Abstract Stimuli responsive double hydrophilic diblock copolymers poly(N-isopropylacrylamide)-b-poly(N,N-dimethylaminopropylacrylamide) (PNIPAM-b-PDMPA) with constant degree of polymerization (DP) of PNIPAM (=127) and varying DP of PDMPA (=31 and 66) were synthesized by RAFT polymerization, and characterized by NMR, FTIR and GPC. In dilute aqueous solutions, the copolymers remain as unimers in equilibrium with loosely bound aggregates and form aggregates with PNIPAM core in the presence of NaCl or at temperatures above the LCST of PNIPAM. However, at higher temperatures i.e. above cloud point temperature (CPT) of PNIPAM127-b-PDMPA66, core-shell micelles are formed with PNIPAM core. The CPT of both block copolymers decrease in the presence of NaCl and in acidic pH, but increases with increase in DP of PDMPA. The copolymer showed enhanced surface activity in the presence of NaCl. The temperature dependent micellization observed from NMR is supported by turbidity and fluorescence. PDMPA is highly protonated in acidic pH; cryo-TEM and SANS confirm the formation of threadlike micelles in the presence of SDS.
- Double hydrophilic block copolymers
- Stimuli responsive