Controlled free radical polymerization chemistry has increased the ease by which polymers with well-defined microstructures are made compared to traditional "living" methods such as ionic polymerization.  For example, acrylic acid can be directly polymerized by controlled radical methods without being in its protected form such as tert-butyl acrylate. Styrene/tert-butyl acrylate (S/t-BuA) as well as styrene/acrylic acid (S/AA) mixtures were copolymerized using nitroxide-mediated polymerization at 115-120^oC using an alkoxyamine unimolecular initiator, 2-[N-tert-butyl-2,2-(dimethylpropyl)aminooxy] propionic acid (BlocBuilder�), along with additional N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide as a free nitroxide (SG1) to observe the effect of additional SG1 on polymerization kinetics and copolymer composition.  Adding 4.5 mol% SG1/BlocBuilder greatly improved the control of random S/t-BuA copolymerization with much lower polydispersities (1.14-1.22) and a linear increase in number average molecular weight M_n with conversion up to 50%.  In contrast without additional SG1, M_n versus conversion was only linear up to ~ 20%.  In both cases, the copolymers were sufficiently "living" to re-initiate styrene polymerization to cleanly extend the chains with narrow and monomodal molecular weight distributions.  S/AA copolymerizations required higher levels of free nitroxide (9 mol% SG1/BlocBuilder) compared to S/t-BuA copolymerizations to compensate for SG1 degradation by attack from the acrylic acid monomer and to avoid excessive exotherms.  Molecular weight distributions were broader for S/AA compared to S/t-BuA random copolymerizations (polydispersities ~ 1.3-1.4 at 9 mol% SG1/BlocBuilder) and chain extensions of S/AA copolymers with styrene resulted in copolymers with broader molecular weight distributions (polydispersities >1.5) compared to their chain-extended S/t-BuA counterparts.