Synthesis and Characterization of Block Copolymers with PMMA Segment Initiated by Organic Lithium†

doi:10.7503/cjcu20140468

Abstract

Abstract:

Well-defined block copolymers polyisoprene-b-poly(methyl methacrylate)(PI-b-PMMA) and poly(butyl methacrylate)-b-poly(methyl methacrylate)(PBMA-b-PMMA were synthesized in THF initiated by n-BuLi and DPHLi with the addition of P-Complex. The polymerizations were carried out under the conditions which could be achieved in industry through adding monomers by sequence. The conversion of MMA was higher than 90% both in PI-b-PMMA and PBMA-b-PMMA, and the molar ratios of each segment in block copolymers detected by ¹H NMR fit to those calculated. The M_n of PI-b-PMMA and PBMA-b-PMMA were 4.0×10⁴ and 1.6×10⁴, respectively. Well-defined triblock polymer PS-b-PI-b-PMMA was synthesized in cyclohexane under the condition which could be achieved in industry. The conversions of monomers were all completed, and the molar ratio in the final triblock polymer was consistent to the one calculated. The final M_n was 7.4×10⁴, and the molecular weight distribution(MWD) was only 1.28.

Key words: Living anionic polymerization, Lithium phenoxide, Methyl methacrylate, Block copolymer

CLC Number:

O632.1

TrendMD:

CHEN Bo, WANG Jiming, SHU Minze, ZOU bin, GUAN Yong, ZHENG Anna. Synthesis and Characterization of Block Copolymers with PMMA Segment Initiated by Organic Lithium^†[J]. Chem. J. Chinese Universities, 2014, 35(9): 2007.

Figures/Tables 9

Table 1 Results of block copolymerization of Ip and MMA

Sample	Temperature^a/℃	Capping agent^b	n_Ip: $n MMA c$	Conversion of MMA(%)
1	50/50	None	1∶0.27	16.8
2	50/0	None	1∶0.26	16.2
3	50/0	St	1∶0.47	29.4
4	50/0	α-mSt	1∶1.32	78.5
5	50/0	DPE	1∶2.19	93.4
6^d	50/0	DPE		36.1

Table 1 Results of block copolymerization of Ip and MMA

Sample	Temperature^a/℃	Capping agent^b	n_Ip: $n MMA c$	Conversion of MMA(%)
1	50/50	None	1∶0.27	16.8
2	50/0	None	1∶0.26	16.2
3	50/0	St	1∶0.47	29.4
4	50/0	α-mSt	1∶1.32	78.5
5	50/0	DPE	1∶2.19	93.4
6^d	50/0	DPE		36.1

Fig.1 1H NMR spectra of PI-b-PMMA polymerized under different conditions

Fig.2 GPC curves(LS signal) of PI(a) and PI-b-PMMA(b) polymerized with DPE as capping agent in THF

Table 2 Results of PBMA-b-PMMA polymerized after different reaction time of BMA

Sample	$t 1 a$ /min	$t 2 b$ /min	n_BMA∶ $n MMA c$	Conversion^d (%)
1	1	20	1∶0.9	94.1
2	2	20	1∶0.87	93.7
3	4	20	1∶0.55	80.5
4	8	20	1∶0.38	72.1
5	16	20	1∶0.29	63.0

Table 2 Results of PBMA-b-PMMA polymerized after different reaction time of BMA

Sample	$t 1 a$ /min	$t 2 b$ /min	n_BMA∶ $n MMA c$	Conversion^d (%)
1	1	20	1∶0.9	94.1
2	2	20	1∶0.87	93.7
3	4	20	1∶0.55	80.5
4	8	20	1∶0.38	72.1
5	16	20	1∶0.29	63.0

Fig.3 1H NMR spectra of PBMA-b-PMMA with different reaction time of BMA at 0 ℃ in THF

Fig.4 GPC curves of PBMA(a) and PBMA-b-PMMA(b) with BMA polymerization time of 1 min at 0 ℃ in THF

Fig.5 Mechanism of lithium phenoxide to the polymerization

Fig.6 1H NMR spectrum of PS-b-PI-b-PMMA synthesized in CH at 50 ℃/50 ℃/0 ℃

Fig.7 GPC curves of PS-b-PI-b-PMMA synthesized in CH at 50 ℃/50 ℃/0 ℃

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