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Abstract

Polyurethane block copolymers were synthesized containing between 33 and 50 wt % hard segments based on 4,4'-diphenylmethane diissocyanate (MDI) and either 1,4-butanediol (BD), or N-methyldiethanolamine (MDEA) as the chain extender. The soft segments were composed of poly(tetramethylene oxide) (PTMO) and fluoropolyether glycol (FPEG) oligomers (Mn = 1000 and 1899, respectively), copolymerized to produce polyurethanes containing 5–100 wt % FPEG soft segment. The PTMO polyol in one sample was substituted with a tetrahydrofuran/ethylene oxide polyol (75 : 25 mole ratio) (Mn = 1140). The MDEA-extended polymer was ionized using 1,3-propane sultone. The bulk and surface properties of these polymers were evaluated by a variety of techniques. Differential scanning calorimetry (DSC) and dynamic mechanical analysis showed that the incorporation of 5–14 wt % FPEG into the soft segment had essentially no effect on the polymer's multiphase structure. The ultimate tensile strength and elongation was reduced by the addition of FPEG. Chain extending with BD as opposed to MDEA improved phase separation and the ultimate tensile strength. In vacuum, surface enrichment of the low surface energy FPEG was observed for all the polymers, using X-ray photoelectron spectroscopy (XPS). The dynamic contact angle results indicate that the polymer surfaces rearranged in an aqueous environment to minimize their interfacial free energy.