Thermal cure behavior and pyrolysis of methyl‐tri(phenylethynyl)silane resin

A polyfunctional organic–inorganic hybrid monomer, methyl‐tri(phenylethynyl)silane (MTPES) could be thermally polymerized by a free radical mechanism to a highly crosslinked structure of interest as a high temperature composite matrix resin. The structural changes during thermal cure process were characterized by fourier transform infrared spectrum and ¹³C‐CP‐MAS‐NMR spectrum. The disappearance of secondary acetylene stretching band at 2166 cm^?1 was used successfully to monitor cure reaction accompanied with the formation of cis‐polyene structure at 1600 and 754 cm^?1. The possible cure mechanism of MTPES was also proposed. The pyrolysis of cured MTPES under a stream of argon to 1450°C gave a ceramic in high yield (81%). Thermal conversion of polymer to ceramic was studied by means of X‐ray diffraction, Raman spectrum, and energy dispersive spectrometer analysis. The results showed that pyrolytic products were made up of β‐SiC, graphite, and glassy carbon. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Bismaleimide‐modified methyl‐di(phenylethynyl)silane blends and composites: Cure characteristics,thermal stability,and mechanical property

Reactive blends of organic‐inorganic hybrid monomer, methyl‐di(phenylethynyl)silane (MDPES) and a modified bismaleimide resin (BMI/DBA) have been prepared. The thermal and oxidative stabilities of MDPES‐BMI/DBA blends were characterized by thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis, dynamic mechanical analysis, and flexural strength retention at 240°C. Scanning electron microscopy was employed to study the surface morphology of MDPES‐BMI/DBA composite after thermal oxidative treatment. With the increase of concentration of BMI/DBA, flexural strength of composites increased from 78 to 331 MPa. The results showed that MDPES‐BMI/DBA blends exhibited excellent thermal and thermal oxidative properties, and the interface between MDPES and glass fiber was improved by the incorporation of BMI/DBA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal curing reaction and heat‐resistance of methyl‐di(M‐ethynylphenyl‐amino)silane

Methyl‐di(m‐ethynylphenyl‐amino)silane (MEAS) is a new kind of silazane with ethynylphenyl groups in the end of the molecule. The studies about the curing reaction kinetics and curing reaction mechanism are important for its application and performance. In this article, differential scanning calorimeter was used to study the curing reaction kinetics of MEAS. The results showed that both of the apparent activation energy (E_a) and the reaction order (n) that were evaluated with the method of Kissinger (113.4 kJ/mol, 0.93) agreed well with those using the method of Ozawa (116.1 kJ/mol, 0.95). According to structural changes during curing characterized using Fourier‐transform infrared spectra, it was inferred that MEAS resin underwent the main four kinds of cross‐linking reaction under the condition of heating. Thermogravimetric analysis was used to characterize the heat‐resistance of MEAS thermoset. The results showed that the temperature of 5% weight loss based on the initial weight (T_d5) of the thermoset was 632.4°C and the residue yield at 900°C was 86.4% in nitrogen. The thermoset sintered at 1450°C in argon transformed into a ceramic with yield of 71%, which was studied by scanning electron microscopy and X‐ray diffraction. The sintered products were smooth and hard solid and its chemical composition was made up of β‐SiC, α‐Si₃N₄ ceramic and free carbon. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

四苯乙炔基硅烷的合成及热性能研究

为得到耐热的含有苯乙炔官能团的有机硅单体,通过苯乙炔锂(由苯乙炔与丁基锂制得)与四氯硅烷的反应,合成了四苯乙炔基硅烷(TPES),通过多次重结晶获得了纯度为99.5%的TPES,并用FTIR、1HNMR、13C NMR、29Si NMR及元素分析对其结构进行了表征。对TPES及其400℃固化物的DSC、FTIR和TGA的分析表明:TPES的熔融温度范围宽达113℃(199℃~312℃);在氮气中失重5%时的温度Td5为710.8℃,800℃残炭率高达93.3%,空气中的Td5为595℃,800℃残炭率也达58.3%,耐热性能十分优异,具备作为一种耐高温聚合物材料的优秀潜质。     

Novel heat resistant methyl‐tri(phenylethynyl)silane resin: Synthesis,characterization and thermal properties

Methyl‐tri(phenylethynyl)silane (MTPES) was successfully synthesized by the reaction of lithium phenylacetylide with methyltrichlorosilane. The structure was characterized by HRMS, FTIR, ¹H‐NMR, ¹³C‐NMR, ²⁹Si‐NMR, and elementary analysis. Thermal cure process was monitored by DSC, DMA, and FTIR. MTPES was heated to free flowing liquid around 130°C and thermally polymerized at 327–377°C to form thermoset. Thermal and oxidative properties were evaluated by TGA analysis. Thermoset exhibits extremely high heat‐resistance and TGA curve in nitrogen shows the temperature of 5% weight loss (Td₅) of 695°C and total weight loss at 800°C of 7.1%. TGA shows a high Td₅ of 565°C even in air, although the total weight loss at 800°C was 56.1% of the initial weight, much higher than that in nitrogen. The high heat resistance of MTPES was ascribed to crosslinking reaction concerning ethynyl groups. Aging studies performed at elevated temperatures in air on a thermoset showed that MTPES is oxidatively stable to 300°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2488–2492, 2006     

两种甲基苯乙炔硅烷的共聚物酰亚胺改性研究

以苯乙炔与甲基二氯硅烷、甲基三氯硅烷在有机锂试剂中反应,合成了甲基二苯乙炔基硅烷(MD-PES)和甲基三苯乙炔基硅烷(MTPES)2种新型耐高温有机硅树脂。TGA和500℃烧蚀测试经酰亚胺(Imide)改性的二者共聚物的复合材料表明:其耐热保持性优异,5%热失量温度最高可达643℃,800℃质量保留率可达94.7%;材料具有较好的力学性能,弯曲强度、硬度及冲击强度可分别达到235 MPa、61和104.5 kJ/m2;复合材料介电常数与介电损耗正切值变化较小,介电性能优异;饱和吸水率在1.15%~4.79%,耐湿性能优异。     

Synthesis,cure and pyrolysis behavior of heat‐resistant boron‐silicon hybrid polymer containing acetylene

The synthesis and characterization of a novel heat‐resistant boron‐silicon hybrid polymer containing acetylene (PBSA) and its conversion to a highly crosslinked thermoset were discussed. The polymer was synthesized from phenylboron dichloride using Grignard reagent method. The structure of PBSA was characterized by using Fourier transform infrared spectra, ¹H‐NMR, ¹³C‐NMR, and gel permeation chromatography. PBSA was thermosetting, highly heat‐resistant, high‐viscous, orange liquid at room temperature and good solubility in common organic solvents. Differential scanning calorimetry and thermogravimetric analysis analyses showed that the PBSA had excellent thermal and oxidative stability and the temperature of 5% weight loss (Td₅) were 650 and 638°C under nitrogen and air, respectively, and the residue at 1000°C were 93.3 and 91.3%, respectively, which indicated that the incorporation of boron and silicon into polymeric backbone was found to improve thermal and oxidative properties. X‐ray diffraction and scanning electron microscope were also used to analyze the formation of pyrolytic products. The results showed that the pyrolysis of PBSA resin was made up of β‐SiC and graphite. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High‐resolution thermogravimetry of poly(4‐methyl‐1‐pentene)

Thermal degradation and kinetics of poly(4‐methyl‐1‐pentene) were investigated by nonisothermal high‐resolution thermogravimetry at a variable heating rate. Thermal degradation temperatures are higher, but the maximum degradation rates are lower in nitrogen than in air. The degradation process in nitrogen is quite different from that in air. The average activation energy and frequency factor of the first stage of thermal degradation for the poly(4‐methyl‐1‐pentene) are 2.4 and 2.8 times greater in air than those in nitrogen, respectively. Poly(4‐methyl‐1‐pentene) exhibits almost the same decomposition order of 2.0 and char yield of 14.3–14.5 wt % above 500°C in nitrogen and air. The isothermal lifetime was estimated based on the kinetic parameters of nonisothermal degradation and compared with the isothermal lifetime observed experimentally. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2201–2207, 1999     

聚甲基(对甲苯基)硅烷的合成与荧光性质

采用钠缩合法，将甲基(对甲苯基)二氟硅烷进行均聚，或分别与二甲基二氟硅烷、甲基苯基二氯硅烷、二苯基二氯硅烷进行共聚，合成了4种聚硅烷。用^1HNMR、IR、GPC进行了结构表征，并研究了聚硅烷固体和溶液的荧光性质。结果表明，聚硅烷的聚集态和构象对其荧光性质有较显著的影响。苯基对位甲基的给电子效应使最大荧光发射波长(λmax)略有红移；侧基的共轭作用和分子对称性可能也对其固体和溶液的λmax有较大影响；链长较长的聚硅烷荧光强度较大。     

N‐(2‐biphenylenyl)‐4‐[2′‐phenylethynyl] phthalimide: 2. Detailed study of the monomer cure and properties of the resulting polymer

A detailed study is presented of the high‐temperature cure of the difunctional monomer N‐(2‐biphenylenyl)‐4‐[2′‐phenylethynyl]phthalimide (BPP) and the thermal properties of the resulting homopolymer. Although the phenylethynyl groups are consumed within 1 h at 370 °C, other reactions continue well after this, leading to a cured polymer whose glass transition temperature (T_g) is highly dependent on cure time and temperature. A T_g of 450 °C is achieved after a 16 h cure at 400 °C. Use of chemometrics to analyse the infrared spectra of curing BPP provides evidence for changes in the aromatic moieties during cure, perhaps indicative of co‐reaction between the biphenylene and phenylethynyl groups; however, other processes also contribute to the overall complex cure mechanism. Despite the high T_g values, BPP homopolymer exhibits unacceptably poor thermo‐oxidative stability at 370 °C, showing a weight loss of about 50 % after 100 h ageing. This is perhaps a result of formation of degradatively unstable crosslink structures during elevated‐temperature cure. Copyright © 2004 Society of Chemical Industry     

Synthesis and thermal properties of poly(methyl methacrylate)‐poly(L‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer

Poly(methyl methacrylate)‐poly(L ‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer was prepared using atom transfer radical polymerization (ATRP). The structure and properties of the copolymer were analyzed using infrared spectroscopy, gel permeation chromatography, nuclear magnetic resonance (¹H‐NMR, ¹³C‐NMR), thermogravimetry, and differential scanning calorimetry. The kinetic plot for the ATRP of methyl methacrylate using poly(L ‐lactic acid) (PLLA) as the initiator shows that the reaction time increases linearly with ln[M]₀/[M]. The results indicate that it is possible to achieve grafted chains with well‐defined molecular weights, and block copolymers with narrowed molecular weight distributions. The thermal stability of PLLA is improved by copolymerization. A new wash‐extraction method for removing copper from the ATRP has also exhibits satisfactory results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal and electrical properties of copoly(1,3,4‐oxadiazole‐ethers) containing fluorene groups

A series of aromatic copolyethers containing 1,3,4‐oxadiazole rings and fluorene groups was prepared by nucleophilic substitution polymerization technique of 9,9‐bis(4‐hydroxyphenyl)fluorene, 1 , or of different amounts of 1 and an aromatic bisphenol, such as 4,4′‐isopropylidenediphenol or phenolphthalein, with 2,5‐bis(p‐fluorophenyl)‐1,3,4‐oxadiazole. The polymers were easily soluble in polar solvents like N‐methylpyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, and chloroform and can be cast from solutions into thin flexible films. They showed high thermal stability, with decomposition temperature being above 425°C. The polymers exhibited a glass‐transition temperature in the range of 195–295°C, with a reasonable interval between glass‐transition and decomposition temperature. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz and 20°C were in the range of 3.16–3.25. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polymerization of methyl methacrylate with a thermal iniferter: Diethyl 2,3‐dicyano‐2,3‐di(p‐tolyl)succinate

A hexa‐substituted ethane type compound, diethyl‐2,3‐dicyano‐2,3‐di(p‐tolyl)succinate (DCDTS), was successfully synthesized and used for initiation of methyl methacrylate (MMA) polymerization. The reaction demonstrated the characteristics of a “living” polymerization; i.e., both the yield and the molecular weight of the resulting polymers increased linearly with increasing reaction time, the molecular‐weight distribution of PMMA obtained was ～1.60 and almost unaffected by the conversion, and the resultant polymer can be chain extended by adding fresh MMA. End group analysis of the resultant PMMA confirmed that DCDTS behaves as a thermal iniferter for MMA polymerization. A block copolymer was prepared from the resultant PMMA, which contains a hexa‐substituted C? C bond functional end group. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2566–2572, 2001     

Thermal degradation and pyrolysis study of phosphorus‐containing polysulfones

This article deals with the thermal decomposition behavior of a polysulfone containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide versus the initial chloromethylated polysulfone under an inert atmosphere and in air. Thermogravimetric characteristics from thermogravimetry and differential thermogravimetry data revealed important differences related to the employed atmosphere, the types of substituted functional groups, or the degree of substitution. The introduction of the 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide pendent group into polysulfone enhanced the thermal stability of the initial chloromethylated polysulfone in both an inert atmosphere and air. Thermal degradation in nitrogen consisted of one degradation step, whereas thermooxidative degradation in air involved more steps. In air, the degradation mechanism was more complex. The volatile products and solid residues that resulted after pyrolysis in an inert atmosphere and in air were analyzed with Fourier transform infrared and mass spectrometry. Environmental scanning electron microscopy showed that the char residues had different morphologies, which suggested that a more compact structure led to better resistance to heat and oxygen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011     

Synergistic extraction of rare earths(III) from chloride medium with mixtures of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate

The synergistic effect of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 (HPMBP, HA) and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate (DEHEHP, B) in the extraction of rare earths (RE) from chloride solutions has been investigated. Under the experimental conditions used, there was no detectable extraction when DEHEHP was used as a single extractant while the amount of RE(III) extracted by HPMBP alone was also low. But mixtures of the two extractants at a certain ratio had very high extractability for all the RE(III). For example, the synergistic enhancement coefficient was calculated to be 9.35 for Y³⁺, and taking Yb³⁺ and Y³⁺ as examples, RE³⁺ is extracted as RE(OH)A₂.B. The stoichiometry, extraction constants and thermodynamic functions such as Gibbs free energy change ΔG (?17.06 kJ mol^?1), enthalpy change ΔH (?35.08 kJ mol^?1) and entropy change ΔS (?60.47 J K^?1 mol^?1) for Y³⁺ at 298 K were determined. The separation factors (SF) for adjacent pairs of rare earths were calculated. Studies show that the binary extraction system not only enhances the extraction efficiency of RE(III) but also improves the selectivity, especially between La(III) and the other rare earth elements. Copyright © 2006 Society of Chemical Industry     

Novel reworkable resins: thermo‐ and photo‐curable di(meth)acrylates

The aim of the study reported in this paper was to develop new di(meth)acrylates having aromatic units and thermally degradable units in their molecules. It was also the aim to clarify the photo‐curing and degradation properties of the new monomers. Di(meth)acrylates having aromatic units and thermally degradable units were synthesized. As thermally cleavable linkages, tertiary ester moieties were incorporated into the di(meth)acrylates. Three types of processes for curing and degradation of the cured resins were studied: thermal curing and thermal degradation; thermal curing and photodegradation; and photo‐curing and thermal degradation. In the thermal curing and photodegradation process, di(meth)acrylate films containing a thermally induced radical initiator and a photoacid generator (PAG) became insoluble in solvents on heating. The cured films became soluble in solvents after ultraviolet irradiation followed by baking. The re‐dissolution behaviors were strongly affected by the structures of the PAGs. A mechanism for the photo‐ or thermo‐curing and photoassisted thermal degradation was studied using Fourier transform infrared, ¹H NMR, thermogravimetric, mass spectrometric and size exclusion chromatographic analyses. Copyright © 2009 Society of Chemical Industry     

5,12-(二苯乙炔基)丁省的合成及其化学发光

由邻苯二甲酸酐与萘作用生成2-α-萘羰基苯甲酸,产率63%。2-α-萘羰基苯甲酸在无水A lC l3、NaC l催化下脱水重排,得到5,12-丁省醌,产率68%。5,12-丁省醌与苯乙炔基锂在二氧六环,DMF中反应4 h,水解后的混合物不经分离直接与氯化亚锡的盐酸溶液避光反应10 h,一步法合成目标物,收率53%。     

Thermal characteristics of interpenetrating polymer networks composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

Interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by the sequential‐IPN method. The thermal characterization of the IPNs was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depression of the melting temperature (T_m) of the PVA segment in IPNs was observed with increasing PNIPAAm content using DSC. DEA was employed to ascertain the glass‐transition temperature (T_g) of IPNs. From the result of DEA, IPNs exhibited two T_g values, indicating the presence of phase separation in the IPNs. The thermal decomposition of IPNs was investigated using TGA and appeared at near 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 881–885, 2003     

The reaction mechanism of diethyl‐2,3‐dicyano‐2,3‐di(p,m‐dimethoxylphenyl) succinate with styrene

The radical polymerization of styrene (ST) can be initiated by diethyl‐2,3‐dicyano‐2,3‐di(dimethoxyphenyl) succinate (ECPS). The reaction mechanism has been studied by means of UV, H¹‐NMR, product analysis, gel permeation chromatography, electronic spin resonance (ESR), and the conversion of monomer via time. These experimental results indicate that ECPS probably takes the place of complex with ST, and the complex interaction between ECPS and ST can take advantage of the dissociation of the C C bond. The complex interaction and thermal effect are the important factors causing the dissociation of C C bond. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1140–1145, 1999     

Biodegradable poly(ester‐ether)s: ring‐opening polymerization of D,L‐3‐methyl‐1,4‐dioxan‐2‐one using various initiator systems

The synthesis and detailed characterization of racemic 3‐methyl‐1,4‐dioxan‐2‐one (3‐MeDX) are reported. The bulk ring‐opening polymerization of 3‐MeDX, to yield a poly(ester‐ether) meant for biomedical applications, in the presence of various initiators such as tin(II) octanoate, tin(II) octanoate/n‐butyl alcohol, aluminium tris‐isopropoxide and an aluminium Schiff base complex (HAPENAlOⁱPr) under varying experimental conditions is here detailed for the first time. Polymerization kinetics were investigated and compared with those of 1,4‐dioxan‐2‐one. The studies reveal that the rate of polymerization of 3‐MeDX is less than that of 1,4‐dioxan‐2‐one. Experimental conditions to achieve relatively high molar masses have been established. Thermodynamic parameters such as enthalpy and entropy of 3‐MeDX polymerization as well as ceiling temperature have been determined. Poly(D ,L ‐3‐MeDX) is found to possess a much lower ceiling temperature than poly(1,4‐dioxan‐2‐one). Poly(D ,L ‐3‐MeDX) was characterized using NMR spectroscopy, matrix‐assisted laser desorption ionization mass spectrometry, size exclusion chromatography and differential scanning calorimetry. This polymer is an amorphous material with a glass transition temperature of about ?20 °C. Copyright © 2010 Society of Chemical Industry