Aggregation and phase separation of hydrophilically modified poly(dimethylsiloxane) in methanol-water mixtures

Abstract

Hydrophilically modified poly(dimethylsiloxane) (HPM-PDMS) bearing quaternized amino groups on the side chains was dissolved in mixtures of methanol (MeOH) and water with a water weight fraction WH2O from 0 to 1 and with 0.1 M sodium acetate added. The degree of substitution and the degree of polymerization of this ionomer sample were 16 mol% and 1050, respectively, and the polymer concentrations were mostly <1%. Although the solutions were almost transparent, they were in the two-phase region at W H2O ≥0.5, and HPM-PDMS formed random aggregates at WH2O <0.5. In the two-phase region, the coexisting concentrated phases formed colloidal particles with radii of gyration ranging from 100 to 300 nm just after dispersion. The colloidal particles, however, gradually coagulated, and the solutions became turbid when they were left standing for several days. The multiplet structure in the melt sample of HPM-PDMS may be responsible for the tentative dispersion of HPM-PDMS even in the two-phase region. © 2014 The Society of Polymer Science, Japan (SPSJ).