| In the recent years, the researches on biocompatibility and anti-biofouling have preferentially focused on those materials which can cause micropatterned surfaces since these microseparated surfaces could be possible for inhibiting protein adsorption. In particular, polyurethanes, one of the typical block copolymers, were widely investigated since they exhibited micropatterned morphologies very easily due to the thermodynamically incompatible components, causing good biocompatibility and mechanical properties. To improve the biocompatibility, anti-biofouling property and chemical stability of polyurethanes, poly(dimethylsiloxane) (PDMS) was usually incorporated into polyurethanes as a soft segment. However, up to now, this kind of research is still very limited since PDMS segments can cover the whole surface very easily even at very low bulk concentration due to their low surface energy relative to other organic components, making the control of microtopographic feature of polymer surface very difficultIn this paper, we synthesized a series of poly(dimethylsiloxane)—-4,4'-diphenylmethanediisocyanate-poly(ethyleneglycol)PDMS-MDI-PEG multiblock copolymers using various molecular weight of PDMS/PEG and different chain length of hard segment by employing growth polyaddtion technique. The phase separation, surface composition and properties were investigated by small angle X-ray scattering (SAXS), atomic force microscopy (AFM), angle-resolved X- ray photoelectron spectroscopy (XPS) and contact angle measurement (CA), respectively, the effect of microphase separation on the protein adsorption and platelets adhesion was also studied. Formation mechanism of surface phase separated pattern was also discussed. The results showed that nanoscopically well-organized phase-separated surfaces consisting of hydrophilic domain from PEG and MDI segments and hydrophobic domain from PDMS segments were clearly observed even the concentration of PDMS segments in the copolymer was more than 50wt%, and the microphase separated pattern depended on the annealing. Almost all the copolymers coatings annealed exhibited microphase separated structures (9-28 nm), increasing the molecular weight of PDMS resulted in the increases of microphase separation of both copolymer bulk and surface, while the increase in the molecular weight of PEG decreased the phase separation extent. The increase in phase separation was accompanied by the increases in average interdomain spacing, long period, crystal thickness, and amorphous layer thickness of hard domain.The results also indicated that the greater the phase separation was, but the lower both the surface enrichment of PDMS and the surface free energy (26-34 mN·m-1) were. However, PDMS segments could not cover the whole surface. All the copolymers with surface microphase separation had good biocompatibility and anti-biofouling properties, but the best phase separation could not guarantee the best biocompatibility and anti-biofouling properties.It was found that increasing annealing temperature availed formation of microphase separation and surface enrichment of PDMS, which was accompanied by increasing average interdomain spacing, long period and the crystallizing degree in the hard domains. But the best microphase separated structure seemed to occur at the annealing temperature of 140°C, exorbitant annealing temperature might demolish the ordered structure.FTIR analyses showed that the urethane hydrogen-bonding might rearrange in the hard segment while the urea hydrogen-bonding at the interfaces was decreasing even disappearing during the annealing process. This also indicated an increasing microphase separated degree with the elevated annealing temperature, which was further confirmed by DSC thermal analysis.
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