Reversible-deactivation Radical Solution Polymerization of Methyl Methacrylate Catalyzed by Tetrabutylammonium Iodide†

doi:10.7503/cjcu20180526

Abstract

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

CLC Number:

O631.5

TrendMD:

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^†[J]. Chem. J. Chinese Universities, 2019, 40(2): 366.

Figures/Tables 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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