Associative properties of hydrophilic tip modified oxyethylene-oxybutylene diblock copolymers in aqueous media: Effect of end-group

摘要

The associative properties of Me _2N (CH _2) _2OE _(58)B _7 and I ~-Me _3N ~+(CH _2) _2OE _(58)B _7 in aqueous solution in the temperature range of 20-50°C have been investigated by dynamic and static laser light scattering. Here E represents an oxyethylene unit and B an oxybutylene unit. The results obtained were compared with results for E _mB _n analog. Our result shows that for micelles of dimethylamino-tipped, the hydrodynamic radius, was large as compared with the thermodynamic radius r _t, suggesting a "soft" micelle. For the trimethylammonium-tipped copolymer, r _h decreases and r _t increase with the increase in temperature. Also the values of association number, N _w, were low but increase with increase in temperature, indicating a change from soft micelle at low temperature to small, less swollen micelles at high temperature. The high values of thermodynamic volume per molecule, r _t/N _w, for a polymer with charged tip could be attributed to intermicellar charge effect. The effect of salt on various micellar parameters has also been discussed.