The aim of this study is to clarify the effect on functional groups on interfacial properties and structure of segmented polyurethane (SPU). A series of SPU having carboxyl (COOH) groups in the hard segment (HS), was synthesized. Relationships between microphase separation and the interfacial and adhesive properties were characterized by thermal analysis, X-ray diffraction, dynamic mechanical analysis, contact angle, electron spectroscopy for chemical analysis, and T-peel test measurements. Incorporation of COOH groups into HS leads SPU to have a more phase mixing structure between hard and soft segments. The COOH groups prefer to localize onto the SPU/PET (polyethylene terephthalate) interface than onto the air surface. This is considered to be due to hydrophilic difference between PET and air, that is, PET is more hydrophilic. In addition, phase mixing brought the high molecular motion of SPU, which stimulates the more localization of COOH groups onto the PET interface. The T-peel strength of SPU also increased up to ca. 4 times by incorporation of COOH groups into the HS.
