Preparation and Properties of Novel Hyperbranched Poly(dimethylsiloxane)s

Abstract

Hyperbranched poly(dimethylsiloxane)s (HPDMSs) were synthesized by the self polycondensation of an AB2 monomer, [bis(diethylaminodimethylsiloxy)methylsiloxy]dimethylsilanol that was generated in situ from a precursor compound, [bis(phenyldimethylsiloxy)methylsiloxy]dimethylsilanol, with bromine and diethylamine. The polymerization was carried out at 80°C without any catalysts. The molecular weight (Mw) of HPDMSs increased with elapsing of the reaction time from 5700 to 11500, where HPDMSs turned from liquid to solid with increasing Mw. HPDMSs with lower Mw showed good solubility from nonpolar solvents to methanol, while higher Mw ones dissolved in ethyl ether and tetrahydrofurane. Dimethylphenylsilyl group was introduced as an end group by adding dimethylphenylsilanol at the end of the polymerization. As the end silane-phenyl bond is cleaved with irradiation of UV light, the properties of HPDMSs with phenylsilyl end group such as viscosity, solubility and Tg were changed after UV irradiation.