AM2Net Advanced Macromolecular Materials By Transition Metal Catalysis; Group 3: "Ring-opening Polymerization Catalysis"; Alkaline-earth (and lanthanide) metal-alkoxide catalysts for oxygenate polymerization

在工业上，人们对从传统单体开发新的聚合物材料越来越感兴趣。在聚合物研究的过去十年中，从“旧”单体中合理设计新材料的关键词是立体选择性聚合。然而，近几年来，通过共聚来设计新材料的趋势越来越明显。许多研究小组专注于单体混合物的统计共聚，作为影响聚合物物理性能的一种方式。我们想集中在一个非常强大的方法在合理的聚合物设计：嵌段共聚。为了实现嵌段共聚物的合成，聚合反应需要是活性的。因此，嵌段共聚物传统上通过使用烷基碱金属作为引发剂的阴离子聚合来制备。我们的目标是联合收割机结合活性嵌段共聚和立体选择性聚合的优点。我们小组的初步工作表明，使用二价碱土引发剂可以部分达到这一目标。这些配合物以活性方式取代苯乙烯，间规度高达91%。我们可以表明，剩余的错误是由于手性链端的反转，这导致立体中心的外消旋化。延缓这些链端反转的一种方法是使用具有三价金属的引发剂：聚合物链和金属之间的键更强，这导致反转更慢。因此，我们想扩大我们的研究与三价金属引发剂的合成是等瓣的二价碱土金属引发剂。将追求两种可能的方法：i）使用等瓣阳离子引发剂和ii）使用等瓣中性引发剂与双阴离子配体体系。金属优选为铝，最近铝在烯烃聚合中显示出相当大的潜力。我们也喜欢冒险进入镧系金属化学，这已被证明是非常有用的聚合催化剂最近。除了三价金属催化剂的合成和结构外，还将研究其聚合性能，特别是其机理。我们特别想集中讨论苯乙烯和丁二烯的嵌段共聚物。预期无规立构丁二烯嵌段内的有规立构苯乙烯嵌段将产生透明且具有不寻常的高冲击的弹性体材料。

Industrially, there is an increasing interest in the development of new polymeric materials from classical monomers. During the last decade of polymer research, the keyword in the rational design of new materials from "old" monomers has been stereoselective polymerisation. The last few years, however, there is an increasing tendency in designing new materials by means of copolymerisation. Many research groups concentrate on statistical copolymerisation of monomer mixtures as a way to influence the physical properties of the polymer. We like to concentrate on a very powerful method in rational polymer design: block-copolymerization. In order to achieve the syntheses of block-copolymers the polymerization reactions need to be living. Therefore, block-copolymers are traditionally prepared by anionic polymerisation using alkalimetal alkyls as initiator. It is our aim to combine the advantages of living block-copolymerisation with those of stereoselektive polymerisation. Preliminary work of our group has shown that this goal can be reached partially by the use of divalent alkaline-earth initiators. These complexes polymerize styrene in a living fashion with syndiotacticities up to r = 91%. We could show that the remaining errors are due to inversion of the chiral chain-end, which leads to racemisation of the stereocenters. One approach to retard these chain-end inversions is the use of initiators with trivalent metals: the bond between polymer chain and metal is stronger and this leads to slower inversion. We therefore like to extend our research with the syntheses of trivalent metal initiators that are isolobal to the divalent alkaline-earth initiators. There are two possible approaches that will be pursued: i) the use of isolobal cationic initiators and ii) the use of isolobal neutral initiators with dianionic ligand systems. The metall will be preferably aluminium for which recently considerable potential in alkene polymerisation has been shown. We also like to venture into lanthanide metal chemistry, which has been shown quite useful in polymerisation catalyses lately. Apart from the syntheses and structures of new catalysts based on trivalent metals, the polymerization properties and especially their mechanisms will be investigated as well. We like to concentrate especially on the block-copolymers of styrene and butadiene. It is expected that stereoregular styrene blocks within atactic butadiene blocks will result in elastomeric materials that are transparent and have an unusual high impact.