Order and mobility in polycarbonate-poly(ethylene oxide) blends studied bysolid-state NMR and other techniques

Solid-state 1D and 2D C-13 CP/MAS MMR and H-1 CRAMPS (combined rotation and multipulse spectroscopy) and Raman spectroscopy, X-ray scattering, and DSC were used to investigate the structure, morphology, and dynamic behavior o f blends of two semicrystalline polymers, polycarbonate (PC) and poly(ethyl ene oxide) (PEO). The splitting of aromatic carbon signals in the C-13 CP/M AS NMR spectra and the absence of spinning sidebands in the H-1 dipolar spe ctra (2D WISE) indicate restricted mobility and hindered cooperative motion s of PC chains resulting from blending of PC with PEO and from fixed orderi ng due to partial crystallinity of PC itself. The observed multiple splitti ngs of; the signals of aromatic and carbonate carbons indicate comparable a mounts of trans-trans and cis-trans conformational structures of the carbon ate group. 2D WISE spectra prove large differences in molecular mobility of amorphous PEO and PC. High mobility of amorphous PEO is not imparted signi ficantly to less mobile PC, despite intimate mixing in the amorphous phase of PC-PEG blends suggested by C-13 CP/MAS NMR spectra and CRAMPS H-1-H-1 ho monuclear dipolar dephasing and proved by 2D CRAMPS and WISE spin diffusion measurements. The morphology and domain sizes at the nanometer scale were determined from analysis of spin diffusion processes.