The heat capacity of solid and liquid polystyrene,p-substituted polystyrenes,and crosslinked polystyrenes

Heat capacities were measured for poly(4-methylstyrene) 300–500K], poly(4-fluorostyrene) 130–350K], poly(4-chlorostyrene) 300–550K], poly(4-bromostyrene) 300–550K], poly(4-iodostyrene) 300–550K] and poly(styrene-co-divinylbenzene) with 1, 2, 4, 8, and 12 wt.% divinylbenzene (technical grade) 300–550K]. Polystyrene and poly(α-methylstyrene) data were found to match the ATHAS data bank collections. Crosslinking causes no significant change in heat capacity, but substitution does. The heat capacities in the solid state are evaluated using approximate group and skeletal vibration spectra. Glass transitions are discussed, and full thermodynamic functions (C_p, H, S, G) can be calculated for amorphous, crystalline, and deuterated polystyrene as well as poly(α-methylstyrene). Glassy polystyrene has an entropy of 7.5 J K^?1 mol^?1 at absolute zero. Changes of the heat capacity at the glass transition are explained and are predicted to go to zero for 50% poly(styrene-co-divinylbenzene) at about 550K.