以有機茂金屬觸媒合成sPS/PAMS與sPS/PPMS共聚物及其物性探討; Physical propertes of sPS/PAMS and sPS/PPMS copolymers using Metallocene catalyst

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题名:	以有機茂金屬觸媒合成sPS/PAMS與sPS/PPMS共聚物及其物性探討;Physical propertes of sPS/PAMS and sPS/PPMS copolymers using Metallocene catalyst
作者:	楊崇明;Chung-Ming Yang
贡献者:	化學研究所
关键词:	苯乙烯;α-甲基苯乙烯;對位甲基苯乙烯;有機茂金屬觸媒;共聚物;結晶動力學;styrene;α-methylstyrene;para-methylstyrene;Metallocene catalyst;copolymer;crystallization kinetics
日期:	2000-06-28
上传时间:	2009-09-22 10:08:09 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	sPS (syndiotactic polystyrene)具有的一些特性有別於非結晶性的無規則聚苯乙烯（atactic polystyrene；aPS），sPS為結晶性高分子，且具有較同排聚苯乙烯（isotactic polystyrene；iPS）結晶速率快的優點，為一種未來性的工程塑膠。本研究以CpTiCl3觸媒分別加入α-methylstyrene（α-Mst）及para-methylstyrene（p-Mst）兩共單體來進行sPS之共聚，且對共單體之甲基在不同位置時其對sPS共聚反應及結晶行為的影響進行探討。首先在sPS/PAMS (syndiotactic poly(styrene-co-α-methylstyrene))系統中，得到當甲基在α位置時會增加進入活化中心的立體障礙，造成其反應性降低，而得到一雜亂共聚物（random copolymer）系統。而在sPS/PPMS(syndiotactic poly(styrene-co-para-methylstyrene))系統中，因為p-Mst之甲基在苯環上造成的對反應之立體障礙不大但對單體上的電子分佈有影響，造成雙鍵更加不穩定加速其反應速率，增加與苯乙烯單體的競爭性，因此sPS/PPMS共聚物為傾向random的結構但帶有較長的平均鏈段。在sPS/PAMS系統的結晶型方面，α-Mst單體的加入會讓sPS鏈段傾向於β-form晶型。而在sPS/PPMS系統中，p-Mst的加入會使得sPS晶型傾向於形成較完美的α”-form晶型。結晶動力學的研究中顯示加入二共單體，Kg（nucleation parameter）、σe（fold surface energy）與q（the work of chain folding）值比sPS單聚物還高，妨礙結晶進行，使結晶速率下降。在sPS/PAMS系統中，其Kg、σe與q值隨α-Mst含量增加而升高，但在sPS/PPMS系統中，加入極少量的p-Mst單體時（2％），Kg、σe與q值快速升高，但與sPS/PAMS系統不同的是當p-Mst大於5％時，Kg、σe與q值反而下降。 Syndiotactic polystyrene (sPS) possesses special properties that are different from atactic and amorphous polystyrene such high crystallinity, faster crystallization rate then isotactic polystyrene (iPS) and exhibit potential as an engineering plastic. This research focuses on the copolymerization of styrene with α-methylstyrene（α-Mst）and para-methylstyrene（p-Mst） using CpTiCl3 catalyst and the effects of methyl substitution position on the crystallization behaviors of sPS. In the sPS-co-(?-methyl styrene) system, ? substituted methyl increases the steric hindrance for monomer incorporation and causes a reduced polymerization activity, as a results the reactivity ration is much lower than polystyrene leading to a random copolymer whereα-Mst monomer is almost isolated. In the sPS-co-(para-methyl styrene) system, the para-substituted methyl group do not create the same hindrance asα-Mst, instead it stabilized the activated reaction intermediate and facilitated the monomer incorporation. As a result, the reactivity ratio is much higher and the copolymer bears longer p-Mst block length. Crystallization kinetic studies revealed that the difference of microstructure has dramatic effects on the crystalliztion behavior. For the poly(styrene-co-alfa methyl styrene) (sPS/PAMS) system, α-Mst has increased chain stiffness with increasingα-Mst content in polymer. This decreases the crystallization rate with more ?-form crystalline modifications. For the poly(styrene-co-para-methyl styrene) (sPS/PPMS) system, long block of p-Mst unit is excluded from the crystallite and also reduces the crystallization rate. The non-crystallizable p-Mst block improves the segmental mobility during crystallization and instead of yielding ?-form crystalline modifications, it gives more perfect ?” crystalline modification. Crystallization kinetic study shows both comonomer increases the values of nucleation parameter, Kg, the fold surface energy,σe and the work of chain folding, q when compared with sPS homopolymer. However, for (sPS/PAMS) they increase with increasingα-Mst, but for (sPS/PPMS) system, rapid incense is found with 2-3 mole % of p-Mst, but decrease afterwards when p-Mst is higher than 5 mole%.
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