Deprotection of the tert-butyl ester of poly(n-butyl methacrylate-b-tert-butyl methacrylate) under flow conditions by heterogeneous catalysts leading to acidic diblock copolymers

The selective deprotection of tertiary-butyl (tert-Bu) esters in diblock copolymers of polyesters was studied via heterogeneous acid catalysts and flow reactors. Diblock copolymers composed of n-butyl methacrylate (nBMA) as the 1^st block and tert-butyl methacrylate (tBMA) as the 2^nd block were prepared by group transfer polymerization (GTP) using diisobutyl ketone (DIBK) as the solvent. The selective deprotection of the tert-Bu ester in the poly(nBMA-b-tBMA) under flow conditions was examined. The results show that the selective deprotection of the tert-Bu ester was achieved successfully via an acidic macroreticular polymeric catalyst, Amberlyst 35DRY, packed in a flow reactor. The deprotection process required 15 min of residence at 180 °C to yield acidic poly(nBMA-b-methacrylic acid) with a polydispersity index (Ð) value as low as 1.28. The durability of the catalyst was also examined during a continuous process for 1500 min by an HPLC pump.