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SYNOPSISA novel family of fluoroterpolymers was prepared, containing perfluoroalkylethyl methacrylate (PFAEM) , methacrylic acid (MAA) , and 2-hydroxyethyl methacrylate (2-HEM)residues. The refractive index of the fluoroterpolymers is in the range of 1.3675 5 n I 1.4275. The surface tension of cured thin films falls in the interval from 15 m N / m to as low as 8 mN/m. Upon heating, these polymers undergo thermally initiated self-crosslinking and develop tenacious bonding to substrates. The associated chemical reactions and products were identified by IR spectroscopy and some thermogravimetric scans. The spectra indicate that the reaction products are ester and anhydride groups. In general, the formation of esters occurs more rapidly and requires lower temperatures ( 2 110°C) than does the formation of anhydrides. Prolonged heating, especially a t higher temperatures ( 2 15OoC), favors the formation of anhydrides. When the molar ratio of MAA to 2-HEM is substantially larger than 1.0, the formation of anhydride is favored when the ratio is 1 : 1, the formation of ester is favored; and when the molar ratio is much smaller than 1.0, the rate of formation of both esters and anhydrides is greatly reduced. In the case of the fluoroterpolymers, the formed esters and anhydrides essentially originate exclusively from the MAA and 2-HEM and seem not to involve any attack on the PFAEM residues. Only after very long heating a t the higher temperatures employed, some loss of C-F band intensity was noted. In a copolymer of PFAEM and MAA, a substantial and rapid attack by the acid on the ester group in the PFAEM residues takes place under relatively mild conditions. Such and more drastic conditions appear not to affect at all a homopolymer of PFAEM alone. This suggests that in the fluoroterpolymers the more polar MMA and 2-HEM tend to aggregate close together, so that, when heated, they preferentially react with each other, forming both esters and anhydrides. In the absence of 2-HEM, the MAA may react with itself or with PFAEM, producing only anhydride groups. Both esters and anhydrides may be intermolecular and/or intramolecular, resulting in a cross-linked system in which the cross-link concentration is directly related to the combined amount of ester and anhydride groups.

The Copolymerization reaction of hexafluoroisobutylene (HFIB) and vinylidene fluoride (VF2) was studied using X‐band electron spin resonance (ESR) by applying a photo‐in situ method. Owing to the toxicity of HFIB monomer, the flow ESR method could not be directly applied without extensive modification. The observed ESR signal with 21‐line hyperfine structure was assigned to the copolymer radical with head‐to‐head configuration. Although the HFIB monomer radical possesses the same hyperfine pattern, the ambiguity has been removed by using CF3 as an initiator radical. Owing to the high steady‐state concentration of the observed copolymer radical with head‐to‐head configuration as well as the nature of the static photo‐in situ ESR method, we believe the actual molecular configuration for HFIB/VF2 copolymer must be head‐to‐tail. The observed hyperfine constant for AβF = 1.74 mT suggests that the geometry for HFIB/VF2 copolymer radicals with both head‐to‐head or head‐to‐tail configurations is possibly similar to that of (CF3)3C· radical. The small value for AβH indicates steric hindrance to rotation about the CαCβ bond, and this is also supported by the experimental results of nonalteration in linewidth during the temperature dependence study from −40 to about 90°C. Attempts to measure directly the monomer reactivities have been unsuccessful owing to the fact that not all the possible radicals were detected, but nevertheless the relative reactivities of VF2 and HFIB could be estimated. The relative reactivities of VF2 and HFIB monomers and the steric hindrance effect indicate that the conformation of the copolymer is head‐to‐tail; this has been further confirmed by infrared analysis.