疏水缔合碱溶性聚合物的相态转变与流变行为

Phase Transition and Rheological Behavior of Hydrophobically Associative Alkali-Soluble Polyacrylic Emulsion

采用单体直接滴加-半连续乳液聚合工艺合成了二十二烷基聚氧乙烯醚甲基丙烯酸酯(BEM)含量不同的疏水改性碱溶性聚丙烯酸乳液(HASE)。控制NaOH/COOH的摩尔比(R),研究了R对HASE体系的pH、透光率、黏度、溶解参数(SP)、表观离解常数(p Ka)及η_0、η_∞、[η]和流变性的影响。结果表明,pH在R=0.1~0.8范围呈平台状,HASE相态转变的起点是R≈0.4,终点是R≈0.8,对应的pH≈7;BEM量越多,质子迁移吉布斯能(ΔGel)越大,相态转变的R值越高;η0、η∞曲线在R≈0.8前后表现出2个斜率,而[η]只有1个斜率,且η0、η∞、[η]具有p H敏感性;稠度系数(K)随pH和BEM增加先增后降,流动指数(n)随p H和BEM先减小后增大。

Hydrophobically-modified alkali soluble polyacrylic emulsions（ HASE） with different amount of methacrylic esters of ethoxylated（ 25 mol EO） C22（ BEM） were synthesized via directly monomer feeding semi-continuous emulsion polymerization. Through the control of Na OH/COOH mole ratio R,effects of R on p H,light transmittance,viscosity,solubility of particle SP,apparent dissociation constant p Kaand η0,η∞,[η] were investigated. The results show that the p H is platform-like at the range of R = 0. 1 ~ 0. 8,the starting point of HASE phase transition from hard spherical latex particle to solution is R≈0. 4,and the end point is R≈0. 8 with the corresponding p H of 7. The more amount of BEM content,the greater proton transfer Gibbs energy ΔGel,the higher R value of phase transition is. The curves of η0 and η∞show two slopes at R approximately 0. 8,while [η]only a slope. η0,η∞ and [η]exhibit sensitive to p H. With the increase of p H and BEM content,the viscosity coefficient K firstly increases and then decreases,and the flow index n firstly decreases and then increases.