Radical addition-fragmentation chemistry in polymer synthesis

Chemical Reviews is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 “Green” Atom Transfer Radical Polymerization: From Process Design to Preparation of Well-Defined Environmentally Friendly Polymeric Materials Nicolay V. Tsarevsky, and Krzysztof Matyjaszewski Chem. Rev., 2007, 107 (6), 2270-2299• DOI: 10.1021/cr050947p • Publication Date (Web): 27 May 2007 Downloaded from http://pubs.acs.org on April 2, 2009

"Green" atom transfer radical polymerization: from process design to preparation of well-defined environmentally friendly polymeric materials.

Devices formed of or including biocompatible polyhydroxyalkanoates are provided with controlled degradation rates, preferably less than one year under physiological conditions. Preferred devices include sutures, suture fasteners, meniscus repair devices, rivets, tacks, staples, screws (including interference screws), bone plates and bone plating systems, surgical mesh, repair patches, slings, cardiovascular patches, orthopedic pins (including bone filling augmentation material), adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, atrial septal defect repair devices, pericardial patches, bulking and filling agents, vein valves, bone marrow scaffolds, meniscus regeneration devices, ligament and tendon grafts, ocular cell implants, spinal fusion cages, skin substitutes, dural substitutes, bone graft substitutes, bone dowels, wound dressings, and hemostats. The polyhydroxyalkanoates can contain additives, be formed of mixtures of monomers or include pendant groups or modifications in their backbones, or can be chemically modified, all to alter the degradation rates. The polyhydroxyalkanoate compositions also provide favorable mechanical properties, biocompatibility, and degradation times within desirable time frames under physiological conditions.

Medical devices and applications of polyhydroxyalkanoate polymers

3.10 - Nitroxide-Mediated Polymerization

Reviews the properties, synthesis, and formulations of a number of well studied polymers increasingly being used in site-specific or systematic administration of pharmaceutical agents. For each of the polymers, discusses the background; chemistry and synthesis; the formulation of microcapsules, solv

/pdf/biodegradable-polymers-as-drug-delivery-systems-43th8shecb.pdf

Biodegradable polymers as drug delivery systems

2-Methylene-1,3-dioxepane 6 polymerized with a quantitative ring opening to form poly-ϵ-caprolactone via a free radical mechanism. On the other hand, 2-methylene-1,3-dioxolane (ethylene ketene acetal) 4 and 2-methylene-1,3-dioxane 5, under the same conditions, generated polymers with mixed ring-opened and nonring-opened structures. In copolymerization monomer 6 also showed a high tendency toward ring opening by which the ester functionality could be conveniently introduced into the backbone of the addition polymers.

Synthesis of poly-ϵ-caprolactone via a free radical mechanism. Free radical ring-opening polymerization of 2-methylene-1,3-dioxepane

Unsaturated spiro-orthocarbonates are monomers that expand on polymerization and will co-polymerize with conventional BIS-GMA based resins. This combination has good physical properties and bonding to enamel with some polymerization expansion evident at 50 C. Dispersion of the carbonate in microcrystalline form in liquid monomer appears to be a method to allow its reaction in the initial polymerization.

Dental Resins with Reduced Shrinkage During Hardening

The cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane (3), was shown to undergo free radical ring-opening polymerization to produce the polyester, poly[γ-(β-phenyl)butyrolactone]. The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cis and trans-2-chloromethyl-4-phenyl-1,3-dioxolane (2) with potassium tert-butoxide in tert-butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring-opening at all temperatures from 60–150°C and also nearly complete regioselective ring-opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4-vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and 1H and 13C NMR spectroscopy.

Synthesis and free radical ring‐opening polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane

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.

/pdf/free-radical-ring-opening-polymerization-4nzpxcvh19.pdf

Free Radical Ring-Opening Polymerization

Stachybotrys atra cultures grown on oats produced five compounds toxic to brine shrimp; three are the sesquiterpenoid mycotoxins known as 12,13-epoxy-Δ9-trichothecenes. One trichothecene is roridin E, a known metabolite of Myrothecium verrucaria. The other two were hydrolyzed to verrucarol, the product of roridin and verrucarin hydrolysis. Spectroscopic data indicate that the two remaining compounds are also 12,13-epoxy-Δ9-trichothecenes. These metabolites are probably among those responsible for stachybotryotoxicosis.

William J. Bailey

Papers

Synthesis of poly-ϵ-caprolactone via a free radical mechanism. Free radical ring-opening polymerization of 2-methylene-1,3-dioxepane

Dental Resins with Reduced Shrinkage During Hardening

Synthesis and free radical ring‐opening polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane

Free Radical Ring-Opening Polymerization

12,13-Epoxy-Δ9-Trichothecenes as the Probable Mycotoxins Responsible for Stachybotryotoxicosis