Hybrid polyurethanes composed of isobutyl-substituted open-cage silsesquioxane in the main chains: synthesis, properties and surface segregation in a polymer matrix

Abstract

Bis(hydroxyethoxypropyldimethylsiloxy)-(triphenylsilyloxy)-heptaisobutyl open-cage silsesquioxane (2) was prepared from bis(dimethylsiloxy)-(triphenylsiloxy)-heptaisobutyl open-cage silsesquioxane (1), following our previous report of a one-pot procedure, from heptaisobutyl trisilanol cage silsesquioxane with triphenylchlorosilane and subsequent reaction with dimethylchlorosilane. The polymerization of 2 with a diisocyanate monomer, i.e. tolylene-2,4-diisocyante (3a), hexamethylenediisocyanate (3b), dicyclohexylmethane 4,4′-diisocyanate (3c) or methylenediphenyl 4,4′-diisocyanate (3d), produced hybrid polyurethanes (4) composed of isobutyl-substituted open-cage silsesquioxane in the main chains. The cast films of the resulting polyurethanes exhibited excellent optical transparency and surface hydrophobicity. The static contact angles of water for the cast films of the polymers were over 100°. In particular, the static contact angle of water for the cast film of 4b exhibited a significantly higher value of 121°, suggesting the higher accumulation of the open-cage silsesquioxane moieties in 4b on the surface. We applied them as surface modifiers in poly(methyl methacrylate) (PMMA) by surface segregation. The static contact angles of water for the hybrid PMMA films were more than 100°, suggesting that they were hydrophobic surfaces. We also applied the hybrid polyurethane presented here as a surface modifier for PMMA nanofibres by electrospinning using a chloroform solution of PMMA with 2 wt% content of 4a.