Two-dimensional J spectroscopy: proton NMR of polysaccharides. Application to capsular heteroglycans and labeled cellulose triacetate
Two-dimensional J spectroscopy: proton NMR of polysaccharides. Application to capsular heteroglycans and labeled cellulose triacetate
复制标题
二维 J 光谱：多糖的质子 NMR。
DOI：
10.1021/ma00229a025
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发表时间：
1982
期刊：
影响因子：
5.5
通讯作者：
M. Vignon
中科院分区：
文献类型：
--
作者：
D. Gagnaire;F. Taravel;M. Vignon
结论主要结论是：(A)新的多晶型聚乙烯-癸二酸乙二酯是亚稳定的，(B)它在70QC以上的温度下转变为稳定的单斜晶型，显然是在固态中，(C)这种形式的成核被微量的水分或癸二酸(可能也有其他极性污染物)抑制，以及(D)它的晶体结构与稳定形式的晶体结构不同，主要是晶胞中心链的平面平行于角链的平面，而不是像稳定的单斜晶型那样与角链的平面成大角度。这种结构上的差异定性地解释了这种多晶型的所有已知性质，包括成核对极性污染物的敏感性。然而，要完全确定结构和对称性，需要对没有稳定形式的取向纤维进行X射线衍射研究。这种纤维的生产尚未实现，但工作仍在继续。感谢DW Dahringer和Lh Sharpe，以及A.J.Lovinger和FJ Padden，Jr.以对手稿的批判性评论的形式，帮助获得DSC数据。
Conclusions Principal conclusions are (a) that the new polymorph of polyethylene sebacate) is metastable,(b) that it transforms to the stable monoclinic form at temperatures above 70 QC, apparently within the solid state,(c) that nucleation of this form is suppressed by traces of moisture or sebacic acid (probably other polar contaminants as well), and (d) that itscrystal structure differs from that of the stable form principally in that the plane of the central chain in the unit cell lies parallel to those of the corner chains and not at a large angle to them as in the stable monoclinic form. This difference in structure accounts qualitatively for all the known properties of the polymorph, including the sensitivity of nucleation to polar contami-nants. A full determination of structure and symmetry, however, requires an X-ray diffraction study of an oriented fiber free of the stable form. Production of such a fiber has not yet been achieved but work is continuing.Acknowledgment. Assistance from DW Dahringer and LH Sharpe in obtaining DSCdata, and from A. J. Lovinger and FJ Padden, Jr., in the form of critical reviews of the manuscript, is gratefully acknowledged.