Free Radical Ring-Opening Polymerization

Abstract

Although unstrained five-or six-membered carbocyclic systems undergo free radical ring-closing polymerization, the introduction of an oxygen into the ring will promote free radical ring-opening polymerization, since the resulting carbon-oxygen double bond is approximately 50 kcal more stable than a carbon-carbon double bond. Thus, cyclic ketene acetals, cyclic ketene aminals, cyclic vinyl ethers, unsaturated spiro ortho carbonates, and unsaturated spiro ortho esters will all undergo free radical ring-opening polymerization. Copolymerization of these monomers with a wide variety of vinyl monomers will introduce an ester, amide, keto or carbonate group into the backbone of an addition polymer and can make possible the synthesis of functionally terminated oligomers, biodegradable addition polymers, thermally stable polymers, and monomers that expand on polymerization. KEY WORDS Free Radical Ring-Opening Polymerization I 2-Methylene-1 ,3-dioxepane 1 Polyesters I Functionally-terminated Oligomers I Unsaturated Spiro a-Carbonates I '\N+

Aliphatic Polyethers: Classical Polymers for the 21st Century

“…Oxetanes exhibit a higher basicity (pK a (oxetane) = −2.02, pK a (oxirane) = −3.70) and lower ring strain (oxetane: 106 kJ mol −1 vs. oxirane: 112 kJ mol −1 ) than oxiranes, which leads to a more facile polymerization following the cationic mechanism in contrast to oxiranes which are polymerized predominantly via an anionic mechanism . However, insertion polymerization, anionic polymerization and free radical ring‐opening polymerization are reported in some cases. As initiators for the CROP different electrophilic reagents can be applied, e.g., acids like trifluoromethane sulfonic acid, Lewis acids like BF 3 ·OEt 2 or SnCl 4 , aluminium alkyl‐based initiators, or preformed trialkyl oxonium ion salts.…”

Synthesis of poly(1‐oxodimethylene) via oxidation of poly(vinyl alcohol) with a hydrogen peroxide/hydrobromic acid system and metal complexation behavior of poly(1‐oxodimethylene)

“…The conversion of the carbonyl groups in poly(1‐oxotrimethylene) to ketals has also been demonstrated by the reaction with 1,2‐diols . Polyketones with ester structures and γ‐diketone structures were also obtained by the radical ring‐opening polymerizations of unsaturated cyclic ethers, and 2,2‐diphenyl‐4‐methylene‐1,3‐dioxolane, and ketene or diketenes. Poly(1‐oxodimethylene) can be obtained either by the oxidation of poly(vinyl alcohol) (PVA) or the cationic polymerization of diketene, and theoretically has the highest amount of the carbonyl group among polyketones.…”

Ring-opening polymerization of heterocycles bearing substituted and unsubstituted exo-methylene groups - a review

“…(6)). (4) (5) (6) Among the selected monomers are also cyclic lactones possessing similar structural features as methacrylates. Akkapeddi describes the synthesis and polymerization of 3-methylene-butyrolactone 21 a [30,31].…”

“…This may be due to the fact, that the parent compound 2-methylene-pyrane 72 was found to be an unsuitable monomer for ring-opening reactions. Reference like [1,3,4,11], report only 4 -8% ring-opening at 120 8C (DtBPO) combined with the statement, that generally the radically induced ring-opening of cyclic ethers should be less extensive than those of comparable ketene acetals possessing the same ring size. Unfortunately no further information is enclosed so that the overall situation remains somewhat unclear.…”

“…Not only vinyl monomers and other olefins, as well as acrylates and methacrylates will almost exclusively be attacked at their methylene functionality, but also cycles bearing symmetrically or unsymmetrically substituted R 1 R 2 C=CR 3 R 4 groups. Whenever R 3 and R 4 are members of a cyclic system and at least one of them is different from a common hydrocarbon group, an interesting variety of structures possessing manifold reaction capabilities will result.…”