Thermal analysis of the conformational disorder in SCLC polymers with rigid backbone - Glass transition studies

Bis [(omega-(4'-cyanobiphenyl)-4-yl)oxy-n-alkyl]norborn-5-ene-2,3-dicarboxy late was polymerised via ring opening metathesis polymerisation (ROMP). Two disubstituted polynorbornene derivatives both of cis configuration with di fferent length of the side-chain were studied. Differential scanning calori metry (DSC) was used to study the effect of thermal history on the assignme nt of the glass transition event associated with the biaxial orientation of a smectic phase. Glass transition temperatures, the change of isobaric spe cific heats at T-g and the enthalpies of isotropisation were calculated. Th e DSC traces only show the classic step-wise change in T-g in some cases, g iving the evidence that the amorphous domains are constrained and highly re stricted in movement due to the morphology developed as a result of the bia xial stretching. Based on the literature data of mono- and disubstituted po lynorbornene derivatives and our calorimetric experiments, the shape of T-g dependence on number of (CH2) units is interpreted. The origin of this sha pe is discussed.