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Preparation of polyurethane with zwitterionic side chains and their protein resistance.

Polyurethane (PU) with zwitterionic side chains has been prepared to resist nonspecific adsorption of proteins. First, dihydroxy-terminated poly(2-(dimethylamino)ethyl methacrylate) (PDEM(OH)(2)) is synthesized by free radical polymerization with 3-mercapto-1,2-propanediol as the chain transfer agent, which polyadds with diisocyanate to yield a PU with PDEM side chains. Such side chains are zwitterionized by 1,3-propane sultone. Proton nuclear magnetic resonance spectroscopy ((1)H NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) show that the zwitterionic side chains are incorporated into the PU. Thermal analysis demonstrates the thermal stability is greatly affected by the content of the side chains. By use of quartz crystal microbalance with dissipation (QCM-D), we have investigated the adsorption of fibrinogen, bovine serum albumin, and lysozyme on a surface constructed by such a PU. It shows the PU has a controllable protein resistance depending on the content of the zwitterionic side chains.