Method for preparing a siloxane based polymeric liquid material and materials made therefrom

Abstract

A polymeric liquid material formed of molecular building blocks of core-shell type architecture, wherein each building block consists of a hyperbranched polysiloxane core and a functional siloxane shell peripherally attached thereto, the material comprising bridging oxygen moieties (Si—O—Si), hydrolysable alkoxy moieties (Si—O—R) and organofunctional moieties (R′—Si—) and (R—S1-R) and less than 0.5 mass percent hydroxy moieties (Si—OH). The core has a degree of polymerization DPin the range of 1.3 to 2.7, the shell is formed of R′-substituted siloxane moieties and has a degree of polymerization DPin the range of 0.3 to 2.5. At least 75 atomic percent of all Si atoms in the core are bonded exclusively to alkoxy or bridging oxygens, the remainder each being bonded to 3 oxygens and 1 carbon. The total Si to free hydrolysable alkoxy molar ratio in the material is 1:1.25 to 1:2.75, and the material has a viscosity in the range of 10-100,000 cP. A method for preparing the polymeric liquid material relies on first forming the hyper-branched polysiloxane core followed by a build-up of the functional siloxane shell. To do so, a reaction scheme based on adding stoichiometric amounts of acetic anhydride in a water-free environment is exploited.