Determination of Absolute Rate Constants for Radical Polymerization and Copolymerization of Ethyl Alpha-Cyanoacrylate in the Presence of Effective Inhibitors against Anionic Polymerization

1025 Makromol. Chem. 184,1025 - 1033 (1983) Determination of Absolute Rate Constants for Radical Polymerization and Copolymerization of Ethyl a-Cyanoacrylate in the Presence of Effective Inhibitors against Anionic Polymerization Bunichiro Yarnada, Minoru Yoshioka, Takayuki Otsu * Department of Applied Chemistry, Faculty of Engineering, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558, Japan (Date of receipt: September 6, 1982) SUMMARY: The absolute rate constants of propagation kp and of termination k, of ethyl a-cyanoacrylate (ECNA) were determined in bulk at 30°C by means of the rotating sector method under conditions to suppress anionic polymerization; k, = 1 622 1. mol-' . s and k, = 4,11 . lo8 l . m o l - ' . s - ' for the polymerization in the presence of acetic acid, and k, = 1610 1 .mol - . s - and kt = 4,04. lo8 1 . mol - . s for the polymerization in the presence of 1,3-propanesultone. The magnitude of k i / k , determined was 6,39. 1. mol-I . s-'. The absolute rate constants for cross-propagation in ECNA copolymerizations were also evaluated. Quantitative comparison of the rate constants with those of common monomers and polymer radicals shows that the strong electron-withdrawing power of the ethoxycarbonyl and cyano groups enable the poly(ECNA) radical to add to monomers as fast as the other polymer radicals. The relatively high reactivity of ECNA, regardless of the type of attacking polymer radical, is interpreted by a transition state greatly stabilized by both the ethoxycarbonyl and the cyano groups. ' ' ' -' Introduction It is known that a-cyanoacrylic esters are highly susceptible to anionic polymerization even in the presence of a trace of a weak base's2), as well as vinylidene cyanide3) and diethyl methylenemal~nate~). a-cyanoacrylates are, however, able to form The homopolymers and copolymers exclusively by a radical chain mechanism5-I1), if the anionic polymerization is suppressed by an effective inhibitor. As the result of the radical copolymerization with a variety of monomers, the a-cyanoacrylates are known to be the most powerful electron-accepting monomers with homopolymerization ability. The e and Q values of methyl a-cyanoacrylate (MCNA) were evaluated to be 2,18 and 17, respectivelyr0),and these values have been explained in terms of the polar and resonance effect of the methoxycarbonyl and cyano group bound directly to the carbon-carbon double bond I ' ) . Recently, the reactivity of MCNA toward the benzoyloxyl radical generated from benzoyl peroxide has been estimated to be much lower than that of styrene (St) in conformity with the highly electronegative character of the reacting carbon-carbon double bond j2). Furthermore, the heat of polymerization evaluated for the radical polymerization of MCNA was as low as 42 kJ . mol-I, owing to destabilization of the polymer chain by the substituents and stabilization of the monomer due to conjugationI3). 0025-116)