Blends of organosilicon polymers with polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide)

Blends of organosilicon polymers with polystyrene, PS, and poly(2,6-dimethyl-1,4-phenylene oxide), PPE, were investigated by transmission electron microscopy and differencial scanning calorimetry. Blends with poly(tetramethylsilphenylenesiloxane), PTMPS, showed a morphology characterized by globular domains dispersed in the organic matrix. An apparent homogeneous system was observed when poly(dimethylsilphenylene), PDSP, was mixed with PPE. A crystalline phase was found in samples with a higher PDSP content. The morphology of PS/PDSP blends with low PDSP content showed a dendritic phase dispersed in the PS-rich matrix. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2609–2616, 1997     

Tailored polymer electrets based on poly(2,6-dimethyl-1,4-phenylene ether) and its blends with polystyrene

Due to the establishment of common thermoplastics such as polyethylene, polypropylene and polytetrafluoroethylene as substrates for modern electrets, research in this field has seen significant progress in recent decades. However, there still is a need for new substrate materials in order to boost modern-day electret applications. Important targets for a further development are electret substrates with a tailored balance between cost and performance especially at elevated temperatures. In this study, experimental results concerning the charge storage behaviour of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) films and its blends with polystyrene (PS) are presented. As demonstrated, the good electret performance of neat PPE can be further enhanced by the addition of suitable weight fractions of PS, a synergistic electret behaviour that is related to morphological blend parameters such as the packaging density and the presence of PS micro-heterogeneities in the PPE/PS matrix. Most importantly, the results highlighted in this study clearly demonstrate the potential of blending as a promising approach towards satisfying the demands of tomorrows’ electret applications.     

Effect of PS‐b‐PCL block copolymer on reaction‐induced phase separation in epoxy/PEI blend

PS‐b‐PCL block copolymer is used to study its influence on the phase evolution of epoxy resin/polyetherimides (PEI) blends cured with methyl tetrahydrophthalic anhydride. The effect of PS‐b‐PCL on the reaction‐induced phase separation of the thermosetting/thermoplastic blends is studied via optical microscopy, scanning electron microscope, and time‐resolved light scattering. The results show that secondary phase separation and typical phase inverted morphologies are obtained in the epoxy/PEI blends with addition of PS‐b‐PCL. It can be attributed to the preferential location of the PS‐b‐PCL in the epoxy‐rich phase, which enhances the viscoelastic effect of epoxy/PEI system and leads to a dynamic asymmetry system between PEI and epoxy. The PS‐b‐PCL block copolymer plays a critical role on the balance of the diffusion and geometrical growth of epoxy molecules. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1395–1402     

Physical aging and deformation kinetics of polycarbonate

Considering the current view that physical aging of glasses results in an increase of activation barriers to plastic deformation, it is surprising that, until now, no influence of physical aging was observed experimentally on the temperature dependence of plastic deformation in polymeric glasses. This study evaluates why such an influence has not been found, and it is shown that detailed analysis of a set of uniaxial compression data on polycarbonate (PC) at different strain rates and temperatures leads to the conclusion that a significant influence indeed exists. As a consequence, the Eyring activation energy depends on the aging history of the material. These experimental observations are rationalized in terms of a simple physical interpretation of the aging phenomenon. The article also contains a discussion of the apparent deaging of amorphous polymers induced by large‐strain plastic deformation. This discussion is of key importance here, because this study compares yield stresses of aged PC with those of mechanically deaged, or rejuvenated, PC. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Charge selective encapsulation by polymeric micelles with cationic,anionic, or zwitterionic cores

Polymeric micelles showing charge selective and pH‐reversible encapsulation are reported. It is found that for a guest mixture of organic cationic–anionic dyes, a unimolecular micelle (PEI@PS) with a polystyrene (PS) as shell and a hyperbranched polyethylenimine (PEI) as core can exclusively entrap the anionic one; and a physical micelle consisting of brush‐like macromolecule (mPS‐PAA) with multi PS‐b‐polyacrylic acid (PAA) as grafts can exclusively entrap the cationic one. A covalent micelle (PEI‐COOH@PS) bearing a zwitterionic core, that is, PEI covalently derived with dense carboxylic acids, can undergo highly pH‐switchable charge selective and pH‐reversible encapsulation. Both PEI@PS and mPS‐PAA can be used for highly charge‐selective separation of ionic dyes but the pH‐reversibility of the encapsulation is relatively limited. In contrast, PEI‐COOH@PS is less effective to differentiate the anionic–cationic dyes but is well recyclable. A physical micelle obtained from the self‐assembly of PEI and mPS‐PAA shows similar property to PEI‐COOH@PS. The combination of these micelles in mixture separation can enhance the recyclability of the micelle and widen the spectrum of mixtures that can be well separated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Intractable high‐Tg thermoplastics processed with epoxy resin: Interfacial adhesion and mechanical properties of the cured blends

The intractable, high‐temperature‐resistant thermoplastics (TPs) polyphenylenether (PPE) and polyetherimide (PEI) were processed by dissolution into epoxy–amine precursors and a subsequent reaction of the precursors. Because the TP concentration was higher than the critical concentration, the phase separation produced a dispersion of crosslinked thermoset (TS) particles into a TP matrix. The morphology of the blends was examined with transmission electron microscopy and dynamic mechanical thermal spectroscopy, which showed completion of the phase separation. The interfacial adhesion at the TP‐matrix/TS‐particle interface was estimated on TP/TS bilayers to be 10 J/m² in PEI blends, whereas it was 70 J/m² in PPE blends, where there is strong evidence for in situ grafting between PPE phenolic chain ends and glycidyl functions of the reactive TS. Yielding in the compressive mode occurred at an intermediate yield stress between the components' values, and the anelastic deformation was separated from the plastic deformation. Fractures in the tensile mode occurred through debonding at the matrix/particle interfaces and coalescence of these defects, which led to microcrack formation and brittle failure. Mode I fracture toughness was, therefore, higher for PPE blends than for PEI blends, a result of the higher interfacial adhesion. However, a decrease from pure TP was observed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 363–373, 2001     

Fast FTIR imaging: A new tool for the study of semicrystalline polymer morphology

The distribution of chemical species and the degree of orientation in semicrystalline polymer systems have been studied using fast Fourier transform infrared (FTIR) imaging. A variety of poly(ethylene glycol) systems, including pure polymer, high and low molecular weight blends, and blends with amorphous polymers, were studied. It is shown that fast FTIR imaging can be used to determine the distribution of species with different molecular weights and can be used to determine the degree of segregation of different components in blends with amorphous polymers. Additionally, by employing an infrared polarizer, the degree of orientation was determined in these systems by the generation of spatially‐resolved dichroic ratio images. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2353–2359, 1999     

Synthesis and hydrolytic degradation of stereoregular aromatic poly(ester amide)s derived from D‐xylose

Stereoregular poly(ester amide)s (PEAs) were prepared by the polycondensation method using naturally occurring D ‐xylose and aromatic diacids as the starting materials. The polymers were characterized by elemental analysis, GPC, IR, and ¹H‐ and ¹³C NMR spectroscopies. Thermal and X‐ray diffraction studies revealed them to be mainly amorphous. The polymers are hydrophilic and their degradation studies were carried out at 37 and 80 °C in buffered salt solution at pH 8. The degradation study was monitored by mass loss, GPC, IR, and NMR spectroscopies. The hydrolytic degradation of these PEAs occurred rapidly by hydrolysis of the ester functions to a final compound, which maintained the amide functions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Poly(silylenemethylene)‐based polymer blends. III. Synthesis and properties of polymer blends containing siloxane‐crosslinked poly(silylenemethylene)s

Soft–hard binary polymer blends consisting of amorphous poly(silylene methylene)s (PSMs) and crystalline poly(diphenylsilylenemethylene) were prepared by both melt processing at 360 °C and in situ polymerization at 300 °C. Linear and siloxane‐crosslinked PSMs were used as amorphous components for the purpose of determining how the crosslinks affected the interactions between the component polymers. Differential scanning calorimetry and dynamic mechanical analysis indirectly suggested that discernable differences between the blends containing linear and crosslinked PSMs were attributable to the degree of interactions between the amorphous and crystalline components. The morphological differences between these blends were studied with transmission electron microscopy. The dispersion phase was smaller in the blends containing crosslinked PSM than that in the blends containing linear PSM. This directly indicated that a larger interaction between the amorphous and crystalline phases was obtained by the introduction of crosslinks because of the smaller viscosity difference between the phases and a larger degree of polymer chain entanglement. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 257–263, 2003     

Transport properties of thermoplastic/thermoset blends

Gas transport properties are reported for two series of films prepared from initially miscible thermoplastic/thermoset blends, respectively, polystyrene PS/thermoset and poly(2,6 dimethyl 1,4 phenylene oxide) PPE/thermoset blends. The thermoplastic contents are such that in both cases, after the phase separation, the continuous phase is the thermoplastic‐rich phase and scanning electron microscopic photomicrographs clearly evidenced the dispersion of thermoset‐rich nodules in the continuous thermoplastic‐rich phase with a more tortuous morphology in the case of PPE based films. Permeability measurements were made for O₂ and CO₂ at 20°C and a reduction in permeability coefficients was observed with increased thermoset content. Analysis using Maxwell law suggests that for all thermoplastic/thermoset blends, the thermoset particles can be considered as impermeable to gas and that the diffusion takes place in the continuous phase. In the case of PPE based films, the higher decrease of permeability than that predicted by the law has been related to the morphology of the blends and thus the tortuosity and to a partial miscibility of the thermoset in the thermoplastic. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 473–483, 1999     

Synthesis and characterization of donor–bridge–acceptor alternating copolymers containing perylene diimide units and their application to photovoltaic cells

We have used Suzuki coupling to prepare a series of alternating copolymers featuring coplanar cyclopentadithiophene and hole‐transporting carbazole units. We observed quenching in the photoluminescence spectra of our polymers after incorporating pendent electron‐deficient perylene diimide ( PDI ) moieties on the side chains, indicating more efficient photoinduced electron transfer. Electrochemical measurements revealed that the PDI ‐containing copolymers displayed reasonable and sufficient offsets of the energy levels of their lowest unoccupied molecular orbitals for efficient charge dissociation. The performance of bulk heterojunction photovoltaic cells incorporating the copolymer/[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester blends (1:4, w/w) was optimized when the active layer had a thickness of 70 nm. The photocurrents of the devices were enhanced as a result of the presence of the PDI moieties, thereby leading to improved power conversion efficiencies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1298–1309, 2010     

Miscibility and transesterification in ternary blends of poly(ethylene naphthalate)/poly(trimethylene terephthalate)/poly(ether imide)

Miscibility and morphology of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate)/poly(ether imide) (PEN/PTT/PEI) blends were investigated by using a differential scanning calorimeter (DSC), optical microscopy (OM), wide-angle X-ray diffraction (WAXD), and proton nuclear magnetic resonance (¹H-NMR). In the ternary blends, OM and DSC results indicated immiscible properties for polyester-rich compositions of PEN/PTT/PEI blends, but all compositions of the ternary blends were phase homogeneous after heat treatment at 300 °C for more than 30 min. An amorphous blend with a single T _g was obtained in the final state, when samples were annealed at 300 °C. Experimental results from ¹H-NMR identified the production of PEN/PTT copolymers by so-called “transesterification”. The influence of transesterification on the behaviors of glass transition and crystallization was discussed in detail. Study results identified that a random copolymer promoted the miscibility of the ternary blends. The critical block lengths for both PEN and PTT hindered the formation of crystals in the ternary blends. Finally, the transesterification product of PEN/PTT blends, ENTT, was blended with PEI. The results for DSC and OM demonstrated the miscibility of the ENTT/PEI blends.     

Effects of miscible diluent of poly(ether imide) on ring-banded morphology of poly(trimethylene terephthalate)

The melting, crystallization, and self-packed ring patterns in the spherulites of miscible blends comprising poly(trimethylene terephthalate) (PTT) and poly(ether imide) (PEI) were revealed by optical, scanning electron microscopies (PLM and SEM) and differential scanning calorimetry (DSC). Morphology and melting behavior of the miscible PTT/PEI blends were compared with the neat PTT. Ringed spherulites appeared in the miscible PTT/PEI blends at all crystallization temperatures up to 220 °C, whereas at this high temperature no rings were seen in the neat PTT. A postulation was proposed, and interrelations between rings in spherulites and the multiple lamellae distributions were investigated. The specific interactions and the segregation of amorphous PEI were discussed for interpreting the morphological changes of 220 °C-melt-crystallized PTT/PEI samples. Interlamellar segregation of PEI might be associated with multiple lamellae in the spherulites of PTT/PEI blends; therefore, rings were more easily formed in the PTT/PEI blends at all crystallization temperatures. A postulated model of uneven lamellar growth, coupled with periodical spiraling, more properly describes the possible origin of ring bands from combined effects of both interactions and segregation between the amorphous PEI and PTT in blends.     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

Chain orientation in polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) blends

The differential orientation of polymer chains has been measured in polystyrene (PS)/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) compatible blends. Density measurements are reported as a function of binary blend composition at 23°C. Drawing was performed by solid-state coextrusion. PS/PPO blend compositions of 90/10 and 75/25 were drawn within sandwiches of polyethylene at 145°C and isotactic polypropylene at 155°C, i.e. at ca. 25°C above the glass transition temperatures of the two blends. The change in Fourier-transform infrared dichroisms on drawing these blends was measured at 906 and 1190 cm^?1, corresponding to predominantly PS and PPO, respectively. The orientation of PS and PPO was observed as a function of draw ratio λ in the range 1–5; orientations increased with λ for both PS and PPO in both blends but to different degrees. Both polymers decreased in orientation with increasing PPO content. Annealing with fixed ends showed that the PPO chains disorient more slowly than those of PS. All binary systems were found to be amorphous and compatible.     

Phase behavior of blends of PCBM with amorphous polymers with different aromaticity

The phase behavior of [6,6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM) blends with amorphous polymers with different degrees of aromaticity has been investigated by differential scanning calorimetry (DSC) and small‐angle neutron scattering (SANS). The polymers investigated are the homologous series of polystyrene (PS), poly(2‐vinyl‐naphthalene) (P2VN), and poly(9‐vinyl‐phenanthrene) (P9VPh). The DSC results show that the miscibility of PCBM in these polymers increases nonlinearly from 16.5 wt % in PS, 57.0 wt % in P2VN, and 74.9 wt % in P9VPh. The SANS results show that at all concentrations of PCBM, the blends are composed of two mixed phases. Analysis shows that the phase dimensions remain largely independent of PCBM content, but there is a strong dependence of the PCBM concentration difference in the two phases with increasing PCBM content. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 994–1001     

Synthesis and property comparison of isomeric AB‐type homo‐ and copoly(etherimide)s

AB‐type homo‐ and copoly(etherimide)s were prepared by the polymerization of 3‐ and 4‐(3,4‐dicarboxyphenyloxy)aniline hydrochlorides ( 3A and 4A ) at 160 °C in dimethylacetamide in the presence of triethylamine and triphenyl phosphite. After the structures of the polymers were characterized, their solubilities, ultraviolet–visible (UV–vis) absorption behaviors, thermal properties, and crystallinities were measured, and these properties are discussed with respect to the structure of the homopolymers and the composition of the copolymers. Poly(etherimide) (PEI) derived from 3A [PEI( 3A )] was amorphous and soluble in chloroform on heating, whereas that derived from 4A [PEI( 4A )] was crystalline and insoluble in common organic solvents even on heating. In UV–vis absorption spectra, PEI( 4A ) showed a small bathochromic shift relative to N‐phenylphthalimide, but PEI(3A) did not. PEI(3A) revealed a glass‐transition temperature (T_g) at 195 °C, but no T_g was detectable for PEI( 4A ). All the measured physical properties of the copoly(etherimide)s showed a good dependence on their composition between PEI( 3A ) and PEI( 4A ). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 402–410, 2000     

Impact of chain architecture (branching) on the thermal and mechanical behavior of polystyrene thin films

The modulus and glass transition temperature (T_g) of ultrathin films of polystyrene (PS) with different branching architectures are examined via surface wrinkling and the discontinuity in the thermal expansion as determined from spectroscopic ellipsometry, respectively. Branching of the PS is systematically varied using multifunctional monomers to create comb, centipede, and star architectures with similar molecular masses. The bulk‐like (thick film) T_g for these polymers is 103 ± 2 °C and independent of branching and all films thinner than 40 nm exhibit reductions in T_g. There are subtle differences between the architectures with reductions in T_g for linear (25 °C), centipede (40 °C), comb (9 °C), and 4 armed star (9 °C) PS for ≈ 5 nm films. Interestingly, the room temperature modulus of the thick films is dependent upon the chain architecture with the star and comb polymers being the most compliant (≈2 GPa) whereas the centipede PS is most rigid (≈4 GPa). The comb PS exhibits no thickness dependence in moduli, whereas all other PS architectures examined show a decrease in modulus as the film thickness is decreased below ～40 nm. We hypothesize that the chain conformation leads to the apparent susceptibility of the polymer to reductions in moduli in thin films. These results provide insight into potential origins for thickness dependent properties of polymer thin films. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Synthesis and properties of new aromatic polyamides with redox‐active 2,4‐dimethoxytriphenylamine moieties

A new triphenylamine‐based diamine monomer, 4,4′‐diamino‐2″,4″‐dimethoxytriphenylamine ( 2 ), was synthesized from readily available reagents and was reacted with various aromatic dicarboxylic acids to produce a series of aromatic polyamides ( 4a–h ) containing the redox‐active 2,4‐dimethoxy‐substituted triphenylamine (dimethoxyTPA) unit. All the resulting polyamides were readily soluble in polar organic solvents and could be solution cast into tough and flexible films. These polymers exhibited good thermal stability with glass transition temperatures of 243–289 °C and softening temperatures of 238–280 °C, 10% weight loss temperatures in excess of 470 °C in nitrogen, and char yields higher than 60% at 800 °C in nitrogen. The redox behaviors of the polymers were examined using cyclic voltammetry (CV). All these polyamides showed two reversible oxidation processes in the first CV scan. The polymers also displayed low ionization potentials as a result of their dimethoxyTPA moieties. In addition, the polymers displayed excellent stability of electrochromic characteristics with coloration change from a colorless neutral state to green and blue‐purple oxidized states. These anodically coloring polyamides showed high green coloration efficiency (CE = 329 cm²/C), high contrast of optical transmittance change (ΔT% = 84% at 829 nm), and long‐term redox reversibility. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3392–3401, 2010     

Energy level tuning of polythiophene derivative by click chemistry‐type postfunctionalization of side‐chain alkynes

A polythiophene derivative substituted with electron‐rich alkynes as a side chain was synthesized using the Suzuki polycondensation reaction. The electron‐rich alkynes underwent the “click chemistry”‐type quantitative addition reaction with strong acceptor molecules, such as tetracyanoethylene (TCNE) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ), resulting in the formation of donor–acceptor chromophores. All polymers showed excellent solubilities in the common organic solvents as well as good thermal stabilities with their 5% decomposition temperatures exceeding 230 °C. The TCNE‐/TCNQ‐adducted polymers displayed well‐defined charge‐transfer (CT) bands in the low energy region. The CT energy of the TCNE‐adducted polymer was 2.56 eV (484 nm), which was much greater than that of the TCNQ‐adducted polymer [1.65 eV (750 nm)]. This result was supported by the electrochemical measurements. The electrochemical band gaps of the TCNE‐adducted polymers were much greater than those of the corresponding TCNQ‐adducted polymers. Furthermore, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, determined from the first oxidation and first reduction peak potentials, respectively, decreased with the increasing acceptor addition amount. All these results suggested that the energy levels of the polythiophene derivative can be tuned by varying the species and amount of the acceptor molecules using this postfunctionalization method. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010