极性单体与乙烯和双烯烃配位共聚合的关键问题和机理研究

Coordination polymerization of polar monomers with ethylene and conjugated dienes is one of the most efficient methods to realize functionalizing and high value-added commonly used polymer materials like polyethylene plastics and poly conjugated diene rubbers. However, the catalysts applied for this coordination copolymerization are usually Lewis acidic transition metals based complexes which are easily poisoned by the Lewis basic polar groups from the polar monomers owing to acid-base interaction, leading to low activity, low molecular weight and low polar group insertion. Thus the coordination polymerization of polar and nonpolar monomers is one of the most challenging projects of polymer science. Recently, we found that the polar group might activate the catalysts and control the stereo-regularity of the monomers. Based on this, in this project, we will design and synthesize a series of rare-earth metal complexes with various sterics and electronics, to explore the possibility of controlling the reversible chelating and the strength between the Lewis basic polar group and the Lewis acidic metal center, and thus influencing the catalytic activity; study the effects of the type and position of the polar substituents on the coordination privilege of the polar monomers to the metal centers and the competitive coordination of the active double bonds from polar and nonpolar monomers, as well as the selectivity; investigate how to vary the intrinsic reaction ratios of monomers to change the polar group insertion rates and their distribution along the polymer chains. Finally to realize the di- and tri-polymerizations of polar styrenes, polar conjugated dienes with ethylene, styrene and dienes to form the block, gradient, taper and random microstructure products, and to reveal the mechanism.

极性单体与乙烯和双烯烃配位共聚合是实现聚乙烯塑料和聚双烯烃橡胶等通用材料功能化、高性能化的重要途径。该共聚反应的催化剂通常是Lewis酸性的过渡金属配合物，极性单体为Lewis碱，二者螯合作用使催化剂毒化，导致共聚活性、产物分子量、极性单体插入率等都非常低。解决上述问题是高分子科学前沿课题之一。最近我们发现极性基团可以“活化”催化剂并控制单体选择性。本课题拟设计与合成不同空间与电子效应的稀土催化剂，探索中心金属Lewis酸性与极性单体Lewis碱性对螯合作用强弱与可逆性、进而对催化活性的影响；研究极性基团的种类与取代位置对极性单体与活性种配位优势的影响、对极性与非极性单体中反应性双键竞争配位-插入的影响及立体选择性的控制；寻求改变单体间固有竞聚率、调节极性基团的插入率并控制其分布的途径。实现极性苯乙烯、极性共轭双烯烃和乙烯、苯乙烯和共轭双烯烃立体可控嵌段、梯度和无规共聚，并揭示机理。

烯烃或共轭二烯烃与极性单体共聚合时将功能化基团引入非极性橡胶材料和塑料的直接方法，简便、高效、可控性好，是通用高分子材料高值化的新途径。然而极性功能基团对催化剂的毒化作用导致催化剂失效是必须解决的关键问题。.本项目设计与合成出一系列茂基、非茂基和限制几何构性催化剂和一系列功能化共轭双烯烃、极性苯乙烯单体、联烯单体。采用上述新催化剂分别实现了独特的2,3-选择性联烯聚合，首次通过配位聚合方法制备出羟基功能化聚丙烯；实现了含硼酸酯乙烯基单体立体规整性聚合并经聚合后氧化反应，首次合成出间规聚乙烯醇。目前唯一商品化含羟基聚乙烯是在极端条件比如高温、高压下自由基聚合制备的，而商业化聚乙烯和聚丙烯通常是配位聚合得到的，丙烯不能自由基聚合，因此，这一策略为开发功能化尤其是羟基功能化聚烯烃提供了新出路。.通过乙烯与极性苯乙烯共聚合，成功将含卤素、甲氧基、甲硫基、氨基等功能基团引入聚乙烯中得到交替、无规和多嵌段链结构的功能化乙烯基共聚物。通过调节活性中心的电子结构，首次合成出含氟乙烯基热塑性弹性体，其有别于Dow化学的链穿梭多嵌段乙烯基弹性体、链行走机理制备的超支化聚乙烯弹性体及ExxonMobil的热塑性聚烯烃弹性体共混物。.通过苯乙烯和极性苯乙烯衍生物共聚合制备出立构规整度可控，以及组成和分布可控的功能化全同、间同聚苯乙烯共聚物、聚苯乙烯低聚物、间规-无规立构嵌段聚苯乙烯。这些共聚物有望用于阻燃剂、手性柱填料等领域。.以生物质原料苯并呋喃为单体，采用Lewis酸开环聚合，制备出高玻璃化温度、高透明度聚合物；以纤维素衍生物羟甲基糠醛为单体，杂蝎型锌氢催化剂，通过逐步-加成新聚合反应模式，制备出聚硅醚等材料。.揭示了极性苯乙烯和共轭双烯烃单体配位均聚合与共聚合时区域与立体选择性控制机理；提出了极性基团位置控制单体竞聚率模型；极性基团如氟原子返扣活性中心导致聚合活性共单体正效应模型；首次提出逐步-加成聚合概念。

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