Effect of different polyethers on surface and thermal properties of poly(urethane-siloxane) copolymers modified with side-chain siloxane

Abstract

Poly(urethane-dimethylsiloxane) (PU-PDMS) copolymers with 4,4'-methylenebis(cyclohexyl isocyanate), different polyethers i.e., poly(oxytetramethylene)diol, poly(ethylene glycol), poly(propylene glycol), and α,ω-dihydroxy terminated polydimethylsiloxane extended with 1,4-butanediol in two-step solution polymerization were obtained. The PU-PDMS were modified using 1.25 mol% of polydimethylsiloxane which was incorporated into main polyurethane backbone as a side chain. The structure of the synthesized PU-PDMS was confirmed by FTIR as well as 1H and 13C-NMR spectroscopy. The effect of different soft segments on free surface energy (FSE) components and thermal stability of poly(urethane-siloxane) copolymers was investigated. The activation energy of the thermal degradation of PU-PDMS using isoconversional methods (Ozawa-Flynn-Wall and Friedman) was calculated. It was concluded that molecular mass, thermal stability, and FSE of PU-PDMS copolymers depend on polyol used. The apparent activation energy at first step of degradation in nitrogen generally increases with the extent of conversion which may result from complex mechanism related to formation of decomposition products. Hydrophobic character of side-chain siloxane on surface properties of the PU-PDMS coatings was confirmed. The obtained coatings are generally soft with the relative hardness in the range of 0.120-0.027. © 2013 The Author(s).