Molecular mechanism of the ring-flip process in polycarbonate

Autor:	Robert Yaris, Jacob Schaefer, Dennis Perchak, Jeffrey Skolnick, Edward O. Stejskal
Rok vydání:	1985
Předmět:	Reaction mechanism Polymers and Plastics Ring flip Chemistry Organic Chemistry Oxide Carbon-13 NMR Inorganic Chemistry Crystallography Dipole chemistry.chemical_compound Lattice (order) visual_art Polymer chemistry Materials Chemistry Spin echo visual_art.visual_art_medium Polycarbonate
Zdroj:	Macromolecules. 18:368-373
ISSN:	1520-5835 0024-9297
DOI:	10.1021/ma00145a012
Popis:	Calculations of the conformational preferences of isolated single chains of poly(2,6-di- methylphenylene oxide) (PPO) and bisphenol-A polycarbonate (PC) predict that the rings of both chains are nearly free rotors at room temperature. However, experimental dipolar rotational spin-echo 13C NMR shows that in the glass, the rings of PPO execute only small-amplitude motions while those of PC undergo primarily 180' ring flips (a hindered rotation) superimposed on some wiggles. Geometrical considerations of the dense packing of chains in the glass suggest that the rings of adjacent chains block rotational freedom. We propose that the mobility of the PC main chain results in lattice distortions which allow ring flips not permitted by the stiffer PPO main chain.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::948eb2d4c3cd3876a826050f11628127 https://doi.org/10.1021/ma00145a012 Zobrazit plný text záznamu