High Resolution NMR

Abstract

(8) In our spectra obtained with a 10-s pulse interval, the carbons associated with the m segment of the heterotactic isomer were sometimes slightly less intense than those associated with the r segment. This fact indicates that there is a stereochemical influence on the dynamic behavior of TBH insofar as it influences 13C nuclear relaxation. (9) A notation is adopted here in which the closer of the two dyads with respect to the carbon under consideration is italicized in the stereosequence designation (e.g., mr) so that the two non-equivalent heterotactic resonances from each of carbons 1, 2, and 3 (7, 6, and 5) may be distinguished. ABSTRACT: Preliminary Fourier transform infrared (FT IR) studies of poly(bisphenol A carbonate) (PC)-poly(e-caprolactone) (PCL) polymer blends have been reported elsewhere. In this publication we present further results pertaining to this gordian polymer blend system. Blends of PC and PCL are compatible in the amorphous state and both polymers are capable of crystallization. Not only is the state of order of the two polymeric components in the blend a function of composition and temperature but it is also markedly dependent upon the method of film preparation. FT IR spectroscopy has been employed to study the variation of crystallinity of both components in the blend from films cast from different solvents and at different evaporation rates. The effect of exposure to acetone vapor of the polymer blend films has also been studied. Additionally, attempts have been made to obtain information concerning the origin, type, and relative strengths of polymer-solvent interactions from solution FT IR studies of PC in a variety of solvents. Finally, stepwise temperature studies of the PC-PCL blends have been performed. Polymer-induced crystallization of PC is readily observed and the results are considered in terms of the predicted Tg of the amorphous phase. The melting point of PCL in the blends may also be determined. Implications concerning the polymer-polymer interaction parameter are discussed. Introduction In a recent paper1 we presented the results of a Fourier transform infrared (FT IR) study of the poly(bisphenol A carbonate) (PC)-poly(e-caprolactone) (PCL) blend system. This is a complex blend of two polymers which are both capable of crystallization and are compatible in