Thermo- and pH-responsive POEGMA-b-PDMAEMA-b-POEGMA triblock copolymers

A series of thermo- and pH-responsive triblock copolymers based on poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) and poly(N, N-dimethylaminoethyl methacrylate) (PDMAEMA) were synthesised by RAFT polymerisation. The kinetics of the polymerisation of OEGMA and DMAEMA have been studied. The effect of the degree of polymerisation (DP) of the OEG side chain of the POEGMA block and the PDMAEMA block, temperature, pH, solvent, and concentration on the phase behaviour of the POEG(x)MA(y)-b-PDMAEMA(z)-b-POEG(x)MA(y) copolymers solutions were investigated comprehensively. At pH 5, the self-assembly of POEG(5)MA(17)-b-PDMAEMA(z)-b-POEG(5)MA(17) copolymers induced by heating was driven by the POEG(5)MA dehydration, resulting in structures with hydrodynamic radii RH > 100 nm. On the other hand, at pH 9,H- 1 NMR studies showed that both blocks, PDMAEMA and POEG5MA, dehydrated with increasing temperature, forming stable aggregates with RH approximate to 20 nm, at a concentration of 0.125 mg mL(-1). However, by increasing the concentration to 5 mg mL(-1), these aggregates precipitated above 70 degrees C. The increase in the DP of the PDMAEMA block caused a decrease in the RH of aggregates at pH 7 and 9 at 25 degrees C. This effect was gradually attenuated by the increase in the DP of the OEG side chain and accompanied by an increase in the T-cp of the PDMAEMA block. Cryo-TEM images showed that the copolymers self-assembled as spherical and elongated micelles depending on their concentration and temperature. The copolymers were capable of Reichardt's dye incorporation at pH 9, demonstrating the hydrophobic nature of the PDMAEMA core of the self-assembled structures.

Automated summary

A series of thermo- and pH-responsive triblock copolymers were synthesized and their phase behavior was comprehensively studied. The copolymers exhibited self-assembly into different aggregates depending on pH and temperature conditions.