ABSTRACT:   Poly(ethylene glycol) methyl ether acrylate (PEGA) nitroxide-mediated polymerizations in bulk were studied at two temperatures (115oC and 125oC) and at concentrations of 5.2-20.7 mol% of added free nitroxide (N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (SG1) relative to the unimolecular initiator 2-[N-tert-butyl-2,2-(dimethylpropyl)-aminooxy] propionic acid (BlocBuilder�).  Polymerizations were more controlled at 115oC with SG1/BlocBuilder� ratios from 10.4-20.7mol% giving polymers with polydispersity indices ( ) as low as 1.17 and a linear increase in number average molecular weight with conversion up to about 50%.  Chain extension of a comb-like poly(PEGA) ( = 8.1 kg/mol, = 1.20) with styrene in 50 wt% dimethylformamide (DMF) at 115oC indicated sufficient "livingness" of the poly(PEGA) chain ends as observed by the linear increase in and monomodal molecular weight distribution as determined by gel permeation chromatography ( = 62.3 kg/mol and = 1.53).  1H nuclear magnetic resonance confirmed the final block copolymer composition to be 23 mol% EG and differential scanning calorimetry revealed two distinct glass transition temperatures T_g indicative of the PPEGA (T_g =  -70^oC) and PS (T_g = 98^oC) segments.