Thermodynamic properties of poly(2,6-dimethyl-1,4-phenylene ether)

The thermodynamic properties of crystalline and amorphous poly(2,6-dimethyl-1,4-phenylene ether) (PPO

1 Registered trademark of General Electric Company.

polymer, General Electric Co.) have been studied calorimetrically between 80 and 570°K. The calculated configurational entropy of this polymer, of similar magnitude to other glass-forming liquids, is consistent with the combination of an unusually high ratio of T_g/T_m, and a low melting entropy.     

Copolymerization of carbon monoxide and norbornene derivatives with ester groups by palladium catalyst

In this article we will discuss the synthesis of the new copolymers of norbornene derivatives with an ester group and carbon monoxide, using Pd(CH₃CN)₄(BF₄)₂ as a catalyst and 2,2′-bipyridine as a ligand in nitromethane/methanol at 60°C. Elementary analysis, infrared spectra, and NMR spectra indicated that copolymers contain ketone, ester, and bicyclic structures. Methanol functions as the coinitiator and chain transfer agent in copolymerization. A decrease in the molar ratio of [CH₃OH]/[Pd] caused an increase in molecular weight and a decrease in yield of the copolymer. The number-average molecular weight of copolymers (M _n) ranged from 3800 to 5300, and the glass transition temperature (T_g) ranged from −32 to 117°C. Thermal analysis revealed that both T and T exceeded 180 and 230°C, respectively. Linear long-chain substituents such as n-C₁₁H₂₃C(O) O CH₂ drastically reduced T_g to a value of −32°C. In general, copolymers having a longer linear side-chain substituents of ester on norbornene have a more desirable solubility. Moreover, X-ray diffraction demonstrated that the degree of crystallinity decreases with an increasing length of side chain substituents. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1785–1790, 1998     

Thermal and ion transport properties of hydrophilic and hydrophobic polymerized styrenic imidazolium ionic liquids

Polymerized ionic liquids (PILs) are a platform for fundamental studies of structure‐property relationships in single ion conductors, with potential applications in energy storage and conversion. The synthesis, thermal properties, and ionic conductivities of homologous, narrow dispersity styrenic PILs are described. Hydrophilic poly(4‐vinylbenzyl alkylimidazolium chloride) (PVBn(alkyl)ImCl) homopolymers with constant average degrees of polymerization were synthesized by post‐synthetic functionalization of a poly(4‐vinylbenzyl chloride) (M_n = 15.9 kg/mol, M_w/M_n = 1.34) master batch with N‐alkylimidazoles (alkyl = ? CH₃ (Me), ? C₄H₉ (Bu), and ? C₆H₁₃ (Hex)). The chloride counterions of PVBnHexImCl were exhaustively metathesized with BF, PF, and bis(trifluoromethanesulfonyl)imide (TFSI^?) to yield a series of hydrophobic PILs. Thermogravimetric analyses indicate that PVBn(alkyl)ImCl homopolymers are unstable above 220 °C, whereas the hydrophobic PILs remain stable up to 290 °C. The glass transition temperatures (T_g) decrease with both increasing alkyl side‐chain length and increasing counterion size, exemplified by T_g = 9 °C for PVBnHexImTFSI. Hydrophilic PILs exhibit high ionic conductivities (as high as ～0.10 S cm^?1) that depend on the relative humidity, water uptake, and the PIL side chain length. The hydrophobic PILs exhibit lower conductivities (up to ～5 × 10^?4 S cm^?1) that depend predominantly on the polymer T_g, however, counterion size and symmetry also contribute. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1287–1296, 2011     

Amino acid‐functionalized ethyl cellulose: Synthesis,characterization, and gas permeation properties

Amino acid esters of ethyl cellulose [R′ = H ( 1 ), CH₃ ( 2 ), CH₂CH(CH₃)₂ ( 3 ), CH₂CONH₂ ( 4 ), CH₂OCH₂C₆H₅ ( 5 , 5′ ), CH₂CH₂CH₂CH₂NHOCOC(CH₃)₃ ( 6 )] were synthesized in moderate to quantitative yields (30–99%) by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids or an activated ester derivative with hydroxy groups of ethyl cellulose [EC; degree of substitution (DS_Et), 2.69]. The amino acid functionalities displaying varied chemical nature, shape, and bulk were used, and bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). ¹H NMR spectra were used to determine the degree of incorporation of amino acid moiety (DS_Est), and almost complete substitution of the hydroxy protons was revealed in 1 , 2 , and 5′ . The onset temperatures of weight loss of 1 – 6 were 198–218 °C, indicating fair thermal stability. The glass transition temperatures of the derivatized polymers were 30–40 °C lower than that of EC (T_g 131 °C; cf. T_g of 1 – 6 , 93.5–103 °C). Free‐standing membranes of EC and its amino acid esters ( 1 , 2 , 5 , 5′ , and 6 ) were fabricated, and enhanced permselectivity for CO₂/N₂ and CO₂/CH₄ gas pairs was discerned, when compared with EC. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3986–3993, 2010     

Crosslinked liquid crystal polymers from liquid crystal monomers: Synthesis and mechanical properties

Difunctional acrylates and methacrylate monomers have been made which are high order smectic liquid crystal (or crystalline) at room temperature. This report discusses materials with the following structure: F–S–M–S–F, where F is a functional group, acrylate or methacrylate (A or M); S is a spacer (CH₂)_n(n), and M is a mesogen—in this case 4,4′-dioxybiphenyl (B). They are codified as BnA or BnM where n is the number of methylenes in the spacer. High conversion with high T_g can be obtained when polymerizing in the smectic state because the reactive end groups are concentrated in a small volume and can react well with little or no diffusion. B2A, B3A, B6A, B11A, and B3M were polymerized in the smectic state and compared to polymers made at temperatures where the monomers were isotropic. High conversion was obtained below final T_g—even then, probably because the polymers were ordered. All the polymers were studied by WAXD and dynamic mechanical spectroscopy. Solid-state NMR on B3A showed that there was very high conversion of the double bonds at all temperatures. B3A photopolymerized in the smectic state (60–76°C) produced a crystalline polymer with T_g = 185°C (1 Hz). When photopolymerized at 85°C, above the isotropization temperature (T_i), a poorly organized polymer was obtained with a T_g of 155°C (1 Hz). Monomers with an odd number of methylene groups as spacers were crystalline after polymerization. With an even number of methylene groups, they lost most of their crystallinity on polymerization below T_i, but retained a low order smectic structure. Similar structures were obtained with all the monomers when they were polymerized above T_i. There was little effect of polymerization temperature on T_g when the spacers had an even number of methylene groups. © 1993 John Wiley & Sons, Inc.     

Synthesis and properties of amino acid esters of hydroxypropyl cellulose

The amino acid esters of hydroxypropyl cellulose (HPC) [R′ = H ( 2a ), CH₃ ( 2b ), CH₂CH(CH₃)₂ ( 2c ), CH₂CONH₂ ( 2d ), CH₂CH₂CONH₂ ( 2e ), CH₂CH₂CH₂CH₂ NHOCOC(CH₃)₃ ( 2f )] were synthesized in good yield by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids with hydroxy groups of HPC ( 1 ; molar substitution (MS), 4.61). The amino acid functionalities displaying varied chemical nature, shape, and bulk were utilized and the bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). The ¹H NMR spectra and elemental analysis were employed to determine the degree of incorporation of amino acid moiety (DS_Est) and almost complete substitution of the hydroxy protons was revealed for 2a , 2b , and 2f . The presence of the peaks characteristic of the carbonyl group in the FTIR spectra furnished further evidence for the successful esterification of HPC. The starting as well as the resulting polymers ( 1 and 2a – f ) were soluble in polar organic solvents; however, the esterification of 1 with bulky organic moieties resulted in an increased hydrophobicity as all of the amino acid‐functionalized polymers ( 2a – f ) were insoluble in water. The onset temperatures of weight loss of 2a – f were 175–230 °C, indicating fair thermal stability. The amino acid functionalization led to the enhanced polymer chain stiffness, and the glass transition temperatures of the derivatized polymers were 30–40 °C higher than that of 1 (T_g 3.9 °C; cf. T_g of 2a – f , 35.1–43.3 °C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2326–2334, 2008     

Gas‐phase chemistry of dihydromyrcenol with ozone and OH radical: Rate constants and products

A bimolecular rate constant, k_{OH + dihydromyrcenol}, of (38 ± 9) × 10^?12 cm³ molecule^?1 s^?1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 2,6‐dimethyl‐7‐octen‐2‐ol (dihydromyrcenol,) at 297 ± 3 K and 1 atm total pressure. Additionally, an upper limit of the bimolecular rate constant, k, of approximately 2 × 10^?18 cm³ molecule^?1 s^?1 was determined by monitoring the decrease in ozone (O₃) concentration in an excess of dihydromyrcenol. To more clearly define part of dihydromyrcenol's indoor environment degradation mechanism, the products of the dihydromyrcenol + OH and dihydromyrcenol + O₃ reactions were also investigated. The positively identified dihydromyrcenol/OH and dihydromyrcenol/O₃ reaction products were acetone, 2‐methylpropanal (O?CHCH(CH₃)₂), 2‐methylbutanal (O?CHCH(CH₃)CH₂CH₃), ethanedial (glyoxal, HC(?O)C(?O)H), 2‐oxopropanal (methylglyoxal, CH₃C(?O)C(?O)H). The use of derivatizing agents O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine (PFBHA) and N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible dihydromyrcenol/OH and dihydromyrcenol/O₃ reaction mechanisms based on previously published volatile organic compound/OH and volatile organic compound/O₃ gas‐phase reaction mechanisms. © 2006 Wiley Periodicals, Inc. *

1 This article is a US Government work and, as such, is in the public domain of the United States of America

Int J Chem Kinet 38: 451–463, 2006     

Polyisobutylene-containing block polymers by sequential monomer addition. IV. New triblock thermoplastic elastomers comprising high Tg styrenic glassy segments: Synthesis,characterization and physical properties

New linear triblock thermoplastic elastomers (TPEs) comprising a rubbery polyisobutylene (PIB) midblock flanked by two glassy endblocks of various styrenic polymers have been synthesized by living carbocationic polymerization by sequential monomer addition. First isobutylene (IB) was polymerized by a bifunctional tert-ether (dicumyl methyl ether) initiator in conjunction with TiCl₄ coinitiator in CH₃Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at ?80°C. After the living narrow molecular weight distribution PIB midblock ( = 1.1–1.2) has reached the desired molecular weight, the styrenic monomers together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to start the blocking of the glassy segments from the living ⊕PIB⊕ chain ends. While p-methylstyrene (pMeSt), p-t-butylstyrene (ptBuSt) and indene (In) gave essentially 100% blocking to the corresponding glassy endblocks, the blocking of 2,4,6-trimethylstyrene (TMeSt) and α-methylstyrene (αMeSt) were ineffective. Uncontrolled initiation by protic impurities was prevented by the use of DtBP. In the simultaneous presence of DtBP and the strong ED N,N-dimethylacetamide (DMA), TPEs with good mechanical properties (10–20 MPa tensile strength, 300–600% elongation) were prepared. The products exhibit a low and a high temperature T_g characteristic of phase separated rubbery and glassy domains. The service temperature of these new TPEs exceeds that of PSt–PIB–PSt triblock copolymers due to the higher T_gs (PpMeSt = 108, PptBuSt = 142 and PIn = 220–240°C) of the outer blocks. The T_g of the glassy blocks can be regulated by copolymerizing two styrene derivatives; a triblock copolymer with outer blocks of poly(pt-butylstyrene-co-indene) showed a single glassy transition T_g = +165°C, i.e., in between that of PptBuSt and PIn. Virgin TPEs have been repeatedly compression molded without deterioration of physical properties. The high melt flow index obtained with a TPE containing PptBuSt endblocks suggests superior processability relative to those with PSt end-blocks. The tensile strength retention at 60°C of the former TPE is far superior to that of a PSt–PIB–PSt triblock of similar composition.     

Preparation and characterization of Co- and homopoly(phenylene etherimideketone)s

Poly(phenylene etherimdeketone)s were prepared by Friedel–Crafts acylation type polymerization using P₂O₅? CH₃SO₃H 1 : 10 (w/v) mixtures. Most of these polymers were semicrystalline. T_gS ranged from 203 to 236°C and crystalline melt temperatures were observed between 306 and 435°C. All of the polymers exhibited high thermal stability and good solvent resistance. © 1993 John Wiley & Sons, Inc.     

Very low-pressure pyrolysis (VLPP) of but-1-yne the heat of formation and stabilization energy of the propargyl radical

The unimolecular decomposition of but-1-yne has been investigated over the temperature range of 1052° – 1152°K using the technique of very low-pressure pyrolysis (VLPP). The primary process is C? C bond fission yielding methyl and propargyl radicals. Application of RRKM theory shows that the experimental rate constants are consistent with the highpressure Arrhenius parameters given by where θ = 2.303 RT kcal/mol. The parameters are in good agreement with estimates based on shock-tube studies. The activation energy, combined with thermochemical data, leads to DH°[HCCCH₂? CH₃] = 76.0, ΔH(HCC?CH_2,g) = 81.4, and DH° [HCCCH₂? H] = 89.2, all in kcal/mol at 300°K. The stabilization energy of the propargyl radical SE° (HCC?CH₂) has been found to be 8.8 kcal/mol. Recent result for the shock-tube pyrolysis of some alkynes have been analyzed and shown to yield values for the heat of formation and stabilization energy of the propargyl radical in excellent agreement with the present work. From a consideration of all results it is recommended that ΔH(HCC?CH_2,g) = 81.5±1.0, DH[HCCCH₂? H] = 89.3 ± 1.0, and SE° (HCC?CH₂) = 8.7±1.0 kcal/mol.     

Polyurethanes containing sulfur. I. New thermoplastic polyurethanes with benzophenone unit in their structure

New thermoplastic nonsegmented thiopolyurethanes were obtained from the low-melting aliphatic–aromatic thiodiols 4,4′-bis(2-hydroxyethylthiomethyl)benzophenone (BHEB), 4,4′-bis(3-hydroxypropylthiomethyl)benzophenone (BHPB), and 4,4′-bis(6-hydroxyhexylthiomethyl)benzenophenone(BHHB) as well as hexamethylene diisocyanate (HDI), both by melt and solution polymerization with dibutyltin dilaurate as the catalyst. The effect of various solvents on molecular-weight values was examined. The polymers with the highest reduced viscosities (0.63–0.88 dL/g) were obtained when the polymerization was carried out in a solution of tetrachloroethane, N,N-dimethylacetamide, and N,N-dimethylacetamide or N,N-dimethylformamide for BHEB-, BHPB-, and BHHB-derived polyurethanes, respectively. These polymers with a partially crystalline structure showed glass-transition temperatures (T_g) in the range of −1 to 39 °C, melting temperatures (T_m) in the range of 107 to 124 °C, and thermal stabilities up to 230 to 240 °C. The BHEB-derived polyurethane is a low-elasticity material with high tensile strength (ca. 50 MPa), whereas the BHPB- and BHHB-derived polyurethanes are more elastic, showing yield stress at approximately 16 MPa. We also obtained segmented polyurethanes by using BHHB, HDI, and 20 to 80 mol % poly(oxytetramethylene) glycol (PTMG) of M̄_n = 1000 as the soft segment. These are high-molecular thermoplastic elastomers that show a partially crystalline structure. Thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. The increase in PTMG content decreases the definite T_g and increases the solubility of the polymers. These segmented polyurethanes exhibit the definite T_g (−67 to −62 °C) nearly independent of the hard-segment content up to approximately 50 wt %, indicating the existence of mainly phase-separated soft and hard segments. Shore A/D hardness and tensile properties were also determined. As the PTMG content increases, the hardness, modulus of elasticity, and tensile strength decrease, whereas elongation at break increases. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4140–4150, 1999     

Hydrogen abstraction from organosilicon compounds. The reactions of fluoromethyl radicals with tetramethylsilane. Polar effects in gas phase reactions

The photolysis of 1,1,3,3-tetrafluoroacetone has been reinvestigated as a source of CHF₂ radicals at temperatures up to 578°K, and the following rate constant ratio was determined for the reactions

1 θ= 2.303 RT in kcal/mole.

1,1-Difluoro- and 1,1,3,3-tetrafluoroacetone were photolyzed in the presence of tetramethylsilane, and Arrhenius parameters were measured for the hydrogen abstraction reactions: R + Me₄Si → RH + Me₃SiCH₂

Fully aromatic thermotropic liquid crystalline polyesters of 3-phenyl-4,4′-biphenol with 4,4′-benzophenone dicarboxylic acid

A series of fully aromatic, thermotropic polyesters, derived from 3-phenyl-4,4′-biphenol (MPBP), nonlinear 4,4′-benzophenone dicarboxylic acid (4,4′-BDA), and various other comonomers was prepared by the melt polycondensation method and characterized for their thermotropic liquid crystalline behavior by a variety of experimental techniques. The homopolymer of MPBP with 4,4′-BDA had a fusion temperature (T_f) at 240°C, exhibited a nematic liquid crystalline phase, and had a narrow liquid crystalline range of 60°C. All of the copolyesters of MPBP with 4,4′-BDA and either 30 mol % 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA) or 50 mol % terephthalic acid (TA), 2,6-naphthale-nedicarboxylic acid (2,6-NDA) and low T_f values in the range of 210–230°C, exhibited a nematic phase, and had accessible isotropization transitions (T_i) in the range of 320–420°C, respectively. As expected, each of them had a broader range of liquid crystalline phase than the homopolymer. They had a “frozen” nematic, glassy order as determined with the wide-angle X-ray diffraction (WAXD) studies. The morphology of each of the “as-made” polyesters had a fibrous structure as determined with the scanning electron microscopy (SEM), which arises because of the liquid crystalline domains. Moreover, they had higher glass transition temperatures (T_g) in the range of 167–190°C than those of other liquid crystalline polyesters, and excellent thermal stabilities (T_d) in the range of 500–533°C, respectively. © 1995 John Wiley & Sons, Inc.     

Synthesis of novel phosphinic acid-containing polymers

Three arylene difluoride monomers containing phosphine oxide ( 1 ), phosphinic acid ( 2 ), or phosphinate ester ( 3 ) groups were prepared and polymerized with bisphenol A to give novel poly-(arylene ether)s ( 4 , 5 , and 6 ). The polymers obtained had moderate molecular weights (η_inh: 0.14–0.30 dL g⁻¹ in N-methylpyrrolidinone) and glass-transition temperatures (T_g: 102–200 °C), depending on the phosphine group in the main chain. Using bis(4-fluorophenyl)sulfone as a comonomer improved the polymerization to give copolymers with higher solution viscosities. The stoichiometric investigation revealed that 7 mol % excess of fluoride monomer gave the highest molecular weight copolymer 8 with η_inh of 0.78 dL g⁻¹, which had a T_g of 176 °C, a T of 432 °C, and formed a hard film by casting from solution. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1854–1859, 2001     

The carbon–hydrogen bond strength in dimethyl ether and some properties of iodomethyl methyl ether

The kinetics and mechanism of the reaction between iodine and dimethyl ether (DME) have been studied spectrophotometrically from 515–630°K over the pressure ranges, I₂ 3.8–18.9 torr and DME 39.6–592 torr in a static system. The rate-determining step is, where k₁ is given by log (k₁/M^?1 sec^?1) = 11.5 ± 0.3 – 23.2 ± 0.7/θ, with θ = 2.303RT in kcal/mole. The ratio k₂/k_?1, is given by log (k₂/k_?1) = ?0.05 ± 0.19 + (0.9 ± 0.45)/θ, whence the carbon-hydrogen bond dissociation energy, DH° (H? CH₂OCH₃) = 93.3 ± 1 kcal/mole. From this, ΔH°_f(CH₂OCH₃) = ?2.8 kcal and DH°(CH₃? OCH₂) = 9.1 kcal/mole. Some nmr and uv spectral features of iodomethyl ether are reported.     

Synthesis,morphology, and viscoelastic properties of cyanate ester/polyhedral oligomeric silsesquioxane nanocomposites

Cyanate ester (PT‐15, Lonza Corp) composites containing the inorganic–organic hybrid polyhedral oligomeric silsesquioxane (POSS) octaaminophenyl(T₈)POSS [ 1 ; (C₆H₄NH₂)₈(SiO_1.5)₈] were synthesized. These PT‐15/POSS‐ 1 composites (99/1, 97/3, and 95/5 w/w) were characterized by X‐ray diffraction (XRD), transmission election microscopy (TEM), dynamic mechanical thermal analysis, solvent extraction, and Fourier transform infrared. The glass‐transition temperatures (T_g's) of the composite with 1 wt % 1 increased sharply versus the neat PT‐15, but 3 and 5 wt % 1 in these cyanate ester composites depressed T_g. All the PT‐15/POSS composites exhibited higher storage modulus (E′) values (temperature > T_g) than the parent resin, but these values decreased from 1 to 5 wt % POSS. The loss factor peak intensities decreased and their widths broadened upon the incorporation of POSS. XRD, TEM, and IR data were all consistent with the molecular dispersion of 1 due to the chemical bonding of the octaamino POSS‐ 1 macromer into the continuous cyanate ester network phase. The amino groups of 1 reacted with cyanate ester functions at lower temperatures than those at which cyanate ester curing by cyclotrimerization occurred. In contrast to 1 , 3‐cyanopropylheptacyclopentyl(T₈)POSS [ 2 ; (C₅H₉)₇(SiO_1.5)₈CH₂CH₂CH₂CN] had low solubility in PT‐15 and did not react with the resin below or at the cure temperature. Thus, phase‐separated aggregates of 2 were found in samples containing 1–10 wt % 2 . Nevertheless, the T_g and E′ values (temperature > 285 °C) of these composites increased regularly with an increase in 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3887–3898, 2005     

Solid-state relaxations in poly(ethylene oxide). I. Study using the differential scanning calorimetry method

Differential scanning calorimetry (DSC) studies show that poly(ethylene oxide) (PEO) exhibits three transition regions below its melting point. The effects of annealing on the intensity and temperature of these transitions enable us to locate T < T_g (T_γ) T_g, and T_α at about 130–140. 190–240, and 263–313°K, respectively. Our results argue for a small transition T_g (L) at 190–200°K with a second T_g (U) above 233°K, the temperature of which increases on annealing. The shape of DSC derivative curves reveals that T < T_g and T_α are complex and suggests the possibility of two steps in these processes. In addition, a splitting of T_α is observed every time a multiple melting endotherm appears as a result of annealing. Up to three separate melting endotherms can be observed. One of them is related to the normal primary crystallization process. Its peak temperature increases linearly with the annealing temperature, yielding an extrapolated value for the equilibrium melting temperature T of 347°K as found before.     

Thermal cured epoxy resins using certain calixarenes and their esterified derivatives as curing agents

The acetyl esterified calixarene (CA) derivatives were prepared from calix[4]resorcinarene (CRA), and p‐tert‐butylcalixarene (BCA[n], n = 4, 6, 8), respectively. Using these CA derivatives as curing agents, the thermal curing reactions of two multifunctional epoxy resins (jER 828, 186 g/equiv., and ESCN, 193.7 g/equiv.) were investigated. The temperatures of glass transition (T_g) and decomposition (T) were measured by DSC and TGA, respectively. Based on the yields, T_gs, and T_ds of the thermal cured jER 828 epoxy resin with CRA‐E100, the curing conditions were optimized to be tetrabutylphosphonium bromide (TBPB) as catalyst in NMP at 160 °C for 15 h. Under this curing condition, the cured materials of jER 828 or ESCN using various CA derivatives as curing agents were prepared. Except for BCA4 derivatives, the yields of thermal curing reaction were higher than 90%. T_gs and Ts of the resultant cured materials were in the range of 113–248 °C and 363–404 °C, respectively. These results mean that the cured epoxy resins with excellent T_gs were successfully formed by using CA derivatives as curing agents. It was also found that the T_gs of cured epoxy resins were strongly affected by the degree of esterification of CA derivatives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1931–1942, 2010     

α-amidoalkylation of polystyrene

Crystal polystyrene was alkylated with N-methylolacetamide (CH₃CONHCH₂OH), boron trifluoride being used as the catalyst. A linear relationship between degree of N-methyleneacetamide substitution and the glass transition temperature T_g of the polystyrene was observed. The T_g values ranged from 104°C for 0% amidization to 125°C for 20% amidization. The critical strain ε_c of these materials was measured at room temperature in air, hexane, and oil (50–50, a cottonsed oil–oleic acid) and an increase in the ε_c above which crazing occurs was observed as the degree of alkylation increased. Thermogravimetric analysis (TGA) of the amidized polystyrenes in air at 250°C showed these materials to become more stable as the amount of N-methylene substitution increased. Tensile data show that the amidized polystyrene, although stronger than the unsubstituted material, exhibits the same elongation at break and tensile modulus.     

Standard Thermodynamic Functions of Crystalline Arsenate Mg<Subscript>0.5</Subscript>Zr<Subscript>2</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>3</Subscript> in the Range from <Emphasis Type="Italic">T</Emphasis> → 0 to 670 K

The temperature dependence of heat capacity C^° _p = f(T) of crystalline arsenate Mg_0.5Zr₂(AsO₄)₃ was studied by precision adiabatic vacuum and differential scanning calorimetry in the temperature range 8?670 K. The standard thermodynamic functions C^° _p (T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) of the arsenate for the range from Т → 0 to 670 K and the standard formation entropy at Т = 298.15 K were calculated from the obtained experimental data. Based on the low-temperature capacity data (30–50 K) the fractal dimension D of the arsenate was determined, and the topology of its structure was characterized. The results were compared with the thermodynamic data for the structurally related crystalline phosphates M_0.5Zr₂(PO₄)₃ (M = Mg, Ca, Sr, Ba, Ni) and arsenate NaZr₂(AsO₄)₃.