Effect of spacer length on the liquid crystalline property of azobenzene-containing ABA-type triblock copolymers via ATRP

摘要

The effect of flexible spacer length on the liquid crystalline property of ABA-type triblock copolymers containing azobenzene groups was investigated.For the study,the monomers,n-[4-(4-ethoxyphenylazo)phenoxy]alkyl methacrylates with varying methylene groups (n = 0,2,6) were used to synthesize a series of azobenzene-containing amphiphilic triblock copolymers PAnC-PEG-PAnC by atom transfer radical polymerization (ATRP).Differential scanning calorimetry (DSC),polarizing optical microscopy (POM),and one-dimensional X-ray diffraction (1D WAXD) have shown that the glass transition temperatures of these copolymers decreased with increasing n,PAOC-PEG-PAOC has no mesophase,while both PA2C-PEG-PA2C and PA6C-PEG-PA6C have a nematic mesophase.These differences derive from the length of spacer groups between the polymer backbone and side-chain LC monomers.