Abstract:

Adsorption, aggregation and membrane structure of dye anions such as methyl orange(MO) and titan yellow(TY) on the cationic surface of vesicle bilayers containing schiff base were studied systemetically. The adsorption and aggregation were revealed through the wavelength shift of absorption maxinmm and precipitation produced in bianery mixture. Blue shift and red shift showed that the aggregate structure was H-aggregate for MO and J-aggregation for TY respectively. pH dependences of dyes in mixture systems indicated that the MO aggregates formed at high pH would be destroyed under low pH, which resulted from the cationic structure formation. TY aggregates were also disaggregated in considerable scale at low pH because of partial protonation, but strong red shift occurred at high pH. With temperature increasing, the aggregation of dyes would gradually be disintegrated following the change states of vesicle bilayer from gel to liquid crystal and finally to molecular dispersion. Differential Scanning Calorimetry(DSC) showed that the adsorption of dyes an action to decrease the phase transition temperature of vesicle and the differential spectra confirmed that the aggregate interaction of vesicle bilayer was weakened. 

Key words: Dye, Vesicle bilayer, Aggregation and absorption