Stress-strain behavior in main chain liquid crystalline elastomers: effect of crosslinking density and transverse rod incorporation on 'Poisson's ratio'

摘要

Stress—strain results are reported for two series of smecticC main chain liquid crystalline elastomers (MCLCEs). Thestructural variable in one series is crosslink density; in the other,transverse rod content. With increasing crosslinker content,the LCEs exhibit increased modulus, a shorter polydomain-to-monodomain (P—M) plateau, and a lower elongation at break.Increasing transverse rod content leads to lower clearingtemperatures and lower modulus. For each series, stress—strainmeasurement was made simultaneously with Poisson's ratio determination. For the variable crosslinker series, typicalbehavior showed the Poisson's ratio increased at small strain,rose to a maximum about 50% strain, then decreased withgreater strain. For the transverse rod series, typical behavioralso showed the Poisson's ratio increased at small strain, roseto a maximum about 50% strain, then decreased with greaterstrain. In both series, the maximum in the Poisson's ratiocorresponded to the onset of the P—M transition. Possibledeformation mechanisms are presented.