Using Controlled Radical Polymerization to Confirm the Lower Critical Solution Temperature of an N-(Alkoxyalkyl) Acrylamide Polymer in Aqueous Solution

N-(3-Methoxypropyl) acrylamide (MPAM) was polymerized by controlled radical polymerization (CRP) methods such as nitroxide-mediated polymerization (NMP) and reversible addition-fragmentation chain-transfer polymerization (RAFT). CRP was expected to yield well-defined polymers with sharp lower critical solution temperature (LCST) transitions. NMP with the BlocBuilder (2-([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino]oxy)-2-methylpropanoic acid) and SG1 ([tert-butyl[1-(diethoxyphosphoryl)-2,2-dimethylpropyl]amino] oxidanyl) initiating system revealed low yields and lack of control (high dispersity, D approximate to 1.5-1.6, and inhibition of chain growth). However, RAFT was far more effective, with linear number average molecular weight, (Mn-n)over-bar, versus conversion, X, plots, low D approximate to 1.2-1.4 and the ability to form block copolymers using N,N-diethylacrylamide (DEAAM) as the second monomer. Poly(MPAM) (with (Mn-n)over-bar=13.7-25.3 kg mol(-1)) thermoresponsive behavior in aqueous media revealed cloud point temperatures (CPT)s between 73 and 92 degrees C depending on solution concentration (ranging from 1 to 3 wt %). The (Mn-n)over-bar and the molecular weight distribution were the key factors determining the CPT and the sharpness of the response, respectively. Poly(MPAM)-b-poly(DEAAM) block copolymer ((Mn-n)over-bar = 22.3 kg mol(-1), D=1.41, molar composition F-DEAAM=0.38) revealed dual LCSTs with both segments revealing distinctive CPTs (at 75 and 37 degrees C for poly(MPAM) and poly(DEAAM) blocks, respectively) by both UV-Vis and dynamic light scattering. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 59-67