从Hansen三维溶度参数探讨TMPTA-St在乙醇-水混合溶剂中沉淀聚合形成单分散聚合物微球的边界条件

REQUIREMENT ON HANSEN SOLUBILITY PARAMETERS FOR THE FORMATION OF UNIFORM POLYMER MICROSPHERES IN PRECIPITATION POLYMERIZATION OF TMPTA-STYRENE IN WATER-ETHANOL MIXED SOLVENTS

以三羟甲基丙烷三丙烯酸酯(TMPTA)作交联剂,苯乙烯(St)作共聚单体,在不同TMPTA/St质量比下在乙醇与水的混合溶剂中进行沉淀聚合,对单体转化率和微球收率以及微球单分散性等参数进行了表征.对相应不同水含量的混合溶剂以及混合单体的Hansen三维溶度参数进行了计算,尝试对不同聚合条件下混合溶剂与混合单体的三维溶度参数进行比较以建立一个形成单分散微球的边界条件,为通过沉淀聚合制备单分散微球提供一个判断方法.在本文实验条件下,使用乙醇或其与水的混合物为聚合介质,当共混溶剂与共混单体的极性溶度参数之差Δδp和氢键溶度参数之差Δδh分别为5.0和12.4,9.2和20.1以及6.0和10.0 MPa1/2时,在由这3个实验点组成的区域之内进行沉淀聚合即可以制得单分散聚合物微球.当Hansen溶度参数之差(Δδp或Δδh)超出此范围时,沉淀聚合所制得聚合物微球分散度迅速变宽,甚至在聚合过程中凝胶化.色散溶度参数变化甚微,难以由此建立单分散微球的形成条件.

With ethanol and water mixture(H2O-EtOH) as the solvent,precipitation polymerization of trihydroxymethyl propane triacrylate(TMPTA,the crosslinker monomer) and styrene(St) was carried out using 2,2′-azobis-(isobutyronitrile)(AIBN) as the initiator.Microspheres of uniform size were obtained in most of the polymerizations done with varied TMPTA/St mass ratio and in H2O-EtOH with different water amounts.The yields of the microspheres and soluble oligomers were determined.Results indicate that both the yields increased with increased TMPTA in the monomer mixture;whereas with increased water amount in the polymerization solvent,the yield of the microspheres was promoted while that of the soluble oligomers was reduced.Number average size and size distribution of the microspheres were obtained from SEM.Hansen three dimensional solubility parameters(δs,δh and δp) were calculated for the monomers and H2O-EtOH binary solvent,and so were the differences between their solubility parameters.Boundary limitations for the formation of the uniform microspheres were established based on the difference(Δδp) of polar solubility parameters(δp) between the solvent and the monomer mixture,and that(Δδh) of hydrogen bonding solubility parameters(δh).With three sets of Δδp and Δδh at(5.0,12.4),(9.2,20.1) and(6.0,10.0)(expressed as Δδp,Δδh),an enclosed experimental zone was set,uniform microspheres can be expected when the polymerization is conducted within the limits of this enclosed zone.