Copolymerization of unsaturated spiro ortho esters with maleic acid derivatives

Abstract

AbstractThe formation of charge‐transfer (CT) complexes of unsaturated spiro ortho esters such as 2‐methylene‐1,4,6‐trioxaspiro[4.4]nonane(I) and 2‐methylene‐1,4,6‐trioxaspiro[4.6]undecane(II) with maleic acid derivatives such as maleic anhydride (Manh), dimethyl maleate (DMM), and N‐ethyl maleimide (NEM) was ascertained by ultraviolet (UV) and nuclear magnetic resonance (NMR) spectroscopy. The stoichiometries of these complexes were estimated as 1:1. The determination of their equilibrium constants (K) was attempted by using the Hanna‐Ashbough equation with NMR spectroscopy. Although K values for I‐DMM and II‐DMM were specified as 0.266 and 0.336 L/mol, respectively, those for the other systems could not be obtained but were assumed to be negligible small (K ≪ 1). Copolymerization of these systems which was carried out without an initiator determined that spontaneous copolymerization occurs in all cases but that the copolymerization rates of I‐DMM and II‐DMM systems are slow. The systems in which Manh or DMM was used as an acceptor monomer gave the alternating copolymers at various monomer to feed ratios. The terpolymerizaton of the I–Manh–DMM system established that DMM takes little part in giving the alternating copolymers I and Manh. Consequently, it was assumed that the reactivity of the CT complex monomer is dependent on the contribution of the dative structure to CT complex.