Routes to carboxylic acid functional acrylonitrile copolymers via N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) free nitroxide based nitroxide‐mediated polymerization

Abstract

AbstractStyrene (S)/acrylonitrile [AN; initial acrylonitrile molar feed compositions (fAN,0's) = 0.10–0.86) and tert‐butyl methacrylate (tBMA)/AN (fAN,0 = 0.10–0.80) copolymers were synthesized at 90°C in 50 wt % 1,4‐dioxane solutions with a unimolecular initiator, N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl) hydroxylamine [BlocBuilder (BB)]. In the tBMA/AN copolymerizations, 8.0–8.5 mol % N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) free nitroxide relative to BB was added. The S/AN copolymers exhibited narrow, monomodal molecular weight distributions (MWDs) with low polydispersities [weight‐average molecular weight (Mw)/number‐average molecular weight (Mn) = 1.14–1.26], and the Mn versus monomer conversion (X) plots were relatively linear (Mn = 18.1 kg/mol, X ≈ 0.7); this suggested that pseudo‐living behavior was approached. AN proved to be an effective controlling comonomer for tBMA because the tBMA/AN copolymers exhibited narrow monomodal MWDs with Mw/Mn = 1.17–1.50 and relatively linear Mn versus X plots to reasonably high X values (Mn = 15.6 kg/mol, X ≈ 0.6). The AN and S monomer reactivity ratios were rAN = 0.07 ± 0.01 and rS = 0.27 ± 0.02 (Fineman–Ross) and rAN = 0.10 ± 0.01 and rS = 0.28 ± 0.02 (Kelen–Tüdos), respectively; these values were in good agreement with conventional free‐radical polymerization. Error‐in‐variables model (EVM) analysis indicated that the use of cumulative composition S/AN data was more effective than typical approaches using low‐X data with the Mayo–Lewis model. The AN and tBMA reactivity ratios [rAN = 0.07 ± 0.01 and rtBMA = 1.24 ± 0.20 (Fineman–Ross) and rAN = 0.14 ± 0.01 and rtBMA = 0.89 ± 0.19 (Kelen–Tüdos)] were similar to those reported for related alkyl methacrylate/AN conventional radical copolymerizations. EVM analysis suggested significant experimental error was associated with the tBMA/AN system, and this warrants further investigation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012