To better understand the stereochemistry of poly (bicyclobutane-1-carbonitrile) (PBBC), 13C NMR studies were performed for a series of 3-substituted cyclobutanes. Of particular interest were the syntheses and NMR assignments for the two dimers (cis-and irans-3-(l-cyanocyclobutyl)cyclobutane-l-carbonitrile) and the four trimers. In all of the molecules studied, substituents at C3, which were cis to the nitrile, led to 13C NMR shifts of the nitrile that were 1-1.5 ppm to high field of those for the trans isomer; therefore the nitrile chemical shift is a very useful probe of cis/trans stereochemistry in cyclobutanecarbonitriles. Using data for cyclobutanecarbonitrile and the two dimers, we obtained additivity relationships; the calculated 13C resonances
SynopsisThe two title monomers were synthesized. In both cases the key cyclobutane intermediates were obtained by cycloaddition of allene to acrylonitrile or chloromaleic anhydride. These two new monomers proved to be highly reactive in free radical polymerization, and each polymerized spontaneously in air at room temperature. Linear polymers were prepared in dimethyl sulfoxide solution at 35" with AIBN and UV light. At higher temperatures crosslinking became a problem in some instances. The structure of the polymers derived from 1,4 polymerization in the diene portion of the monomers was confirmed by '3c-NMR, 'H-NMR and I R spectra. Copolymers were prepared with methyl methacrylate, styrene, and p-methoxystyrene and were always rich in the methylenecyclobutene monomers used. Films of homopolymers and copolymers codd be cast from chloroform solution.
Homopolymers and copolymers of vinyl fluoride are based on free‐radical polymerization of vinyl fluoride and comonomers, usually under high pressure. Du Pont first commercialized a poly(vinyl fluoride)‐based film in 1961 under the trade name Tedlar. Poly(vinyl fluoride) homopolymers and copolymers have excellent resistance to sunlight degradation, chemical attack, water absorption, and solvent; they have a high solar energy transmittance rate. These properties have resulted in the utilization of poly(vinyl fluoride) (PVF) film and coating in outdoor and indoor functional and decorative applications. These films are used where exceptional high temperature stability, outdoor longevity, stain resistance, adherence, and release properties are required.
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