自缩合乙烯基聚合体系中的环化效应

doi:10.7503/cjcu20160824

摘要/Abstract

摘要：

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.

关键词: 自缩合乙烯基聚合反应, 超支化聚合物, 生长代数模型, 环化效应, 溶剂效应

Abstract:

We present the effect of intramolecular reaction on the average properties of hyperbranched polymers formed in the self-condensing vinyl polymerization system by the method of Monte Carlo simulation. A model to specify the generations of all units in a branched polymer was proposed to model intramolecular reaction, from which a set of kinetic differential equations was given to describe the growth of various polymers. The simulation was performed by means of the intermolecular and intramolecular reaction rates under different solvent conditions. As a result, the number of treelike and cyclic polymers, the size distribution of rings and weight-average molecular weights were obtained, by which the effect of cyclization on the average properties of polymers was discussed. Furthermore, it is shown that cyclization depends on the cooperation of monomer concentration and solvent quality, where monomer concentration plays a key role in intramolecular reaction, while solvent quality becomes significant only at a high concentration. It is expected that the present study is helpful to design the related materials.

Key words: Self-condensing vinyl polymerization, Hyperbranched polymer, Generation model, Intramolecular reaction, Solvent effect

中图分类号:

O631
O641

TrendMD:

王云明, 常沛杨, 顾芳, 王海军. 自缩合乙烯基聚合体系中的环化效应. 高等学校化学学报, 2017, 38(4): 660.

WANG Yunming, CHANG Peiyang, GU Fang, WANG Haijun. Intramolecular Reaction in Self-condensing Vinyl Polymerization System with Solvent Effect^†. Chem. J. Chinese Universities, 2017, 38(4): 660.

图/表 12

Fig.1 Schematic illustration of the formation of a 5-membered ring in treelike polymer of 11-mer

Table 1 Scaling exponents α under various concentrations and solvent qualities

Solvent quality and concentration	α	Solvent quality and concentration	α
Good solvent and dilute solution	$5 2 (d + 2)$	Concentrated solution or melt	$1 d$
Θ-solvent and dilute solution	$7 4 (d + 1)$	Zimm-stockmayer: mean field theory	$14$

Table 1 Scaling exponents α under various concentrations and solvent qualities

Solvent quality and concentration	α	Solvent quality and concentration	α
Good solvent and dilute solution	$5 2 (d + 2)$	Concentrated solution or melt	$1 d$
Θ-solvent and dilute solution	$7 4 (d + 1)$	Zimm-stockmayer: mean field theory	$14$

Table 2 Reaction types and probabilities in the present SCVP system

Reaction type	Probability	Reaction type	Probability
P_i+P_n-i→P_n	knP_iP_n-i/2 $Ω T n$	P_n-i+R_i→R_n	k $∑ m$ iP_n-i $R i (m)$ / $Ω R n$
P_n→R_n	$∑ i, m k R, n (m) B n (m)$ (i)/ $Ω R n$	P_n-i+ $R i (m)$ → $R n (m)$	iP_n-i $R i (m)$ /[ $∑ m$ iP_n-i $R i (m)$ ]
P_n→ $R n (m)$	$∑ i k R, n (m) B n (m)$ (i)/[ $∑ i, m k R, n (m) B n (m)$ (i)]

Table 2 Reaction types and probabilities in the present SCVP system

Reaction type	Probability	Reaction type	Probability
P_i+P_n-i→P_n	knP_iP_n-i/2 $Ω T n$	P_n-i+R_i→R_n	k $∑ m$ iP_n-i $R i (m)$ / $Ω R n$
P_n→R_n	$∑ i, m k R, n (m) B n (m)$ (i)/ $Ω R n$	P_n-i+ $R i (m)$ → $R n (m)$	iP_n-i $R i (m)$ /[ $∑ m$ iP_n-i $R i (m)$ ]
P_n→ $R n (m)$	$∑ i k R, n (m) B n (m)$ (i)/[ $∑ i, m k R, n (m) B n (m)$ (i)]

Fig.2 Plots of Mn(a) and Mw(b) against conversion p in SCVP system without cyclizationThe inset is the plot of Pn with p=0.98 against n.

Fig.3 Plots of R(m) against p and m in SCVP system in a dilute good solvent(A, ϕ=0.01, α=1/2) and in a concentration solution(B, ϕ=0.5, α=1/3)

Fig.4 Plots of Mw and PI(inset) against p in SCVP system for the cases of ϕ=0.01 and α=1/2, ϕ=0.5 and α=1/3 and without cyclization

Fig.5 Plots of MTw(a, a') and MRw(b, b') against p in SCVP system under the same conditions as in Fig.3a, b. ϕ=0.01, α=1/2; a', b'. ϕ=0.5, α=1/3.

Fig.6 Plots of pT(a, b) and pR(a', b') against p in SCVP system under the same conditions as in Fig.3a, a'. ϕ=0.01, α=1/2; b', b'. ϕ=0.5, α=1/3.

Fig.7 Plots of fR(a, b) and fRunit(a', b') against p in SCVP system under the same conditions as in Fig.3a, a'. ϕ=0.01, α=1/2; b', b'. ϕ=0.5, α=1/3.

Fig.8 Plots of pR and fRunit(inset) against p in SCVP system for α=7/16, α=1/3 and different ϕ

Fig.9 Plots of pR/p and pR against p in SCVP system for different ϕ and α

Fig.10 Plots of fRunit against p in SCVP system for different ϕ and α

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