Synthesis and properties of segmented polyurethanes with hydroquinone ether derivatives as chain extender

Abstract

Two series of 4, 4′-diphenylmethane diisocyanate (MDI) type polyurethanes based on poly(tetramethyleneoxide) glycol (PTMO) and polybutylene adipate glycol (PBA) as soft segments were synthesized by one-step bulk polymerization process. Various hard segments were obtained from hydroquinone ether derivatives with or without ether oxygen structure bonded with the aromatic units in main chain, including hydroquinone (HQE), hydroquinone bis(b-hydroxyethy) ether (HQEE), and 4-hydroxyethyl ethyl oxygen-1-hydroxy ethyl benzene ether (HQEE-L) as chain extenders. The effect of chain extender structure on aggregation structure, thermal and mechanical properties was studied. ATR-FTIR suggested that hydrogen bonding interactions were significantly changed in the presence of flexible ether oxygen structure in hard segment. HQEE-based polyurethanes and HQEE-L-based polyurethanes displayed microphase separation and microphase mixing behavior respectively based on DMA and DSC results. XRD curves confirmed that flexible ether oxygen chain bonded with the rigid aromatic units played a balancing role in the steric effect caused by aromatic chain extender. Thermal properties of polyurethanes were affected mainly by the hard segment packing while mechanical properties were influenced by both phase separation and phase mixing which possess strong hydrogen bonding interactions. The excellent elongation in PTMO/HQEE-L and the high ultimate tensile strength in PBA/HQEE-L can be attributed to the phase mixing with strong hydrogen bonding interactions presented in HQEE-L-based polyurethanes.