SYNTHESIS OF DENDRIMERS BY SELF-CONDENSING GROUP TRANSFER POLYMERIZATION

近年来，树枝状聚合物作为一种具有新颖物理性质的材料受到了广泛的关注。然而，树状大分子只能通过多步合成来获得，这限制了它们的可用性。最近，Frechet等人描述了乙烯基自缩聚法制备树枝状超支化聚苯乙烯。本课题研究了基团转移聚合法制备超支化聚甲基丙烯酸酯。由此制备了由甲基丙烯酸酯段和乙烯基硅氧烷缩醛段组成的2-（2-甲基-1-三乙基硅氧烷-1-丙烯氧基）甲基丙烯酸乙酯1，用于甲基丙烯酸酯的自凝聚聚合。以氟离子为催化剂，在四氢呋喃中进行了1的聚合。所得聚合物可溶于多种有机溶剂。GPC法估计聚合物的分子量约为1万。用^1H和^<13>C核磁共振谱对聚合物的支链结构进行了清晰的表征。聚合物中的烯酮硅基缩醛残基转化为各种官能团。因此，通过引入羧酸阴离子和铵离子官能团作为聚合物的末端基团，合成了水溶性超支化聚甲基丙烯酸酯。这些聚合物表现为单分子胶束；它们溶于水并通过疏水相互作用与有机分子（来宾）结合。紫外可见光谱和荧光光谱监测表明，掺杂受客体和主体聚合物之间的静电力控制。聚合物的空腔大小取决于其表面电荷密度的变化。事实上，当聚合物的电荷中和时，客体分子被释放出来。

Dendrimers have recently received much attention as materials with novel physical properties. However, dendrimers are accessible only through multi-step syntheses that limit their availability. Recently, Frechet et al.has described self-condensing vinyl polymerization to produce dendrimer-like hyperbranched polystirene.In this research project, synthesis of hyperbranched polymethacrylates by the group transfer polymerization was carried out. Thus, 2- (2-methyl-1-triethylsiloxy-1-propenyloxy) ethyl methacrylate 1, which consisted of a methacrylate moiety and a ketene silyl acetal moiety, was prepared for the self-condensing polymerization of methacrylates. The polymerization of 1 was carried out in THF with fluoride ion as a catalyst. The resulting polymers were soluble in various organic solvents. Molecular weights of the polymers were about ten thousand estimated by GPC.The branched structure of the polymers was clearly characterized by ^1H and ^<13>C NMR spectroscopy.The ketene silyl acetal residues in the polymers were converted to various functional groups. Thus, water-soluble hyperbranched polymethacrylates were synthesized by introduction of ionic functional groups such as carboxylate anion and ammonium cation as the terminal groups of the polymers.These polymers behaved as unimolecular micelles ; they dissolved in water and incorporated organic molecules (guests) by hydrophobic interaction. Monitoring by UV-Vis and fluorescence spectroscopy revealed that the incorporation was controlled by the electrostatic force between the guests and the host polymers. The cavity size of the polymers depended on the change of their surface charge density. In fact, guest molecules were released when the charge of the polymers neutralized.