Heat of polymerization of alpha-methylstyrene from heats of combustion of monomer and 4 polymer fractions

Measurements have been made wi t h a bomb calorimeter of t he heats of combustion (-!!.HcO ) a t 25° C to form gaseous carbon dioxide and liquid water, of liq uid alpha-meth ylstyren e (l-methyl-1-phenylethylene) and four fractions of its sold polymer having number average molecular weights of (I ) 5,400, (II) 3,750, (III) 2,200, and (IV) 1,300.The values of heat of combustion a re: monom er, 1204.87 k cal/mole; fraction I , 1196.04 ; fra otion II, 1195.83;fra ction III, 1195.50 ; and f"action IV, 1194.74 k calj C9H lO unit.Values of heats of polym eri zation ( -t..HpO) at 25° C of liquid a lpha-methylstyre ne to its solid p olymers have bee n calcu la ted from t he heats of combustion .The values of hea t of po lyme rization are: fraction I , 8.83; fra ction II, 9.04 ; fra ction III, 9.37 ; and fra ction IV, 10.13 k cal jm ole of monomer.The standarcl deviat ion of t he mean for heat of combustion are n ot more than 0.30 kcaljmol e, and for heat of pol y meri zation, no t m ore t han 0.26 kcal/mole.The cl ec rease in heat of poly me ri zation wi t h in creasin g m olec ular weigh t is di sc ussed .The low valu es of heats of polyme ri zation a re a scribed in part to s teri c in terference betwee n t he substit ue nt groups of the poly m er chain .