Polymerization of Methyl Methacrylate with α-Diimine Nickel(Ⅱ)†

doi:10.7503/cjcu20140298

Abstract

Abstract:

Four α-diimine nickel(Ⅱ) complexes: [(t-Bu)—NCH—CHN—(t-Bu)]NiBr₂(C1), [C₆H₅—NC(Me—C(Me) N—C₆H₅]NiBr₂(C2), [(2,6-C₆H₃(Me)₂)—NC(Me)—C·(Me) N—(2,6-C₆H₃(Me)₂)]NiBr₂(C3) and [(2,6-C₆H₃(i-Pr)₂)—NC(An)—C(An) N—(2,6-C₆H₃(i-Pr)₂)]NiBr₂(An=acenaphthyl)(C4), in the presence of methylaluminoxane(MAO) as cocatalyst, were applied in the polymerization of methyl mathacrylate(MMA). The influence of polymerization parameters, such as molar ratio of Al/Ni, monomer concentration, polymerization temperature and time, as well solvents were studied with complex C2/MAO system. Based on these results, all nickel complexes were compared under optimized polymerization conditions{1.6 μmol catalyst, n(Al)/n(Ni)=800, [MMA]=2.9 mol/L, toluene as solvent, 60 ℃ for 4 h}. In each case, syndiotactic enriched polymer was obtained. The complexes with more bulky frame work exhibit lower catalytic activities, for example, C1 with the smallest bulky frame work gives the highest activity, 107.8 kg/(mol Ni·h) while C4 with the biggest bulky frame work gives the lowest activity, 7.8 kg/(mol Ni·h); The complexes with more electronic donor substituents exhibit higher activities and molecular weight of PMMA. The activity of C2 is 62.5 kg/(mol Ni·h), and the molecular weight of PMMA is 5.0×10⁴, while that of C3 is 96.9 kg/(mol Ni·h) and produce higher molecular weight of PMMA(7.6×10⁴).

Key words: Late transition metal catalyst, α, -Diimine nickel complex, Methyl methacrylate, Polymerization

CLC Number:

O631
O614.81

TrendMD:

ZHANG Danfeng, LI Sen, YU Wen, MENG Jiangang. Polymerization of Methyl Methacrylate with α-Diimine Nickel(Ⅱ)^†[J]. Chem. J. Chinese Universities, 2014, 35(7): 1559.

Figures/Tables 8

References 23

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Entry	n(Al)/n(Ni)	Yield/g	Conversion(%)	Activity/(kg·mol^-1 Ni·h^-1)	10^-4 M_n	PDI
1	200	0.13	3.0	20.3	18.5	2.0
2	400	0.25	5.8	39.1	14.6	2.2
3	600	0.32	7.4	50.0	6.2	2.4
4	800	0.40	9.2	62.5	5.0	2.3
5	1000	0.33	7.4	51.6	2.9	3.1

Entry	n(Al)/n(Ni)	Yield/g	Conversion(%)	Activity/(kg·mol^-1 Ni·h^-1)	10^-4 M_n	PDI
1	200	0.13	3.0	20.3	18.5	2.0
2	400	0.25	5.8	39.1	14.6	2.2
3	600	0.32	7.4	50.0	6.2	2.4
4	800	0.40	9.2	62.5	5.0	2.3
5	1000	0.33	7.4	51.6	2.9	3.1

Entry	[MMA]/(mol·L^-1)	Yield/g	Conversion(%)	Activity/(kg·mol^-1 Ni·h^-1)	10^-4M_n	PDI
1	1.6	0.13	3.0	20.3	12.2	3.3
2	2.9	0.40	9.2	62.5	5.0	2.3
3	5.6	0.95	21.8	148.4	4.1	3.2

Entry	[MMA]/(mol·L^-1)	Yield/g	Conversion(%)	Activity/(kg·mol^-1 Ni·h^-1)	10^-4M_n	PDI
1	1.6	0.13	3.0	20.3	12.2	3.3
2	2.9	0.40	9.2	62.5	5.0	2.3
3	5.6	0.95	21.8	148.4	4.1	3.2

Entry	T/℃	Yield/g	Conversion(%)	Activity/(kg·mol^-1 Ni·h^-1)	10^-4 M_n	PDI
1	20	0.13	3.0	20.3	41.9	1.5
2	40	0.28	6.4	43.8	38.4	1.4
3	60	0.40	9.2	62.5	5.0	2.3
4	80	0.53	12.2	82.8	9.6	2.1
5	100	0.38	8.7	59.4	4.0	3.3