Organic/inorganic hybrids by linear PDMS and caged MA-POSS for coating

Abstract

Novel organic/inorganic hybrids of PDMS-b-PMMAm-b-P(MA-POSS)n are synthesized by linear poly(dimethylsiloxane) (PDMS) macroinitiator initiating methyl methacrylate (MMA) and caged methacrylisobutyl-polyhedral oligomeric silsesquioxane (MA-POSS) via a two-step ATRP technique. The chemical structures of obtained hybrids are proved to be PDMS-b-PMMA408-b-P(MA-POSS)4.5, 8.2, 13.6 with molecular weight of 50,090–58,650 g mol−1 (PDI = 1.215–1.391). With the increase of P(MA-POSS)n content from 0%wt to 23.93%wt, the glass transition temperature of PDMS-b-PMMA408-b-P(MA-POSS)n is enhanced from 95 °C to 137 °C, and the corresponding storage modulus of mechanical property is increased from 579 ± 3 MPa to 902 ± 5 MPa. The surface of PDMS-b-PMMA408-b-P(MA-POSS)8.2 film casting from CHCl3 solution obtains higher water contact angle (120°) and higher water adsorption (Δf = −2300 Hz), but lower viscoelasticity (ΔD = 26 × 10−6) than the film casting from tetrahydrofuran (THF) solution (114°, Δf = −1540 Hz, ΔD = 52 × 10−6). This is because that 200–500 nm core/shell micelles of PMMA core and PDMS/P(MA-POSS) shell formed in CHCl3 solution are favor of the migration of PDMS and P(MA-POSS) onto film surface to improve the surface roughness (2.480 nm) and to get silicon-rich surface (14.62%) than 220 nm P(MA-POSS) core/PMMA shell/PDMS-corona micelles formed in THF solution (0.906 nm, 7.86%). Therefore, the accumulated P(MA-POSS) cages on the film surface are able to store absorbed water but do not increase the viscoelasticity of film. The results indicate that PDMS-b-PMMA408-b-P(MA-POSS)n are promising to be the solvent-dependent coating materials.