共查询到20条相似文献,搜索用时 109 毫秒
1.
2.
乙烯系单体自由基聚合的阻聚效应 Ⅹ.羟胺类化合物对苯乙烯自由基聚合的阻聚及历程 总被引:5,自引:0,他引:5
The inhibiting effects of N,N'-diethydroxylamine(DEHA), N,N'-diisopropylhydroxylamine (DIPHA), 2,2,6,6-tetramethyl-4-hydroxyl-piperidinhydroxylarnine (TMHPHA), 4-hydroxyl-morpholine(MPHA), N-phenylhydroxylamine(PHA) and N, N'-diphenylhydroxylamine (DPHA), on the AIBN-initiated, bulk polymerization of styrene(St) have been studied by dilatomatric method. The inductive period of polymerization(ti), the rate of propagating after the ti(Rp), the MW of polystyrene (Mn) the retardating coefficient (K) and the inhibi-ting factor (F) have been obtained. The results reveal that R2NOH have been proved to be very efficient inhibitors and their inhibiting efficiency have been found to depend on the rate and stability of the nitroxide radical formed in reaction. Relative inhibiting reactiveties of several R2NOH have been determined as in the following order; DEHA>TMHPHA>DPHA>DIPHA>MPHA. Other stable nitroxides formed in polymerization of St inthe pre-sence of several R2NOH have also been indentified by ESR and mechanism of inhibition and retardation has been discussed. 相似文献
3.
乙烯系单体自由基聚合的阻聚效应──XIX.取代哌啶羟胺和二叔丁基羟胺及其稳定自由基对苯乙烯-丙烯腈共聚合的影响 总被引:3,自引:0,他引:3
研究了二叔丁基羟胺(DTBHA),二叔丁基氮氧自由基(DTBNO),2,2,6,6-四甲基-4-羟基哌啶羟胺(TMHPHA)和2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基(TMHPO)对过氧化苯甲酰(BPO)60℃引发的苯乙烯(M1)-丙烯腈(M2)共聚合的阻聚物行为。结果表明,这些阻聚剂对St-AN共聚均表现良好的阻聚行为,其中氮氧自由基优于相应羟胺。同时观察到St-AN竞聚率的改变,羟胺 相似文献
4.
5.
6.
利用正丁基锂(n-BuLi)与炭黑(CB)表面含氧基团反应制得了表面含-OLi基团的反应型炭黑,以该炭黑与聚氧乙烯-聚氧丙烯-聚苯乙烯(PEO-PPO-PS)多嵌段聚合物组成的阴离子引发体系作活性中心,研究了苯乙烯在炭黑表面的阴离子接枝聚合。FT-IR,TEM和DSC分析表明在接枝炭黑表面存在苯乙烯的聚合物。接枝炭黑在甲苯中有良好的分散稳定性。 相似文献
7.
在UV光照射下, 以Irgacure 1103/TEMPO为引发剂, 实现了苯乙烯的低温光引发可控聚合, 得到了低分散性的聚苯乙烯. 与热引发聚合相比较, 光聚合的反应条件更温和, 聚合速率更快. 探讨了聚合体系中光引发剂及光强等因素的影响, 实现了光聚合产物的扩链反应. 相似文献
8.
10.
本文研究了二甲基硅二苯基硅共聚物(P(DMS-co-DPS))作为光敏引发剂,引发苯乙烯进行光聚合的过程。结果表明,聚合为自由基引发的链式反应,聚合速率与P(DMS-co-DPS)浓度的0.37次方成正比;本体聚合活化能为30.6KJ/mol,氧气对聚合无明显影响。 相似文献
11.
12.
引发剂结构对原子转移自由基聚合反应的影响 总被引:4,自引:0,他引:4
研究了三种不同结构的引发剂,溴代乙酸乙酯(EBrA)、α-溴代丁乙酯(EBrB)、α-溴代异丁酸乙酸(EBriB)引发的苯乙烯的原子转移自由基聚合反应(ATRP)。发现EBrA引发的苯乙烯的ATRP不是“活性”聚合。EBriB引发的苯乙烯的ATRP引发效率不够高,也不是典型的“活性”聚合。EBrB引发的苯乙烯的ATRP是较为典型的“活性”聚合:聚合物的分子量可以通过调节单体/引发剂的投料量及反应时间来控制,所得聚合物的分子量分布很窄,且有随转化率的增加而逐渐变窄的趋势。 相似文献
13.
F. David-Quillot A. Duchêne J.-M. Catala A. Balland-Longeau J. Thibonnet 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):461-467
Fourteenth group oganometallic styrene derivatives were synthesised by nitroxide-mediated controlled radical polymerization using di-tert butyl nitroxide (A-T) as initiator. This is the first time that nitroxide-controlled radical polymerization has been successfully adapted for the synthesis of new polystyrenes bearing organometallic species with controlled molecular weights and narrow polydispersities. Monomer reactivity ratios were determined in controlled nitroxide-mediated radical copolymerization between styrene and substituted styrene. All experiments permitted the synthesis of new organometallic polymers that will be used for the development of a polymer capsule for Inertial Confinement Fusion Experiments. 相似文献
14.
A bifunctional alkyl halide, namely l, 2-bis(2′-bromobutyryl) ethane (BBrBE), was synthesized and used to initiate the bulk atom transfer radical polymerization (ATRP) of styrene (St) at 110°C in the presence of CuBr/2,2′-bipyridyl. The narrow polydispersity of polystyrene (PSt) with precisely two arms could be synthesized. The initiate ability of the two active bromide functional groups at both sides of BBrBE for St and the propagation ability of the two arms were confirmed to be similar by the characterization of the individual arms obtained upon hydrolysis of the ester link between the core and the branches. 相似文献
15.
Batch and semibatch styrene polymerizations are carried out using a heterogeneous ATRP catalyst system that provides excellent molecular‐weight control. The observed initiator efficiency is lower for semibatch operation due to the high initiator concentrations required to make a low‐MW polymer. Experiments verified that the insoluble metal complex does not participate in the polymerization and that Cu(I) solubility is an order of magnitude higher than that of Cu(II). A mechanistic model, using kinetic coefficients from literature and the solubility data from this study, provides a good representation of the experimental results.
16.
NMRP is a controlled polymerization technique with the ability to produce polymers with a highly controlled microstructure. The properties of the thus obtained polymers make it desirable to scale this technique to an industrial level, but there are still some challenges to be faced, e.g., to develop emulsion NMRP at low temperatures (lower than about 100 °C) with inexpensive, commercially available nitroxides such as TEMPO. Here, the emulsion NMRP of styrene using TEMPO at temperatures lower than 100 °C is described. An optimal control of molecular weights and polydispersities and a fast polymerization rate are obtained.
17.
以不同结构的含氯化合物与铜试剂反应合成了4种链引发-转移-终止剂(Iniferter)。研究了它们引发苯乙烯的聚合反应过程,重点考察了Iniferter结构对聚合产物的影响。采用核磁共振氢谱和凝胶渗透色谱对聚合物分子量和分子量分布进行了测定。结果表明:Iniferter结构对聚合反应速率、分子量实测值与理论值间的对应关系及分子量分布均有明显影响,当其形成的初级自由基上带有使其稳定的基团时,引发效率就高,聚合反应速率较快,而且分子量理论值与实测值两者更接近。加入四甲基秋兰姆化二硫组成双组份Iniferter引发体系可以在一定程度上使聚合物分子量分布变窄。 相似文献
18.
A Study on Anti-oxidative Activity of Soybean Peptides with Linoleic Acid Peroxidation Systems 总被引:3,自引:0,他引:3
Introduction Freeradicalsproducedbyperoxidationcancause cellulardamageandforfeitureofavarietyofphysiologi calfunctions[1,2].Inrecentyears,ithasbeenreported thatsomenon enzymicsmallmolecularcompounds,suchasVitaminC(VC)andVitaminE(VE),glutathi one(GSH),SODm… 相似文献
19.
Enrique Saldívar‐Guerra Jos Bonilla Fabiola Becerril Gregorio Zacahua Martha Albores‐Velasco Roberto Alexander‐Katz Leticia Flores‐Santos Larissa Alexandrova 《Macromolecular theory and simulations》2006,15(2):163-175
Summary: The range of validity of two popular versions of the nitroxide quasi‐equilibrium (NQE) approximation used in the theory of kinetics of alkoxyamine mediated styrene polymerization, are systematically tested by simulation comparing the approximate and exact solutions of the equations describing the system. The validity of the different versions of the NQE approximation is analyzed in terms of the relative magnitude of (dN/dt)/(dP/dt). The approximation with a rigorous NQE, kc[P][N] = kd[P N], where P, N and P N are living, nitroxide radicals and dormant species respectively, with kinetic constants kc and kd, is found valid only for small values of the equilibrium constant K (10−11–10−12 mol · L−1) and its validity is found to depend strongly of the value of K. On the other hand, the relaxed NQE approximation of Fischer and Fukuda, kc[P][N] = kd[P N]0 was found to be remarkably good up to values of K around 10−8 mol · L−1. This upper bound is numerically found to be 2–3 orders of magnitude smaller than the theoretical one given by Fischer. The relaxed NQE is a better one due to the fact that it never completely neglects dN/dt. It is found that the difference between these approximations lies essentially in the number of significant figures taken for the approximation; still this subtle difference results in dramatic changes in the predicted course of the reaction. Some results confirm previous findings, but a deeper understanding of the physico‐chemical phenomena and their mathematical representation and another viewpoint of the theory is offered. Additionally, experiments and simulations indicate that polymerization rate data alone are not reliable to estimate the value of K, as recently suggested.
20.
红外光谱法研究苯乙烯原子转移自由基聚合反应动力学 总被引:3,自引:1,他引:3
利用红外光谱法测定反应转化率研究原子转移自由基聚合反应动力学。在环己酮溶液中,以卤代烃为引发剂,过渡金属卤化物与配位剂2,2‘-联吡啶为催化体系,进行了苯乙烯聚合。分别就反应温度,反应物浓度和引发体系对苯乙烯聚合速率的影响进行了动力学测定,证实了原子转移自由基聚合具有活性聚合的特征,同时计算并讨论了苯乙烯原子转移自由基聚合反应的动力学数据。 相似文献