Tricomponent thermoresponsive polymers based on an amine-containing monomer with tuneable hydrophobicity: Effect of composition

In the present study, six dual-responsive ABC triblock copolymers were synthesised via group transfer polymerisation (GTP) and investigated through visual inspections in terms of their thermoresponsive behaviour. The copolymers consist of i) penta(ethylene glycol) methyl ether methacrylate (PEGMA), which is hydrophilic and thermoresponsive at high temperatures, ii) n-butyl methacrylate (BuMA) as the hydrophobic counterpart to promote self-assembly, and iii) 2-(diethylamino)ethyl methacrylate (DEAEMA), which is pH-responsive by adjusting its hydrophilicity depending on the pH. The effect of the degree of ionisation of DEAEMA units as well as the ionic strength effect on the self-assembly behaviour of the copolymers was tested via dynamic light scattering (DLS). The dissociation constants (pKa) of the amine units of DEAEMA were determined via potentiometric titrations. The thermoresponse has been primarily been investigated in means of cloud points (CPs) at various pH values in deionised water. Detailed phase diagrams were constructed for all the polymer solutions in phosphate buffered saline (PBS), with the interest being focused on the gelation area. It has been clearly proven that gelation is promoted as the content in BuMA and DEAEMA is increased. The polymer that presented the widest gelation area has been further investigated via rheology in terms of its gelation temperature, gelation time and shear-thinning properties