³¹P and ¹³C NMR of Cyclotriphosphazene Derivatives : Orientational Characteristics and Shielding Anisotropy

Abstract

³¹P and ¹³C NMR are observed for a smectic A phase of hexakis(4-(4'-dodecyl)-biphenoxy)cyclotetraphosphazene. In an intense magnetic field, the long axes of biphenylene fragments and alkyl chains align along the magnetic field, and the cyclotriphosphazene(ctp) ring-normal points preferentially at the same direction. Orientational order parameter for inorganic moiety (ctp fragment) and that for organic moiety (biphenylene fragment) are determined independently from ³¹P and ¹³C NMR spectroscopies. The two order parameters are revealed to take the same value of 0.45. which is smaller than that of the conventional smectic A liquid crystals consisting of small organic molecules. Contrasting shielding axis for ³¹P lies on the ctp ring normal, while that for aromatic ¹³C lies along the line connecting the two phenylene rings.