Synthesis and surface properties of PDMS-containing latexes by emulsion polymerization using AIBN as the initiator

Abstract

In this article, a series of PBMA-g-PDMS latexes with high polydimethylsiloxane (PDMS) content up to 60wt% were prepared by emulsion copolymerization of extremely hydrophobic PDMS-macromonomers (PDMS-M) and n-butyl methacrylate (BMA). High yields of PDMS-containing latex particles were obtained and the PDMS-Ms were fully incorporated into the acrylic backbone by using 2,2′-azobisisobutyronitrile (AIBN) as the initiator and sodium dodecyl sulfate (SDS) as the surfactant. The key of successfully incorporating the PDMS segment to the acrylic polymer was the use of the oil-soluble initiator, AIBN, via a miniemulsion mechanism during which no transport of hydrophobic PDMS-Ms through the aqueous phase was needed. Use of a water-soluble initiator like potassium persulfate (KPS) led to particle flocculation and unsuccessful incorporation of PDMS-M in the latex particle. The particle diameter of prepared latexes was 60–170nm, with the polydispersity index (PDI) of 0.1–0.3. All the prepared latexes were very stable, as indicated by the ζ-potential of around −80mV. DSC and GPC results confirmed that PDMS was chemically linked to the PBMA backbone. The advancing water contact angles (CA) on the films from the PBMA-g-PDMS latexes were above 100°, and the receding water CA reached as high as 94°, indicating the film surface was significantly enriched in PDMS. The surface activity of the PDMS-g-PBMA copolymer was further demonstrated by the high water CA on the film from a blend of the copolymer latex and a conventional acrylic latex.