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A process for preparing active, strong base and acid self-standing individual membranes and printed structures is established by electrospinning and two-dimensional (2D) printing of the correspondi...

Surface-modified carbon nanotubes (CNTs) have become well-established filler materials for polymer nanocomposites. However, in immiscible polymer blends, the CNT-coating is selective toward the more compatible phase, which suppresses their homogeneous distribution and limits harnessing the full potential of the filler. In this study, we show that multiwalled CNTs with a patchy polystyrene/poly(methyl methacrylate) (PS/PMMA) corona disperse equally well in both phases of an incompatible PS/PMMA polymer blend. Unlike polymer-grafted CNTs with a uniform corona, the patchy CNTs are able to adjust their corona structure to the blend phases by selective swelling/collapse of respective miscible/immiscible surface patches. Importantly, the high interfacial activity of patchy CNTs further causes a significant decrease in PMMA droplet size with increasing filler content. The combined effect of compatibilization and homogeneous distribution makes patchy CNTs interesting materials for polymer blend nanocomposites, where next to the compatibilization, a homogeneous filler distribution is important to gain the desired materials property (e.g., reinforcement).

Multiresponsive polymers that can respond to several external stimuli are promising materials for a manifold of applications. Herein, a facile method for the synthesis of triple‐responsive (pH, temperature, CO2) poly(N,N‐diethylaminoethyl methacrylamide) by a post‐polymerization amidation of poly(methyl methacrylate) (PMMA) is presented. Combined with trivalent counterions ([Fe(CN)6]3−) both an upper and lower critical solution temperature (UCST/LCST)‐type phase behavior can be realized at pH 8 and 9. PMMA and PMMA‐based block copolymers are readily accessible by living anionic and controlled radical polymerization techniques, which opens access to various responsive polymer architectures based on the developed functionalization method. This method can also be applied on melt‐processed bulk PMMA samples to introduce functional, responsive moieties at the PMMA surface., Making PMMA responsive: PMMA can be converted into a triple‐responsive polymer, being responsive to temperature, pH and CO2 gas, by a quantitative post‐polymerization amidation with N,N‐diethylethylenediamine. This will open access to a large variety of responsive macromolecular architectures, because this method can be applied to PMMA and PMMA‐based block copolymers, being easily accessible by living anionic or controlled radical polymerization (see scheme).

Functional, hierarchically mesostructured nonwovens are of fundamental importance because complex fiber morphologies increase the active surface area and functionality allowing for the effective immobilization of metal nanoparticles. Such complex functional fiber morphologies clearly widen the property profile and enable the preparation of more efficient and selective filter media. Here, we demonstrate the realization of hierarchically mesostructured nonwovens with barbed wire-like morphology by combining electrospun polystyrene fibers, decorated with patchy worm-like micelles, with solution-processed supramolecular short fibers composed of 1,3,5-benzenetricarboxamides with peripheral N,N-diisopropylaminoethyl substituents. The worm-like micelles with a patchy microphase-separated corona were prepared by crystallization-driven self-assembly of a polyethylene based triblock terpolymer and deposited on top of the polystyrene fibers by coaxial electrospinning. The micelles were designed in a way that their patches promote the directed self-assembly of the 1,3,5-benzenetricarboxamide and the fixation of the supramolecular nanofibers on the supporting polystyrene fibers. Functionality of the mesostructured nonwoven is provided by the peripheral N,N-diisopropylaminoethyl substituents of the 1,3,5-benzenetricarboxamide and proven by the effective immobilization of individual palladium nanoparticles on the supramolecular nanofibers. The preparation of hierarchically mesostructured nonwovens and their shown functionality demonstrate that such systems are attractive candidates to be used for example in filtration, selective separation and heterogenous catalysis.

Electrospinning is a simple, low cost, and high throughput technique that allows for processing of polymers into fibers. The process can be controlled to allow access for well-defined continuous fibers that are of interest for a wide range of applications including as tissue scaffolds, as nanowires in optoelectronic devices, and in catalysis. Conventional electrospinning processes use polymer solutions with high molecular weights. Here, we report the electrospinning of one-dimensional (1D) fiber-like block copolymer micelles containing a crystalline core. We successfully accessed core-shell microfibers in which 1D micelles containing a crystalline poly(ferrocenyldimethylsilane) (PFS) core are immobilized on a polystyrene microfiber via coaxial electrospinning. Furthermore, we describe efforts to extend this approach to the use of 1D micelles comprising of a crystalline, π-conjugated poly(di-n-hexylfluorene) (PDHF) core. Electrospinning was also successfully used to prepare microfibers consisting solely of 1D micelles with a PFS crystalline core, the first examples where a template material is not required.

The confinement assembly of block copolymers shows great potential regarding the formation of functional microparticles with compartmentalized structure. Although a large variety of block chemistries have already been used, less is known about microdomain degradation, which could lead to mesoporous microparticles with particularly complex morphologies for ABC triblock terpolymers. Here, we report on the formation of triblock terpolymer-based, multicompartment microparticles (MMs) and the selective degradation of domains into mesoporous microparticles. A series of polystyrene-block-polybutadiene-block-poly(L-lactide) (PS-b-PB-b-PLLA, SBL) triblock terpolymers was synthesized by a combination of anionic vinyl and ring-opening polymerization, which were transformed into microparticles through evaporation-induced confinement assembly. Despite different block compositions and the presence of a crystallizable PLLA block, we mainly identified hexagonally packed cylinders with a PLLA core and PB shell embedded in a PS matrix. Emulsions were prepared with Shirasu Porous Glass (SPG) membranes leading to a narrow size distribution of the microparticles and control of the average particle diameter, d ≈ 0.4 µm–1.8 µm. The core–shell cylinders lie parallel to the surface for particle diameters d < 0.5 µm and progressively more perpendicular for larger particles d > 0.8 µm as verified with scanning and transmission electron microscopy and particle cross-sections. Finally, the selective degradation of the PLLA cylinders under basic conditions resulted in mesoporous microparticles with a pronounced surface roughness.

A series of cationic diblock copolymers were synthesized via sequential anionic polymerization of 2-vinylpyridine and ethylene oxide and further quaternization of the resulting diblock copolymers with dimethyl sulfate. Diblock copolymers with a degree of polymerization (DP) of the cationic block equal to 40 and DP of the poly(ethylene oxide) (PEO) block equal to 45, 210 and 450, as well as a cationic homopolymer with DP = 40 (control), were adsorbed on the surface of anionic liposomes of 40–60 nm in diameter. The liposomes were constructed with egg lecithin admixed with 0.1 mole fraction of a doubly anionic lipid, cardiolipin. The liposome–polymer complexes were characterized using electrophoretic mobility measurements, dynamic light scattering, conductivity, fluorescence and UV spectroscopy, and differential scanning calorimetry. Adsorption of the polymers causes the liposomes to aggregate; the only exception is the diblock copolymer with DP of the PEO block of 450, which shows an aggregation-preventing effect. In all cases, the integrity of liposomes is retained upon their complexation with polymers. The diblock copolymer with a short PEO block induces clustering of anionic lipid in the outer leaflet of the membrane; this effect becomes less pronounced with increasing DP of the PEO block. The differences in behaviour of the diblock copolymers are explained in terms of copolymer cluster formation via hydrogen bonding between neighbouring PEO blocks. These observations are important for interpretation of biological effects produced by cationic polymers and selection of cationic polymers for biomedical applications. © 2017 Society of Chemical Industry

By influencing both the interfacial adhesion and the morphology, compatibilizers determine the mechanical properties of polymer blends. Here, we study the mechanical properties, in particular the fatigue crack propagation (FCP) of immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether)/poly(styrene- co -acrylonitrile) (PPE/SAN), compatibilized with Janus nanoparticles (JPs) and linear polystyrene- block -polybutadiene- block -poly(methyl methacrylate) (SBM) triblock terpolymers. Synergistic effects of a mixture of both compatibilizers improve the FCP behavior and reveal the important role of interface stiffness and flexibility on the mechanical properties of polymer blends. The triblock terpolymer and JPs allow at the same time an elastic and stiff linkage at the blend interface and induce multiple deformation mechanisms such as crack bridging and matrix fibrillation that can dissipate energy and contribute to an improved FCP behavior. The presented concept allows tailoring macro-mechanical properties of immiscible polymer blends by adjusting blend morphology and interfacial properties.

One-dimensional patchy nanostructures are interesting materials due to their excellent interfacial activity and their potential use as carrier for functional nanoparticles. Up to now only wormlike crystalline-core micelles (wCCMs) with a nonfunctional patchy PS/PMMA corona were accessible using crystallization-driven self-assembly (CDSA) of polystyrene-block-polyethylene-block-poly(methyl methacrylate) (SEM) triblock terpolymers. Here, we present a facile approach toward functional, patchy wCCMs, bearing tertiary amino groups in one of the surface patches. The corona forming PMMA block of a SEM triblock terpolymer was functionalized by amidation with different N,N-dialkylethylenediamines in a polymer analogous fashion. The CDSA of the functionalized triblock terpolymers in THF was found to strongly depend on the polarity/solubility of the amidated PMMA block. The lower the polarity of the amidated PMMA block (increased solubility), the higher is the accessible degree of functionalization upon which define...

Gold nanoparticles (AuNP) with pyridyl end-capped polystyrenes (PS-4VP) as "quasi-monodentate" ligands self-assemble into ordered PS-4VP/AuNP nanostructures with 3D hexagonal spatial order in the dried solid state. The key for the formation of these ordered structures is the modulation of the ratio AuNP versus ligands, which proves the importance of ligand design and quantity for the preparation of novel ordered polymer/metal nanoparticle conjugates. Although the assemblies of PS-4VP/AuNP in dispersion lack in high dimensional order, strong plasmonic interactions are observed due to close contact of AuNP. Applying temperature as an external stimulus allows the reversible distortion of plasmonic interactions within the AuNP nanocomposite structures, which can be observed directly by naked eye. The modulation of the macroscopic optical properties accompanied by this structural distortion of plasmonic interaction opens up very interesting sensoric applications.

There are only a few non-ionic polymers known for showing thermoresponsivity of UCST-type. Copolymers of acrylamide (AAm) and acrylonitrile (AN) represent one of such thermoresponsive polymers. The present work shows pH-dependent UCST-transitions of this copolymer system. Herein, systematic studies were carried out to show hydrolytic stability and retention of UCST of the copolymer under various conditions. Regeneration of lost UCST-type transitions under extreme pH conditions could be achieved by changing pH, and by addition of electrolytes. Reversible addition fragmentation chain transfer (RAFT) was employed as a tool to synthesize copolymers of AAm and AN. Hydrolysis reactions were carried out intentionally under acidic and alkaline conditions, in order to analyze the chemical stability of the synthesized copolymers as well as to introduce carboxylic groups into the polymer structure. The obtained results showed high tolerance of poly(AAm-co-AN) samples under acidic conditions even after long periods of storage (25 days at pH 3) or after use of pH 0 and increased temperatures (40 °C). In the case of base catalyzed hydrolysis, the thermoresponsive behavior was significantly influenced during hydrolysis in buffer solution of pH 9. Loss and regeneration of the phase transition temperature of these copolymers could be achieved by changing the pH from basic to acidic. Meanwhile, hydrolysis at pH 14 at 40 °C influenced the thermoresponsive behavior and the chemical stability of the polymer, increasing the phase transition temperature over 30 °C. Further, we observed that additives, e.g. formamide can act as a sacrificial agent for providing stable UCST-type transitions even under alkaline conditions as well as at high temperatures (85 °C).

The effect of compatibilization with a symmetrical polystyrene- block -polybutadiene- block -poly(methyl methacrylate) (SBM) triblock terpolymer on the morphological and mechanical properties (specifically toughness) of immiscible poly(2,6-dimethyl-1,4-phenylene ether)/poly(styrene- co -acrylonitrile) (PPE/SAN) blends with different blend (w/w) ratios is investigated. We study the effect of blend viscosity on the localization of the compatibilizer at the blend interface, influencing the mechanical properties of the macroscopic material. The impact of the specific morphology of the blends, known as “raspberry morphology”, on the final material will be explained using thermomechanical analysis and revealing relevant deformation mechanisms. The correlations between domain size, toughness of the blends and the corresponding toughening mechanisms are explained. After compatibilization, the fracture toughness is increased due to better bonding and stress transfer between the phases and smaller domain sizes with strong interface impose shear yielding of the matrix. Very small inter-domain distances hinder matrix deformations, which forces debonding as a “weaker” main deformation mechanism. It is found that a PPE/SAN ratio of 60/40 (w/w) has the optimum viscosity during processing to control the morphology. At this blend ratio the dispersed PPE domains have a low packing density, allowing shear deformations of the matrix.

The self-assembly of block copolymers in the bulk phase enables the formation of complex nanostructures with sub 100 nm periodicities and long-range order, both relevant for nanotechnology applications. Here, we map the bulk phase behavior of polystyrene-block-polybutadiene-block-poly(tert-butyl methacrylate) (SBT) triblock terpolymers on a series of narrowly distributed polymers with widely different block volume fractions, ϕS, ϕB and ϕT. In dependence of ϕ, we find the lamella–lamella, core-shell cylinder, cylinder-in-lamella and core-shell gyroid morphology, but also a rarely observed cylinder-in-lamella phase. The bulk morphologies are thoroughly characterized by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) and display unusually broad stability regions, i.e. morphologies are observed over a broad range of compositions. We attribute this phase behavior to the asymmetric distribution of block–block incompatibilities, along the SBT block sequence, which are relatively large for S/B and S/T interfaces, but small for B/T. The higher enthalpic penalties at the S/B and S/T interface cause B to preferentially spread on the T microdomain thereby adopting its geometry. The morphological behavior of SBT is thus dominated by the volume ratio of the end blocks, ϕS and ϕT, which reduces the number of potential morphologies to only a few, mostly the core-shell analogue of diblock copolymer morphologies. In general, a simplified terpolymer bulk behavior with large stability regions for morphologies offers straightforward synthetic targeting of specific morphologies that usually only appear in a small parameter space as demonstrated here on the core-shell gyroid.

In this paper, preparation method and actuation properties of an innovative composite membrane composed of thermo- and pH-responsive poly(N-isopropylacrylamide-co-acrylic acid) fibers (average diameter ≈ 905 nm) embedded within a passive thermoplastic polyurethane (TPU) matrix at different angles with degree of alignment as high as 98% are presented. The composite membrane has a gradient of TPU along the thickness. It has the capability of temperature- and pH-dependent direction-, and size-controlled actuation in few minutes. The stresses generated at the responsive fiber and nonresponsive matrix provide actuation, whereas the angle at which fibers are embedded in the matrix controls the actuation direction and size. The temperature has no effect on actuation and actuated forms at pH 7 and above, whereas the size of the actuated forms can be controlled by the temperature at lower pH. The membranes are strong enough to reversibly lift and release ≈426 times weight of their own mass (2.47 g metal ring is lifted by a 5.8 mg membrane). Soft actuators are of interest as smart scaffolds, robotics, catalysis, drug release, energy storage, electrodes, and metamaterials.

A new route for the preparation of enzymatically degradable amphiphilic conetworks (APCNs) based on unsaturated polyesters by radical ring-opening copolymerization of vinylcyclopropane (VCP) with cyclic ketene acetal (CKA) is presented in this article. In the first step, the unsaturated biodegradable polyesters with random distribution of cross-linkable double bonds and degradable ester units were prepared by radical ring-opening copolymerization of VCP and CKA such as 2-methylene-4-phenyl-1,3-dioxolane (MPDO). Very similar reactivity ratios (rVCP = 0.23 ± 0.08 and rMPDO = 0.18 ± 0.02), unimodal gel permeation chromatography (GPC) curves and 2D NMR technique (heteronuclear multiple bond correlation, HMBC) showed the formation of random copolymers with unsaturation and ester units. The unsaturated units were used for cross-linking by radical polymerization with a hydrophilic macromonomer (oligo(ethylene glycol) methacrylate, OEGMA) in a second step for the formation of enzymatically degradable amphiphilic conetworks (APCNs). Enzymatic degradability was studied using Lipase from Pseudomonas cepacia. Due to the hydrophilic (HI) and hydrophobic (HO) microphase separation, the APCNs showed swelling in both water and organic solvents with different optical properties. The method provides an interesting route for making functional biodegradable APCNs using radical chemistry in the future by choosing appropriate vinyl comonomers.

The chemical structure and high aspect ratio of carbon nanotubes (CNTs) give rise to numerous exceptional physical properties but are also the origin for their intrinsic tendency to agglomerate. Since the full potential of CNTs is harnessed in homogeneous dispersions, e.g. in a polymer matrix, bundling of CNTs must be suppressed by compatibilizing unfavorable interfaces. We present a robust, noncovalent functionalization of multiwalled CNTs via physical grafting of polystyrene-block-polyethylene-block-poly(methyl methacrylate) (SEM) triblock terpolymers to the CNT surface in organic media. In an ultrasound-assisted approach at ambient temperature, the polyethylene (PE) middle block of SEM strongly adsorbs to the CNTs surface, yielding long-term stable dispersions of well-separated 1D hybrids with up to 3 wt % CNT content. Importantly, the strong affinity of PE toward CNTs prevents polymer desorption irrespective of the solvent conditions. The incompatible polystyrene (PS) and poly(methyl methacrylate) (PM...

Ease of catalyst separation from reaction mixtures represents a significant advantage in heterogeneous photocatalytic wastewater treatment. However, the activity of the catalyst strongly depends on its surface-to-volume ratio. Here, we present an approach based on cylindrical polybutadiene- block -poly(2-vinylpyridine) polymer brushes as template, which can be simultaneously loaded with zinc oxide (ZnO) and gold (Au) nanoparticles. Pyrolytic template removal of the polymer yields in mesostructured ZnO/Au composites, showing higher efficiencies in the photocatalytic degradation of ciprofloxacin and levofloxacin (generic antibiotics present in clinical wastewater) as compared to neat mesostructured ZnO. Upscaling of the presented catalyst is straightforward promising high technical relevance.

We introduce a modular route for the synthesis of well-defined ABC miktoarm star terpolymers. To this aim, the synthesis of a 1,1-diphenylethylene derivative bearing a protected alkyne function (1-[(4-(tert-butyldimethylsilyl)ethynyl)phenyl]-1-phenylethylene) was developed. This compound was for the first time employed in sequential anionic polymerization to readily prepare alkyne mid-functionalized diblock copolymers with polybutadiene as first and a poly(alkyl methacrylate) (poly(tert-butyl methacrylate), poly(N,N-dimethylaminoethyl methacrylate)) as second block. For the third arm controlled radical polymerization methods (polystyrene, poly(tert-butyl methacrylate), poly(N,N-dimethylaminoethyl methacrylate)) and anionic ring-opening polymerization (poly(ethylene oxide)) were used to separately prepare homopolymers with an azido function. Afterward, azide–alkyne Huisgen cycloaddition was successfully employed to synthesize a library of ABC miktoarm star terpolymers with different molecular weights and c...

We present a straightforward approach to well-defined 1D patchy particles utilizing crystallization-induced self-assembly. A polystyrene- block -polyethylene- block -poly(methyl methacrylate) (PS- b -PE- b -PMMA) triblock terpolymer is cocrystallized in a random fashion with a corresponding polystyrene- block -polyethylene- block -polystyrene (PS- b -PE- b -PS) triblock copolymer to yield worm-like crystalline-core micelles (wCCMs). Here, the corona composition (PMMA/PS fraction) can be easily adjusted via the amount of PS- b -PE- b -PMMA triblock terpolymer in the mixture and opens an easy access to wCCMs with tailor-made corona structures. Depending on the PMMA fraction, wCCMs with a mixed corona, spherical PMMA patches embedded in a continuous PS corona, as well as alternating PS and PMMA patches of almost equal size can be realized. Micelles prepared by cocrystallization show the same corona structure as those prepared from neat triblock terpolymers at identical corona composition. Thus, within a certain regime of desired corona compositions the laborious synthesis of new triblock terpolymers for every composition can be circumvented.

Aqueous solutions of a double responsive P2VP62-b-PEO452-b-P(GME36-co-EGE36) triblock terpolymer were investigated by means of small-angle neutron scattering (SANS) in order to derive information about structural changes going along with the temperature triggered gel-sol-gel transition at pH = 7, and the sol-gel transition at pH = 3.5, respectively, observed by rheology. SANS measurements on dilute samples at different pH and temperature confirmed the formation of core-shell-corona micelles under conditions, where only one of the outer blocks is insoluble. In addition, temperature-dependent scattering experiments were performed for higher volume fractions, that is, the concentration range where hydrogels were formed. This allowed us to identify the structural transitions, being responsible for the gel-sol-gel transition at pH = 7, and the structure of the gel phase formed at low pH and elevated temperatures.

We report on the synthesis and characterization of linear and star-shaped poly(N,N-diethylaminoethyl methacrylate) (PDEA). The synthesis was accomplished by Atom Transfer Radical Polymerization (ATRP) via a core-first approach using sugar-based multifunctional initiators. The investigation of the solution properties in water shows that PDEA is both pH- and temperature-responsive, analogous to the behavior of poly(N,N-dimethylaminoethyl methacrylate) (PDMA). In literature, PDEA is frequently referred to as being only pH-sensitive. The critical pH values for the aggregation are close to the apparent pKa values in all cases, i.e. a high charge density is necessary to keep the polymers soluble. The cloud points show a strong dependence on the pH value of the solution but no dependence on either molecular weight or architecture. Thus, the two polymers differ only quantitatively, as PDEA has cloud points about 40 K lower than PDMA and critical pH values which are 1.5–2 units lower than PDMA.

The synthesis of star-shaped polymers, which are threaded regularly along a common backbone, is described. Thus, two different approaches for preparation of so-called pearl necklace polymers (synonyms: multigraft copolymers, barbwire or centipedes polymers, multiple dumbbells or star-oligomers) are presented. Poly(ethylene oxide) (PEO) was used as a thread and poly(dimethylaminoethyl methacrylate) (PDMAEMA) stars were used as pearls. In the first approach, a polycondensation reaction of PEO macromonomers with partly protected dipentaerythritol leads first to a multiblock PEO. Afterward, the protected hydroxy groups of dipentaerythritol, which is situated at the junction points of the blocks, can be released for the anchoring of PDMAEMA chains. In the second approach, anionic polymerization of ethylene oxide leads directly to a diblock PEO with an interior dipentaerythritol unit. The chain ends can be modified with further dipentaerythritols, giving access after selective deprotection to either star dimers...

The synthesis of several diblock copolymers with DMAEMA via anionic polymerization is presented; PS-b-PDMAEMA, PB-b-PDMAEMA, poly(p-tert-butoxystyrene)-b-PDMAEMA, and PEO-b-PDMAEMA. The latter was synthesized using sec-butyllithium as initiator in presence of the phosphazene base t-BuP 4 , enabling a facile changeover from an oxyanion to a carbanion. All reactions resulted in narrowly distributed block copolymers (PDI < 1.1). For PEO-b-PDMAEMA, diblock copolymers with a high blocking efficiency and a near-narrow molecular weight distribution (PDI < 1.40) could be prepared. The advantage of the presented one-pot synthesis is a significant higher blocking efficiency compared to commercially available PEO macroinitiators under similar conditions.

We describe detailed investigations on the self-assembly of polybutadiene-block-poly(2-vinylpyridine) diblock copolymers into so-called crew-cut micellar aggregates in aqueous media. Three analogous diblock copolymers with different short segments of poly(2-vinylpyridine) were synthesized via anionic polymerization. The self-assembled aggregates are studied in dioxane/water mixtures by means of dynamic light scattering and transmission electron microscopy. Depending on the added volume fraction of water, spherical micelles, branched cylindrical micelles, and vesicles can be found. These aggregates can be cross-linked in a facile fashion using a UV photoinitiator. The structures of the crew-cut aggregates remain intact during cross-linking, yielding stabilized polymeric nanoparticles. A transfer of these nanoparticles into common, only slightly selective solvents, in which no aggregates or different type of aggregates would exist without cross-linking, is possible. The cross-linked nanoparticle structures remain unchanged during this process. Moreover, a new pathway for the phase transition of cylindrical micelles to vesicles was found and is elucidated.

The thermo-reversible formation of wormlike micelles from a polystyrene-block-polyethylene-block-poly(methyl methacrylate) (PS-b-PE-b-PMMA) triblock terpolymer with a crystallizable middle block in organic media is presented. The formation of wormlike micelles is rather unexpected, because PE containing diblock copolymers usually form platelet-like structures. Transmission electron microscopy (TEM) investigations revealed a core−corona structure for the wormlike micelles. The core is formed by crystalline PE domains, and the soluble corona exhibits a patched structure composed of microphase-separated PS and PMMA chains. Microphase separation of the coronal chains was proven by 2D 1H nuclear Overhauser effect spectroscopy (NOESY) and TEM investigations of selectively stained samples. A combination of various techniques, such as differential scanning calorimetry (DSC), dynamic light scattering (DLS), and scanning force microscopy (SFM), indicated that the wormlike micelles might be formed by crystallization...

The isothermal crystallization kinetics of PEO and PE blocks within various triblock terpolymers were studied by DSC. The effect of the geometry of the microdomains was analyzed by studying different compositions of PE-b-PS-b-PEO triblock terpolymers. The crystallization rate decreased for decreasing block content for both crystallizable blocks. The effect of the microdomain geometry, confinement or chain tethering on the crystallization of PEO was extensively studied by comparing pairs of triblock terpolymers with differences either in the nature (crystalline, glassy, amorphous) or in the location of the other blocks in the terpolymer.

The confined crystallization of poly(ethylene oxide) (PEO) in predominantly spherical microdomains formed by several diblock copolymers was studied and compared. Two polybutadiene-b-poly(ethylene oxide) diblock copolymers were prepared by sequential anionic polymerization (with approximately 90 and 80 wt % polybutadiene (PB)). These were compared to equivalent samples after catalytic hydrogenation that produced double crystalline polyethylene-b-poly(ethylene oxide) diblock copolymers. Both systems are segregated into microdomains as indicated by small-angle X-ray scattering (SAXS) experiments performed in the melt and at lower temperatures. However, the PB-b-PEO systems exhibited a higher degree of order in the melt. A predominantly spherical morphology of PEO in a PB or a PE matrix was observed by both SAXS and transmission electron microscopy, although a possibly mixed morphology (spheres and cylinders) was formed when the PEO composition was close to the cylinder-sphere domain transitional composition as indicated by SAXS. Differential scanning calorimetry experiments showed that a fractionated crystallization process for the PEO occurred in all samples, indicating that the PE cannot nucleate PEO in these diblock copolymers. A novel result was the observation of a subsequent fractionated melting that reflected the crystallization process. Sequential isothermal crystallization experiments allowed us to thermally separate at least three different crystallization and melting peaks for the PEO microdomains. The lowest melting point fraction was the most important in terms of quantity and corresponded to the crystallization of isolated PEO spheres (or cylinders) that were either superficially or homogeneously nucleated. This was confirmed by Avrami index values of approximately 1. The isothermal crystallization results indicate that the PE matrix restricts the crystallization of the covalently bonded PEO to a higher degree compared to PB.

The mechanical performance of immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN) and the subsequent influence of compatibilisation by tailored polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymers (SBM) on the mechanical performance under static and dynamic loads is analysed in detail. A PPE/SAN 60/40 blend was selected as a base system for the compatibilisation experiments. The observed static tensile behaviour is described by micromechanical models and correlated to the blend microstructures as observed by transmission electron microscopy. In most cases, the addition of the SBM triblock terpolymers further enhances the ductility of the blend while only leading to a minor reduction of modulus and strength. Triblock terpolymers with symmetric end blocks, mainly located at the interface between PPE and SAN, led to nearly isotropic specimens. In contrast, SBM materials with a longer polystyrene block predominantly formed micelles in the PPE phase and the blends revealed a highly anisotropic morphology. Comparative investigations of the fatigue crack growth behaviour parallel to the direction of injection also reflected this variation in mechanical anisotropy of the compatibilised blends. A poor toughness and a predominant interfacial failure were observed in the case of the SBM with a long polystyrene block. In contrast, a considerable improvement in properties as a result of pronounced plastic deformations was observed for blends compatibilised by triblock terpolymers with symmetric end blocks. The systematic correlation between morphology and mechanical performance of compatibilised PPE/SAN blends established in this study provides an efficient way for the desired selection of suitable and effective compatibilising agents, ensuring both a superior multiaxial toughness as well as a high strength and modulus of the overall system.

A first attempt was made to produce novel ABC triblock terpolymers with three potentially crystallisable blocks: polyethylene (PE), poly(ethylene oxide) (PEO), and poly(e-caprolactone) (PCL). Polybutadiene-b-poly(ethylene oxide) diblock copolymers were synthesized by living anionic polymerization. Then, a non-catalyzed thermal polymerization of e-caprolactone from the hydroxyl end group of the PB-b-PEO diblock precursors was performed. Finally, hydrogenation by Wilkinson catalyst produced PE-b-PEO-b-PCL triblock terpolymers. Side reactions were detected that lead to the formation of undesired PCL-b-PEO diblock copolymers, however, these impurities were successfully removed by purification. A range of triblock terpolymers with PCL and PEO minor components were prepared. Topological restrictions on the PEO middle block prevented this block from crystallizing while the complex crystallization behavior of the PE and PCL blocks was documented by DSC and WAXS measurements.

We present a convenient method to synthesize polymers with primary amino groups by end-capping of living anionic chain ends with nitriles followed by reduction in a one-pot process. As an example, the addition of pivalonitrile to the chain ends of oligobutadienyllithium in toluene, followed by the reduction with sodium borohydride quantitatively leads to ω-amino-oligo-1,4-butadiene, as demonstrated by 1 H and 13 C NMR, thin-layer chromatography and MALDI-ToF mass spectrometry.

Immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN) with a weight composition of 60/40 were compatibilised by polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymers (SBM) using a two-stage melt-processing approach. In order to investigate the influence of the SBM composition on the compatibilisation efficiency, the block lengths of the triblock terpolymers were systematically varied. The resulting morphological features of the blend systems as function of SBM composition and processing parameters are correlated with the resulting thermal and thermo-mechanical properties. In the ideal case, SBM should be located at the interface as PS is miscible with PPE while PMMA is miscible with SAN. The elastomeric middle block as an immiscible component should remain at the interface. This particular morphological arrangement is known as the ‘raspberry morphology’. A detailed TEM analysis of the blend morphologies following initial extrusion-compounding revealed a high compatibilisation efficiency of the SBM types with equal lengths of the end blocks and, furthermore, the desired raspberry morphology was achieved. In contrast, high PS contents in comparison to the other blocks led to a pronounced micelle formation in the PPE phase. Further evaluation of the blend structures following injection-moulding indicated that the morphologies remain relatively stable during this second melt-processing step. A detailed thermal analysis of all blend systems supports the interpretation of the observed morphological features. The fundamental correlation between SBM composition and blend morphology established in this study opens the door for the controlled development of interfacial properties of such compatibilised PPE/SAN blends during melt-processing.

We discuss the use of fluorescence correlation spectroscopy (FCS) to study the diffusion of single dye-labeled polymer chains in organic solvents. Monodisperse batches of polystyrenes labeled with a single Rhodamine B molecule have been synthesized via anionic polymerization of styrene and ethylene oxide end-capping followed by a polymer analogous coupling reaction. MALDI-ToF mass spectrometry is used to characterize the resulting material. A commercial FCS system has been modified to permit FCS measurements in volatile organic solvents. FCS was used to determine the molecular weight dependence of the diffusion coefficient of 10 nM solutions of end-labeled polystyrenes in toluene. The data are utilized to establish a calibration procedure for FCS measurements in organic solvents.

Fourier-transform near-infrared (FT-NIR) fiber-optic spectroscopy was successfully used to monitor the anionic polymerization of ethylene oxide (EO). Kinetic data are provided for the polymerization of EO with the sec-BuLi/Bu t P 4 initiating system under different initiators and reaction conditions on the polymerization of EO is investigated. Online monitoring using NIR spectroscopy revals an unexpected induction period present in EO homopolymerizations as well as in the synthesis of PEO containing block copolymers with [Li/Bu t P 4 ] + counterions. The resulting polymers are characterized by size exclusion chromatography (SEC). A low-molecular-weight polystyrene-block-poly(ethyelen oxide) (PS-b-PEO) diblock copolymer was synthesized to gain more insight into the observed induction period by matrix-assisted laser desorption ionization time-of-flight mass spectrometrhy (MALDI-ToF MS) on samples taken during EO polymerization. The induction period is believed to be a result of different factors involved in the formation of active centers, for example, the break up of lithium alkoxide aggregates by the phosphazene base Bu t P 4 , and chain lenght effects. It depends on reaction temperature, concentration of the phosphazene base Bu t P 4 , as well as the structure of the initiator.

The influence of different confinements active during crystallization within polybutadiene-block-polyisoprene-block-poly(ethylene oxide) (PB-b-PI-b-PEO) and the corresponding hydrogenated polyethylene-block-poly(ethylene-alt-propylene)-block-poly(ethylene oxide) (PE-b-PEP-b-PEO) triblock copolymers on the self-nucleation behavior of the crystallizable PEO and PE blocks is investigated by means of differential scanning calorimetry (DSC). In triblock copolymers with PEO contents ≤ 20 wt.-% crystallizationof PEO is confined within small isolated microdomains (spheres or cylinders), and PEO crystallization takes place exclusively at high supercoolings. Self-nucleation experiments reveal an anomalous behavior in comparison to the classical self-nucleation behavior found in semicrystalline homopolymers. In these systems, domain II (exclusive self-nucleation domain) vanishes, and self-nucleation can only take place at lower temperatures in domain III SA , when annealing is already active. The self-nucleation behavior of the PE blocks is significantly different compared with that of the PEO blocks. Regardless of the low PE content (10-25 wt.-%) on the investigated PE-b-PEP-b-PEO triblock copolymers a classical self-nucleation behavior is observed, i.e., all three self-nucleation domains, usually present in crystallizable homopolymers, can be located. This is a direct result of the small segmental interaction parameter of the PEP and PE segments in the mel. As a consequence, crystallization of PE occurs without confinement from a homogeneous mixture of PE and PEP segments. Self-nucleation regimes of a block copolymer showing confined crystallization by means of DSC.

The preparation of polyethylene-block-poly(ethylene-alt-propylene)-block-poly(ethylene oxide) (PE-b-PEP-b-PEO) triblock copolymers by homogeneous catalytic hydrogenation of the precursor poly(1,4-butadiene)-block-poly(1,4-isoprene)-block-poly(ethylene oxide) (PB-b-PI-b-PEO) triblock copolymers, which were synthesized by sequential anionic polymerization, is described. Thermal analysis using differential scanning calorimetry (DSC) reveals differences in the crystallization behavior of the PEO and PE blocks arising from different morphological confinements active during crystallization. If the PEO block is confined into isolated spherical or cylindrical microdomains, crystallization can only be induced by high supercoolings resulting from the vast number of microdomains (spheres or cylinders) compared to the number of available heterogeneities. In contrast, crystallization of PE proceeds via heterogeneous nucleation regardless of the composition, which can be attributed to the miscibility of PEP and PE segm...

The morphology of copoly(ether ester) elastomers, based on poly(butylene terephthalate) (PBT) hard blocks and poly(ethylene oxide)-block-poly(ethylene-stat-butylene)-block-poly(ethylene oxide) (PEO-b-PEB-b-PEO) soft blocks, has been investigated by various solid-state NMR methods. 13C IRCP and 1H T1ρ NMR experiments show a heterogeneity in molecular motions for the PEO and PBT segments, indicating the presence of a PEO-rich phase and a PEO/PBT mixed phase. In contrast, for the PEB segments a homogeneous NMR relaxation behavior is observed, indicating the presence of a separate pure PEB phase. Deuterium NMR spectra recorded of block copolymers with selectively deuterated PBT clearly show at least two distinct motional environments of PBT already at room temperature: a broad peak which is assigned to PBT segments in a crystalline phase and an extremely narrow peak which is assigned to highly mobile PBT segments embedded in an amorphous matrix (PBT/PEO mixed phase). For copoly(ether ester)s with a relativel...

We have been able to prepare a molecular complex between the poly(ethylene oxide) block of a poly(ethylene)-b-poly(ethylene-alt-propylene)-b-poly(ethylene oxide) triblock copolymer and p-nitrophenol (PNP). The composition of the copolymer employed was: 24% PE, 57% PEP and 19% PEO in weight percent. The pure copolymer exhibited a nonconventional thermal behavior since the PEO block displayed a fractionated crystallization process during cooling. The PEO block /PNP complex did not show any apparent crystallization during cooling, instead cold crystallization during heating was observed and an approximately 30 °C increase in melting point as compared to the neat PEO block within the copolymer. This caused an overlap in the melting regions of the PE block and the PEO block/PNP complex. The self-nucleation of the PE-b-PEP-b-PEO/PNP complex is very different from that of the neat triblock copolymer. An increased capacity for self-nucleation of the PEO block was produced by the complexation with PNP and therefore the three self-nucleation domains were clearly encountered for both the PE block and for the PEO block/PNP complex. Self-nucleation was able to show that the two crystallizable blocks can be self-nucleated and annealed in an independent way, thereby ascertaining the presence of separate crystalline regions in the triblock copolymer. Through the use of PNP, both the crystallinity and the melting point of the PE-b-PEP-b-PEO block copolymer employed here can be substantially increased. Similar results were obtained by complexation of the same ABC triblock copolymer with resorcinol.

The elasticity of commonly known poly(butylene terephthalate)−poly(tetramethylene oxide) (PBT−PTMO)-based copoly(ether ester)s is increased by replacement of PTMO soft segments with poly(ethylene oxide)-block-poly(ethylene-stat-butylene)-block-poly(ethylene oxide) (PEO-b-PEB-b-PEO) triblock copolymer soft segments containing a nonpolar middle block based on hydrogenated polybutadiene (PEB). The incorporation of this strongly incompatible PEB block resulted in the aimed increased phase separation between the PBT hard blocks and the soft segment phase, leading to a disperse PBT phase and hence to an increased elasticity. Dynamic shear experiments in combination with small-angle X-ray scattering revealed that crystallization of the PBT hard segments occurs from a microphase-separated melt. The resulting dispersed PBT hard phase in these materials is shown using transmission electron microscopy (TEM) and scanning force microscopy (SFM), whereas the increased elasticity is demonstrated using mechanical charact...

The confinement of crystallizable blocks within AB or ABC microphase-separated block copolymers in the nanoscopic scale can be tailored by adequate choice of composition, molecular weight, and chemical structure. In this work we have examined the crystallization behavior of a series of AB and ABC block copolymers incorporating one or two of the following crystallizable blocks: polyethylene, poly(e-caprolactone), and poly(ethylene oxide). The density of confined microdomain structures (MD) within block copolymers of specific compositions, in cases where the MD are dispersed as spheres, cylinders, or any other isolated morphology, is much higher than the number of heterogeneities available in each crystallizable block. Therefore, fractionated crystallization takes place with one or several crystallization steps at decreasing temperatures. In specific cases, the clear observation of exclusive crystallization from homogeneous nuclei was obtained. The results show that, regardless of the specific morphologica...

Nature is an intriguing inspiration for designing a myriad of functional materials. However, artificial mimicking of bioinspired structures usually requires different specialized procedures and setups. In this study, a new upscalable concept is presented that allows to produce two bioinspired, bicomponent fiber morphologies (side-by-side and coaxial bead-on-string) using the same electrospinning setup, just by changing the employed spinning solvent. The generated fiber morphologies are highly attractive for thermoresponsive actuation and water harvesting. Another challenge solved in this work is the compositional characterization of complex fiber morphologies. Raman imaging and atomic force microscopy is introduced as a powerful method for the unambiguous characterization of complex bicomponent fiber morphologies. The work opens the way for the construction of heterostructured fiber morphologies based on different polymers combinations, offering high potential for applications as actuators, smart textiles, water management, drug release, and catalysis.

We describe the synthesis, characterization, and properties of polystyrene-block-poly- (ethylene-alt-propylene)-block-polyethylene (PS-b-PEP-b-PE) and polystyrene-block-poly(ethylene-alt- propylene)-block-polystyrene (PS-b-PEP-b-PS) triblock copolymers. Morphological investigations using TEM, SEM, and SFM reveal for the PS-b-PEP-b-PE triblock copolymers a morphology consisting of PS cylinders and PE crystallites within a matrix of the PEP block, whereas the PS-b-PEP-b-PS triblock copolymer shows interconnected, distorted PS cylinders in the PEP matrix. Mechanical characterization of these triblock copolymers demonstrated that for small strains the PS-b-PEP-b-PE triblock copolymers exhibit the aimed smaller plastic deformations, i.e. better elastic properties, compared to the polystyrene- based ABA type thermoplastic elastomer. However, at high strains the PS-b-PEP-b-PS triblock copolymer shows a significantly better elastic recovery. The high plastic set at high elongations in PS-b-PEP-b-PE triblock copolymers is attributed to the weaker resistance of the PE crystallites compared to amorphous PS domains in the PS-b-PEP-b-PS triblock copolymer.

The preparation of polystyrene-b-poly(ethylene oxide)-b-poly(-caprolactone) triblock co- polymers using three different strategies is described. Experimentally, a method we have called "thermal" is the simplest one of the three employed. However, it presents serious limitations for the preparation of high molecular weight triblock copolymers with low polydispersity. The titration method is a more elegant alternative to prepare the PS-b-PEO-b-PCL triblock copolymers. Nevertheless, the stoichiometric titration of the precursor terminal hydroxyl groups requires much expertise, and it becomes more difficult as the concentration of such terminal groups decreases when the precursor molecular weight increases. Finally, the sequential method may be regarded as the most convenient one. However, the experimental steps involved a solvent exchange during polymerization that must be performed under conditions of strict purity and high vacuum. Several triblock and pentablock copolymers of varying compositions and molecular weights were successfully prepared. The fact that these copolymers contain two crystallizable blocks, i.e., PEO and PCL, makes them very interesting from a structural point of view. The copolymers were found to be phase segregated according to evidence provided by DSC and WAXS. The crystallization and melting behavior of both PEO and PCL blocks is greatly affected by composition. Fractionated crystallization phenomena were detected when either one or both blocks constituted the minor components within the block copolymers.

The incorporation of hydroxy-functionalized hydrogenated polybutadienes (HO−PEB−OH, KRATON liquid polymer) into PBT-based copolyesters by a conventional two-step melt polycondensation procedure is described. The usually occurring macrophase separation with nonpolar soft segments is avoided by chain extension of HO−PEB−OH with ethylene oxide to yield the corresponding hydroxy-terminated PEO−PEB−PEO triblock copolymers. Several PEO−PEB−PEO triblock copolymers with different PEO block lengths have been synthesized by means of anionic synthesis and incorporated into PBT-based copolyesters with varying PBT content. We show that the chain extension of HO−PEB−OH with ethylene oxide compatibilizes the nonpolar KRATON with the polar reactants 1,4-butanediol and dimethyl terephthalate during melt polycondensation, leading to a complete incorporation of the triblock copolymer into the copolyester. Morphological studies using SFM as well as mechanical testing show that the morphology is strongly influenced by the sof...

Small-angle neutron scattering (SANS) measurements under steady shear were performed to determine the exact nature and degree of structural order within a hydrogel based on poly(2-vinylpyridine)-block-poly(ethylene oxide)-block-poly(glycidyl methyl ether-co-ethyl glycidyl ether) (P2VP(56)-b-PEO410-b-P(GME(48)-co-EGE(48))) triblock terpolymer micelles. Previous static SANS measurements indicated the presence of a simple cubic (sc) or body centered cubic (bcc) packing. By exposing the sample to steady shear, different macroscopic structural transitions were induced, indicated by a stress plateau and a significant change of the 2D SANS patterns. A comparison of these 2D patterns with patterns from analogous systems reported in literature and theoretical predictions revealed the presence of a bcc structure. Furthermore, with increasing shear rate the structural alignment changes from a nonoriented state to an intermediate state consisting of polycrystalline bcc domains with weak preferential orientation, and finally to a highly aligned state in which twinned bcc domains exist. The [111] axis of the twinned bcc crystals is aligned in the direction of the shear flow, and the {110} slipping planes are preferentially aligned parallel to the shear plane (walls of the Couette cell). A minor fraction of twinned bcc domains, probably located in regions of lower shear velocity, i.e., close to the inner wall of the Couette cell (stator), is tilted by an angle of 90 degrees with respect to the shear plane.

We present a facile access route to hydroxy-functional narrow disperse microspheres of well-defined grafting density (GD). Ethylene oxide has been grafted from highly crosslinked poly(divinyl benzene) microspheres by anionic ring-opening polymerization using sec-butyllithium as activator together with the phosphazene base t-BuP(4) . Initially, core microspheres have been prepared by precipitation polymerization utilizing divinyl benzene (DVB, 80 wt.-%). The grafting of poly(ethylene oxide) (PEO) from the surface resulted in the formation of functional core-shell microspheres with hydroxy-terminal end groups. The number average particle diameter of the grafted microspheres was 3.6 µm and the particle weight increased by 5.7%. The microspheres were characterized by SEM, FT-IR spectroscopy, elemental analysis, and fluorescence microscopy. The surface GD (determined via two methods) was 1.65 ± 0.06 and 2.09 ± 0.08 chains · nm(-2) , respectively.