Acrylic anhydrides and polymers derived therefrom

Abstract

The free‐radical polymerization of four acrylic anhydrides—methacrylic anhydride, acrylic anhydride, acrylic methacrylic anhydride, and acrylic propionic anhydride—under a variety of conditions has been studied. The polymers and their polyacid and polyester derivatives were characterized by solubility, infrared spectroscopy, and x‐ray diffraction. Methacrylic anhydride could be polymerized in bulk and in hydrocarbon solvents from −50°C. to 80°C. to give soluble, linear cyclopolymers in high conversions. In a polar solvent such as dimethyl sulfoxide, gelation would result at high monomer concentrations and at high conversions. Acrylic anhydride, however, appeared to become crosslinked more readily; soluble polymers could be obtained only by polymerization in nonpolar solvents. Most of the previous and somewhat conflicting results on the cyclopolymerization of these two monomers can now be reconciled by the present findings. The physical properties of cast poly(methacrylic anhydride) suggest that it has a stiff backbone with hindered functional groups and that the monomer itself was perhaps intramolecularly associated. Some improvements in the aqueous hydrolysis of poly(methacrylic anhydride) and in the esterification of the derived polyacid by diazomethane were described. By these refinements, poly(methyl methacrylate), derived from a −50°C. poly(methacrylic anhydride), had previously been shown to possess a novel, mixed syndiotactic and syndioduotactic (++−−++−−) configuration. Acrylic methacrylic anhydride could be cyclopolymerized very much like methacrylic anhydride. The polyacid and polyester derived from this unsymmetrical anhydride are expected to have unique structures; the acrylic or methacrylic units in the derivatives do not occur more than twice in succession. Acrylic propionic anhydride, when homopolymerized, readily changed to a soluble polymer and an unidentified, immiscible liquid. Its soluble copolymer with methyl methacrylate, however, could be crosslinked by heating. An intramolecular and intermolecular disproportionation reaction was postulated to explain these two interesting observations, respectively.

Radical cyclo‐ and cyclocopolymerization

“…Polymerization of methacrylic anhydride has been shown to be accompanied by a volume shrinkage of only 13.7 ml/M of unsaturation as compared to 22-23 ml/M for methyl, ethyl, and n-propyl methacrylates [63]. The low volume shrinkage was interpreted to indicate a preorientation of the molecule to a cyclic conformation, thus requiring little volume change on polymerization.…”

Free radical polymerization of unconjugated dienes, 15. Dependence of the composition of poly(methacrylic anhydride) on the monomer concentration

“…Specifically, the sample F ratios, defined as with 1 degree of freedom in the numerator and n-2 degrees of freedom in the denominator, have been computed; the hypothesis _a (estimated) = 1 (4) is to be rejected if the probability of exceding the sample F value is sufficiently small. Specifically, the sample F ratios, defined as with 1 degree of freedom in the numerator and n-2 degrees of freedom in the denominator, have been computed; the hypothesis _a (estimated) = 1 (4) is to be rejected if the probability of exceding the sample F value is sufficiently small.…”

Further evaluation of sequences in methyl methacrylate/methacrylic acid copolymers by 1H‐NMR in different solvents and 13C‐NMR

“…Radical-initiated PMMA (1 g) was dissolved in pyridine (20 g) in a strong-walled glass ampoule. After slow addition of H2O (5 g), it was purged with N2, sealed and heated to 145 "C. After hydrolysis times of 6,9,14,16,18,20,24 h, copolymers of P(A)= 0,83, 0,80, 0,61, 0,58, 0,47, 0,38, 0,26 were obtained, resp. The ampoule was opened and the contents poured into H 2 0 (700ml) at 80°C.…”