Influence of filming process on macromolecular structure and organization of a medical segmented polyurethane

摘要

A medical segmented polyurethane, Tecoflex(R), based on methylene bis(p-cyclohexyl isocyanate) and 1,4-butanediol as hard segments (HS), and poly(tetramethylene glycol) as soft segments (SS), was studied to evaluate the influence of different filming procedures on macromolecular structure and organization. Size-exclusion chromatography (SEC) and Fourier transform infrared (FTIR) spectroscopy were used to highlight differences between solvent-cast and hot compression-molded films (160 to 200 degreesC). For compression-molded films, FTIR spectra showed weakened vibration bands attributed to HS and SS groups; SEC results indicated a decrease of M,, and M molecular weights that was dependent on processing time and temperature. These modifications were the result of both thermooxidation of soft segments and thermal dissociation of urethane linkages. Concerning solvent-cast films, no chemical or molecular modifications were observed. Moreover, we have highlighted that this procedure enhanced macromolecular organization: the carbonyl stretching region presented several bands assigned to free carbonyls and H-bonded carbonyls with different environments. Particularly, we observed a band at 1660 cm(-1) reported in only one publication; we demonstrated that it originated from a bonded carbonyl in a well-ordered structure. We have concluded that solvent casting has to be preferred because it enhances macromolecular ordering without chain degradation. (C) 2002 Wiley Periodicals, Inc. [References: 32]