PEG−POSS Multiblock Polyurethanes: Synthesis, Characterization, and Hydrogel Formation

Abstract

We report the synthesis and characterization of a series of multiblock thermoplastic polyurethane hydrogels synthesized with PEG as the soft segment and incorporating an isobutyl-functionalized POSS diol (TMP POSS diol) in the hard segment. The molecular weight of PEG was systematically varied to include 10, 20, and 35 kg/mol, while the molar ratio of POSS diol (as chain extender) to PEG was varied from 3:1 to 8:1 reported for a polymer series with PEG held constant at 10 kg/mol. The diisocyanate employed for TPU polymerization was 4,4′-methylenebis(phenyl isocyanate) (MDI). Wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) experiments revealed that both hydrophilic soft segments (PEG) and hydrophobic hard segments (POSS) can form crystalline structures driven by microphase separation due to the thermodynamic incompatibility. Consequently, the POSS nanocrystals serve as physical cross-linking points consisting, themselves, of an inorganic−organic hybrid networks. Interestingly, t...