Copolymerization of styrene with maleic anhydride initiated by thiol compounds

Copolymerization of styrene (ST) with maleic anhydride (MAH) initiated by thiol compound was investigated under various conditions. The kinetics of copolymerization of ST with MAH initiated by p-toluenethiol (pTT) was studied in dioxane in the temperature range of 25–60°C, and the rates (R_p) of copolymerization and activation energy were determined. R_p was found to depend on [pTT],^0.6 ([ST] + [MAH])^2.7. The overall energy of activation was 10.8 kcal/mol in the temperature range of 25–60°C. A mechanism involving the formation of a complex between MAH and pTT the decomposition of which yields the initial radical is suggested.     

High-yield synthesis and characterization of 1,2-bis(p-vinylphenyl)ethane

The quantitative synthesis and complete characterization of 1,2-bis(p-vinylphenyl)ethane (p,p-BVPE) and its meta-, para-mixed isomers are reported. These crosslinkers copolymerize randomly with p-methylstyrene, leading to random crosslink distributions. The crosslinkers are prepared by Grignard coupling of (m,p)-vinylbenzyl chloride in tetrahydrofuran at low temperature to give the statistical mixture of m,m-, m,p-, and p,p-isomers in quantitative yield. Pure p-vinylbenzyl chloride is converted to pure p,p-BVPE. p,p-BVPE has also been separated from the mixture of isomers. The isomers are characterized by elemental analysis, mass spectrometry, ¹H-NMR, and ¹³C-NMR and by reversed-phase HPLC. © 1994 John Wiley & Sons, Inc.     

Thermochemical and thermal analysis on N-(p-methylphenyl)-N'-(2-pyridyl)urea

Low temperature heat capacities of N-(p-methylphenyl)-N'-(2-pyridyl)urea were determined by adiabatic calorimetry method in the temperature range from 80 to 370 K. It was found that there was not any heat anomaly in this temperature region. Based on the experimental data, some thermodynamic function results were obtained. Thermal stability and decomposition characteristics analysis of N-(p-methylphenyl)-N'-(2-pyridyl)urea were carried out by DSC and TG. The results indicated that N-(p-methylphenyl)-N'-(2-pyridyl)urea started to melt at ca. 426 K (153°C) and the melting peak located at 447.01 K (173.86°C). The melting enthalpy was 204.445 kJ mol^-1 (899.6 J g^-1). The decomposition peak of N-(p-methylphenyl)-N'-(2-pyridyl)urea was found at 499.26 K (226.11°C) from DSC curve. This result was similar with that from TG and DTG experiment, in which the mass loss peak was determined as 500.4 K (227.2°C). This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and characterization of certain new poly(bisimide)s. I

Maleic and citraconic anhydrides were reacted with several diamines to obtain a novel class of high temperature resistant bisimides.^1–3 The bisimides were characterized by melting points, elemental analysis, UV–Vis, ¹H- and ¹³C-NMR, and mass spectral analysis. The bisimide monomers were then polymerized by the addition process. A poly(amidemaleimide) was also synthesized by reacting maleic anhydride with p-aminobenzhydrazide. The thermal stability of these highly crosslinked poly(bisimide)s were examined by TGA and DTA. A neat bisimide monomer obtained from 2,2′-bis[4(p-aminophenoxy)phenyl] propane with maleic anhydride namely, 2,2′-bis[4-(p-maleimidophenoxy)phenyl]propane was reacted with 2,2′-bis[4(p-aminophenoxy)phenyl]propane by the Michael reaction.⁴ A fiber glass cloth reinforced laminate was prepared from bismaleimide and amine mixture and the mechanical properties of the test laminate evaluated.     

2-甲基-2-丁醇的低温热容和热力学性质

本文用精密自动绝热量热仪测定了2-甲基-2-丁醇在80～305 K温区的热容,从热容曲线(Cp-T) 发现三个固－固相变和一个固－液相变, 其相变温度分别为T = 146.355, 149.929, 214.395, 262.706 K。从实验热容数据用最小二乘法得到以下四个温区的热容拟合方程。在80～140K温区, Cp,m = 39.208 + 8.0724X - 1.9583X2 + 10.06X3 + 1.799X4 - 7.2778X5 + 1.4919X6, 折合温度X = (T –110) / 30; 在 155 ～ 210 K温区, Cp,m = 70.701 + 10.631X + 12.767X2 + 0.3583X3 - 22.272X4 - 0.417X5 + 12.055X6, X = (T –182.5) /27.5; 在220 ～ 250 K温区, Cp,m = 99.176 + 7.7199X - 26.138X2 + 28.949X3 + 0.7599X4 - 25.823X5 + 21.131X6, X = (T – 235)/15; 在 270～305 K温区, Cp,m =121.73 + 16.53 X- 1.0732X2 - 34.937X3 - 19.865X4 + 24.324X5 + 18.544X6, X = (T –287.5)/17.5。从实验热容计算出相变焓分别为0.9392, 1.541, 0.6646, 2.239 kJ×mol-1; 相变熵分别为6.417, 10.28, 3.100, 8.527 J×K-1×mol-1。根据热力学函数关系式计算出80～305 K温区每隔5 K的热力学函数值 [HT –H298.15]和 [ST –S298.15]。     

Exactly alternating silarylene-siloxane polymers. III. Structure-property relationships for polymers containing p-phenylene and p,p′-diphenyl ether silarylene units

A series of 12 different exactly alternating silarylene-siloxane polymers was prepared by low temperature condensation polymerization of arylenedisilanol with bisureidosilane monomers. The structural characterization of the polymers was carried out by ¹H NMR spectroscopy, ¹³C NMR spectroscopy, infrared (IR) spectrometry, gel permeation chromatography (GPC). dilute solution viscometry, and differential scanning calorimetry (DSC). Homopolymers and copolymers that contained either or both p-phenylene and p,p′-diphenyl ether units in the silarylene group and dimethyl or methylvinyl units in the siloxane group were prepared in high molecular weights.     

1-( p -Fluorophenyl)-2-(2′-pyridyl)ethanol and 1-( p -fluorophenyl)-2-(2′-pyridyl)ethene obtained from the condensation reaction of 2-picoline and p -fluorophenylaldehyde under catalyst-and solvent-free conditions

The novel intermediate 1-(p-fluorophenyl)-2-(2′-pyridyl)ethanol or 2-[2′-(1-hydroxy-1-(p-fluorophenyl)ethyl]pyridine and the corresponding novel dehydration compound 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene or 2-[p-fluorophenylvinyl]pyridine were obtained from the condensation reaction of p-fluorophenylaldehyde and 2-picoline under catalyst-and solvent-free conditions. The intermediate 1-(p-fluorophenyl)-2-(2′-pyridyl)ethanol was obtained at 42 h reaction time and temperature of 120°C, respectively. ¹H-NMR, IR spectroscopic data of the 1-(p-fluorophenyl)-2-(2-pyridyl)ethanol clearly showed the presence of the-CH₂-CHOH-group. The compound was obtained as a white powder with m.p. 121–122°C and a yield of 8%. For 1-(p-fluorophenyl)-2-(2-pyridyl)ethene, the reaction conditions were similar, but the reaction temperature was increased to yield the double bond in the 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene. At the reaction temperature of 140°C, the compound was a slightly brown powder with a m.p. of 78°C and yield of 18%. ¹H-NMR, IR spectroscopic data for the 1-(p-fluorophenyl)-2-(2′-pyridyl)ethene showed the presence of a double bond in trans configuration (-CH=CH-), characteristic of a styrylpyridine.     

Electron spin resonance and kinetic study of the photolysis of p-Flouranil (tetrafluoro-p-benzoquinone) in dioxane

The photochemistry of p-fluoranil in dioxane was studied by electron spin resonance (ESR) and the ESR-rotating sector technique. The transient photoradical is identified as the p-tetrafluorobenzosemiquinone neutral radical with a hyperfine splitting of 1.1 gauss for the hydroxy proton and the fluorine hyperfine splittings of 3.8 and 14.1 gauss for the meta and ortho fluorines, respectively. The radicals decayed by self-disproportionation with a second-order rate constant at room temperature of approximately 3.2 × 10⁹M^?1s^?1. The activation energy of the decay process is found to be about 2.4 ± 0.4 kcal/mole.     

Kinetics of polymerization of methyl methacrylate initiated with cyclohexanone. Part I

The kinetics of radical polymerization of methyl methacrylate were investigated in a dioxane solution with cyclohexanone as initiator. It was found that the overall rate of reaction initiated with cyclohexanone (R_p) is proportional to the concentration of monomer and to the square root of the concentration of the initiator. The effect of temperature on the R_p in the temperature range of 65–95°C was discussed. The Arrhenius activation energy E_a estimated for the temperature range of 65–75°C was 137 kJ mol^?1.     

New UV-Curable Prepolymer: Synthesis,Characterization, and Kinetics Analysis

A new UV-curable prepolymer, 2-hydroxy-3-[p-(1-{p-[2-hydroxy-3-(vinylcarbonyloxy)propoxy]phenyl}-1-(p-methoxyphenyl)ethyl)phenoxy]propylacrylate (HEPPA) was synthesized and characterized by ¹H-NMR,¹³C-NMR, and FT-IR spectroscopy. Photocuring studies were carried out by a medium-pressure mercury vapor lamp with temperature controller. The effects of various photoinitiators and temperatures on the kinetics of the photopolymerization were studied by FT-IR. The accelerated weathering test of UV-cured polymers was analyzed by a xenon arc lamp in an Atlas Xenon Alpha Tester. The result shows that weight loss (%) of BISGA-cured polymer was higher than that of HEPPA-cured polymer. This showed that synthesized prepolymer, HEPPA, was more suitable for coating industries than the commercial prepolymer, BISGA.     

Structure and properties of the graft copolymer of starch and p‐hydroxybenzoic acid using horseradish peroxidase

A modified starch tannage was synthesized by free radical graft copolymerization of degraded starch with p‐hydroxybenzoic acid (pHA) using horseradish peroxidase/H₂O₂ as the initiator. In this study, the effects of the degree of degradation of the starch, dosage of pHA, polymerization temperature, system pH, and horseradish peroxidase content on the tanning properties of the graft copolymer were investigated. The shrinkage temperature of leather tanned by the graft copolymer was 78 °C. The thickness increment ratio of the retanned leather was 21.6%, and meanwhile the retanned leather showed better softness. The results indicate that the graft copolymer has excellent tanning and retanning properties. The structure of the graft copolymer was analyzed by Fourier Transform Infrared Spectroscopy (FTIR), ¹Hydrogen‐Nuclear Magnetic Resonance (¹H‐NMR), and ¹³Carbon‐Nuclear Magnetic Resonance (¹³ C‐NMR) and Gel Permeation Chromatography (GPC). Compared with conventional methods, we show that a “green” leather tannage could be achieved using a radical graft copolymerization of starch and phenols. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of the stereochemical configuration on the radical polymerization of methacrylic monomers: cis‐ and trans‐(2‐cyclohexyl‐1,3‐dioxan‐5‐yl) methacrylate

The synthesis of two new isomeric monomers, cis‐(2‐cyclohexyl‐1,3‐dioxan‐5‐yl) methacrylate (CCDM) and trans‐(2‐cyclohexyl‐1,3‐dioxan‐5‐yl) methacrylate (TCDM), starting from the reaction of glycerol and cyclohexanecarbaldehyde, is reported. The process involved the preparation of different alcohol acetals and esterification with methacryloyl chloride of the corresponding cis and trans 5‐hydroxy compounds of 2‐cyclohexyl‐1,3‐dioxane. The radical polymerization reactions of both monomers, under the same conditions of temperature, solvent, monomer, and initiator concentrations, were studied to investigate the influence of the monomer configuration on the values of the propagation and termination rate constants (k_p and k_t ).The values of the ratio k_p /k_t ^1/2 were determined by UV spectroscopy by the measurement of the changes of absorbance with time at several wavelengths in the range 275–285 nm, where an appropriate change in absorbance was observed. Reliable values of the kinetics constants were determined by UV spectroscopy, showing a very good reproducibility of the kinetic experiments. The values of k_p /k_t ^1/2, in the temperature interval 45–65 °C, lay in the range 0.40–0.50 L^1/2/mol^1/2s^1/2 and 0.20–0.30 L^1/2/mol^1/2s^1/2 for CCDM and TCDM, respectively. Measurements of both the radical concentrations and the absolute rate constants k_p and k_t were also carried out with electron paramagnetic resonance techniques. The values of k_p at 60 °C were nearly identical for both the trans and cis monomers, but the termination rate constant of the trans monomer was about three times that of the cis monomer at the same temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3883–3891, 2000     

Dipole moment characterization of phenol–, o-cresol–, and p-cresol–formaldehyde resins

Dipole moments and their temperature dependence have been measured in p-dioxane for fractionated novolac phenol–, o-cresol–, and p-cresol–formaldehyde polymers. The phenol–formaldehyde fractions covered a molecular weight range of 200 to 6100, and the limiting dipole moment ratio 〈μ²〉/xm² is 1.48. The p-cresol–formaldehyde dipole-moment ratio at a DP of 4 is 2.47, whereas the phenol–formaldehyde dipole-moment ratio is 1.40. That for o-cresol–formaldehyde is intermediate in value. The dipole-moment temperature coefficients are positive for p-cresol chains and negative for the phenol–formaldehyde chains. These results indicate that the hydroxyl groups along the p-cresol–formaldehyde polymer are highly ordered, with the aromatic rings closer to the sterically hindered planar position than in the phenol–formaldehyde polymers.     

Sequence analysis of glycolide and p‐dioxanone copolymers

Low and medium molecular weight copolymers constituted by glycolide and p‐dioxanone units have been synthesized by a ring‐opening polymerization. The p‐dioxanone monomer was obtained from (2‐hydroxyethoxy)acetate or by thermal depolymerization of poly(p‐dioxanone). ¹H and ¹³C NMR spectra were highly sensitive to the chemical sequences, which were effectively assigned by considering the data from samples with different compositions, and the acquisition of heteronuclear ¹H and ¹³C NMR‐correlated spectra. End groups were also identified, allowing methylene protons of sequences involving up to two glycolide units to be distinguished. These data seem basic to analyze degradation products or the influence of thermal treatments in chain microstructure. Glycolide/p‐dioxanone copolymers are an interesting system because changes on chemical sequences can easily occur due to a depolymerization reaction that eliminates p‐dioxanone residues. Furthermore, depending on the polymerization conditions, the occurrence of transesterification reactions may be highly significant. These reactions have a great impact in properties such as the melting temperature and can be easily quantified by NMR spectroscopy because of the occurrence of a new chemical sequence. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Thermal stability of para- and ortho-isomers of tris-decyl-(ethyl-benzyl)-ammonium chloride

Thermal stability of para (p--) and ortho (o-) isomers was investigated by CRTG and reaction kinetic analysis. The temperature started the mass decrease of o-isomer was about 20°C lower than that of p-isomer by CRTG. The activation energies of thermal decomposition of o- and p-isomers were 136.9 and 153.4 kJ mol^–1, respectively. The effect of steric hindrance on heat of formation was calculated by AM1 method using Win MOPAC3.0 for the model compound of p- and o-isomers. The lower stability of o-isomer was the results of the steric hindrance between the ethylene unit of aromatic ring and three alkyl chains.     

STRUCTURES IN SOLUTION OF ADDUCTS OF HEXAMETHYLPHOSPHORUS TRIAMIDE AND SUBSTITUTED BENZILS

Abstract

Hexamethylphosphorus triamide has been allowed to react with p,p′-dinitrobenzil, p-chlorobenzil, p,p′-difluorobenzil, p,p′-dimethylbenzil and p,p′-dimethoxybenzil. All of these materials in benzene-d₆ had negative δ ³¹P chemical shifts except for the p,p′-dinitro adduct whose resonance was found at δ + 17.6. In dichloromethane-d₂ the resonances ranged from δ + 38.2 for the p,p′-dinitro adduct to δ ? 22.5 for the p,p′-dimethoxy adduct. The ¹³C NMR spectra of these compounds all showed coupling J _POCC to the ipso carbons except for the p,p′-dinitro adduct. These data indicate that the p,p′-dinitro adduct is ionizing rapidly and that the others are phosphoranes. On cooling the coupling was lost for the p,p′-difluoro adduct and for the p-chloro adduct. These spectral changes are attributed to rapid ionization which occurs because of the change of the dielectric constant with change in temperature.     

Estimation of activation parameters for the propagation rate constant of styrene

For a temperature range of −11.8–92.6°C, the propagation rate constant k_p of styrene has been determined with the use of pulsed-laser polymerization (PLP). The temperature dependency of the obtained k_p data was evaluated using the Arrhenius equation. The NLLS error-in-variables method (EVM) is recommended for this fit. The resulting activation energy is 32.6 kJ mol⁻¹ and the pre-exponential factor is 10^7.66 dm³ mol⁻¹ s⁻¹. A joint confidence interval for these parameters is given. © 1996 John Wiley & Sons, Inc.     

Kinetics,Mechanism, and Rheological Properties of the Copolymers of 2-Ethylhexylacrylate and Styrene

Abstract

Copolymerization of 2-ethylhexylacrylate (2-EHA) and styrene (Sty) initiated by α,α′-azobisisobutyronitrile (AIBN) was carried out at 60, 65, and 70 ± 0.1°C in bulk in the presence of zinc chloride (ZnCl₂). R _p was a direct function of [ZnCl₂] and temperature. R _p showed an initial increase with [monomers] followed by a subsequent decrease after a maximum was reached. The accelerating effect of ZnCl₂ was predicted by a lowering of the activation energy from 42.78 to 34.38 kJ·mol^?1 and an increase in the specific rate constants ratio (k ² _p/k _t) from 4.64 to 5.83 L·mol^?1·s^?1. The product of the reactivity ratios of the two monomers was 0.018 and 0.648, favoring alternating and random copolymer structures, respectively. The copolymerization reaction mechanism was a radical complex. Rheological investigations favored Bingham and Ostwald models for the flow behaviors of alternating and random copolymers, respectively.     

The thermodynamic functions of fullerene derivative (<Emphasis Type="Italic">t</Emphasis>-Bu)<Subscript>12</Subscript>C<Subscript>60</Subscript> over the temperature range from <Emphasis Type="Italic">T</Emphasis> → 0 to 420 K

The temperature dependence of heat capacity C _p ^o = f(T) of fullerene derivative (t-Bu)₁₂C₆₀ has been measured by a adiabatic vacuum calorimeter over the temperature range T = 6–350 K and by a differential scanning calorimeter over the temperature range T = 330–420 K for the first time. The low-temperature (T ≤ 50 K) dependence of the heat capacity was analyzed based on Debye’s the heat capacity theory of solids and its fractal variant. As a consequence, the conclusion about structure heterodynamicity is given. The experimental results have been used to calculate the standard thermodynamic functions C _p ^o (T), H ^o(T)−H ^o(0), S ^o(T) and G ^o(T) − H ^o(0) over the range from T → 0 to 420 K. The standard entropy of formation at 298.15 K of fullerene derivative under study was calculated. The temperature of decomposition onset of derivative was determined by differential scanning calorimetery and thermogravimetric analysis. The standard thermodynamic characteristics of (t-Bu)₁₂C₆₀ and C₆₀ fullerite were compared.     

Carbosilane dendrimer of second generation with terminal methoxyundecylenate groups

The thermodynamic properties of carbosilane dendrimer of second generation with terminal methoxyundecylene groups were studied between 6 and 340 K by adiabatic vacuum calorimetry: the temperature dependence of the molar heat capacity C_p ⁰ was measured, the physical transformations were established and their thermodynamic characteristics were obtained. The experimental data were used to calculate the thermodynamic functions C_p ⁰ (T), H ⁰(T)-H ⁰(0), S⁰(T), G ⁰(T)-H ⁰(0) of the compound in the range 0 to 340 K. from the relation C_p ⁰ (T) the fractal dimension of the dendrimer was experimentally determined. The heat capacity of the dendrimer was compared with the corresponding additive values calculated from the properties of its constituents - a dendritic matrix (carbosilane dendrimer of second generation) and the corresponding amount of moles of methyl ester of 11-(tetramethyldisiloxy)undecanoic acid serving as terminal groups. This revised version was published online in July 2006 with corrections to the Cover Date.