Order and Mobility in Polycarbonate−Poly(ethylene oxide) Blends Studied by Solid-State NMR and Other Techniques

Abstract

Solid-state 1D and 2D 13C CP/MAS NMR and 1H CRAMPS (combined rotation and multipulse spectroscopy) and Raman spectroscopy, X-ray scattering, and DSC were used to investigate the structure, morphology, and dynamic behavior of blends of two semicrystalline polymers, polycarbonate (PC) and poly(ethylene oxide) (PEO). The splitting of aromatic carbon signals in the 13C CP/MAS NMR spectra and the absence of spinning sidebands in the 1H dipolar spectra (2D WISE) indicate restricted mobility and hindered cooperative motions of PC chains resulting from blending of PC with PEO and from fixed ordering due to partial crystallinity of PC itself. The observed multiple splittings of the signals of aromatic and carbonate carbons indicate comparable amounts of trans−trans and cis−trans conformational structures of the carbonate group. 2D WISE spectra prove large differences in molecular mobility of amorphous PEO and PC. High mobility of amorphous PEO is not imparted significantly to less mobile PC, despite intimate mixing in the amorphous phase of PC−PEO blends suggested by 13C CP/MAS NMR spectra and CRAMPS 1H−1H homonuclear 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.