If there are suitable molecular interactions between nematic and non-nemati
c molecules and the resulting complexes have suitable length-to-width ratio
, nematic-isotropic phase transition temperature (T-NI) can rise contrary t
o usually observed fall. This types of rise in T-NI were observed in binary
systems composed of 5CB and aromatic acids, and were ascribed to the forma
tion of hydrogen bonded complexes between 5CB solvent and non-nematic solut
es [1-3].
We newly found that the T-NI rose in the binary systems in which there can
not be expected to exist any hydrogen-bonded complexes. We studied the poss
ibility of the complex formation by molecular interactions other than inter
molecular hydrogen bonding between 5CB and non-nematic solutes. Their conse
quences on thermal properties of binary systems were investigated.