Comb-like polysiloxanes with oligo(oxyethylene) and sulfonate groups in side chains for solvent-free dimethoxysilyl-terminated polypropylene oxide waterborne emulsions

The paper provided a new nonionic-anionic silicone surfactant—comb-like polysiloxanes with oligo(oxyethylene) and sulfonate groups (ESPS) in side chains, which was synthesized by successive hydrosilylation of poly(dimethylhydro)siloxane with allyl poly(ethylene glycol) acetic ester (M n = 540) and allyl glycidyl ether, then ring-opening reaction of oxirane groups with sodium bisulfite. 1H NMR, FT-IR, and gel permeation chromatography (GPC) were used to confirm the chemical structure of the surfactant. The thermal transition behavior of ESPS studied with differential scanning calorimetry (DSC) analysis showed that the surfactant had low glass-transition temperature of − 59.3 °C. Surface tension measurement result indicated that the the surface tension at the critical micelle concentration (cmc, 69.8 mg L−1) was 29.4 mN m−1, which was much lower than those of conventional hydrocarbon surfactants, indicating the higher surface activity of ESPS. The solvent-free dimethoxysilyl-terminated polypropylene oxide waterborne emulsions were prepared using ESPS as the single emulsifier via phase-inversion emulsification technique. An obvious abrupt changing point appearing at the conductivity curves indicated that the phase inversion was completely accomplished. The emulsions prepared with about 3.0 wt% ESPS content in oil phase exhibited excellent storage stability at 50 °C for 42 days and freeze-thaw stability.