Anionic polymerization and block copolymerization of N,N-diethylacrylamide in the presence of triethylaluminum.: Kinetic investigation using in-line FT-NIR spectroscopy

We present the first kinetic study of the anionic polymerization of a N,N-dialkylacrylamide, i.e., N,N-diethylacrylamide (DEAAm). The polymerization was initiated by ethyl alpha-lithioisobutyrate (EiBLi), poly-(tert-butyl acrylate)-Li, and poly(tert-butyl methacrylate)-Li in the presence of triethylalurninum (Et3Al) in tetrahydrofuran at -78 degrees C. In situ Fourier transform near-infrared (FT-NIR) fiberoptic spectroscopy was successfully used to follow the polymerization kinetics to elucidate its mechanism. The kinetics of this process are very complex. They involve two equilibria: activation of the monomer and deactivation of chain ends by Et3Al. These two effects are in a delicate balance that depends on the ratio of the concentrations of Et3Al, monomer, and chain ends. Polymers with narrow-molecular-weight distribution are produced, whereas broadly distributed polymer is obtained in the absence of Et3Al. By using this method, well-defined poly(N,N-diethylacrylamide) (PDEAAm), poly(tert-butyl acrylate)-block-PDEAAm, and poly(tert-butyl methacrylate)-block-PDEAAm (co)-polymers were successfully synthesized, although the initiator or blocking efficiencies remained low (f < 0.70). The polymers obtained in the presence of Et3Al are rich in heterotactic triads, whereas highly isotactic polymer is obtained in the absence of Et3Al. In both cases, the polymers exhibit an lower critical solution temperature (LCST) with a cloud point at Tc approximate to 31 degrees C in water.