One-Step Poly(styrene-alt-maleic anhydride)-block-poly(styrene) Copolymers with Highly Alternating Styrene/Maleic Anhydride Sequences Are Possible by Nitroxide-Mediated Polymerization

Abstract

Styrene/maleic anhydride (S/MA) copolymerizations at initial molar MA feed concentrations fMA,0 = 0.10−0.55 were done at 80−110 °C in 50 wt % 1,4-dioxane using 5 mol % {tert-butyl-[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino}oxidanyl (SG1) relative to -2-({tert-butyl-[1-(diethoxyphosphoryl)-2,2-(dimethylpropyl)amino}oxy)-2-methylpropionic acid (BlocBuilder). As fMA,0 increased, the apparent rate constants increased dramatically. Copolymerizations performed with nearly equimolar feeds fMA,0 = 0.45−0.55 at 110 °C had apparent rate constants ∼20 times that of styrene at the same temperature. S/MA copolymerizations performed at 110 °C with practically equimolar feeds resulted in nearly alternating S/MA/S structures while those performed with fMA,0 = 0.1−0.4 possessed little to no S/MA/S alternating structures as indicated by 13C NMR spectroscopy. However, NMP of S/MA done at 90 °C with a styrene-rich feed composition (fMA,0 = 0.2) resulted in a poly(S-alt-MA)-block-poly(S) diblock in a single step. 13C NMR revealed two significant populations of triads corresponding to S/MA/S alternating sequences and to S/S/S homopoly(styrene) sequences. BlocBuilder enabled the polymerization of these one-step block copolymers with a strictly alternating S/MA first block by NMP, thus permitting NMP to join reversible addition−fragmentation transfer polymerization as another controlled radical polymerization method to attain alternating S/MA microstructures.