Non-Ionic Water-Soluble Polysilanes and Polysilynes, Chameleons in Solution

Abstract

By incorporating non-ionic oligo(oxyethylene) and crown ether containing substituents, previously inaccessible water soluble linear polysilanes [SiRR'] n and branched polysilynes [SiR] n have been prepared. Their remarkable σ-conjugation related properties are a sensitive probe for silicon backbone conformation. In aqueous solution at ambient temperatures the polymers appear to be dissolved in a highly folded random coil. At the lower critical solution temperature (LCST; 45-50°C) the solution becomes turbid and the polymers aggregate in a more extended conformation. This temperature-induced formation of ordered particles shows remarkable metal cation responsiveness.Polysilanes -(SiRiR 2 ) n -are one-dimensional polymers with an a//-silicon backbone and organic substituents (Ri, R 2 ) (/). They attract considerable attention due to their remarkable optical and electronic properties, which differ considerably from their related a//-carbon analogues, as a result of the occurrence of σ-conjugation (2). The degree of σ-conjugation, which is strongly dependent on the conformation of the silicon backbone, markedly affects these properties. As a result, a variety of useful electrical and optical properties are found. Examples of these properties include hole-and photoconduction, 238