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Raman spectroscopic investigations of the structure and phase transitions of liquid crystalline lead(II) alkanoates

 

作者: J. Schwede,   L. Köhler,   H.P. Großmann,   M. Pietralla,   H.D. Burrows,  

 

期刊: Liquid Crystals  (Taylor Available online 1994)
卷期: Volume 16, issue 2  

页码: 267-276

 

ISSN:0267-8292

 

年代: 1994

 

DOI:10.1080/02678299408029151

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

Lead(II) alkanoates with even chain lengths from octanoate to octadecanoate have been investigated by Raman spectroscopy. In the low frequency region, transverse and longitudinal acoustical modes (TAM, LAM) have been assigned. It was shown that LAM-1 is the vibration of the double chain with the node of the vibration in the Pb2+layer. A fully extended conformation of the chains in the low temperature phase was confirmed. The frequencies and intensities of the LAMs as compared with those of the alkanes and the fatty acids led to an estimate of the force constant and polarizability of the Pb2+-COO−bond relative to the C-C bond. The defects at the chain ends were investigated in the ρ(CH3) andv(CC) region. For the intermediate (CM) phase, both the Pb2+layer distance reduction and the chain length independent enthalpy contributions can be attributed mainly to defects at the chain ends.

 

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