THE IONIC POLYMERIZATIONS OF METHYL GLYOXYLATE

Methyl glyoxylate has been polymerized in CH2Cl2 solution either cationically or anionically to give the corresponding polyacetal. Thermodynamic and kinetic results of the polymerizations initiated by CF3SO3H, BF3OEt2, and NEt3 are reported here. Monomer conversion was followed by UV and active centers concentrations were determined through phosphorus end-capping. A ceiling temperature of 26-degrees-C was observed for M(eq)=1 mol.l-1 (T(c)) =109-degrees-C for bulk) with DELTAH-degrees=-29.5 kJ.mol-1 and DELTAS-degrees=-99 J mol-1.K-1. Both initiations were found instantaneous and quantitative, and no termination was observable within the time scale of the reaction (second to hour). Cationic propagation appears to take place essentially on free ions (k(p+) almost-equal-to 60 l.mol-1.s-1 at -20-degrees-C) in equilibrium with a larger amount (K(d) almost-equal-to 6.7.10(-6) mol.l-1) of much less reactive ion-pairs (k(p+)/- almost-equal-to 0.16 +/- 0.03 l.mol-1.s-1). A stopped-flow device was used to follow the much more rapid anionic polymerization (k(p,app) almost-equal-to 8 +/- 2.10(3) l.mol.s-1 at -20-degrees-C).