Novel temperature‐ and pH‐responsive graft copolymers composed of poly(L‐glutamic acid) and poly(N‐isopropylacrylamide)

A series of novel temperature‐ and pH‐responsive graft copolymers, poly(L ‐glutamic acid)‐g‐poly(N‐isopropylacrylamide), were synthesized by coupling amino‐semitelechelic poly(N‐isopropylacrylamide) with N‐hydroxysuccinimide‐activated poly(L ‐glutamic acid). The graft copolymers and their precursors were characterized, by ESI‐FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (¹H NMR). The phase‐transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering. The solution behavior of the copolymers showed dependence on both temperature and pH. The cloud point (CP) of the copolymer solution at pH 5.0–7.4 was slightly higher than that of the solution of the PNIPAM homopolymer because of the hydrophilic nature of the poly(glutamic acid) (PGA) backbone. The CP markedly decreased when the pH was lowered from 5 to 4.2, caused by the decrease in hydrophilicity of the PGA backbone. At a temperature above the lower critical solution temperature of the PNIPAM chain, the copolymers formed amphiphilic core‐shell aggregates at pH 4.5–7.4 and the particle size was reduced with decreasing pH. In contrast, larger hydrophobic aggregates were formed at pH 4.2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4140–4150, 2008     

Investigation on thermoresponsive behavior of biodegradable poly(γ‐glutamic acid)‐graft‐L‐phenylalanine ethyl ester

The thermosensitivity of biodegradable and non‐toxic amphiphilic polymer derived from a naturally occurring polypeptide and a derivative of amino acid was first reported. The amphiphilic polymer consisted of poly(γ‐glutamic acid) (γ‐PGA) as a hydrophilic backbone, and L ‐phenylalanine ethyl ester (L ‐PAE) as a hydrophobic branch. Poly(γ‐glutamic acid)‐graft‐L ‐phenylalanine (γ‐PGA‐graft‐L ‐PAE) with grafting degrees of 7–49% were prepared by varying the content of a water‐soluble carbodiimide (WSC). γ‐PGA‐graft‐L ‐PAE with a grafting degree of 49% exhibited thermoresponsive phase transition behavior in an aqueous solution at around 80°C. The copolymers with grafting degrees in the range of 30–49% showed thermoresponsive properties in NaCl solution. A clouding temperature (T_cloud) could be adjusted by changing the polymer concentration and/or NaCl concentration. The thermoresponsive behavior was reversible. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Proton conductivity survey of the acid doped copolymers based on 4‐vinylbenzylboronic acid and 4(5)‐vinylimidazole

In this work, poly(4‐vinylbenzylboronic acid‐co‐4(5)‐vinylimidazole) (poly(4‐VBBA‐co‐4‐Vim)) copolymers were synthesized by free‐radical copolymerization of the monomers 4‐VBBA and 4‐Vim at various monomer feed ratios. The copolymers were characterized by ¹H MAS NMR and ¹¹B MQ‐MAS NMR methods and the copolymer composition was determined via elemental analysis. The membrane properties of these copolymers were investigated after doping with phosphoric acid at several stoichiometric ratios. The proton exchange reaction between acid and heterocycle is confirmed by FTIR. Thermal properties of the samples were investigated via thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The morphology of the copolymers was characterized by x‐ray diffraction, XRD. The temperature dependence of proton conductivities of the samples was investigated by means of impedance spectroscopy. Proton conductivity of the copolymers increased with the doping ratio and reached to 0.0027 S/cm for poly(4‐VBBA‐co‐4‐Vim)/2H₃PO₄ in the anhydrous state. The boron coordination in the copolymer was determined by ¹¹B MQ‐MAS experiment and the coexistence of three and four coordinated boron sites was observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1267–1274, 2009     

Crystallization and melting of poly(glycerol adipate)‐based graft copolymers with single and double crystallizable side chains

The crystallization and melting behavior of a series of poly(glycerol adipate) (PGA) based graft copolymers with either poly(ε‐caprolactone) (PCL), poly(ethylene oxide) (PEO), or PCL‐b‐PEO diblock copolymer side chains (i.e., PGA‐g‐PCL, PGA‐g‐PEO, and PGA‐g‐(PCL‐b‐PEO)) was studied using polarized light optical microscopy (POM), differential scanning calorimetry (DSC), small‐angle X‐ray scattering (SAXS), and wide‐angle X‐ray diffraction (WAXD). These results were compared with the behavior of the corresponding linear analogs (PEO, PCL, and PCL‐b‐PEO). POM revealed that spherulitic morphology was retained after grafting. However, spherulite radius as well as radial growth rate was significantly smaller in the graft copolymers. Evaluation of isothermal crystallization kinetics by means of the Avrami theory revealed that the nucleation density was much higher in the graft copolymers. The DSC results indicated that the degree of crystallinity decreased strongly upon grafting while the melting temperatures of PGA‐g‐PCL and PGA‐g‐PEO were found to be close to the values of neat PCL and PEO, respectively. This was attributed to the absence of specific thermodynamic interactions, and, additionally, to lamella thicknesses being similar to those of the homopolymers. The latter point was confirmed by SAXS measurements. In case of PCL‐b‐PEO diblock copolymers and PGA‐g‐(PCL‐b‐PEO) graft copolymers, the crystallization behavior and thus the resulting lamellar morphology is more complex, and a suitable model was developed based on a combination of DSC, WAXD, and SAXS data. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1581–1591     

Crystal modifications and multiple melting behavior of poly(L‐lactic acid‐co‐D‐lactic acid)

The crystal modifications and multiple melting behavior of poly(L ‐lactic acid‐co‐D ‐lactic acid) (98/2) as a function of crystallization temperature were studied by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). It was found that the disorder (α′) and order (α) phases of poly(L ‐lactic acid) (PLLA) were formed in cold‐crystallized poly(L ‐lactic acid‐co‐D ‐lactic acid) samples at low (<110 °C) and high (≥110 °C) temperatures, respectively. A disorder‐to‐order (α′‐to‐α) phase transition occurred during the annealing process of the α′‐crystal at elevated temperatures, which proceeded quite slowly even at the peak temperature of the exotherm P_exo but much more rapidly at higher temperature close to the melting region. The presence or absence of an additional endothermic peak before the exotherm in the DSC thermograph of the α′‐crystal was strongly dependent on the heating rate, indicating that a melting process involved during the α′‐to‐α phase transition. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Effect of the sulfonic acid group on copolymers of aniline and toluidine with m‐aminobenzene sulfonic acid

This article describes the results of the preparation and characterization of self‐doped conducting copolymers of aniline and toluidine with m‐aminobenzene sulfonic acid. The copolymers have an intrinsic acid group that is capable of doping polyaniline. Spectroscopic, morphological, and electrical conductivity studies have provided insight into the structural and electronic properties of the copolymers. The differences in the properties of polyaniline and polytoluidine due to the sulfonic acid ring substituent on the phenyl ring are discussed. The scanning electron micrographs of the copolymers reveal regions of sharp‐edged, needle‐shaped structures, whereas the X‐ray diffraction patterns show that the copolymers are relatively more crystalline in nature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4065–4076, 2002     

Thermal behavior and crystallization kinetics of random poly(ethylene‐Co‐2,2‐Bis[4‐(ethylenoxy)‐1,4‐phenylene]propane terephthalate) copolyesters

The thermal behavior of poly(ethylene‐co‐2,2‐bis[4‐(ethylenoxy)‐1,4‐phenylene]propane terephthalate) (PET/BHEEBT) copolymers was investigated by thermogravimetric analysis and differential scanning calorimetry. A good thermal stability was found for all the samples. The thermal analysis carried out using DSC technique showed that the T_m of the copolymers decreased with increasing BHEEBT unit content, differently from T_g, which on the contrary increased. Wide‐angle X‐ray diffraction measurements permitted identifying the kind of crystalline structure of PET in all the semicrystalline samples. The multiple endotherms similar to PET were also evidenced in the PET/BHEEBT samples, due to melting and recrystallization processes. By applying the Hoffman–Weeks' method, the T_m° of PET and its copolymers was derived. The isothermal crystallization kinetics was analyzed according to Avrami's treatment and values of the exponent n close to 3 were obtained, independently of T_c and composition. Moreover, the introduction of BHEEBT units was found to decrease PET crystallization rate. Lastly, the presence of a crystal‐amorphous interphase was evidenced. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1441–1454, 2005     

Neopenthyl glycol containing poly(propylene terephthalate)s: structure–properties relationships

Poly(propylene/neopenthyl terephthalate) random copolymers (PPT‐PNT) and poly(neopenthyl terephthalate) (PNT) were synthesized and subjected to molecular characterization. Afterwards, the polyesters were examined by TGA, DSC, andX‐ray. The copolymers, which displayed a good thermal stability, at room temperature appeared as semicrystalline materials: the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of the melting temperature with respect to homopolymer PPT. XRD measurements allowed the identification of the PPT crystalline structure in all cases. Amorphous samples were obtained after melt quenching, with the exception of PPT‐PNT5, and an increment of T_g as the content of NT units is increased was observed due to the effect of the side methylene groups in the polymeric chain. The Wood equation described well T_g‐composition data. Lastly, the presence of a rigid‐amorphous phase was evidenced in the copolymers, whose amount depended on composition and on thermal treatment. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 170–181, 2008     

Synthesis and self‐assembly of novel amphiphilic copolymers poly(lactic acid)‐block‐poly(ascorbyl acrylate)

In this study, a novel type of amphiphilic block copolymers poly(lactic acid)‐block‐poly(ascorbyl acrylate) (PLA‐block‐PAAA) with biodegradable poly(lactic acid) as hydrophobic block and poly(ascorbyl acrylate) (PAAA) as hydrophilic block was successfully developed by a combination of ring‐opening polymerization and atom transfer radical polymerization, followed by hydrogenation under normal pressure. The chemical structures of the desired copolymers were characterized by ¹H NMR and gel permeation chromatography. The thermal physical properties and crystallinity were investigated by thermogravimetric analysis, differential scanning calorimetry, and wide angle X‐ray diffraction, respectively. Their self‐assembly behavior was monitored by fluorescence‐probe technique and turbidity change using UV–vis spectrometer, and the morphology and size of the nanocarriers via self‐assembly were detected by cryo‐transmission electron microscopy and dynamic light scattering. These polymeric micelles with PAAA shell extending into the aqueous solution have potential abilities to act as promising nanovehicles for targeting drug delivery. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly(γ‐glutamic acid) esters with reactive functional groups suitable for orthogonal conjugation strategies

We report on a series of novel poly(γ‐glutamic acid) (PGGA) esters, in which the chemical structure and composition, and the molecular weight are systematically changed. Modification of PGGA of microbial origin, used either as the sodium salt or in the free acid form, by means of alkylation with highly reactive bromides under S_N2 conditions, affords copolymers with an essentially random microstructure. These reaction conditions are applied iteratively to achieve full esterification, obtaining allyl or propargyl ester functionalities within the polymer backbone, diluted with inert functional groups, such as benzyl, ethyl, or hexyl ester functionalities. The copolymers have been characterized regarding their chemical structure and thermal and bulk properties using nuclear magnetic resonance, thermogravimetry, differential scanning calorimetry, and X‐ray diffraction techniques. We demonstrate that allyl and propargyl ester groups can be efficiently transformed using click chemistries, such as thiol‐ene or copper(I)‐catalyzed azide–alkyne cycloaddition reactions; such efficient conjugation strategies will be required to transform the native bacterial biopolymer into a material with tailored properties for bulk scale or biomedical applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effects of carbon nanotubes on dynamic mechanical property,thermal property,and crystal structure of poly(L‐lactic acid)

Effects of carbon nanotubes (CNT) on the dynamic mechanical property, thermal property, and crystal structure of poly(L ‐lactic acid) (PLLA) were investigated. Dynamic mechanical analysis (DMA) found that CNT via grafting modification with PLLA (CNT‐g‐PLLA) could result in effective reinforcing effects. Tan δ of DMA found that CNT‐g‐PLLA was compatible with the PLLA matrix, giving a single T_g of the composite with a higher CNT‐g‐PLLA loading giving a higher T_g of the composite. Wide angle X‐ray diffraction (WAXD) data demonstrated that CNT could assist the disorder‐to‐order (α′‐to‐α) transition in PLLA crystals but did not lead to a more compact chain packing of the crystal lattice in PLLA composites than in pure PLLA. The equilibrium melting temperature (T) obtained from Hoffman‐Weeks plots were found to increase with increasing CNT‐g‐PLLA content. Small angle X‐ray scattering data revealed that thicknesses of crystal layer and amorphous layer of PLLA both decreased with increasing CNT contents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 145–152, 2010     

Preparation of oriented β‐form poly(L‐lactic acid) by solid‐state extrusion

Melt‐crystallized, low molecular weight poly(L ‐lactic acid) (PLLA) consisting of α crystals was uniaxially drawn by solid‐state extrusion at an extrusion temperature (T_ext) of 130–170 °C. A series of extrusion‐drawn samples were prepared at an optimum T_ext value of 170 °C, slightly below the melting temperature (T_m) of α crystals (～180 °C). The drawn products were characterized by deformation flow profiles, differential scanning calorimetry (DSC) melting thermograms, wide‐angle X‐ray scattering (WAXD), and small‐angle X‐ray scattering as a function of the extrusion draw ratio (EDR). The deformation mode in the solid‐state extrusion of semicrystalline PLLA was more variable and complex than that in the extensional deformation expected in tensile drawing, which generally gave a mixture of α and β crystals. The deformation profile was extensional at a low EDR and transformed to a parabolic shear pattern at a higher EDR. At a given EDR, the central portion of an extrudate showed extensional deformation and the shear component became progressively more significant, moving from the center to the surface region. The WAXD intensities of the (0010)_α and (003)_β reflections on the meridian as well as the DSC melting thermograms showed that the crystal transformation from the initial α form to the oriented β form proceeded rapidly with increasing EDR at an EDR greater than 4. Furthermore, WAXD showed that the crystal transformation proceeded slightly more rapidly at the sheath region than at the core region. This fact, combined with the deformation profiles (shear at the sheath and extensional at the core), indicated that the crystal transformation was promoted by shear deformation under a high pressure rather than by extensional deformation. Thus, a highly oriented rod consisting of only β crystals was obtained by solid‐state extrusion of melt‐crystallized, low molecular weight PLLA slightly below T_m. The structure and properties of the α‐ and β‐form crystals were also studied. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 95–104, 2002     

Pseudopoly(amino acid)s: Copolymerization of trans‐4‐hydroxy‐L‐proline and α‐hydroxy acids

A series of novel copolymers of trans‐4‐hydroxy‐L ‐proline (Hpr) and α‐ hydroxy acids [D,L ‐mandelic acid (DLMA) and D,L ‐lactic acid (DLLA)] were synthesized via direct melt copolymerization with stannous octoate as a catalyst. These new copolymers had pendant amine functional groups along the polymer backbone chain. The optimal reaction conditions for the synthesis of the copolymers were obtained with 4 wt % stannous octoate at 140 °C under vacuum for 16 h. The synthesized copolymers were characterized by IR spectrophotometry, proton nuclear magnetic resonance, differential scanning calorimetry, and Ubbelohde viscometry. The effects of the kinds of comonomers and the comonomer molar ratio on the polycondensation and glass‐transition temperature (T_g) were investigated. The T_g's of the copolymers shifted to lower temperatures with an increasing comonomer molar ratio. As expected, the T_g's of the N‐Z‐Hpr/DLMA copolymers were higher than the N‐Z‐Hpr/DLLA copolymers, the pendant groups on the monomers (N‐Z‐Hpr) became larger and more flexible, and the T_g's of the resulting polymers declined. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 724–731, 2001     

Synthesis,self‐assembly,drug‐release behavior,and cytotoxicity of triblock and pentablock copolymers composed of poly(ε‐caprolactone), poly(L‐lactide), and poly(ethylene glycol)

Biocompatible and biodegradable ABC and ABCBA triblock and pentablock copolymers composed of poly(ε‐caprolactone) (PCL), poly(L ‐lactide) (PLA), and poly(ethylene glycol) (PEO) with controlled molecular weights and low polydispersities were synthesized by a click conjugation between alkyne‐terminated PCL‐b‐PLA and azide‐terminated PEO. Their molecular structures, physicochemical and self‐assembly properties were thoroughly characterized by means of FT‐IR, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, dynamic light scattering, and transmission electron microscopy. These copolymers formed microphase‐separated crystalline materials in solid state, where the crystallization of PCL block was greatly restricted by both PEO and PLA blocks. These copolymers self‐assembled into starlike and flowerlike micelles with a spherical morphology, and the micelles were stable over 27 days in aqueous solution at 37 °C. The doxorubicin (DOX) drug‐loaded nanoparticles showed a bigger size with a similar spherical morphology compared to blank nanoparticles, demonstrating a biphasic drug‐release profile in buffer solution and at 37 °C. Moreover, the DOX‐loaded nanoparticles fabricated from the pentablock copolymer sustained a longer drug‐release period (25 days) at pH 7.4 than those of the triblock copolymer. The blank nanoparticles showed good cell viability, whereas the DOX‐loaded nanoparticles killed fewer cells than free DOX, suggesting a controlled drug‐release effect. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Novel fluorinated stabilizers for ring‐opening polymerization in supercritical carbon dioxide

Ring‐opening polymerization (ROP) in supercritical carbon dioxide (scCO₂) has been the subject of much recent interest, although few publications describe the development of stabilizers to produce biodegradable particles of poly(L ‐lactide) (PLLA) and polyglycolide (PGA). Here we describe the synthesis of a series of novel fluorinated diblock copolymers by the acid‐catalyzed esterification of well‐defined blocks of polycaprolactone (PCL) with Krytox 157FSL, a carboxylic acid terminated perfluoropolyether. These diblock copolymers were then tested as stabilizers in the ROP of glycolide and L ‐lactide, or a mixture of the two, in scCO₂, and this resulted in the corresponding homopolymers or random copolymers. In the absence of stabilizers, only aggregated solids were formed. When the reaction was repeated with a stabilizer, PGA and PLLA were obtained as discrete microparticles. The stabilizer efficiency increased as the length of the polymer‐philic PCL block increased. One optimized stabilizer worked at loadings as low as 3% (w/w) with respect to the monomer, demonstrating these to be extremely effective stabilizers. It was found that to produce microparticles with this process, the product polymers must be semicrystalline; amorphous polymers, such as poly(lactide‐co‐glycolide), are plasticized by scCO₂ and yield only aggregated solids rather than discrete particles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6573–6585, 2005     

Thermally stimulated depolarization current in electron‐irradiated poly(vinylidene fluoride‐trifluoroethylene) (56/44 mol %) copolymers

The effect of electron irradiation on poly(vinylidene fluoride‐trifluoroethylene) (56/44 mol %) copolymers was studied with dielectric constant measurements, differential scanning calorimetry (DSC), X‐ray diffraction, thermally stimulated depolarization current (TSDC) spectroscopy, and polarization hysteresis loops. The dielectric relaxation peaks, obeying the Vogel–Fulcher law, indicated that the copolymers were transformed from a normal ferroelectric to a relaxor ferroelectric. The X‐ray and DSC results showed that both the crystalline and polar ordering decreased after irradiation, indicating a partial recovery from trans–gauche bonds to local trans bonds (polar ordering). Moreover, the peak temperature decreased with the irradiation dose in the TSDC spectra; this demonstrated fewer dipoles and crystalline regions in the irradiated copolymer films during the ferroelectric–paraelectric transition and was consistent with polarization hysteresis loop measurements. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1099–1105, 2004     

Octa(maleimido phenyl) silsesquioxane copolymers

Octa(maleimido phenyl) silsesquioxane (OMPS) was prepared from octa(aminophenyl) silsesquioxane (OAPS) and maleic anhydride. Initially, octaphenyl silsesquioxane was prepared, and it was nitrated to obtain octa(nitrophenyl) silsesquioxane; subsequently, reduction was carried out to obtain OAPS. These compounds were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and wide‐angle X‐ray diffraction. Differential scanning calorimetry scans of OMPS showed an exotherm above 100 °C, and it was attributed to the curing. The peak maximum temperature depended on the heating rate. Both Ozawa's and Kissinger's methods were used to determine the activation energy for the curing reaction, which was approximately 29 kcal/mol. OMPS was copolymerized with various molar percentages of (1) N,N′‐p‐phenylenedimaleimide (PPMI) and (2) urethane methacrylate (UMA) by thermal and free‐radical polymerization, respectively. The copolymers were characterized with differential scanning calorimetry, dielectric analysis, thermogravimetric analysis, and wide‐angle X‐ray diffraction. In the PPMI and UMA copolymer series, the glass‐transition temperature increased with an increase in the OMPS concentration. The permittivity of the UMA copolymers decreased and tan δ increased with an increase in the OMPS concentration. In air and nitrogen atmospheres, the thermal stability of the PPMI and UMA copolymers increased with an increase in the OMPS concentration. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2483–2494, 2005     

Synthesis and characterization of poly(L‐lactic acid)–poly(ε‐caprolactone) multiblock copolymers by melt polycondensation

An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845 New multiblock copolymers derived from poly(L‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with ? NCO terminals. Fourier transform infrared (FTIR), ¹³C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between ? NCO groups at the end of the PCL and ? OH (or ? COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass‐transition temperature (T_g), melting temperature (T_M), crystallizing temperature (T_c), melting enthalpy (ΔH_m), crystallizing enthalpy (ΔH_c), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight‐average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004     

Cobalt‐mediated radical polymerization routes to poly(vinyl ester) block copolymers

Cobalt‐mediated radical polymerizations (CMRPs) utilizing redox initiation are demonstrated to produce poly(vinyl ester) homopolymers derived from vinyl pivalate (VPv) and vinyl benzoate (VBz), and their block copolymers with vinyl acetate (VAc). Combining anhydrous Co(acac)₂, lauroyl peroxide, citric acid trisodium salt, and VPv at 30 °C results in controlled polymerizations that yield homopolymers with M_n = 2.5–27 kg/mol with M_w/M_n = 1.20–1.30. Homopolymerizations of scrupulously purified VBz proceed with lower levels of control as evidenced by broader polydispersities over a range of molecular weights (M_n = 4–16 kg/mol; M_w/M_n = 1.34–1.65), which may be interpreted in terms of the decreased nucleophilicity of these less electron donating propagating polymer chain ends. Based on these results, we demonstrate that sequential CMRP reactions present a viable route to microphase separated poly(vinyl ester) block copolymers as shown by small‐angle X‐ray scattering analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Copoly(peryleneimide)s containing 1,3,4‐oxadiazole rings: Synthesis and properties

New copolyimides containing perylenediimide, oxadiazole and hexafluoroisopropylidene moieties were prepared by one‐step polycondensation reaction in solution at high temperature of aromatic diamines containing preformed oxadiazole ring with a mixture of a dianhydride having a perylene ring and another dianhydride with hexafluoroisopropylidene unit. The thermal stability and glass transition temperatures of these copolyimides were measured and compared with those of related polyimides. The solid polymers were also studied by polarized light microscopy and X‐ray diffraction which revealed a semicrystalline state consisting of face‐to‐face arranged columns of perylenediimide units. The film‐forming ability and properties of the resulting thin films were investigated by using atom force microscopy and scanning electron microscopy which showed that the films were organized into self‐assembled rod‐like structures. The UV‐Vis and photoluminescence properties in solution and in solid state were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4230–4242, 2010