Structural Control and Property Development of Silicone Polymers

Abstract

Typical silicones, including poly(dimethyl siloxane)(PDMS), are amorphous, but poly(tetramethyl-p-silphenylene-siloxane)(PTMPS) containing phenyl rings in the main chain is crystalline. A combination of in situ X-ray and NMR measurements during heating of PTMPS indicates that the molecular motion of the phenyl rings exhibits remarkable anisotropy even in the molten state, suggesting rigidity of the PTMPS molecules. Therefore, a melt-drawing technique could be successfully applied to PTMPS. The obtained melt-drawn PTMPS membrane is transparent but exhibits an excellent tensile modulus and strength of 1.7 GPa and 20 MPa, which are enough for various industrial applications. Similar introduction of phenyl rings in the main chain is also effective for property development of silicone elastomer. Blend films of PTMPS and silicone elastomer exhibits the characteristic phase separation, depending on the blending compositions. Such blend films give the remarkably higher tensile strength than the original silicone elastomer, due to the crystalline component.