四丁基碘化铵催化甲基丙烯酸甲酯的可逆-休眠自由基溶液聚合

doi:10.7503/cjcu20180526

摘要/Abstract

摘要：

以四丁基碘化铵(BNI) 为有机催化剂, 碘单质(I₂) 与偶氮二异庚腈(ABVN) 原位生成的碘代异庚腈为引发剂, 进行甲基丙烯酸甲酯(MMA) 的溶液聚合. 以甲苯为溶剂, MMA:I₂:ABVN的摩尔比为200:1:1.7, 考察了催化剂用量对聚合的影响. 结果表明, 加入催化剂可以缩短诱导期, 当I₂:BNI摩尔比为1:1时聚合反应的诱导期最短(1.7 h); 当BNI:I₂摩尔比为0.25:1~2:1之间时, 聚合物实测分子量与理论值十分接近, 分子量分布较窄, 分子量分布指数(M_w/M_n) 多在1.2以下. 考察了在N,N'-二甲基甲酰胺(DMF)、四氢呋喃(THF)、苯甲醚、苯和甲苯5种溶剂中的聚合反应, 发现在苯和甲苯中聚合可控性最佳, M_w/M_n多在1.2以下; 苯甲醚和THF中聚合速率较快, 聚合物分子量分布较苯中的略宽. 以DMF为溶剂时所得聚合物分子量分布很宽, 聚合可控性差. 核磁共振分析聚合物为碘封端结构, 碘原子封端的聚合物链所占比为91.6%.

关键词: 四丁基碘化铵催化剂, 甲基丙烯酸甲酯溶液聚合, 可逆络合聚合, 可逆-休眠自由基聚合

Abstract:

Tetrabutylammonium iodide(BNI) has been found to be a highly efficient organic catalyst for the reversible-deactivation radical polymerization(RDRP) of methyl methacrylate with an in situ formed alkyl iodine initiator. The polymerization results exhibited typical features of “living”/controlled radical polymerization. The polymerization process efficiently controls the molecular weight and chemical structure of the poly(methyl methacrylate)(PMMA). Furthermore, the inhibition period was shortened and the polymerization rate was increased upon the addition of BNI as compared to blank controls. The effect of BNI contents on the controllability of MMA polymerization was also investigated in detail. The results showed that good agreement between theoretical and experimental molar masses(characterized by GPC) was observed for the used molar ratio of I₂ to BNI(1:2, 1:1, 1:0.5, 1:1 and 1:0). The molar ratio of n(MMA):n(I₂):n(ABVN):n(BNI)=200:1:1.7:1 is an optimum formula affording polymers with predetermined molecular weight and low-polydispersity polymers(M_w/M_n<1.2) at relatively high polymerization rate. The polymerizations of MMA in different solvents were carried out. The polymerizations have good control effect in toluene and benzene(M_w/M_n<1.2). The molecular structure and the chain end fidelity of the obtained low-molecular-weight PMMA(M_n,GPC=3300, M_w/M_n=1.15) prepared by reversible complexation mediated polymerization(RCMP) were demonstrated by ¹H NMR spectrum. The calculated M_n,NMR was in good agreement with M_n,th and the fraction of iodine chain end of the PMMA chains was up to 91.6%.

Key words: Tetrabutylammonium iodide catalyst, Methyl methacrylate solution polymerization, Reversible complexation mediated polymerization, Reversible-deactivation radical polymerization

中图分类号:

O631.5

TrendMD:

张晓涛, 王延安, 惠嘉, 石艳, 付志峰, 杨万泰. 四丁基碘化铵催化甲基丙烯酸甲酯的可逆-休眠自由基溶液聚合. 高等学校化学学报, 2019, 40(2): 366.

ZHANG Xiaotao,WANG Yan’an,HUI Jia,SHI Yan,FU Zhifeng,YANG Wantai. Reversible-deactivation Radical Solution Polymerization of Methyl Methacrylate Catalyzed by Tetrabutylammonium Iodide^†. Chem. J. Chinese Universities, 2019, 40(2): 366.

图/表 6

Scheme 1 Mechanism of reversible chain transfer catalyzed polymerization(RTCP)(Ⅰ) and reversible complexation mediated polymerization(RCMP)(Ⅱ)

Fig.1 Plots of ln([M]0/[M]) vs. time for the MMA/I2/ABVN/BNI systems(in toluene) with different BNI concentrations(A), number-average molecular weight(B) and molecular weight distribution vs. conversion for RCMP with different BNI concentrations in toluene(C)Polymerization conditions: n(MMA):n(I2):n(ABVN)=200:1:1.7; temperature: 65 ℃; Mn,th=MA-I + 2[M]0/ [I2]0 × MMMA × conversion.

Table 1 Monomer conversion, Mn, Mn,th and Mw/Mn of PMMA with different BNI concentrations in toluene(at 65 ℃)

n(MMA):n(I₂):n(ABVN):n(BNI)	Time/h	Conversion(%)	M_n(M_n,th)	M_w/M_n
200:1:1.7:0.25	3	15.4	1400(1800)	1.38
	4	42.2	4000(4500)	1.18
	5	60.1	5500(6200)	1.17
	6	69.2	6400(7000)	1.18
200:1:1.7:0.5	3	24.6	3000(2700)	1.18
	4	46.8	4900(4900)	1.15
	5	63.6	5900(6500)	1.19
	6	74.6	6700(7600)	1.19
200:1:1.7:1	3	37.1	3700(3900)	1.19
	4	53.9	5100(5600)	1.14
	5	63.7	6000(6600)	1.19
	6	70.8	6500(7300)	1.21
200:1:1.7:2	3	32.1	3400(3400)	1.12
	4	52.2	5100(5400)	1.18
	5	67.8	6800(7000)	1.23
	6	76.4	7300(7900)	1.15
200:1:1.7:0	3.5	28.7	2800(3100)	1.60
	4	40.1	3700(4200)	1.67
	4.5	48.3	4200(5000)	1.82
	5	53.6	5000(5600)	1.79
	5.5	59.7	5400(6200)	1.84

Fig.2 Plots of ln([M]0/[M]) vs. time for the RCMP of MMA in different solvents(A), Mn,GPC(B)and Mw/Mn vs. monomer conversion in various solvents(C)Polymerization conditions: n(MMA):n(I2):n(ABVN):n(BNI)=200:1:1.7:1; temperature: 65 ℃. Mn,th=MA-I + 2[M]0/ [I2]0 × MMMA × conversion.

Fig.3 UV-Vis absorption spectra of I2 in MMA(a) and complexes of I2 with DMF(b), THF(c), anisole(d), toluene(e) and benzene(f) in MMA

Fig.4 1H NMR spectrum of the PMMA sample(in CDCl3) synthesized by solution polymerization(50% toluene) with n(MMA):n(I2):n(ABVN):n(BNI)=200:1:1.7:1 at 65 ℃ for 3.0 h

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