共查询到18条相似文献,搜索用时 137 毫秒
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利用Monte Carlo模拟方法研究了加核自缩合乙烯基聚合反应体系中超支化高分子的二次回转半径随双键转化率的变化情况. 在模拟中, 重点考察了两类活性基团的反应活性差异、 引发核的配比及基团数等因素对超支化高分子均方回转半径的影响. 结果表明, 上述因素对于超支化高分子的尺度有着显著影响, 从而可为调控体系中高分子的空间尺度提供有效途径. 相似文献
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利用Monte Carlo模拟方法研究了由单体、引发单体和引发核组成的三元自缩合乙烯基聚合反应体系. 重点考察了两类活性基团反应活性的差异、引发单体分数、引发核的配比及活性基团数等因素对体系中无核和有核两类超支化高分子Z均回转半径的影响. 结果表明, 这些因素对超支化高分子的结构和尺度影响显著, 因而通过调节有关参数可以实现对超支化高分子结构和尺度的调控. 相似文献
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AB_g型超支化高分子反应的统计力学和反应动力学研究 总被引:2,自引:2,他引:0
以ABg型超支化高分子反应为例,对该反应体系的反应动力学和统计力学进行了研究,并探讨了二者之间的关系.进一步给出反应体系的反应程度与体系的Gibbs自由能等热力学量间的解析表达式以及反应程度与浓度和时间等物理量之间的关系. 相似文献
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通过Monte Carlo 模拟方法对加核自缩合乙烯基体系在分批投料模式下的聚合行为进行研究, 考察了引发核的加入时间及分批投料方式对超支化高分子的重均分子量及多分散指数的影响. 研究结果表明, 不同的分批投料方式对超支化高分子的重均分子量和多分散性具有显著的调控作用. 通过调整投料方式、 投料次数、 引发核官能度和转化率等因素, 可以得到分子量较高且多分散性较好的超支化高分子. 相似文献
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基于超支化高分子的生长代数模型,利用Monte Carlo模拟方法研究了不同溶剂条件下自缩合乙烯基聚合(SCVP)体系的环化效应.根据SCVP体系的反应机理给出含环反应的微分动力学方程,并通过环化反应的内在特征确定了分子间反应和内环化反应的速率常数.在此基础上,利用Monte Carlo模拟方法得到了高分子的数量分布函数、重均分子量、环数以及含环分子的链段分数等相关物理量,分析了环化效应对于体系平均物理量的影响.进一步根据模拟结果对单体浓度和溶剂效应等对内环化反应的影响予以分析.结果表明,环化效应取决于单体浓度和溶剂效应之间的协同作用,其中单体浓度在环化反应中起着主导作用. 相似文献
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GU Fang WANG HaiJun & ZHAO ZuoFei College of Chemistry Environment Science Hebei University Baoding China International Centre for Materials Physics Chinese Academy of Sciences Shenyang China Key Laboratory of Medicinal Chemistry Molecular Diagnosis Ministry of Education China 《中国科学B辑(英文版)》2011,(3)
The thermodynamic properties of a binary self-condensing vinyl polymerization system consisting of monomers and inimers are investigated by the principle of statistical mechanics.In detail,in terms of two types of canonical partition functions constructed from different viewpoints,the equilibrium free energy,the law of mass action and the size distribution of hyperbranched polymers are obtained.As an application,the specific heat,equation of state and isothermal compressibility concerning the polymerization... 相似文献
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A ternary self-condensing vinyl polymerization(SCVP) system consisting of monomers, inimers and core initiators is studied by the principle of statistical mechanics. Starting from partition functions for polymerization that constructed from two different viewpoints, explicit expressions of the size distribution function(SDF), equilibrium free energy, and the law of mass action are obtained. For two types of hyperbranched polymers(HBPs) formed in the system, the first, the second, and the third mean-square radii of gyration(MSRG) are presented under various conditions. Furthermore, the solvent effect and excluded volume effect are taken into account in the calculation of the MSRG. With these results, the effects of monomers, inimers and core initiators on the spatial dimension of HBPs are discussed. It is shown that the competition between polymers with and without a core in the growing process results in a significant influence on the average properties of the system. 相似文献
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To deeply understand the dependence of hyperbranched polymerization on the specialties of molecular chain and chemical reaction, the reaction kinetics of nonideal hyperbranched polymerizations considering the chain rigidity and reaction reversibility are studied using the reactive three‐dimensional bond fluctuation lattice model. It is found that, with the increase of chain rigidity, the formation probability of intramolecular rings decreases and less intramolecular rings with larger size are formed. It results in the increase of the degrees of polymerization and polydispersity index with the rise of chain rigidity at higher conversion. Furthermore, our simulation shows that the reversibility of reaction has strong influences on the equilibrium state and kinetic process of hyperbranched polymerizations. When the ratio of reverse reaction probability to forward reaction probability is larger, the conversion and degrees of polymerization quickly grow to the equilibrium value simultaneously. At smaller reverse reaction probability, however, the weigh‐average degree of polymerization and polydispersity index further increase slowly after approaching the equilibrium conversion. Our results are well‐consistent with the experiments to indicate that the introduction of the specialties of macromolecule and chemical reaction are necessary for quantitative analysis of the realistic hyperbranched polymerizations. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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T. Zeiner C. Browarzik D. Browarzik S. Enders 《The Journal of chemical thermodynamics》2011,43(12):1969-1976
The (liquid + liquid) equilibrium of solutions of hyperbranched polyesters is calculated with the lattice-cluster theory (LCT) combined with a chemical association model. The considered solvents are n-alkanes as well as propan-1-ol and butan-1-ol. The structure of the solvents is also considered in the framework of the LCT, assuming the solvent molecules as linear chains of several segments. For polymer solutions with the non-associating n-alkanes only the self association of the hyperbranched polymer molecules has to be considered by the chemical association lattice model (CALM). For the solutions of the type alcohol + hyperbranched polymer additionally the cross association is taken into account by a modified version of the extended chemical association lattice model (ECALM). The association effects are proved to influence strongly the phase equilibrium. Calculating the cloud-point curve and the critical point the polydispersity of the polymer samples is neglected. There is a reasonable agreement of the calculated curves with the experimental data taken from the literature. 相似文献
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两亲性超支化聚合物作为一种新型功能性材料.近年来引起了人们的广泛关注.两亲性超支化聚合物的合成丰要是利用不同亲水性的链段对超支化聚合物端基进行改性,或者首先在超支化聚合物末端产生活性位点,再利用超支化分f作为大分子引发剂引发烯类单体进行斤环聚合、原子转移自由基聚合等得到以超支化聚合物为核的两亲性超支化共聚物;这些分子由... 相似文献
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Low-viscosity liquid epoxidized aromatic hyperbranched polymers are synthesized by the reaction between epichlorohydrin (ECH) and carboxy-end hyperbranched polymers prepared from low-cost products trimellitic anhydride (B3 TMA) and dihydroxy alcohols (A2). The low-viscosity property, especially the lowest viscosity of epoxidized aromatic hyperbranched polymers is only 350 cp which has not reported among epoxidized aromatic hyperbranched polymers before, make them can be used to coatings and adhesion fields without organic solvent hopefully. The properties of the epoxidized aromatic hyperbranched polymers are measured by GPC, FT-IR and viscometer. 相似文献