Preparation and properties of new polyurethane gels with a stress-distributing function for medical applications

The purpose of this study is to prepare new polyurethane gels that can be used as stress- or pressure-distributing materials, particularly by being combined with selective plasticizers for medical or clinical applications. Because low-molecular-weight plasticizer molecules in polymer gels intrinsically tend to migrate to the surface of the gels by the so-called entropy effect in polymer miscibility, the stress-distributing function may decrease gradually after a certain amount of time. Correspondingly, both the chemical nature of the plasticizer and polymer gels and the compatibility between the polymer segments and plasticizer should be deliberately considered as important factors in determining the thermophysical properties and stress-distributing performance of polymer gels. New polyurethane gels comprising separated phases of soft and hard segments, the glass-transition temperature of which was around the ambient temperature, were prepared, and selective plasticizers were combined to obtain an optimized formulation of gels for stress-relieving properties. The glassy-to-rubbery transition of semicrystalline hard segments occurring around the ambient temperature caused the rearrangement of chain conformations, leading to the reduction of the pressure applied to the surface; this indicated that the pressure buildup or loss was somewhat related to the heat regulation by thermal absorption and release in the phase-transition range. (c) 2006 Wiley Periodicals, Inc.