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Polybenzimidazoles (PBIs) are attractive membrane materials for H 2 /CO 2 separation at hydrocarbon fuel derived synthesis gas operating conditions due to their exceptional physicochemical stability and promising permselectivity character. PBI molecular structure modification is a viable approach to disrupt chain packing altering the free-volume architecture which results in improved gas transport characteristics. This work is focused on the synthesis and characterization of novel PBI random copolymers for application as elevated temperature H 2 /CO 2 membranes. The co-polymerization route is expected to result in tailorable permeability and selectivity by combining the high H 2 permeability aspect of the highly disrupted loosely packed hexafluoroisopropylidene diphenyl group containing PBI segments (6F-PBI) with the highly selective tightly packed phenylene group containing PBI segments (m-PBI). 6F/m-PBI copolymers with varying 6F-PBI and m-PBI ratios having high inherent viscosity were synthesized. The structure and ratio of the 6F- and m-PBI fractions were confirmed using FTIR and NMR spectroscopic techniques. The measured gas transport properties of copolymer thin films cast in controlled environment were measured as a function of the operating conditions. The H 2 permeability increased while H 2 /CO 2 selectivity decreased as the 6F-PBI copolymer fraction was increased. [ABSTRACT FROM AUTHOR]

Charge-containing polymeric materials have been widely studied for a range of applications. The fundamental relationships between the charge species, charge density, and the microscale morphology of charge-containing polymers are critical for defining the application in which they may be used. In this work, a series of thermoplastic poly(arylene ether sulfone) (PAES) copolymers with controllable sulfobetaine charge contents (0–100 mol%) and high molecular weights (Mw ∼ 65 kDa) were prepared. All the zwitterionic PAESs synthesized showed thermal stability up to 250 °C. DSC and tensile tests showed a decreased T g and mechanical strength with the incorporation of increasing charge density, which suggests a plasticization effect by the charged group. Electron microscopy and X-ray scattering data confirmed the absence of microphase separation in the ion-containing random copolymer system, which corroborated with the observation of a single T g for all zwitterionic copolymers studied. Furthermore, the relative hydrophilicity of the samples was evaluated by water uptake measurements, which revealed that the water uptake of the zwitterionic PAESs can reach up to 64% for the 72 mol% zwitterion copolymer while the free-standing film in the wet state still maintains a Young's modulus of 185 MPa. The thermoplastic charge-containing copolymers in this work demonstrated potential for applications such as coatings or water purification membranes, in which balancing hydrophilicity, processibility, and thermomechanical performance are important. [Display omitted] • A series of zwitterionic polysulfone copolymers with sulfobetaine content (0–100%) and high M w ∼ 65 kDa was synthesized. • The STEM/SAXS/WAXS data confirm the absence of ionic aggregates and support the single-T g observation for the copolymers. • The T g and Young's modulus decreased with an increase in charge content suggesting a plasticization effect by the zwitterion. • Water uptake of the zwitterionic polysulfones increased up to 64 wt%. • Freestanding films in the wet state exhibited a Young's modulus of up to 183.4 ± 86.3 MPa. [ABSTRACT FROM AUTHOR]

We performed dynamic Monte Carlo simulations of strain-induced crystallization of homopolymer and random copolymers under cyclic loading of strains. We found that since the second loading random copolymers shift down the onset strain of crystallization and raise up the crystallinity, in contrast to homopolymer. We attributed the strong memory to the remaining of sequence-length segregation raised by copolymer crystallization during the first loading of strains. The mechanism is consistent with that for the strong memory of copolymer crystallization under cyclic cooling, as revealed by previous experiments and simulations. Our results showed a new effect of chain-sequence defects on the cyclic loading performance of rubbers. [ABSTRACT FROM AUTHOR]

The opto-electrical, charge transport and photovoltaic properties of the highly efficient large band gap polymer, P(BDT-TDPPDT), containing electron rich 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT) and a weak electron accepting 2,5-dioctyl-4,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (TDPPDT) units were modulated by the incorporation of a relatively strong electron deficient thieno[3,4-b]thiophene (TT) unit on its backbone. A new random copolymer (RP2) was prepared by polymerizing the BDT derivative with TDPPDT and TT derivatives at a 2:1:1 ratio. The estimated optical band gap ( E g ) and highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) energy levels of RP2 were 1.70 eV and −5.30 eV/−3.60 eV, respectively. The determined hole mobility of RP2 was 4.0 × 10 −4 cm 2 V −1 s −1 . The polymer solar cells (PSCs) prepared with a simple device configuration of ITO/PEDOT:PSS/RP2:PC 70 BM/Al offered a maximum power conversion efficiency ( PCE ) of 5.12% with an open circuit voltage ( V oc ) of 0.75 V, a current density ( J sc ) of 12.99 mA/cm 2 , and a fill factor ( FF ) of 53%. The incorporation of a TT unit on the P(BDT-TDDPT) backbone was found to reduce the band gap by 0.41 eV and increase slightly the hole mobility of the resulting copolymer, RP2. Consequently, the PSC prepared from RP2 showed the enhanced photocurrent compared with that of the PSC prepared from P(BDT-TDPPDT). [ABSTRACT FROM AUTHOR]

In homopolymer/random copolymer blends, it is still unclear how the two crystallizable components contribute to secondary nucleation and the radial growth rate of spherulites. There are two highly possible nucleation pathways in the blends of homopolymer and the random copolymer with a low content of amorphous co-monomers. One, similar to regime II, the spherulitic growth rate G of the blends is affected by both secondary nucleation and tertiary nucleation, with the former contributed by homopolymers and the latter by random copolymers. The other, similar to regime I and III, the growth rate G of the blends is mainly determined by secondary nucleation, which is involved by both homopolymer and random copolymer. For the two cases, quantitative equations are established to correlate the spherulitic radial growth rate with the volume fraction of the homopolymer and the volume percentage of the crystallizable repeating units in the random copolymer. By analyzing the radial growth rate of the spherulites of poly(butylene succinate)/poly(butylene succinate- co -butylene 2-methylsuccinate) blends, we reveal the microscopic mechanism for the nucleation of homopolymer and random copolymer chains in the blends. Fitting of the experimental results with the theoretical equations precludes the first regime II like possibility that the homopolymer and the random copolymer contribute to secondary nucleation and tertiary nucleation, respectively. It is shown that both the homopolymer and the random copolymer contribute to secondary nucleation in the blends. Namely, a critical secondary nucleus of the blends consists of the crystallizable units from both homopolymer and random copolymer chains. The higher the homopolymer content, the more crystallizable units in a critical nucleus are derived from the homopolymer. In contrast, when the concentration of crystallizable units in the random copolymer becomes larger, more crystallizable units in a critical nucleus come from the random copolymer. Combining theory and experiments, we could determine the quantitative contribution of each crystallizable component to the secondary nucleation in the blends. [Display omitted] • Theoretical equations were derived for co-nucleation in homopolymer/random copolymer blends. • Spherulitic radial growth rate varied with the blend ratio and copolymerization composition. • Quantitative contribution of each component to secondary nucleation was revealed from data fitting. [ABSTRACT FROM AUTHOR]

Abstract: The influence of temperature on the crystallization process of isotactic propylene-1-butylene (P–B) random copolymer with low comonomer concentration subjected to uniaxial tensile force was studied in-situ by using synchrotron-based wide- and small-angle X-ray scattering techniques (WAXS/SAXS). Data analysis was performed on the whole-pattern base. P–B copolymer was stretched at three temperatures, i.e., 100 °C, 60 °C and 25 °C. Before stretching, the static sample contained both γ- and α-phase of isotactic polypropylene (iPP) homopolymer, with the γ-phase being the dominant crystal modification. When subjected to uniaxial stretching, γ-phase adopted a tilted cross-β configuration, with the c-axis forming a tilting angle with respect to the fiber axis at all temperatures. At 100 °C and 60 °C, γ-phase was transformed to α-phase with parallel orientation of polymer chains. Daughter lamellae of the α-phase were observed at 100 °C but not at 60 °C. At room temperature, large lamellar crystals could not be formed due to strong tensile force applied to the polymer network. Low temperature stretching was featured with the formation of mesomorphic phase which was composed of tiny β-form crystals and of about 50% of oriented amorphous phase. The c-axis of the β-form crystal was in parallel to the fiber axis. The crystals were so small that no ordered texture was observed at the length scale of nanometers. [Copyright &y& Elsevier]

Abstract: A series of random conjugated copolymers (labeled PMLTQT, PMLT2T, and PMLT3T) consisting of 3,4-diphenyl-maleimide and various thiophene derivatives has been designed and synthesized via Stille cross-coupling for application in polymer solar cells. These copolymers were readily soluble in common organic solvents, thermally stable from 405 to 437 °C upon heating, and exhibited good absorption in the UV and visible regions from 300 to 650 nm. The intensities of the PL emission spectra of these copolymers in a solid film were dramatically quenched by the addition of 50 wt% [6,6]-phenyl C61 butyric acid methyl ester (PC61BM). Their electrochemical properties indicated that the highest occupied molecular orbital levels of these copolymers were in the range of −5.63–5.73 eV, characteristic of better air stability and a high open-circuit voltage (V oc) suitable for application to photovoltaic cells. Bulk heterojunction photovoltaic devices composed of an active layer of electron-donor copolymers blended with the electron acceptor PC61BM or [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) at a weight ratio of 1:3 were investigated. The photovoltaic device containing PMLT3T and PC71BM (1:3, w/w) as the active layer afforded the best performance among these copolymers, with a V oc of 0.74 V, J sc of 7.4 mA cm−2 and a PCE of 1.20% under AM 1.5 G simulated solar light. [Copyright &y& Elsevier]

Abstract: Cervical cancer remains a critical problem that is second only to breast cancer affecting women worldwide. The objective of this study was to develop formulation of docetaxel-loaded biodegradable poly(ɛ-caprolactone-co-lactide)-d-α-tocopheryl polyethylene glycol 1000 succinate (PCL-PLA-TPGS) nanoparticles for cervical cancer chemotherapy. A novel random copolymer, PCL-PLA-TPGS, was synthesized from ɛ-caprolactone, lactide and d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) by ring-opening polymerization. The obtained polymers were characterized by 1H NMR, FTIR, GPC and TGA. The docetaxel-loaded PCL-PLA-TPGS nanoparticles were prepared by a modified solvent extraction/evaporation technique and characterized in terms of size and size distribution, morphology, surface charge and physical state of encapsulated docetaxel. Cellular uptake and in vitro cytotoxicity of nanoparticle formulations were done in comparison with commercial formulation Taxotere® to investigate the efficacy of PCL-PLA-TPGS nanoparticles. In vitro cellular uptakes of such nanoparticles were investigated with CLSM, demonstrating the coumarin 6-loaded PCL-PLA-TPGS nanoparticles could be internalized by Hela cells. In vitro cancer cell viability experiment showed that judged by IC50, the PCL-PLA-TPGS nanoparticle formulation was found to be more effective in cell number reduction than the Taxotere® after 48 h (p < 0.05), 72 h (p < 0.05) treatment. In conclusion, the PCL-PLA-TPGS copolymer could be acted as a novel and promising biologically active polymeric matrix material for nanoparticle formulation in cervical cancer treatment. [ABSTRACT FROM AUTHOR]

Abstract: Liver-targeting ribavirin-conjugating nanoparticles were successfully constructed via self-assembly of the lactose-functionalized amphiphilic random copolymer, which was facilely prepared by a two-step chemoenzymatic synthetic route. Aggregation morphology of the resulting self-assemblies observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) was regularly spherical shape, and hydrodynamic diameter determined by dynamic light scattering (DLS) was 174±27nm. Critical aggregation concentration (CAC) was measured by fluorescence probe technology using pyrene as the hydrophobic molecule, and the CAC value was about 0.1mg/L. Cell cytotoxicity tests performed by MTT assay showed that the nanoparticles had effective growth-inhibitory activity in hepG2 human hepatoma cells. Moreover, ribavirin could be slowly released from the copolymer with pseudo zero-order kinetics in different incubation media. The targeting nanoparticles self-assembled from amphiphilic random copolymers could be used as novel potential drug delivery vehicles. [Copyright &y& Elsevier]

Abstract: The physical properties and gas permeation behavior of a series of homo/random copolymers of 4,4′-difluorobenzophenone (DFBP)–2,2-bis(4-hydroxy-phenyl)propane (BPA)/2,2-bis(4-hydroxy-3,5-dimethyl-phenyl)propane (TMBPA) have been investigated by systematically varying the diol ratios. The tetramethyl substitution group on the phenyl rings simultaneously increases polymer free volume and chain stiffness. These were confirmed by experimental and simulated methods. With the increase in TMBPA content, the gas permeation coefficients, diffusion and solubility coefficients of H2, O2, N2, CO2 and CH4 were found to increase. The gas transport coefficients of the copolymers predicted from the additional rule were compared with the experimental results and the results obtained were within the expectations. In addition, the logarithm of gas permeation coefficients and the reciprocal of fractional free volume (1/FFV) also exhibited a good correlation. However, with the incorporation of TMBPA moiety, the permselectivity of gas pairs such as H2/N2, O2/N2 and CO2/CH4 remains reasonably high. As a result, the gas separation performance of TMBPA modified poly(aryl ether ketone) approaches the upper bound of the corresponding gas pairs. After comparing this work with gas separation performance of other methyl substituted polymers, one may conclude there is a general phenomenon that methyl substitution increases the gas permeability of the modified polymer with a small loss in gas selectivity for small gas pairs. [Copyright &y& Elsevier]

Abstract: Blends of styrene–butadiene diblock copolymer (S–B, 52wt% styrene content) and styrene–butadiene random copolymer (SBR) of various styrene compositions were studied by small-angle X-ray scattering, light scattering, and transmission electron microscopy. The composition of random copolymer plays an important role in the solubilization of SBR in S–B. The order–disorder transition temperature, T ODT, decreases linearly with the addition of SBR. T ODT decreases as the symmetry in SBR composition increases and shows the highest value in the case of homopolymers. Asymmetric butadiene-rich SBR dissolves mostly into PB microdomain of S–B to increase lamella microdomain spacing, D, and its addition makes the overall microdomains of S and B in the mixture more asymmetrical. Symmetric SBR is localized into the interface of S–B microdomain to reduce unfavorable S–B contact at the interface. The phase diagram for S–B containing asymmetric SBR shows a succession of mixed mesophases of different morphologies from lamellae and cylinder to disordered liquid phases, whereas the phase diagram containing symmetric SBR shows two homogeneous phases and one region of two-phase coexistence, where macroscopically separated phases coexist together. [Copyright &y& Elsevier]

Glass transition temperatures (Tg) of thin poly(styrene-co-methyl methacrylate) and poly(2-vinyl pyridine-co-styrene) films coated on a native oxide surface of Si wafer (100) were measured by ellipsometry. The thickness dependence of Tg can be properly fitted by previously suggested equation developed for homopolymers, based upon a continuous multi-layer model, although one component in thin random copolymer films demonstrates a slightly favorable interaction between a substrate and thin film, and another demonstrates a strongly favorable interaction. Surface and interface have a strong influence on Tg of thin film coated on substrate: the surface has the effect of reducing Tg, whereas the interface increases the Tg according to the degree of interaction between a substrate and thin film. This degree of interaction can be quantified as an interaction parameter (k), and is dependent on the composition of random copolymers. For the estimation of k values of thin random copolymer films, we proposed a parallel type additive function (1/kran=w1/k1+w2/k2) where w is a weight fraction of component. [Copyright &y& Elsevier]

The isothermal crystallization of three random copolymers of &epsiv;-caprolactone with different contents of 2,2-dimethyltrimethylene carbonate (DTC) (DTC: 5, 9 and 18 mol%) and poly(&epsiv;-caprolactone) (PCL) was studied using DSC and PLM methods. The isothermal crystallization data were analyzed with the Avrami equation. The exponent n, from 3 of PCL to 2 of P(82%CL-ran-18%DTC), suggests a change of crystal form. The crystallization rate was lowered by the addition of DTC units, which interrupted the perfect crystallization of PCL. [Copyright &y& Elsevier]

Electrospinning is a process by which sub-micron polymer fibers can be produced using an electrostatically driven jet of polymer solution (or polymer melt). Electrospun textiles are of interest in a wide variety of applications including semi-permeable membranes, filters, composite applications, and as scaffolding for tissue engineering. The goal of the research presented here is to demonstrate that it is possible to produce sub-micron fibers with a specific surface chemistry through electrospinning. This has been accomplished by electrospinning a series of random copolymers of PMMA-r-TAN from a mixed solvent of toluene and dimethyl formamide. X-ray Photoelectron Spectroscopy (XPS) analysis shows that the atomic percentage of fluorine in the near surface region of the electrospun fibers is about double the atomic percentage of fluorine found in a bulk sample of the random copolymer, as determined by elemental analysis. These results are in good agreement with XPS and water contact angle results obtained from thin films of the same copolymer materials. [Copyright &y& Elsevier]

The aging behavior of a series of polypropylene random copolymer (PP-RCP) reactor powder samples was studied by NMR relaxometry, a.k.a. Industrial Magnetic Resonance (IMR). The samples, which had been stored for two years since polymerization, were heated for 20 min at 120 °C to mimic the morphology of freshly polymerized samples, then cooled down and stored at ambient temperature for one month during which NMR experiments were conducted to observe the morphological changes. Sixteen PP-RCP samples with a wide range of compositions were found to follow a rather consistent trend. For most samples, crystallinity increased during aging, at the expense of the amorphous population, while the interfacial population remained mostly unchanged. In the meantime, the segmental mobility of the interfacial phase steadily decreased. A strong correlation was found between the population of the amorphous component and the T 2 relaxation time of the interfacial component, the precise mechanism of which is unknown. The likely mechanism of the morphological change during ambient temperature aging is secondary crystallization of the γ form on the lateral surface of the scaffold crystallites. [Display omitted] • Aging of PP random copolymers with a broad range of XS was studied by TD-NMR. • Subtle changes in the populations and dynamics of three phases could be detected. • Crystallinity increased and interfacial components became more rigid. • Observations support secondary crystallization on scaffold crystallite surface. [ABSTRACT FROM AUTHOR]