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国家教育部博士点基金(20110001110084)

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Helix-sense-selective radical polymerization of bulky styrenic monomers: chiral induction and liquid crystallinity
2014年
Eight chiral vinylterphenyl monomers, (+)-2,5-bis{4'-[(S)-1"-methylpropyloxy]phenyl}styrene (Ia), (+)-2,5-bis{4'-[(S)-2"- methylbutyloxy]phenyl}styrene (Ib), (+)-2,5-bis{4'-[(S)-3"-methylpentyloxy]phenyl}styrene (Ic), (+)-2,5-bis{4'-[(S)-4"- methylhexyloxy]phenyl}styrene (Id), (-)-2,5-bis{4'-[(R)-1"-methylpropyloxy]phenyl}styrene (le), (+)-2-/4'-[(S)-l"-methyl- propyloxy]phenyl}-5-{4'-[(R)-1"-methylpropyloxy]phenyl}styrene (Ⅱa), (-)-2-{4'-[(R)-1"-methylpropyloxy]phenyl}-5-{4'- [(S)- 1 "-methylpropyloxy]phenyl } styrene (lib), and (+)-2- { 4'-[(S)-2"-methylbutyloxy]phenyl }-5- { 4'-[(S)- 1"-methylpropyl- oxy]phenyl}styrene (Ⅲ), were synthesized and radically polymerized. These molecules were designed to further understand long-range chirality transfer in radical polymerization and to possibly tune the chiroptical properties of the polymers by varying the spatial configuration, position, and various combination of the stereogenic centers at the ends ofp-terphenyl pendants. The resultant polymers adopted helical conformations with a predominant screw sense. When the stereogenic centers ran away from the terphenyl group as in Ⅰb-d, the corresponding polymers changed the direction of optical rotation in an alternative way and showed no obvious stereomutation upon annealing in tetrahydrofuran. The two stereogenic centers of Ⅱa, Ⅱb, and Ⅲ acted concertedly in chiral induction, whereas those of la and Ie played a counteractive role. The five polymers derived from Ⅰa, Ⅰe, Ⅱa, Ⅱb, and Ⅲ underwent stereomutation when annealed in tetrahydrofuran. The polymers PIa-e had good thermal stability and high glass transition temperatures (Tgs). They generated liquid crystalline phases at above Tgs that could be kept upon cooling, with the exception of Pie. This result was consistent with the extended helical structures.
ZHAO ZhiYuanBAI JianWeiZHANG JieLIU AnHuaWAN XinHua
关键词:CHIRALHELICAL
Synthesis and Chiroptical Properties of Helical Vinylaromatic Polymers
<正>Helix is an important asymmetric structure.Synthesizing the helical polymer with a dominant screw sense req...
Jie ZhangFei ZhangXinhua Wan
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Chiral Teleinduction in Helix-Sense-Selective Polymerization of Vinyl Aromatics
<正>Although stereoregular poly(α-olefin)s have long been known to take helical conformations in crystalline or...
Xinhua Wan
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