褐藻酸铜配合物膜催化VAc自由基聚合

以褐藻酸钠膜浸渍在15%CuCl2*2H2O水溶液中48 h的方法，于室温制备了疏水性的褐藻酸铜(Ⅱ)配位聚合物膜，并通过ESR、 UV-Vis、 IR、 XPS和电导率等手段，研究此配位催化剂褐藻酸铜(Ⅱ)配位聚合物膜表面的组成、配位结构和性质，得知1个Cu2+ 是以dsp2杂化空轨道与褐藻酸2个链节单元的2个羧羟基氧及其2个脱质子带负电荷氧的孤对电子发生配位作用，形成低自旋构型的褐藻酸铜(Ⅱ)配位聚合物，中心Cu2+ 的配位数为4，这对于低分子配合物而言，其空间构型一般是正方形，但在褐藻酸铜(Ⅱ)配位聚合物中，由于褐藻酸分子链的缠绕和卷曲，使上述的空间构型被扭曲，甚至有些配位体没有到位，导致该配位聚合物的中心Cu2+ 存在一些空位中心而具有配位催化活性，因此，HSO3-能按配位催化机理产生初级自由基氢，使醋酸乙烯酯(VAc)按自由基加聚反应历程进行聚合，这有别于CuCl2-Na2SO3-H2O氧化还原引发聚合体系。测定VAc在本体系和室温、pH=7条件下聚合的诱导期为90 s，反应时间24 h。聚醋酸乙烯酯(PVAc)得率82%， mw=1.02×106, mn=2.27×105, mw/mn=4.49。

VAc Free-Radical Polymerization Catalyzed by Copper Alginate Complex Film

A hydrophobic Cu(Ⅱ)-alginate coordination polymer film was prepared by soaking sodium alginate film into 15% CuCl2·2H2O aqueous solution at room temperature over 24 h. The composition, structure and property of Cu(Ⅱ)-alginate as coordination catalyst were studied by ESR, UV-Vis, IR, XPS and electric conductivity methods. It was shown that low spin Cu(Ⅱ) complex was formed as a result of the acceptance of dsp2hydrid orbitals with nonpair electrons transferred from oxygen atoms of two carbonyl hydroxyl groups and negative charge oxygen atoms of two deprotonated carbonyl hydroxyl groups of two alginate chains. The coordination number of center Cu(Ⅱ) in Cu(Ⅱ)-alginate is four. It can be concluded that the vacant site and catalysis active resulted from the distorted tetragonal configuration that was caused by wine and crimp of alginate molecular chain. HSO3-could produce primary free-radical hydrogen by coordination catalysis mechanism, and VAc conducted polymerization by free-radical mechanism, which is different from that of polymerization initiated by CuCl2-Na2SO3-H2O oxidation-reduction system. The induction period for VAc polymerization is 90 s and yield is 82%,mw, mnand mw/mnof PVAc obtained is 1.02×106, 2.27×105and 4.49, respectively.