Synthesis and characterization of new highly organosoluble poly(etherimide)s derived from 1,1‐bis{4‐[4‐(3,4‐dicarboxyphenoxy)phenyl]‐4‐phenylcyclohexane} dianhydride

A new bulky pendent bis(ether anhydride), 1,1‐bis[4‐(4‐dicarboxyphenoxy)phenyl]‐4‐phenylcyclohexane dianhydride, was prepared in three steps, starting from the nitrodisplacement of 1,1‐bis(4‐hydroxyphenyl)‐4‐phenylcyclohexane with 4‐nitrophthalonitrile to form bis(ether dinitrile), followed by alkaline hydrolysis of the bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). A series of new poly(ether imide)s were prepared from the bis(ether anhydride) with various diamines by a conventional two‐stage synthesis including polyaddition and subsequent chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.50–0.73 dL g^?1. The gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 57,000 and 130,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility in comparison with the other polyimides derived from adamantane, norbornane, cyclododecane, and methanohexahydroindane and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. These polymers had glass‐transition temperatures of 226–255 °C. Most of the polymers could be dissolved in chloroform in as high as a 30 wt % concentration. Thermogravimetric analysis showed that all polymers were stable up to 450 °C, with 10% weight losses recorded from 458 to 497 °C in nitrogen. These transparent, tough, and flexible polymer films could be obtained by solution casting from DMAc solutions. These polymer films had tensile strengths of 79–103 MPa and tensile moduli of 1.5–2.1 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2066–2074, 2002     

Living cationic polymerization of α‐methyl vinyl ethers using SnCl4

Cationic polymerization of α‐methyl vinyl ethers was examined using an IBEA‐Et_1.5AlCl_1.5/SnCl₄ initiating system in toluene in the presence of ethyl acetate at 0 ～ ?78 °C. 2‐Ethylhexyl 2‐propenyl ether (EHPE) had a higher reactivity, compared to corresponding vinyl ethers. But the resulting polymers had low molecular weights at 0 or ?50 °C. In contrast, the polymerization of EHPE at ?78 °C almost quantitatively proceeded, and the number‐average molecular weight (M_n) of the obtained polymers increased in direct proportion to the EHPE conversion with quite narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.05). In monomer‐addition experiments, the M_n of the polymers shifted higher with low polydispersity as the polymerization proceeded, indicative of living polymerization. In the polymerization of methyl 2‐propenyl ether (MPE), the living‐like propagation also occurred under the reaction conditions similar to those for EHPE, but the elimination of the pendant methoxy groups was observed. The introduction of a more stable terminal group, quenched with sodium diethyl malonate, suppressed this decomposition, and the living polymerization proceeded. The glass transition temperature of the obtained poly(MPE) was 34 °C, which is much higher than that of the corresponding poly(vinyl ether). This poly(MPE) had solubility characteristics that differed from those of poly(vinyl ethers). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2202–2211, 2008     

Thermally induced phase separation of poly(vinylidene fluoride)/diluent systems: Optical microscope and infrared spectroscopy studies

Thermally induced phase separation (TIPS) has been developed to prepare porous membranes. The porous structures are mainly dependent on diluents adopted in the TIPS process. We obtained two typical morphologies of poly(vinylidene fluoride) (PVDF) membranes using cyclohexanone (CO) and propylene carbonate (PC) as diluents, respectively. SEM observation displays that porous spherulites are formed from PVDF/CO system, whereas smooth particles result from PVDF/PC system. The TIPS processes of these two systems have been investigated in detail by optical microscope observation and temperature‐dependent FTIR combined with two‐dimensional infrared correlation analysis. Rapid crystallization of PVDF can be seen around 110 °C in the PVDF/CO system, which is consistent with the results of temperature‐dependent FTIR spectra. The spectral evolution indicates a transform of PVDF from amorphous to α‐phase after 110 °C. The ν_s(C?O) band at 1712 cm^?1 narrows and the ν_s(C? F) band at 1188 cm^?1 shifts to 1192 cm^?1 before crystallization, which implies the destruction of interaction between PVDF and CO. In contrast, the PVDF/PC system shows slow crystallization with all‐trans conformation assigned to β‐phase and γ‐phase below 60 °C but no obvious change of polymer?diluent interaction. We propose two mechanisms for the different phase behaviors of PVDF/CO and PVDF/PC systems: a solid?liquid phase separation after destruction of polymer?diluent interaction in the former, and a liquid?liquid phase separation process coupled with rich‐phase crystallization in the later. This work may provide new insight into the relationship among morphologies, crystal forms, and phase separation processes, which will be helpful to adjust membrane structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1438–1447     

Thermal stability of porous it‐PMMA thin film obtained by the extraction of st‐PMAA from it‐PMMA/st‐PMAA stereocomplex with layer‐by‐layer assembly on a substrate

The functionality of porous isotactic (it) poly(methyl methacrylate) (PMMA) thin films, which were previously developed by the selective extraction of syndiotactic (st) poly(methacrylic acid) (PMAA) from the it‐PMMA/st‐PMAA stereocomplex thin film on a substrate using the layer‐by‐layer assembly method was investigated after thermal treatment (70, 80, and 90 °C) in water for 4 h. Quartz crystal microbalance analysis and infrared spectra measurements revealed that the st‐PMAA incorporation ability of the porous it‐PMMA thin film decreased in order at 80 and 90 °C, while there was no decrease observed at 70 °C. X‐ray diffraction analysis also supported the thermal stability of the porosity at 70 °C, whereas two it‐PMMA crystalline peaks (2θ = 9° and 14°) were generated during heating at 90 °C. The loss of the functionality of the it‐PMMA thin film was thus shown to be due to crystallization, which was caused by the increase in polymer‐chain mobility during the heating process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3265–3270, 2010     

Film‐formation property of vinylidene chloride‐methyl methacrylate copolymer latex. II. Effect of latex storage temperature

Changes in the minimum film‐formation temperature (MFFT) of 91:9 wt % vinylidene chloride (VDC)‐methyl methacrylate (MMA) latex prepared by the seeded batch process during storage at 5, 20, and 40 °C were investigated. MFFT of the latex rose the fastest at 20 °C. Infrared absorption of fresh and stored latexes and wide‐angle X‐ray diffraction of powder polymers obtained by lyophilization of fresh and stored latexes indicated a much greater increase in polymer crystallinity during latex storage at 20 °C than at 5 and 40 °C. Observed increases in MFFT during latex storage correlated with increases in polymer crystallinity. Infrared absorption of polymer stored at 5–60 °C in the dry state, such as lyophilized polymer and coating film, indicated that a polymer crystallinity increase was greater during storage at higher temperatures. These results showed that crystallization behavior of 91:9 wt% VDC‐MMA copolymer latex differed from that of VDC‐MMA copolymer in the dry state. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 948–953, 2002     

Poly(vinylidene fluoride)/clay nanocomposites prepared by melt intercalation: Crystallization and dynamic mechanical behavior studies

The preparation and properties of poly(vinylidene fluoride) (PVDF)/clay nanocomposites are reported for the first time. PVDF/clay nanocomposites were prepared by melt intercalation with organophilic clay. The composites were characterized with X‐ray diffraction, differential scanning calorimetry, and dynamic mechanical analysis. X‐ray diffraction results indicated intercalation of the polymer into the interlayer spacing. PVDF in the nanocomposites crystallized in the β form. Differential scanning calorimetry nonisothermal curves showed an increase in the melting and crystallization temperatures along with a decrease in crystallinity, as evidenced by the melting and crystallization peaks. Isothermal crystallization studies showed an enhanced rate of crystallization with the addition of clay, as evidenced by a reduction in the crystallization time. Dynamic mechanical analysis indicated significant improvements in the storage modulus over a temperature range of ?100 to 150 °C. The tan δ peak signifying the glass‐transition temperature of PVDF shifted to higher temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1682–1689, 2002     

Synthesis and characterization of new highly organosoluble poly(ether imide)s based on 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride

A new bis(ether anhydride), 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride ( 3 ), was prepared in three steps: the nitro displacement of 4‐nitrophthalonitrile with 2,2‐bis(4‐hydroxy‐3,5‐dimethylphenyl)propane, the alkaline hydrolysis of the intermediate bis(ether dinitrile), and the subsequent dehydration of the resulting bis(ether diacid). A series of new highly soluble poly(ether imide)s with tetramethyl and isopropylidene groups were prepared from the bis(ether anhydride) 3 with various diamines by a conventional two‐stage synthesis including polyaddition and chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.54–0.73 dL g^?1. Gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 54,000 and 124,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. Most of the polymers could be dissolved with chloroform concentrations as high as 30 wt %. These polymers had glass‐transition temperatures of 244–282 °C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight losses recorded above 463 °C in nitrogen. These transparent, tough, and flexible polymer films were obtained through solution casting from N,N‐dimethylacetamide solutions. These polymer films had tensile strengths of 81–102 MPa and tensile moduli of 1.8–2.0 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2556–2563, 2002     

Intercalated poly(vinylidene fluoride)/clay nanocomposites: Structure and properties

The preparation and characterization of melt‐intercalated poly(vinylidene fluoride) (PVDF)/clay nanocomposites are reported. Organophilic clay (clay treated with dimethyl dihydrogenated tallow quaternary ammonium chloride) was used for the nanocomposite preparation. The composites were characterized with X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). XRD results indicated the intercalation of the polymer in the interlayer spacing. The incorporation of clay in PVDF resulted in the β form of PVDF. DSC nonisothermal curves showed an increase in the melting and crystallization temperatures along with a decrease in crystallinity. Isothermal crystallization studies show an enhanced rate of crystallization with the addition of clay. DMA indicated significant improvements in the storage modulus over a temperature range of ?100 to 150 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 31–38, 2003     

Micro ATR‐FTIR study of the hydration state of poly(N‐tert‐butylacrylamide‐co‐acrylamide) copolymers during phase transition in aqueous media and in the mixture of water–methanol

Coil‐globule transition of poly(N‐tert‐butylacrylamide‐co‐acrylamide) P(NTBAM‐co‐AM) copolymers is investigated in the aqueous solution and in the mixture of water–methanol by micro ATR‐FTIR spectroscopy technique. In this study the microstructure and its changes in the hydration states of the distinct groups of these copolymers are investigated by micro ATR/FTIR technique. The results showed that by heating the solution above the LCST hydrogen bonding between C?O and water was decreased but the hydrogen bonding between polymeric chains increased, which prove the aggregation of polymer chain during phase separation. The chemical shifts of IR bands are also studied in the mixture of water–methanol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 356–363, 2010     

Miscibility,melting, and crystallization of poly(butylene‐2,6‐naphthalate)/poly(ether imide) blends

We prepared blends of poly(butylene‐2,6‐naphthalate) (PBN) and poly(ether imide) (PEI) by solution‐casting from dichloroacetic acid solutions. The miscibility, crystallization, and melting behavior of the blends were investigated with differential scanning calorimetry (DSC) and dynamic mechanical analysis. PBN was miscible with PEI over the entire range of compositions, as shown by the existence of single composition‐dependent glass‐transition temperatures. In addition, a negative polymer–polymer interaction parameter was calculated, with the Nishi–Wang equation, based on the melting depression of PBN. In nonisothermal crystallization investigations, the depression of the crystallization temperature of PBN depended on the composition of the blend and the cooling rate; the presence of PEI reduced the number of PBN segments migrating to the crystallite/melt interface. Melting, recrystallization, and remelting processes occurring during the DSC heating scan caused the occurrence of multiple melting endotherms for PBN. We explored the effects of various experimental conditions on the melting behavior of PBN/PEI blends. The extent of recrystallization of the PBN component during DSC heating scans decreased as the PEI content, the heating rate, the crystallization temperature, and the crystallization time increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1694–1704, 2004     

Investigation of sulfonated poly(ether ether ketone sulfone)/heteropolyacid composite membranes for high temperature fuel cell applications

The sulfonated poly(ether ether ketone sulfone) (SPEEKS)/heteropolyacid (HPA) composite membranes with different HPA content in SPEEKS copolymers matrix with different degree of sulfonation (DS) were investigated for high temperature proton exchange membrane fuel cells. Composite membranes were characterized by Fourier transfer infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR band shifts suggested that the sulfonic acid groups on the copolymer backbone strongly interact with HPA particles. SEM pictures showed that the HPA particles were uniformly distributed throughout the SPEEKS membranes matrix and particle sizes decreased with the increment of copolymers' DS. The holes were not found in SPEEKS‐4/HPA30 (consisting of 70% SPEEKS copolymers with DS = 0.8 and 30% HPA) composite membrane after composite membranes were treated with boiling water for 24 h. Thermal stabilities of the composite membranes were better than those of pure sulfonated copolymers membranes. Although the composite membranes possessed lower water uptake, it exhibited higher proton conductivity for SPEEKS‐4/HPA30 especially at high temperature (above 100 °C). Its proton conductivity linearly increased from 0.068 S/cm at 25 °C to 0.095 S/cm at 120 °C, which was higher than 0.06 S/cm of Nafion 117. In contrast, proton conductivity of pure SPEEKS‐4 membrane only increased from 0.062 S/cm at 25 °C to 0.078 S/cm at 80 °C. At 120 °C, proton conductivity decreased to poor 0.073 S/cm. The result indicated that composite membranes exhibited high proton conductivity at high temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1967–1978, 2006     

Film‐formation property of vinylidene chloride‐methyl methacrylate copolymer latex. I. Effect of emulsion‐polymerization process

Changes in minimum film‐formation temperature (MFFT) during storage of latexes prepared from 91:9 wt % vinylidene chloride (VDC)‐methyl methacrylate (MMA) monomer mixture by seeded batch and seeded semicontinuous emulsion polymerization were investigated, with attention centered on polymer‐crystallization behavior during storage in the dispersed state. MFFT of latex prepared by the seeded batch process rose to 47 °C, whereas that of latex prepared by seeded semicontinuous process remained below 14 °C with storage at 20 °C for 12 weeks. Infrared absorption of latexes in the dispersed state and wide‐angle X‐ray diffraction of powder polymers obtained by lyophilization of fresh and stored latexes both indicated a much greater increase in polymer crystallinity during storage with latex prepared by the seeded batch process than with that prepared by the seeded semicontinuous process. Analysis of the copolymer composition drift calculated from reactivity ratios and ¹H NMR analysis indicated a wider sequence distribution and longer VDC sequences in polymer prepared by the seeded batch process than in polymer prepared by the seeded semicontinuous process. This explained the higher rate of crystallization during storage with latex prepared by the seeded batch process than with that prepared by the seeded semicontinuous process. Rising crystallinity during storage in the dispersed state is believed to have caused the MFFT rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 939–947, 2002     

Star‐shaped polymers having side chain poss groups for solid polymer electrolytes; synthesis,thermal behavior,dimensional stability,and ionic conductivity

A series of organic/inorganic hybrid star‐shaped polymers were synthesized by atom transfer radical polymerization using 3‐(3,5,7,9,11,13,15‐heptacyclohexyl‐pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]‐octasiloxane‐1‐yl)propyl methacrylate (MA‐POSS) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomers and octakis(2‐bromo‐2‐methylpropionoxypropyldimethylsiloxy)octasilsesquioxane as an initiator. Star‐shaped polymers with methyl methacrylate (MMA) and PEGMA moieties were also prepared for comparison purposes. Dimensionally stable freestanding film could be obtained from the hybrid star‐shaped polymer containing 26 wt % of MA‐POSS moieties although its glass transition temperature is very low, ?60.9 °C. As a result, the hybrid star‐shaped polymer electrolyte containing lithium bis(trifluoromethanesulfonyl)imide showed ionic conductivities (1.75 × 10^?5 S/cm at 30 °C), which were two orders of magnitude higher than those of the star‐shaped polymer electrolyte with MMA moieties. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Biodegradable thermoset shape‐memory polymer developed from poly(β‐amino ester) networks

The purpose of this study was to develop a degradable thermoset shape‐memory polymer from poly(β‐amino ester) (PBAE) networks. PBAE was chosen to be the crosslinker as it is biodegradable and has been projected as a potential material for biomedical applications. The low glass transition temperature of PBAE was increased to a biomedically relevant range using methyl methacrylate and methyl acrylate as the linear chain builders. The thermo‐mechanical properties of the networks were tailored such that they exhibited onset of glass transition temperature in between the room temperature (22 °C) and the body temperature (37 °C). Free‐strain recovery tests under heating and isothermal conditions were performed to quantify shape‐memory behavior. Testing showed that sampled programmed at 10 °C initiated deformation recovery at a lower temperature and a faster rate as compared to programming at 60 °C. Higher thermal conductivity of water enabled the samples to recover faster in water than in air. Samples with higher PBAE crosslinking densities exhibited higher normalized mass loss under regular and accelerated conditions. The amount of water absorption in the networks also increased with the crosslinker concentration independent of the testing conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Spontaneous thinning/thickening deformation observed for plastic blend films and some factors affecting film deformation

The fully amorphous films of highly syndiotactic poly[(R,S)‐3‐hydroxybutyrate] (s‐PHB)/atactic poly(4‐vinylphenol) (PVPh) blends show reversible thinning/thickening phenomena at 37 °C in aqueous medium. On the other hand, isotactic poly[(R)‐3‐hydroxybutyrate] (i‐PHB)/PVPh blend film, in which i‐PHB blend component was partially crystalline, did not show any thinning/thickening phenomena under the same conditions. To elucidate the factors influencing these phenomena, the structure and molecular interaction in these blends were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, and wide‐angle X‐ray diffraction. The FTIR spectra indicated that the ester carbonyl of PHB and the phenolic hydroxyl of PVPh formed hydrogen bonds in both the thinned and thickened s‐PHB/PVPh blend films. The blend composition, intermolecular hydrogen‐bonding interaction, crystallization behavior, miscibility, and the glass‐transition temperature of the blends affected the thinning/thickening phenomena. Some other polyesters such as poly(?‐caprolactone), poly (L‐lactic acid), atactic poly(D,L‐lactic acid), and poly(ethylene terephthalate) had no ability to exhibit thinning/thickening phenomena in water at 37 °C when they were blended with PVPh. This result implies that s‐PHB/PVPh is the rare example with the ability to show reversible thinning/thickening phenomena. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2736–2743, 2002     

Synthesis and properties of new aromatic poly‐(ether benzoxazole)s from 2,2′‐bis(4‐amino‐3‐hydroxyphenoxy)biphenyl and aromatic dicarboxylic acid chlorides

A new bis(o‐aminophenol) with a crank and twisted noncoplanar structure and ether linkages, 2,2′‐bis(4‐amino‐3‐hydroxyphenoxy)biphenyl, was synthesized by the reaction of 2‐benzyloxy‐4‐fluoronitrobenzene with biphenyl‐2,2′‐diol, followed by reduction. Biphenyl‐2,2′‐diyl‐containing aromatic poly(ether benzoxazole)s with inherent viscosities of 0.52–1.01 dL/g were obtained by a conventional two‐step procedure involving the polycondensation of the bis(o‐aminophenol) monomer with various aromatic dicarboxylic acid chlorides, yielding precursor poly(ether o‐hydroxyamide)s, and subsequent thermal cyclodehydration. These new aromatic poly(ether benzoxazole)s were soluble in methanesulfonic acid, and some of them dissolved in m‐cresol. The aromatic poly(ether benzoxazole)s had glass‐transition temperatures of 190–251 °C and were stable up to 380 °C in nitrogen, with 10% weight losses being recorded above 520 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2656–2662, 2002     

Dual entropic and enthalpic processes in the lower critical solution temperature phase separation of poly(vinyl methyl ether) aqueous solutions

In the lower critical solution temperature phase separation of poly(vinyl methyl ether) aqueous solutions, the process corresponding to the weakening of the hydrogen bond interaction with increasing temperature is dominant and occurs over the entire concentration region of solutions and over a broad temperature range from 30 to 41°C, giving rise to the energetic enthalpic effect during phase separation, while the conformational change, that is, collapse of the swollen polymer coils, occurs only in the swelling polymer solution when the water concentration is above 38.3 wt %, giving rise to the entropic effect during phase separation. In addition, the entropic process corresponding to the collapse of the polymer coils occurs in a much narrow theta temperature range from 35.5 to 37°C. If the solution is held at a constant temperature for a sufficiently long time, 90% collapse of the polymer coils occurs in only the 0.5 °C temperature region between 35.5 and 36°C. Accordingly, in the enthalpic process, the most dramatic blueshift of the νC‐O bond peak occurs in the temperature range between 35 and 41°C, while this blueshift is only approximately 2 cm^?1 in the temperature range from 30 to 35°C, prior to the collapse of the polymer coils due to the entropic effect. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 323–330     

Poly(p‐phenylene sulfide) nonisothermal cold‐crystallization

The poly(p‐phenylene sulfide) (PPS) nonisothermal cold‐crystallization behavior was investigated in a wide heating rate range. The techniques employed were the usual Differential Scanning Calorimetry (DSC), and the less conventional FT‐IR spectroscopy and Energy Dispersive X‐ray Diffraction (EDXD). The low heating rates (Φ) explored by EDXD (0.1 K min^?1) and FT‐IR (0.5–10 K min^?1) are contiguous and complementary to the DSC ones (5–30 K min^?1). The crystallization temperature changes from 95 °C at Φ = 0.05 K min^?1 to 130 °C at Φ = 30 K min^?1. In such a wide temperature range the Kissinger model failed. The model is based on an Arrhenius temperature dependence of the crystallization rate and is widely employed to evaluate the activation energy of the crystallization process. The experimental results were satisfactorily fit by replacing in the Kissinger model the Arrhenius equation with the Vogel–Fulcher–Tamann function and fixing U* = 6.28 k J mol^?1, the activation energy needed for the chains movements, according to Hoffmann. The temperature at which the polymer chains are motionless (T_∞ = 42 °C) was found by fitting the experimental data. It appears to be reasonable in the light of our previously reported isothermal crystallization results, which indicated T_∞ = 48 °C. Moreover, at the lower heating rate, mostly explored by FT‐IR, a secondary stepwise crystallization process was well evidenced. In first approximation, it contributes to about 17% of the crystallinity reached by the sample. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2725–2736, 2005     

Synthesis,characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Melt‐processable liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid (HPAA) and 3‐(4‐hydroxyphenyl)propionic acid (HPPA) with terephthalic acid and 2,6‐naphthalene diol were synthesized by one‐step acidolysis melt polycondensation followed by postpolymerization and were characterized with viscosity studies, Fourier transform infrared (FTIR) and NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscopy, and wide‐angle X‐ray diffraction. The melting behaviors and liquid‐crystalline transition temperatures of the terpolyesters were dependent on the composition of the HPAA/HPPA content. The transition temperatures of the polyesters could be effectively reduced by the introduction of an even number of built‐in short methylene spacers in combination with the 2,6‐naphthalene offset structure. A terpolyester with an HPPA content of 33% (NTP33) showed optimum properties for the glass‐transition temperature, around 71 °C, and the melting temperature, near 240 °C, with a Schlieren nematic texture. The polymer showed excellent flow behavior in a Brabender plasticorder. It was also thermally stable up to 400 °C. NTP33 showed 2.5% in vitro hydrolytic degradation in buffer solutions of pH 10 at 60 °C after 540 h. Considerable enzymatic degradation was also observed with porcine pancreas lipase/buffer solutions in comparison with Candida rugosa lipase after 60 days. The degradation was also followed with FTIR, DSC, and TGA. Apart from the temperature and pH of the buffer solution, several structural parameters, such as the aromatic content, crystallinity percentage, and composition of the polymer, affected the degradation behavior. FTIR studies indicated the involvement of chain scission during degradation. Scanning electron microscopy studies further showed that surface erosion also played a major role in the degradation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1845–1857, 2002     

Effects of filler–polymer interactions on cold‐crystallization kinetics in crosslinked,silica‐filled polydimethylsiloxane/polydiphenylsiloxane copolymer melts

Crystallization in a series of variable crosslink density poly(dimethyl‐diphenyl)siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), nuclear magnetic resonance (NMR), and X‐ray diffraction (XRD). The silicone composite studied was composed of 94.6 mol % dimethoylsiloxane, 5.1 mol % diphenylsiloxane, and 0.3 mol % methyl‐vinyl siloxane (which formed crosslinking after peroxide cure). The polymer was filled with a mixture of 21.6 wt % fumed silica and 4.0 wt % precipitated silica previously treated with 6.8 wt % ethoxy‐end‐blocked siloxane processing aid. Molecular weight between crosslinks and filler–polymer interaction strength were modified by exposure to γ‐irradiation in either air or in vacuo. Isothermal DMA experiments illustrated that crystallization at ?85 °C occurred over a 1.8 hour period in silica‐filled systems and 2.2–2.6 hours in unfilled systems. The crystallization kinetics for irradiated samples were found to be dependent on crosslink density. Irradiation in vacuo resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface for samples irradiated in air. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1898–1906, 2006