Hydrogen bonding and polyurethane morphology. II. spectroscopic, thermal and crystallization behavior of polyether blends with 1,3-dimethylurea and a model urethane compound

Abstract

Thermal, structural and spectroscopic behavior of the blends of poly(ethylene oxide)glycol (PEO) with a model urethane compound bis(4-butylcarbamatocyclohexyl)methane and 1,3-dimethylurea (DMU) were investigated by differential scanning calorimetry (DSC) and hot-stage optical microscopy (HOM). Blends with a wide range of compositions were prepared in tetrahydrofuran (THF) solutions and dried. DSC results indicated the formation of two-phase structures consisting of a pure polyether phase and a highly mixed DMU-polyether phase. As the amount of polyether in the blends was increased, die melting endotherm of DMU became much broader and shifted to lower temperatures, indicating extensive mixing with PEO. The mixed phase was also crystalline. This was strongly supported by HOM results. While pure PEO and DMU crystals showed spherulitic structures, mixed DMU-PEO phase showed fibrillar crystals. Consecutive heating-cooling cycles of the blends did not result in any changes in the blend morphologies. Formation of strong hydrogen bonding between DMU and PEO was also demonstrated by FTIR spectroscopy from the shifts in (N-H and C = O) absorption peaks.