ON THE STABILITY OF EMULSIFIER-FREE ALKYL METHACRYLATE LATEXES SIGNIFICANTLY DIFFERING IN THEIR SOLUBILITY IN WATER

The role of electrostatic and structural factors in the stability of e mulsifier-free alkyl methacrylate latexes, which have a water contact angle theta = 26-degrees - 90-degrees, was studied. The region of the maximum stability was discovered at contact angles theta = 40-degrees - 65-degrees. The zeta-potential of the particles, which serves as a m easure of the electrostatic stabilization, increases within the whole range of the investigated contact angles. The coefficient K of structu ral forces, estimated on the basis of consideration of the latex coagu lation in the primary potential minimum, increases and indicates the d estabilizing role of the structural factor with an increase in the pol ymer hydrophobicity. The opposite influence of the electrostatic and s tructural factors on the latex stability with an increase in the polym er hydrophobicity makes it possible to explain the discovered region o f their stability: the stability loss at a high content of hydrophylic monomer results from the low zeta-potential values of the particle su rface, whereas, at high contents of hydrophobic monomer, this loss res ults from the destabilizing action of the structural interaction force s.