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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 (Cp, 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.

Samples of poly(viny1idene fluoride) with weight average molecular weights between 100,000 to 500,000 were analyzed using differential scanning calorimetry to study the influence of molecular weight on crystallization. Isothermal crystallization from the melt was investigated between 140 and 145°C. Crystallization rates were analyzed in terms of the Avrami equation. Avrami exponents between 3 and 11 were observed depending upon the microstructure, molecular weight, and cooling rate. The midrange molecular weight samples were found to crystallize slower than the high and low molecular weight materials.

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