Incorporation of methyl groups into hard segments of segmented polyurethane: microphase separation and adhesive properties

A series of segmented polyurethanes (SPU), having methyl (CH3) groups in hard segments (HS), was synthesized. Relationships between the microphase separation and the surface properties as well as adhesive properties of SPU were investigated by thermal analysis, X-ray diffraction, dynamic mechanical analysis, contact angle, electron spectroscopy for chemical analysis, and T-peel test measurements. The incorporation of CH3 groups into HS leads SPU to have a more phase mixing structure between hard and soft segments, which brings about increases of the surface free energy. These changes in the bulk and the surface properties result in the enhancement of adhesive properties of the SPU.