The copolymerization of myrcene with styrene by the half-sandwich scandium complexes (C
5
H
5
)Sc(CH
2
SiMe
3
)
2
(THF) (
1
) and (C
5
Me
4
SiMe
3
)Sc(CH
2
SiMe
3
)
2
(THF) (
2
) was studied. The structures and thermal properties of the obtained copolymers were characterized by NMR
GPC and DSC. The copolymerization of myrcene with styrene at room temperature had been achieved and the copolymerization activity reached up to 10
4
g polymer mol
Sc
–1
h
–1
. The myrcene-styrene copolymers with controllable compositions (myrcene content = 22 mol% – 83 mol%)
high molecular weight (
M
n
= 4.8 × 10
4
– 11.3 × 10
4
) and narrow molecular weight distribution (
M
w
/
M
n
= 1.49 – 1.99) were conveniently obtained by changing the feed ratio of myrcene and styrene. Significant influence of catalyst structure on the stereoselectivity and comonomer distribution sequences in the resulting copolymers was observed. In the copolymerization of myrcene and styrene catalyzed by scandium complex
1
styrene started to incorporate into chains after myrene was almost completely consumed
and diblock copolymers containing
cis
-1
4-polymyrcene (selectivity 95%) block and atactic polystyrene block were obtained. The obtained copolymers with different myrcene contents possessed two glass transition temperatures (
T
g
– 63 and 96 °C)
close to those of
cis
-1
4-polymyrcene and atactic polystyrene. In contrast
in the copolymerization of myrcene and styrene catalyzed by scandium complex
2
myrene content showed a gradient decline accompanied by styrene content increasing gradually
producing gradient copolymers containing 3
4-polymyrcene (3
4-selectivity 75%
cis
-1
4-selectivity 25%) and syndiotactic polystyrene. The obtained copolymers with different myrcene contents possessed a
T
g
at –35 °C and a melting temperature (
T
m
) at 254 °C
originating from polymyrcene block and syndiotactic polystyrene block
respectively. There is a great difference in the reactivity ratios between myrcene and styrene in the copolymerization catalyzed by scandium
1
(
r
My
>
>
r
St
). However
the gap between the reactivity ratios of myrcene and styrene in the copolymerization catalyzed by scandium complex
2
was much smaller (
r
My
= 8.47
r
St
= 0.76) and gradient copolymers were generated.
关键词
单茂钪月桂烯苯乙烯共聚合
Keywords
ScandiumMyrceneStyreneCopolymerization
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