Radical copolymerization of acrylonitrile with 2,2,2-trifluoroethyl acrylate for dielectric materials: Structure and characterization

Radical copolymerization based on acrylonitrile (AN) and 2,2,2-Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting pol- y(AN-co-ATRIF) copolymers were characterized by 1 H, 13 C, and 19 F NMR and IR spectroscopy, and size exclusion chromatogra- phy (SEC). Their compositions were assessed by 1 H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 � C from initial (AN)0/(ATRIF)0 molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer—polymer copolymer- ization curve, the Fineman-Ross and Kelen-T€ laws enabled to assess the reactivity ratios (rAN5 r1 5 1.25 6 0.04 and rATRIF 5 r2 5 0.93 6 0.05 at 70 � C) while the revised pat- terns scheme led to r12 5 rAN 5 1.03, and r21 5 rATRIF 5 0.78 at 70 � C. In all cases, rAN x rATRIF product was close to unity, which indicates that poly(AN-co-ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN-ATRIF, AN-AN, and ATRIF-ATRIF dyads. The Q and e values for ATRIF were also assessed (Q2 5 0.62 and e2 5 0.93). The glass transi- tion temperature values, Tg, of these copolymers increased from 17 to 61 � C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN-co-ATRIF) copolymers showed a good thermal sta- bility compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3856-3866