Monomers Urethane Dimethacrylate

The addition—reaction product of bisphenol A [80-05-07] and glycidyl methacrylate [106-91-2] is a compromise between epoxy and methacrylate resins (245). This BSI—GMA resin polymerizes through a free-radical induced covalent bonding of methacrylate rather than the epoxide reaction of epoxy resins (246). Mineral fillers coated with a silane coupling agent, which bond the powdered inorganic fillers chemically to the resin matrix, are incorporated into BSI—GMA monomer diluted with other methacrylate monomers to make it less viscous (245). A second monomer commonly used to make composites is urethane dimethacrylate [69766-88-7]. 

The majority of resins are composed of two dimethacrylate monomers, 2,2 -bis [4(2-hydroxy-3-methacryloyloxypropyloxy)phenyl] propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) [22-28]. Typically, TEGDMA or other methacrylate monomers are added as viscosity modifiers to Bis-GMA to make the solution less viscous and more appropriate for clinical use. These diluents also allow for better distribution of the components during manufacture of these composite systems. Another common monomer used to make dental composites, especially those manufactured in Europe, is urethane dimethacrylate [24,29, 30], Ethoxy bisphenol A dimethacrylate is another modification of the Bis-GMA monomer that can be used to make a more hydrophobic polymer that would better withstand the wet oral environment. Other diluents include low viscosity diacrylates and dimethacrylates. Table 1 lists some of these monomers [31-37]. 

Pit and Fissur Sealants. Resin sealants consist of a free-radical polymerizable monomer mixture, having a viscosity low enough to penetrate easily into narrow pits and fissures, capable of being cured to a hard and durable sealing material. BisGMA, urethane dimethacrylate, and other methacrylates are very popular as monomers for resin sealants, along with other monomers, to lower... 

There is another type of dimethacrylate that is finding significant use in dental monomers. These are the urethane dimethacrylates, which are synthesized from hydroxyalkyl methacrylates and aliphatic diisocyanates (7,8). The synthesis of this non-aromatic type of monomer is shown in Fig. 2A. The molecular bulk of these monomers is similar to that of BIS-GMA. 

Polymers bearing side-chain anthraquinone moieties have also been reported. In particular, poly(2-acrylamidoanthraquinone) [poly(AAQ)] is found [51] to exhibit, in combination with a tertiary amine such as p-diethylaminobenzoate, higher solubility and the same photoactivity as the monomer in a mixed vinyl-urethane/triethyleneglycol dimethacrylate prepolymer system, when irradiated by visible light. 

Urethane-modified acrylates and methacrylates are known from the literature (I, 2). These monomers are high boiling and viscous enough to be suitable for solventless applications. Two interesting monomers of this type have been prepared from readily available commercial materials. Compound I is a monourethane monomethacrylate it is a liquid with a viscosity of 40 cps at 28°C. Compound II is a diurethane dimethacrylate it is a white, waxy solid that melts around 65°C. Several other monomers of this type have been examined, but these two form the basis of this work. 

The base methacrylate monomers utilized were a polyethyleneglycol dimethacrylate (PEGMA - produced by Loctite), an ethoxylated bisphenol—A dimethacrylate (EBIPMA - produced by AKZO), a urethane methacrylated capped poly(butadiene acrylonitrile) polyol, and hydroxy-propyl methacrylate (HPMA - Rohm and Haas). The following maleimide capped monomer/prepolymers were examined N-phenyl maleimide (NPM), meta-phenylene dimaleimide (m-PDM), and a reaction product of methylenedi-aniline and excess methylenedianiline bismaleimide (P-MDA-2MDABM), sold by Rhodia Corp. under the tradename of Keramide... 

Other substitutes that have been advanced are derivatives of BIS-GMA obtained by selective reaction of the secondary hydroxyl groups, (e,g, esters, urethanes) as shown in Fig, 2C (11,12), Still more hydrophobic variants of BIS-GMA include the dimethacrylate ester of bisphenol A (BIS-MA) and 2,2-bis[p-(2 -methacryloxyethoxy) phenyl] propane (Fig, 2D), These solid monomers, which are relatively easy to purify by recrystallization, should permit the formulation of highly pure monomer systems based on these dimethacrylates (13,14),... 

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