SYNTHESIS AND CHARACTERIZATION OF PERFECTLY ALTERNATING POLYORGANOSILOXANE-POLYARYLESTER AND POLYORGANOSILOXANE-POLY(ARYL FORMAL) BLOCK COPOLYMERS

Passive damping has been defined as a key element in vibration control. It is believed that the approach to passive damping could be addressed through the use of carefully designed viscoelastic polymeric materials. This article describes the synthesis and characterization of multiphase, transparent block copolymers that are potential candidates for passive damping applications in large space structures. Well defined, perfectly alternating polyorganosiloxane-polyarylester block copolymers of relatively high molecular weight were prepared via a silylamine-hydroxyl condensation reaction, as were polyorganosiloxane-polyaryl formal block copolymers. Due to the high degree of incompatibility between the 'soft' siloxane segments and the 'hard' ester or formal segments in the block copolymers, a multiphase microstructure developed at relatively low block molecular weights. To vary the miscibility of the siloxane and ester phases, and in turn the physical properties of the block copolymers, the block molecular weights and the siloxane block compositions (dimethyl, dimethyl-co-diphenyl, or dimethyl-co-trifluoropropylmethyl) were controlled. Structure analysis by nuclear magnetic resonance (proton and silicon) and Fourier transform infra-red (FTi.r.) verified that the desired difunctional oligomers and block copolymers were successfully prepared. The influence of copolymer composition on physical properties was studied by thermal, mechanical and surface characterization techniques. © 1990.