Aromatic polyamides. XI. Effect of the halogen substitution on the thermal and flammability behavior of poly(1,4-phenylene terephthalamide)

This article concerns the synthesis and characterization of poly(1,4-phenylene terephthalamide) and halogenated derivatives thereof. It was found that the halogen substitution affected significantly the thermal characteristic and flame resistance of that polyamide. In a nonoxygen atmosphere two-step decomposition process for the halogenated, while only one-step for unsubstituted polyamides were observed. The results supported the previous suggestion, that in the case of the halogenated polyamides the char yield enhancement and the flame resistance improvement are associated with halogen release and ring-forming reactions during their pyrolysis.     

Nonadiabatic dynamics in the CH3+HCl-->CH4+Cl(2PJ) reaction

Nonadiabatic dynamics in the title reaction have been investigated by 2+1 REMPI detection of the Cl(2P(3/2)) and Cl*(2P(1/2)) products. Reaction was initiated by photodissociation of CH(3)I at 266 nm within a single expansion of a dilute mixture of CH(3)I and HCl in argon, giving a mean collision energy of 7800 cm(-1) in the center-of-mass frame. Significant production of Cl* was observed, with careful checks made to ensure that no additional photochemical or inelastic scattering sources of Cl* perturbed the measurements. The fraction of the total yield of Cl(2P(J)) atoms formed in the J=1/2 level at this collision energy was 0.150+/-0.024, and must arise from nonadiabatic dynamics because the ground potential energy surface correlates to CH(4)+Cl(2P(3/2)) products.     

Thermal properties of wholly aromatic polyamides

Various wholly aromatic polyamides based on m-and p-phenylene diamines and isophthaloyl and terephthaloyl chloride have been synthesized and their thermal properties and oxygen index values have been studied. The effect of different substituents on the aromatic ring of the diamine have been explored by comparing their differential thermal analysis (DTA) and thermogravimetric analysis (TGA) behavior, their relative char yields at 700°C, and their oxygen indices. The ? Cl, ? NO₂, and ? OH substituted polyamides have been found to produce the highest char yields. The high char yields are probably associated with crosslinking occurring at high temperatures. Attempts at correlating char yield with oxygen index indicated enhancement for the chlorosubstituted aramids.     

Pionic Kα X-ray energy and linewidth IN 20Ne and 22Ne

We have measured the energies and linewidths of the pionic K_α X-rays for ²⁰Ne and ²²Ne using a natural liquid-neon target. The results are

     

115.

新型正极材料三硫代环磷氮烯无机聚合物的合成   总被引：1，自引：0，他引：1  

徐国祥  其鲁  闻雷  陈永翀  晨晖  慈云祥 《无机化学学报》2005,21(11):1609-1613

采用缩合聚合方法合成了新型三硫代环磷氮烯无机聚合物[(NPS₃)₃]_n，利用红外光谱测试与元素含量分析技术证明了[(NPS₃)₃]_n的分子结构与组成，并对聚合物材料的粒度、比表面积及微观形貌进行了考察。TG/DTA 实验证明材料在200 ℃ 以下具有良好的热稳定性。循环伏安测试表明[(NPS₃)₃]_n正极材料在锂电池体系具有2.15 V的电化学还原电位和2.45 V的电化学氧化电位，经充放电循环实验观察，材料的首次放电容量达到749.0 mAh·g^-1，与理论容量(759.0 mAh·g^-1)十分接近；经过50次充放电循环后，放电容量保持在674.8 mAh·g^-1，具有很高的使用容量和优秀的循环性能。     

116.

Thermal oxidation of blends of poly(vinyl methyl ether) and modified polystyrenes     

Hyunkil Park  Eli M. Pearce  W. H. Starnes  T. K. Kwei 《Journal of polymer science. Part A, Polymer chemistry》1990,28(5):1079-1089

Thermal oxidation of blends of poly(vinyl methyl ether) and styrene copolymers containing hydroxyl groups as hydrogen-bond donors was studied. The hydrogen-bonding interaction provide for improved miscibility between the component polymers and more extensive crosspropagation/cross-termination reactions. In addition to their contribution to improved miscibility, phenol groups in the copolymers exhibited apparent antioxidant and prooxidant effects.     

117.

Inequalities for the Perimeter of an Ellipse     

Roger W. Barnard  Kent Pearce  Lawrence Schovanec 《Journal of Mathematical Analysis and Applications》2001,260(2):295

     

118.

Recent developments in entropy‐driven ring‐opening metathesis polymerization: Mechanistic considerations,unique functionality,and sequence control     

Amanda K. Pearce  Jeffrey C. Foster  Rachel K. O'Reilly 《Journal of polymer science. Part A, Polymer chemistry》2019,57(15):1621-1634

Entropy‐driven ROMP (ED‐ROMP) involves polymerization of olefin‐containing macrocyclic monomers under entropically favorable conditions. Macrocycles can be prepared from a variety of interesting molecules which, when polymerized, impart unique functionality to the resulting polymer backbone such as degradable linkages, biological moieties, crystallizable groups, or supramolecular hosts. In addition, the sequence of atoms in the cyclic monomer is preserved within the polymer repeating units, allowing for facile preparation of sequence‐defined polymers. In this review article, we consider how the mechanism of ROMP applies to ED polymerizations, how olefinic macrocycles are synthesized, and how polymerization conditions can be tuned to maximize conversion. Recent works in the past 10 years are highlighted, with emphasis on methods which can be employed to achieve fast polymerization kinetics and/or selective head‐to‐tail regiochemistry, thus improving polymerization control. ED‐ROMP, with its unique capability to produce polymers with well‐defined polymer backbone microstructure, represents an essential complement to other, well‐established, metathesis methodologies such as ROMP. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1621–1634     

119.

Role of self‐assembly conditions and amphiphilic balance on nanoparticle formation of PEG‐PDLLA copolymers in aqueous environments     

Hien Phan  Robert I. Minut  Phoebe McCrorie  Catherine Vasey  Ryan R. Larder  Eduards Krumins  Maria Marlow  Ruman Rahman  Cameron Alexander  Vincenzo Taresco  Amanda K. Pearce 《Journal of polymer science. Part A, Polymer chemistry》2019,57(17):1801-1810

The production of well‐defined and reproducible polymeric nanoparticles (NPs), in terms of size and stability in biological environments, is undoubtedly a fundamental challenge in the formulation of novel and more effective nanomedicines. The adoption of PEGylated lactide (LA) block copolymers as biodegradable and biocompatible nanocarriers at different clinical stages has rendered these materials an attractive polymeric platform to be exploited and their formulation is further understood. In the present work, we synthesized a library of linear polyethylene glycol‐poly(D,L‐lactide) block copolymers with different lengths of LA (15, 25, 50, and 100 LA units) via simple and metal‐free ring‐opening polymerization, in order to alter the amphiphilic balance of the different macromolecules. The produced polymers were formulated into NPs while varying a series of key parameters in the solvent displacement process, including solvent:nonsolvent ratios and the nature of the two media, and the effect on size and stability was assessed. In addition, stability to protein–NPs interaction and aggregation was studied, highlighting the different NP final properties according to the nature of the amphiphilic balance and nanoformulation conditions. Therefore, we have illustrated a systematic and methodological process to optimize a series of NPs parameters balancing particle size, size distribution, surface charge, and stability to guide future works in the nanoformulation field. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1801–1810     

120.

Isotopically characterised N2O reference materials for use as community standards     

Joachim Mohn  Christina Biasi  Samuel Bodé  Pascal Boeckx  Paul J. Brewer  Sarah Eggleston  Heike Geilmann  Myriam Guillevic  Jan Kaiser  Kristýna Kantnerová  Heiko Moossen  Joanna Müller  Mayuko Nakagawa  Ruth Pearce  Isabell von Rein  David Steger  Sakae Toyoda  Wolfgang Wanek  Sarah K. Wexler  Naohiro Yoshida  Longfei Yu 《Rapid communications in mass spectrometry : RCM》2022,36(13):e9296

     

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20Ne	22Ne
Neenergy (keV)	239.12±0.14	230.49±0.88
width (keV)	15.43±0.41	12.65±3.51

新型正极材料三硫代环磷氮烯无机聚合物的合成

采用缩合聚合方法合成了新型三硫代环磷氮烯无机聚合物[(NPS₃)₃]_n，利用红外光谱测试与元素含量分析技术证明了[(NPS₃)₃]_n的分子结构与组成，并对聚合物材料的粒度、比表面积及微观形貌进行了考察。TG/DTA 实验证明材料在200 ℃ 以下具有良好的热稳定性。循环伏安测试表明[(NPS₃)₃]_n正极材料在锂电池体系具有2.15 V的电化学还原电位和2.45 V的电化学氧化电位，经充放电循环实验观察，材料的首次放电容量达到749.0 mAh·g^-1，与理论容量(759.0 mAh·g^-1)十分接近；经过50次充放电循环后，放电容量保持在674.8 mAh·g^-1，具有很高的使用容量和优秀的循环性能。     

Thermal oxidation of blends of poly(vinyl methyl ether) and modified polystyrenes

Thermal oxidation of blends of poly(vinyl methyl ether) and styrene copolymers containing hydroxyl groups as hydrogen-bond donors was studied. The hydrogen-bonding interaction provide for improved miscibility between the component polymers and more extensive crosspropagation/cross-termination reactions. In addition to their contribution to improved miscibility, phenol groups in the copolymers exhibited apparent antioxidant and prooxidant effects.     

Recent developments in entropy‐driven ring‐opening metathesis polymerization: Mechanistic considerations,unique functionality,and sequence control

Entropy‐driven ROMP (ED‐ROMP) involves polymerization of olefin‐containing macrocyclic monomers under entropically favorable conditions. Macrocycles can be prepared from a variety of interesting molecules which, when polymerized, impart unique functionality to the resulting polymer backbone such as degradable linkages, biological moieties, crystallizable groups, or supramolecular hosts. In addition, the sequence of atoms in the cyclic monomer is preserved within the polymer repeating units, allowing for facile preparation of sequence‐defined polymers. In this review article, we consider how the mechanism of ROMP applies to ED polymerizations, how olefinic macrocycles are synthesized, and how polymerization conditions can be tuned to maximize conversion. Recent works in the past 10 years are highlighted, with emphasis on methods which can be employed to achieve fast polymerization kinetics and/or selective head‐to‐tail regiochemistry, thus improving polymerization control. ED‐ROMP, with its unique capability to produce polymers with well‐defined polymer backbone microstructure, represents an essential complement to other, well‐established, metathesis methodologies such as ROMP. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1621–1634     

Role of self‐assembly conditions and amphiphilic balance on nanoparticle formation of PEG‐PDLLA copolymers in aqueous environments

The production of well‐defined and reproducible polymeric nanoparticles (NPs), in terms of size and stability in biological environments, is undoubtedly a fundamental challenge in the formulation of novel and more effective nanomedicines. The adoption of PEGylated lactide (LA) block copolymers as biodegradable and biocompatible nanocarriers at different clinical stages has rendered these materials an attractive polymeric platform to be exploited and their formulation is further understood. In the present work, we synthesized a library of linear polyethylene glycol‐poly(D,L‐lactide) block copolymers with different lengths of LA (15, 25, 50, and 100 LA units) via simple and metal‐free ring‐opening polymerization, in order to alter the amphiphilic balance of the different macromolecules. The produced polymers were formulated into NPs while varying a series of key parameters in the solvent displacement process, including solvent:nonsolvent ratios and the nature of the two media, and the effect on size and stability was assessed. In addition, stability to protein–NPs interaction and aggregation was studied, highlighting the different NP final properties according to the nature of the amphiphilic balance and nanoformulation conditions. Therefore, we have illustrated a systematic and methodological process to optimize a series of NPs parameters balancing particle size, size distribution, surface charge, and stability to guide future works in the nanoformulation field. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1801–1810