Relation between the phase structure and surface structure of films made from polyurethane dispersions

Segmented polyurethane dispersions (SPUD) having carboxyl groups in soft segments (SS) or hard segments (HS) were synthesized. Phase, surface, and interface structures of films made from those SPUD were examined by differential scanning calorimeter (DSC), contact angle, and X-ray photoelectron spectroscopy (XPS) measurements. Segmented polyurethanes (SPU) with the same structures as SPUD were also synthesized in the organic solvent system, and the properties and behaviors of these SPU films were compared with the SPUD films. It was indicated by the DSC measurements that the film made from SPUD having carboxyl groups in the soft segments (S-SPUD) had higher crystallinity and crystal growth rate than the film made from SPUD having carboxyl groups in the hard segments (H-SPUD) in spite of steric hindrance. On the other hand, the film made from SPU having carboxyl groups in the hard segments (H-SPU) had higher crystallinity than the film made from SPU having carboxyl groups in the soft segments (S-SPU). Further, the crystal growth rate of SPU was faster than that of SPUD, regardless of the position of carboxyl groups. These results indicated that the phase structure of SPUD film was affected by the phase structure in the dispersion particle. Surface and interface structure of SPUD film was rearranged with a change of the phase structure. But the degree of this change was higher in the surface structure than in the interface structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 741–748, 1999