Abstract
The 13C CP/MAS(cross polarization/magic angle spinning) NMR spectrum of solid poly(γ-benzyl l-glutamate) (PBLG) was measured at the slow spinning rate of 1.9 kHz. The exact principal values of the 13C chemical shift tensor (δ11, δ22, and δ33) for the main-chain carbonyl carbons of PBLG were obtained from an intensity analysis of the spinning sidebands, according to Hertzfeld−Berger method. Further, the 13C CP/MAS NMR spectra and static 13C CP NMR of PBLG were measured in a liquid crystalline solution, where PBLG takes the α-helix form. The experimental results show that there exists a linear relationship between the order parameter S and the observed main-chain carbonyl 13C chemical shift, δobs, such as S = 0.024 × δobs − 3.758. Using the δobs value and the S-δobs relation, the order parameter S of PBLG in the liquid crystalline state was determined to be 0.875 ± 0.025. The δobs value was then used as a monitor for determining the degree of orientation of PBLG in the PBLG gel. Furthermore, the diffusional...
Published Version
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