Isopropyl alcohol: an unusual, powerful, 'green' solvent for the preparation of silicone-urea copolymers with high urea contents

Abstract

Isopropyl alcohol (IPA) is used as the reaction solvent for the preparation of silicone-urea copolymers. Reactivity of isopropanol with bis(4-isocyanatocyclohexyl)methane (HMDI) was investigated at 23 degreesC using infrared spectroscopy. Spectroscopic studies indicated very low reactivity of IPA towards HMDI at 23 degreesC. High molecular weight segmented silicone-urea copolymers were prepared through the reaction of HMDI with aminopropyl and N-methylaminopropyl terminated polydimethylsiloxane (PDMS) oligomers and three different chain extenders, ethylene diamine (ED), hexamethylene diamine (HMDA) and 2-methyl-1,5-diaminopentane (Dytek A). Number average molecular weights of PDMS oligomers varied between 900 and 7000 g/mol, respectively. Reactions were carried out at room temperature in IPA. Silicone-urea copolymers with urea hard segment content between 10 and 42% by weight were prepared. Thermal and mechanical characterization of the copolymers indicated the formation of microphase-separated systems with excellent tensile strengths. Interestingly, structure of the diamine chain extender did not show any influence on the mechanical properties of the homologous series of silicone-urea copolymers.