NEWLY DESIGNED POLYSILOXANE-GRAFT-POLY(OXYETHYLENE) COPOLYMERIC SURFACTANTS - PREPARATION, SURFACE-ACTIVITY AND EMULSIFICATION PROPERTIES

Two sets of comb-grafted polymeric surfactants based on poly( methylhy drogen siloxane) (PHMS) and/or poly(dimethylsiloxane) (PHMS-PDMS) were prepared by sililation of the active Si-H group with an active omega- vinyl group of specially designed undecenoic-polyethyleneglycol esters (UPEG) to form ''newly-designed'' polysiloxane-grafted-polyethylenegl ycol comb-copolymeric surfactants. The hydrophilic moieties are hooked to the hydrophobic backbone through a ''spacer'' (undecenoic acid). T he variations in the surfactants' structures were in the length and de nsity of the grafted hydrophilic moieties, the chain length (DP) and n ature of the hydrophobic backbone. The first 12 different polymeric su rfactants (set 1), termed PHMS-UPEG, were found to be ineffective emul sifiers with limited ability to stabilize oil-in-water emulsions. The second set of surfactants, named PHMS-PDMS-UPEG comb-grafted copolymer s, significantly reduced the oil-water interfacial tension and effecti vely stabilized several types of oil-in-water emulsions. The best emul sifier of this set (PHMS-PDMS-52-UPEG-45), seems to be the one whose a nchor backbone (PHMS-PDMS) dissolves (rather than spreads) in the oil phase, and whose stabilizing moieties are sufficiently long (45 EO uni ts) and ''hooked'' to the silicone backbone at high density (52% subst itution).