Pulsed-laser and quantum mechanics study of n-butyl cyanoacrylate and methyl methacrylate free-radical copolymerization

The free-radical polymerization (FRP) kinetics for n -butyl cyanoacrylate (BCA) and methyl methacrylate (MMA) copolymerization are studied in bulk at 30–70 °C using both a pulsed-laser polymerization technique and Quantum Mechanics (QM). Through the addition of 1 v% dichloroacetic acid, the notoriously rapid anionic polymerization of alkyl-cyanoacrylates (ACA) is successfully suppressed without affecting the FRP process. A strongly alternating copolymer sequence distribution is confirmed by reactivity ratio estimates determined using 1 H-NMR composition analysis ( r BCA = 0.236 ± 0.042 and r MMA = 0.057 ± 0.008), in excellent agreement with QM predictions ( r BCA = 0.272 and r MMA = 0.057) made at 50 °C. For MMA-rich monomer mixtures (0.50 ≤ f MMA ≤ 0.97), overall propagation rate coefficients ( k p,cop ) greater than twice the value for MMA homopolymerization ( k p,MMA ) are facilitated by the strongly alternating copolymerization kinetics, whereas the BCA propagation rate coefficient ( k p,BCA ) is estimated to be only 336 ± 20 L mol −1 s −1 at 50 °C, approximately half the value of k p,MMA . These detailed results renew our understanding of the FRP kinetics for this class of monomer, important to adhesive and biomedical applications, and illustrate that an extensive and otherwise inaccessible ( via anionic polymerization) level of control can be achieved over poly(ACA) final properties.