Preparation of poly(tert-butyl acrylate)-poly(acrylic acid) amphiphilic copolymers via radiation-induced reversible addition-fragmentation chain transfer mediated polymerization of tert-butyl acrylate

Poly(tert-butyl acrylate) (PtBA) is a versatile hydrophobic macromolecule usually preferred in the development of new materials for a host of applications. PtBA homopolymers with well-defined structure and controlled molecular weight in a wide range were successfully synthesized via radiation-induced reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a trithiocarbonate type RAFT agent. The polymerization of tBA was performed under Co-60 gamma-irradiation in the presence of 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) as the RAFT agent in toluene at room temperature with three [tBA]/[DDMAT] ratios (400, 600 and 1000) and different irradiation times. Radiation-induced polymerization of tBA displayed controlled free radical polymerization characteristics: a narrow molecular weight distribution (M-w/M-n similar to 1.1), pseudo first order kinetics and controlled molecular weights. The system followed the RAFT polymerization mechanism even at very low amounts of RAFT agent ([tBA]/[DDMAT] = 1000), and molecular weights up to 113 900 with narrow dispersity ( =1.06) were obtained. PtBA was further hydrolysed into different amphiphilic PtBA-co-poly(acrylic acid) (PAA) copolymers by low (27.5%) and high (77.3%) degrees of hydrolysis. The pH sensitivity of the two copolymers was investigated by dynamic light scattering at pH 2 and pH 9 (above and below the pK(a) value of PAA) and their hydrodynamic diameters and zeta potential values were determined. (c) 2020 Society of Chemical Industry