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951.
Tsuneyuki Sato Yoshinori Maeda Makiko Seno Tomohiro Hirano 《Journal of polymer science. Part A, Polymer chemistry》2001,39(13):2196-2205
The polymerization of N‐methyl‐α‐fluoroacrylamide (NMFAm) initiated with dimethyl 2,2′‐azobisisobutyrate (MAIB) in benzene was studied kinetically and with electron spin resonance. The polymerization proceeded heterogeneously with the highly efficient formation of long‐lived poly(NMFAm) radicals. The overall activation energy of the polymerization was 111 kJ/mol. The polymerization rate (Rp) at 50 °C is given by Rp = k[MAIB]0.75±0.05 [NMFAm]0.44±0.05. The concentration of the long‐lived polymer radical increased linearly with time. The formation rate (Rp?) of the long‐lived polymer radical at 50 °C is expressed by Rp? = k[MAIB]1.0±0.1 [NMFAm]0±0.1. The overall activation energy of the long‐lived radical formation was 128 kJ/mol, which agreed with the energy of initiation (129 kJ/mol), which was separately estimated. A comparison of Rp? with the initiation rate led to the conclusion that 1‐methoxycarbonyl‐1‐methylethyl radicals (primary radicals from MAIB), escaping from the solvent cage, were quantitatively converted into the long‐lived poly(NMFAm) radicals. Thus, this polymerization involves completely unimolecular termination due to polymer radical occlusion. 1H NMR‐determined tacticities of resulting poly(NMFAm) were estimated to be rr = 0.34, mr = 0.48, and mm = 0.18. The copolymerization of NMFAm(M1) and St(M2) with MAIB at 50 °C in benzene gave monomer reactivity ratios of r1 = 0.61 and r2 = 1.79. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2196–2205, 2001 相似文献
952.
Hajime Yasuda 《Journal of polymer science. Part A, Polymer chemistry》2001,39(12):1955-1959
The organo‐rare‐earth‐metal‐initiated living polymerization of methyl methacrylate (MMA) was first discovered in 1992 with (C5Me5)2LnR (where R is H or Me and Ln is Sm, Yb, Y, or La) as an initiator. These polymerizations provided highly syndiotactic (>96%) poly(methyl methacrylate) (PMMA) with a high number‐average molecular weight (Mn > 1000 × 103) and a very narrow molecular weight distribution [weight‐average molecular weight/number‐average molecular weight (Mw/Mn) < 1.04] quantitatively in a short period. Bridged rare‐earth‐metallocene derivatives were used to perform the block copolymerization of ethylene or 1‐hexene with MMA, methyl acrylate, cyclic carbonate, or ?‐caprolactone in a voluntary ratio. Highly isotactic (97%), monodisperse, high molecular weight (Mn > 500 × 103, Mw/Mn < 1.1) PMMA was first obtained in 1998 with [(Me3Si)3C]2Yb. Stereocomplexes prepared by the mixing of the resulting syndiotactic and isotactic PMMA revealed improved physical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1955–1959, 2001 相似文献
953.
对由原子转移自由基聚合(ATRP)方法得到的具有“活性”聚合特征的对-氯苯乙烯(S)和丙烯酸甲酯(M)梯度共聚物结构进行了表征.通过1H、13C 核磁共振(NMR)方法和对羰基13C峰峰面积的拟合积分研究了该共聚物的单体以及以M为中心的三元组序列结构的组成含量随转化率的变化.研究结果表明:共聚物链中S和M单体含量随着转化率的增加分别表现出减小和增大的变化趋势;三元组序列结构的含量变化中,SMS和MMM分别呈现出单调下降和上升的变化,而MM/MMS则随着转化率的增加达到一个最大值,然后呈现下降趋势.本文还尝试运用了以M为中心的五元组序列结构对羰基13C峰峰面积进行更精确的拟合积分,其拟合峰面积的计算结果显示了与上述三元组序列结果相同的变化规律. 相似文献
954.
噻吩含氮衍生物在菜籽油中的摩擦学行为 总被引:4,自引:2,他引:2
利用四球摩擦磨损试验机考察了所合成添加剂[S-(2H-噻吩-2-基)甲基]N、N-二烷基二硫代氨基甲酸酯和噻吩对菜籽油摩擦学性能的影响以及添加剂结构和性能的关系,用X射线光电子能谱仪和扫描电子显微镜观察分析了磨损表面的形貌和元素化学状态。结果表明:噻吩/菜籽油润滑剂对钢-钢摩擦副有增摩促磨作用,而噻吩氨基甲酸酯衍生物添加剂在适当浓度下可改善菜籽油的减摩抗磨性能和承载能力;含上述添加剂的菜籽油在摩擦过程中发生摩擦化学反应,生成由菜籽油甘油酯和添加剂摩擦化学反应产物组成的边界润滑膜,从而改善菜籽油的摩擦学性能。 相似文献
955.
956.
957.
甲基苯基碳酸酯标准品的制备及其定量分析 总被引:5,自引:0,他引:5
利用甲基苯基碳酸酯(MPC)歧化反应的可逆性及逆反应在热力学上有利进行的特点,提出了以碳酸二甲酯 (DMC)和碳酸二苯酯 (DPC)为原料,在TiO2/SiO2催化下合成DMC与苯酚酯交换反应的中间产物MPC的新方法。反应产物经减压精馏、碱洗、水洗、干燥等精制处理,得到了纯度较高的MPC标准品。采用气相色谱-质谱法对所制备的MPC样品进行定性分析,结果表明其中还含有少量的苯酚和DPC杂质。卡尔·费休水分测定结果表明,MPC样品中的含水量为0.26%(质量分数)。使用常规气相色谱仪,采用OV-101毛细管色谱柱,以苯甲酸乙酯为内标物,对自制的MPC标准品中的微量苯酚和DPC进行定量分析,苯酚和DPC的含量分别为2.04%和1.59%(均为质量分数)。根据杂质分析结果可知自制的MPC标准品的纯度为96.11%。以此作为标准品,解决了对DMC与苯酚酯交换反应的中间产物MPC的准确定量问题。 相似文献
958.
PP-b-PMMA has been synthesized by a combination of metallocene catalysis and the controlled radical polymerization technique ATRP. Cp2ZrCl2/MAO and (Me4Cp)SiMe2(N-tert-Bu)TiCl2/MAO were used for the synthesis of atactic polypropylene. By a series of chemical modifications pp macroinitiators for the ATRP polymerization of MMA were synthesized. The PP-b-PMMA with polydispersities from 1.8–2.8 and an Mn ranging from 8 to 26 kg/mol was characterized by 1H-NMR,SEC and DSC. 相似文献
959.
Copolymers and terpolymers of N-t-butylacrylamide (TBA) with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and N-hydroxy methyl acrylamide (NHMAAM) were prepared by solution polymerization in a 1:1 (v/v) mixture of methanol and water at 50 °C keeping the TBA content in the feed constant at 60% based on mole ratio. The contents of AMPS or NHMAAM used for the preparation of TBA-AMPS and TBA-NHMAAM copolymers were 40 mole %. Molar percentages of AMPS and NHMAAM monomers in the feed for the preparation of TBA-AMPS-NHMAAM terpolymers were varied as 10:30, 20:20, and 30:10, respectively. The effects of temperature, AMPS and crosslinker contents, and the drying of swollen gels on the swelling behavior of ionic and non-ionic TBA gels were investigated in distilled water between 10–50 °C and in buffer solutions having various pHs (1.9, 3.1, 5.6, 7.1, and 9.8) with constant ionic strength of 0.08 M at 20 °C using both the dry and the swollen forms of gels. The chemical structures and microscopic morphologies of the polymers were investigated by FTIR and SEM, respectively. 相似文献
960.