Temperature Dependence of Hydrophobically End-Capped Poly(ethylene oxide): End Chain Effect Using 13C MAS NMR
journal contributionposted on 13.11.2003, 00:00 by Youngil Lee, Jinwoo Choi, Young-Wook Choi, Daewon Sohn
13C magic angle spinning (MAS) NMR was used to determine the conformational change of hydrophobically end-capped poly(ethylene oxide), HEUR. The hydrophobic alkyl chains on both ends changed from trans to gauche with increasing temperature, while the poly(ethylene oxide) (PEO) main chain was either crystalline or amorphous (less-ordered crystalline) depending on temperature. The increased crystallinity due to intermolecular interaction of the PEO main chains increases the affinity of end hydrocarbons and results in a phase transition from trans to gauche form. Hydrocarbons on both ends functioned as spacers, and they increase the intermolecular spacing between the PEO main chains, where deshielding of 13C signal and distinct crystalline and amorphous 13C NMR peaks were observed.