Bulk polymerization of diallyl benzene-dicarboxylates. II. Effect of temperature on the gel point

The effect of bulk polymerization temperature on the gelation of diallyl phthalate (DAP), diallyl isophthalate (DAI), and diallyl terephthalate (DAT) has been investigated in the temperature range 353–568 K (80–295°C). The critical double‐bond conversion at the gel point increases significantly with temperature in a different manner for each of the monomers: for DAP, from ca. 17% at 353 K up to 46% at 568 K, whereas for DAI and DAT, from 15% and 13.5% up to 32 and 33%, respectively. These values are, on average, four to six times higher than those predicted according to Stockmayer's equation. Surprisingly, the yield of prepolymer precipitated just before the gel point is almost the same for DAP, DAI, and DAT at every polymerization temperature despite different tendencies to cyclization for each of the monomers. The yield increases significantly with the temperature: from ca. 24% at 353 K up to above 60% at 568 K. These yields are four to six times higher than are critical prepolymer contents predicted according to Gordon's theory. Empirical relationships between the gel point parameters and temperature have been developed.