without a crystallized surface layer were prepared onto silicon wafers. In the former and latter cases, the surface mobility in the film was depressed and enhanced, respectively. The glass transition temperature (Tg) of the amorphous PET film decreased with the reduction of the film thickness, exhibiting a remarkable nanoconfinement effect. However, once the surface region of the thin film was crystallized, or frozen in terms of the segmental motion, Tg of the films recovered to that of the bulk. Concurrently, the apparent activation energy of the segmental motion in the surface-crystallized film was in good accordance with the bulk value as well. These results make it clear that the mobility in the surface region plays an essential role in the glass transition of the thin films. [ABSTRACT FROM AUTHOR]

The phase behavior of an athermal film of a polymer-nanoparticle blend (PNB) driven by depletion attraction is investigated by dissipative particle dynamics for nanospheres and nanocubes. Surface segregation is observed at low nanoparticle concentrations, while bulk aggregation is seen at high concentrations. Surface excess and the aggregation number can be controlled by tuning the nanoparticle concentration. As surface-roughened or polymer-grafted nanoparticles are used, uniform PNBs are acquired due to the lack of depletion. Thus, addition of surface-roughened nanoparticles into PNBs of smooth nanoparticles can be employed to tune the phase characteristics. It is found that bulk aggregation is suppressed for both polymer-nanosphere and polymer-nanocube blends. However, surface segregation is impeded for polymer-nanosphere blend but enhanced for polymer-nanocube blend owing to the distinct influence of the nanoparticle shape on depletion. [ABSTRACT FROM AUTHOR]

The application of a top-coating of 4-methoxy cinnamic acid (MCA) onto a photoinactive liquid crystalline polymeric film containing benzoic acid (BA) side groups (P6BAM) is shown to enable thermally stimulated, photoinduced reorientation of the polymer structure. Annealing the MCA-coated P6BAM films leads to H-bond formation between BA and MCA, which also effectively smooths the film surface. Exposure to linearly polarized (LP) UV light initiates axis-selective photoreaction of the MCA groups; subsequent thermal treatment in the LC temperature range of P6BAM amplifies molecular reorientation of the BA side groups, while simultaneously eliminating the MCA molecules. Selective inkjet coating of MCA provides a facile route for the fabrication of patterned, oriented, and rewritable P6BAM films with multiple controlled alignment directions. [ABSTRACT FROM AUTHOR]

Controlling the balance between stability and functional group density in grown plasma polymer films is the key to diverse applications such as drug release, tissue-engineered implants, filtration, contact lenses, microfluidics, electrodes, sensors, etc. Highly functional plasma polymer films typically show a limited stability in air or aqueous environments due to mechanisms like molecular reorganization, oxidation, and hydrolysis. Stabilization is achieved by enhancing cross-linking at the cost of the terminal functional groups such as -OH and -COOH, but also -NH2, etc. To overcome such limitations, a structural and chemical gradient was introduced perpendicular to the surface plane; this vertical gradient structure is composed of a highly cross-linked base layer, gradually changing into a more functional nanoscaled surface termination layer. This was achieved using CO2/C2H4 discharges with decreasing power input and increasing gas ratio during plasma polymer deposition. The aging behavior and stability of such oxygen-functional vertical gradient nanostructures were studied in air and in different aqueous environments (acidic pH 4, neutral pH ≈ 6.2, and basic pH 10). Complementary characterization methods were used, including angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) as well as water contact angle (WCA) measurements. It was found that in air, the vertical gradient films are stabilized over a period of months. The same gradients also appear to be stable in neutral water over a period of at least 1 week. Changes in the oxygen depth profiles have been observed at pH 4 and pH 10 showing structural and chemical aging effects on different time scales. The use of vertical gradient plasma polymer nanofilms thus represents a novel approach providing enhanced stability, thus opening the possibility for new applications. [ABSTRACT FROM AUTHOR]

In spite of the huge research interest, ionic polymers could not have been synthesized in the vapor phase because the monomers of ionic polymers contain nonvolatile ionic salts, preventing the monomers from vaporization. Here, we suggest a new, one-step synthetic pathway to form a series of cross-linked ionic polymers (CIPs) in the vapor phase via initiated chemical vapor deposition (iCVD). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) and 4-vinylbenzyl chloride (VBC) monomers are introduced into the iCVD reactor in the vapor phase to form a copolymer film. Simultaneously in the course of the deposition process, the tertiary amine in DMAEMA and benzylic chloride in VBC undergo a Menshutkin nucleophilic substitution reaction to form an ionic ammonium-chloride complex, forming a highly cross-linked ionic copolymer film of p(DMAEMA-co-VBC). To the best of our knowledge, this is the first report on the synthesis of CIP films in the vapor phase. The newly developed CIP thin film is further applied to the surface modification of the membrane for oil/water separation. With the hydrophilic and underwater oleophobic membrane whose surface is modified with the CIP film, excellent separation efficiency (>99%) and unprecedentedly high permeation flux (average 2.32 x 105 L m-2 h-1) are achieved. [ABSTRACT FROM AUTHOR]

Using Monte Carlo simulations combined with a geometric primitive path analysis method (Z1 algorithm), we investigate the effects of polymer-wall interactions on the entanglements and dynamics of the polymer films capped between two walls. We introduce a new parameter, the average number of near-neighboring particles of each monomer, to understand the effects of the polymer-wall interactions on the entanglements and dynamics of these confined systems. Our results show that the number of entanglements increases from the attractive polymer-wall interactions to the repulsive polymer-wall interactions. When the film thickness is greater than the bulk chain dimensions, the diffusion coefficient is a slowly decreasing function of the film thickness; however, when the film thickness is smaller than the bulk chain dimensions, the diffusion coefficient is an increasing function of the film thickness. However, for stronger polymer-wall interactions, although the number of entanglements decreases, the average number of the near-neighboring particles rapidly increases, which screens the effect of the disentanglements and thus limits the diffusivity of the polymers. Moreover, our simulations demonstrate that a critical attractive energy exists in the polymer-wall systems, where the diffusion coefficient reaches a maximum value and decreases toward stronger attractions or stronger repulsions. Our simulations provide new insights into the molecular mechanisms of the effects of polymer-wall interactions on the confined polymer films. [ABSTRACT FROM AUTHOR]

We used differential scanning calorimetry and spectroscopic ellipsometry to measure the molecular weight (MW) dependence of bulk fragility (mbulk) and spectroscopic ellipsometry to measure the thickness dependences of the glass transition temperature (Tg) and fragility (m) in supported thin films of low MW cyclic or ring polymer. The effects of confinement on Tg and m of thin polymer films are important in a range of advanced technology applications, including nanoimprinting. It has previously been shown that nanoconfined films of high MW linear polystyrene (PS) exhibit major Tg- and m-confinement effects whereas films of low MW cyclic PS (c-PS) show at most a very weak Tg-confinement effect. In the absence of chain ends, c-PS exhibits very weak Tg,bulk- and mbulk-MW dependences compared to linear PS. Despite low MW c-PS having mbulk values similar to that of high MW linear PS, we found that low MW c-PS films show a very weak m-confinement effect because of a weak free-surface effect; e.g., m for a 27 nm thick film of 3.4 kg/mol c-PS is the same as mbulk within error. Overall, these results support a strong correlation between the susceptibility of fragility perturbation and the susceptibility of Tg perturbation caused by MW reduction, chain topology, and/or confinement. [ABSTRACT FROM AUTHOR]

We study the line roughness in poly(styrene-b-methyl methacrylate) symmetric block copolymer thin films and propose a phenomenological model to fit and describe the observed line edge, width, and placement roughness. Owing to the layering structure of symmetric block copolymers, we build from the model used to describe the thermal fluctuations in bilayer membranes and add a term for the bulk composition fluctuations in a phase segregated system. We use the peristaltic and undulatory modes of bilayer membranes to describe the width and placement roughness, respectively. We also include the correlations between adjacent domains to capture the cross-talk between alternating domains. We find that the model reproduces most of the main features observed in the power spectral density of our block copolymer films, providing a baseline to understand the physical properties that influence line roughness in a system relevant to nanolithography. [ABSTRACT FROM AUTHOR]

After more than 2 decades of intense research, the density variation in confined polymer films still remains a puzzling problem subject to controversy as the methods utilized to determine the density are often model dependent. Here, we propose a direct and model independent method to detect the density/refractive index variations in polymer thin films through the adsorption of ceria nanoparticles (NPs) onto their surface. The amount of adsorbed NP scales with the polymer film refractive index; hence, any increase/decrease in the NP surface coverage directly indicates an increase/decrease in the film refractive index and density. Experimenting our proposed novel approach on two well-studied polymers, we found that the density of polystyrene (PS) thin films deposited on oxide-free Si substrate increases with a reduction of the film thickness. On the contrary, poly(methyl methacrylate) (PMMA) films deposited on wafers with native silicon oxide show a decrease of their density when the film thickness is reduced. [ABSTRACT FROM AUTHOR]

In this comprehensive review, recent progress and developments on perfluorinated sulfonic-acid (PFSA) membranes have been summarized on many key topics. Although quite well investigated for decades, PFSA ionomers' complex behavior, along with their key role in many emerging technologies, have presented significant scientific challenges but also helped create a unique cross-disciplinary research field to overcome such challenges. Research and progress on PFSAs, especially when considered with their applications, are at the forefront of bridging electrochemistry and polymer (physics), which have also opened up development of state-of-the-art in situ characterization techniques as well as multiphysics computation models. Topics reviewed stem from correlating the various physical (e.g., mechanical) and transport properties with morphology and structure across time and length scales. In addition, topics of recent interest such as structure/transport correlations and modeling, composite PFSA membranes, degradation phenomena, and PFSA thin films are presented. Throughout, the impact of PFSA chemistry and side-chain is also discussed to present a broader perspective. [ABSTRACT FROM AUTHOR]

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work. [ABSTRACT FROM AUTHOR]

The glass transition temperature (Tg), in-plane diffusivity (D), and effective viscosity (ηeff) were measured for the same thin film system of poly(isobutyl methacrylate) supported by silica (PiBMA/SiOx). We found that both the Tg and D were independent of the film thickness (h0), but ηeff decreased with decreasing h0. We envisage the different h0 dependencies to be caused by Tg, D, and ηeff being different functions of the local Tg's (Tg,i) or viscosities (ηi), which vary with the film depth. By assuming a three-layer model and that Tg(h0) = ⟨Tg,i⟩, D(h0) ∼ kBT/⟨ηi⟩, and ηeff(h0) = h03/3Mtot(ηi), where ⟨...⟩ denotes spatial averaging and Mtot is the mobility of the films, we were able to account for the experimental data. By extending these ideas to the analogous data of polystyrene supported by silica (PS/SiOx), a resolution was found for the long-standing inconsistency regarding the effects of confinement on the dynamics of polymer films. [ABSTRACT FROM AUTHOR]