Heats of combustion and solution of liquid styrene and solid polystyrene and heat of polymerization of styrene

Abstract Bomb calorimetric measurements have yielded for the heats of combustion (—ΔHoc) at 25°C. of liquid styrene and solid polystyrene to form gaseous carbon dioxide and liquid water the values 4394.88 ± 0.67 int. kjoule per mole (1050.58 ± 0.14 kcal. per mole), and 4325.09 ± 0.42 int. kjoule per C8H8 unit (1033.89 ± 0.10 kcal. per C8H8 unit), respectively, and for the heat of polymerization of liquid styrene to solid polystyrene at 25°C. the value 69.79 ± 0.66 int. kjoule per mole (16.68 ± 0.16 kcal. per mole). The results obtained on two samples of polystyrene of different molecular weight were in agreement within the precision of the measurements. Measurements of the heat of solution of solid polystyrene in liquid monomeric styrene gave the value 3.59 ± 0.21 int. kjoule (0.86 ± 0.05 kcal.) evolved per C8H8 unit of polystyrene at 25°C. Addition of this to the value for the heat of polymerization of liquid styrene to solid polystyrene gives the value 73.38 ± 0.69 int. kjoule (17.54 ± 0.16 kcal.) per mole of styrene for the heat of polymerization of liquid styrene at 25°C., when the final product is a solution of polystyrene in styrene containing 6.9% by weight of polystyrene.