Iodine transfer copolymerization of fluorinated α-methylstyrenes with styrene using 1-iodoperfluorohexane as the chain transfer agent

Journal article

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 chain transfer agent (CTA) are presented. The resulting poly(F-ST-co-ST) copolymers were characterized by 1H, 13C, and 19F NMR spectroscopy that evidenced a satisfactory incorporation of fluorinated α-methylstyrenes (F-ST, ca. 9-16 mol % almost as that inserted in the feed). Both fluoromonomer conversions and the vanishing of the CTA were also monitored by 19F NMR spectroscopy versus time. The controlled character of these copolymerizations was studied by both supplying a linear evolution of the experimental molar masses (Mns) versus the monomer conversion and evaluating the chain extension ability of the formed copolymers. The amounts of dead chains in all copolymers were lower than 5%. The bulkier CF3 group induced a slightly lower reactivity of TFMST comonomer since in the first step, the experimental Mns of the copolymers containing TFMST reached 43 000 g mol-1 while those based on FMST displayed 65 000 g mol-1. In the second step, the produced 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 were assessed (Cex = ca. 1.8 at 70 °C). Finally, the thermal properties of the resulting copolymers were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The insertion of a small amount (<10 mol %) of fluorinated monomeric units promoted a significant rise of the glass transition temperatures of the resulting copolymers up to 117 °C and a better thermal stability than PST. Indeed, poly(TFMST-co-ST) copolymers were the most thermally stable, with a 10% weight loss at 351 °C. Additionally, the correlation of difference in the wettability of such partially fluorinated copolymers to changes in the chemical composition of the films was explored by contact angle measurements that reached 116° with 10-15 mol % of TFMST units.

Authors: Walkowiak-Kulikowska, J; Szwajca, A; Boschet, F; Gouverneur, V; Ameduri, B

• Publisher: American Chemical Society
• Journal: Macromolecules
• Volume: 47
• Issue: 24
• Pages: 8634-8644
• Publication date: 2014-12-23
• DOI: 10.1021/ma501828w
• EISSN: 1520-5835
• ISSN: 0024-9297
• Language: English