Homo- and copolymers of 4-fluorostyrene (FSt) and styrene (St) were synthesized with different feed ratios using free radical bulk polymerization with azobisisobutyronitrile (AIBN) as initiator. It yielded series of (co)polymers with various amounts of included FSt, P(St-co-FSt) (5-50 mol%) and PFSt. The effect of the initiator concentration on the molecular weights of the homopolymers, that is, PSt and PFSt was investigated. Copolymer compositions were determined by nuclear magnetic resonance spectroscopy. The relative reactivity ratios of both comonomers were determined by applying the conventional linearization methods of Jaacks (J), Finemann-Ross (F-R), inverted Finemann-Ross (IF-R), and Kelen-Tudos (K-T). The reactivity ratios values of St and FSt obtained from J plot are 1.06 and 0.84, F-R plot are 1.18 and 1.06, IF-R 1.01 and 0.86, and K-T plot 1.04 and 0.88, respectively. Thermal properties of prepared (co)polymers, that is, glass transition temperature (T-g) and thermal stability, were determined from differential scanning calorimetry and thermogravimetrical measurements. The lack of significant influence of FSt comonomer content on T-g of (co)polymers was observed. Additionally, the thermal degradation kinetics of obtained PSt and PFSt was studied by thermogravimetric analysis. Kinetic parameters such as the thermal decomposition activation energy (E) and frequency factor (A) were estimated by Ozawa model [E(O) and A(O), respectively] and Kissinger model [E(K) and A(K), respectively]. The activation energy and the frequency factor of PFSt (253 kJ/mol) were higher than PSt (236 kJ/mol). The resulting activation energies estimated using the two methods were quite close. POLYM. ENG. SCI., 54:1170-1181, 2014. (c) 2013 Society of Plastics Engineers