Abstract
Bulk iodine transfer copolymerizations (ITcoPs) of styrene(ST) with either α-fluoromethylstyrene (FMST) or α-trifluoromethylstyrene(TFMST) in the presence of a 1-iodoperfluorohexane as the chaintransfer agent (CTA) are presented. The resulting poly(F-ST-co-ST)copolymers were characterized by 1H, 13C, and 19F NMR spectroscopythat evidenced a satisfactory incorporation of fluorinated α-methylstyrenes(F-ST, ca. 9−16 mol % almost as that inserted in the feed). Bothfluoromonomer conversions and the vanishing of the CTA were alsomonitored by 19F NMR spectroscopy versus time. The controlled character of these copolymerizations was studied by bothsupplying a linear evolution of the experimental molar masses (Mns) versus the monomer conversion and evaluating the chainextension ability of the formed copolymers. The amounts of dead chains in all copolymers were lower than 5%. The bulkier CF3group induced a slightly lower reactivity of TFMST comonomer since in the first step, the experimental Mns of the copolymerscontaining TFMST reached 43 000 g mol−1 while those based on FMST displayed 65 000 g mol−1. In the second step, theproduced diblock copolymers had Mns twice higher than those of the starting copolymers, still containing the iodine end-group,as evidenced by a further azidation. In addition, the exchange constants characteristic of both degenerative transfer reactions wereassessed (Cex = ca. 1.8 at 70 °C). Finally, the thermal properties of the resulting copolymers were investigated by differentialscanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The insertion of a small amount (<10 mol %) offluorinated monomeric units promoted a significant rise of the glass transition temperatures of the resulting copolymers up to117 °C and a better thermal stability than PST. Indeed, poly(TFMST-co-ST) copolymers were the most thermally stable, with a10% weight loss at 351 °C. Additionally, the correlation of difference in the wettability of such partially fluorinated copolymers tochanges in the chemical composition of the films was explored by contact angle measurements that reached 116° with 10−15mol % of TFMST units.