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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.
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.