THERMOPHYSICAL STUDY OF LEAD(II) N-ALKANOATES BY DSC, OPTICAL MICROSCOPY, FTIR AND RAMAN-SPECTROSCOPY

Thirteen members of the lead(II) n-alkanoate series (from the n-hexano ate to the n-octadecanoate) have been synthesized, purified, and studi ed by differential scanning calorimetry, polarizing light microscopy, and FTIR and Raman spectroscopy. A solid-solid transition was found fo r all members of the series. A mesomorphic state, implying a fusion an d a clearing point, was identified as smectic C, and was present only in the lower members of the series below the n-tridecanoate. The highe r members form the isotropic liquid through a regular fusion. Temperat ures and enthalpies for the phase transitions have been measured and t he corresponding entropy changes calculated. Heat capacity measurement s between 280 K and 400 K were also carried out. A study of these magn itudes versus number of carbons was made. The solid phase previous to the liquid crystal in the lower members and to the isotropic liquid in the higher members could be identified as a 'condis' crystal (conform ationally disordered phase) by an FTIR versus temperature study.