Effect of Spacer Length on the Liquid Crystalline Property of Azobenzene-Containing ABA-Type Triblock Copolymers via ATRP
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 as n increases. PA0C-PEG-PA0C has no mesophase, while both PA2C-PEG-PA2C and PA6C-PEG-PA6C have a nematic mesophase. These differences derive of the length of spacer groups between the polymer main chain and side chain.
Yuan Ming Huang
X. D. Tang et al., "Effect of Spacer Length on the Liquid Crystalline Property of Azobenzene-Containing ABA-Type Triblock Copolymers via ATRP ", Key Engineering Materials, Vols. 428-429, pp. 67-70, 2010