Chapter 16
Synthesis of Novel Hydrophilic and Hydrophobic Multifunctional Acrylic Monomers 1
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Joseph M. Antonucci , Jeffrey W. Stansbury , and G. W. Cheng 1
Dental and Medical Materials Group, Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 West China University of Medical Sciences, People's Republic of China
Downloaded by UNIV OF ARIZONA on June 1, 2013 | http://pubs.acs.org Publication Date: November 30, 1993 | doi: 10.1021/bk-1994-0540.ch016
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A unique formaldehyde/acrylate insertion-condensation reaction can be used to form novel difunctional and multifunctional hydrophilic and hydrophobic monomers and oligomers. Hydrophilic polyethylene glycol diacrylates, formed more viscous, water soluble oligomeric products without the need for a solvent. Because of the predominant 1,6-arrangement of double bonds in these oligomers, they have a propensity to undergo cyclopolymerization as well as the usual crosslinking associated with the free radical polymerization of multifunctional monomers and oligomers. However, the synthesis of analogous hydrophobic difunctional monomers and multifunctional oligomers derived from highly fluorinated and siloxane-containing acrylic monomers required the use of a dipolar aprotic solvent such as dimethyl sulfoxide. The siloxane oligomers had the expected predominance of 1,6-diene structure. In contrast, the fluorinated difunctional monomers and multifunctional oligomers were characterized by a predominantly 1,4-diene structure. These novel oligomeric monomers have potential utility in a wide spectrum of dental and medical applications. Novel difunctional acrylic monomers and multifunctional acrylic oligomers with a propensity for intra-intermolecular addition polymerization (cyclopolymerization) have been conveniently synthesized from conventional acrylates or diacrylates and paraformaldehyde under neat conditions using l,4-diazabicyclo[2,2,2]octane (DABCO) as the catalyst (1-5). The mechanism for the formation of oxybismethacrylates such as 2 (Figure 1) from monoacrylates (and presumably the oligomeric monomers derived from diacrylates as well) appears to involve an unusual base catalyzed self etherification of the intermediate α-hydroxy methyl acrylate 1 (i,
