Carbochain polymers and copolymers — X. Polymerization in bulk of methyl methacrylate in the presence of tributylboron

Abstract

IT has been established previously by us that tributylboron is a polymerization catalyst for methyl methacrylate ill bulk [1] and in solution [2]. To clarify the basic laws of methyl methacrylate polymerization in bulk in the presence of tribl~tylboron we undertook all investigation on the effect of various factors on the course of the polymerization process. The method of carrying out the experiments was as follows. A solution of tributylboron in the methyl methacrylate was used to fill a dilatometer, the volume of which was known for the temperature at which the polymerization was carried out, as well as the volume of a unit of the capillary. The filled dilatometer was put into a thermostat at the given temperature and the changes in the height of the liquid column in the capillary were registered. For calculation of the yield of polymer we used the data [3] of Schulz and Harborth, who determined the volume changes of methyl methacrylate for full conversion to polymer at various temperatures, and showed that there is a direct relationship between the yield of polymer and the decrease in volume. At the end of the experiment the dilatometer was broken, the polymethyl methacrylate dissolved in dichlorethane and reprecipitated by introducing this solution drop by drop into a large volume of methyl alcohol with vigorous agitation. The characteristic viscosity of the reprecipitated polymer was determined at 20°C (solution in dichlorethane). On the basis of the results obtained the velocity constants were calculated for polymerisation of methyl n;ethacrylate as a reaction of the first order. In the first series of experiments we studied the effect of polymerization temperature on the velocity of the process for constant concentrations of tributylboron (0.10 tool %) on the methyl methacrylate. The results of this series of experiments are given in Table 1. The mean values of the velocity constants at 30, 40, 50, 60 and 70 ° are respectively l . ] 4× l0 --5, 3.63× ]0 -5, 5.82× l0 -5, 14.8x l0 -5 and 23.1X l0 -5 sec -1. The