Radical and anionic polymerization of alkyl α-cyanoacrylates have been studied using BPO and DMF as an initiator.
1. Radical polymerization.
Solution polymerization in nitromethane was 1/2 order in concentration of BPO and 1st order in concentration of the monomer.
The activation energies of the polymerization were calculated to be as follows : for methyl ester, 22.9 ; ethyl ester, 20.1; isopropyl ester, 18.8 ; n-butyl ester, 20.6 ; isobutyl ester, 20.1; and 2-ethylhexyl ester, 20.9 kcal/mol. On the other hand, the activation energies in bulk polymerization were found to be as follows : for methyl ester, 22.2; and ethyl ester, 20.4 kcal/mol.
The interrelationships among R_p, monomer concentration, and initiator concentration at 67°C were shown as follows :
R_p 2.21 × 10^-4 (BPO) ^1/2 (CNM)
R_p=2.44×10^-4 (BPO) ^1/2. (CNE)
where
(BPO) : the initial concentration of BPO (mol/l)
(CNM) : the initial concentration of methyl α-cyanoacrylate (mol/l)
(CNE) : the initial concentration of ethyl α-cyanoacrylate (mol/l)
Copolymers with methyl acrylate, methyl methacrylate, or styrene were characterized by the alternating and azeotropic nature.
2. Anionic polymerization.
Solution polymerization in nitromethane was 2 nd order in concentration of DMF and 1st order in concentration of the monomer. The activation energies of the polymerization were calculated to be as follows : for methyl ester, 9.9; ethyl ester, 8.6; isopropyl ester, 7.4; n-butyl ester, 7.6; isobutyl ester, 7.9; and 2-ethylhexyl ester, 8.0 kcal/mol.
The interrelationships among R_p, monomer concentration, and initiator concentration at 50°C were shown as follows :
R_p =2.94 × 10^-5 (DMF) ². (CNE)
where
(DMF) : the initial concentration of DMF (mol/l)
(CNE) : the initial concentration of ethyl α-cyanoacrylate (mol/l)