Cyclopolymerization

Butler, George B.

doi:10.1016/b978-0-08-096701-1.00138-5

Cited by 11 publications

(9 citation statements)

References 135 publications

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“…When preliminarily evaluating these cyclopolymerizing monomers for use in dentistry, STANSBURY found a potential for developing high-conversion, low-shrinking monomers, A 30 to 40% reduction in shrinkage was observed upon homopolymerization of oxybismethacrylate monomers and oligomers compared with dimethacrylates commonly used in dentistry (125,126). The reduction in polymerization shrinkage was originally thought to result from a pre-orientation of the carbon-carbon double bonds to give a pseudo-cyclic conformation (127). According to STANSBDRY (125), a more likely explanation is the larger apparent free volume swept out by a cyclic structure in a constrained polymer, compared with that occupied by a more mobile, linear structure.…”

Section: Non-shrinking Monomersmentioning

confidence: 99%

Resin composites in dentistry: the monomer systems

Peutzfeldt

1997

European J Oral Sciences

805

485

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The present review outlines the history of monomers used in resin composites, motivates further development, and highlights recent and ongoing research reported in the field of dental monomer systems. The monomer systems of most present-day resin composites are based on BisGMA, developed some 40 years ago, or derivatives of BisGMA. In the remaining resin composites, urethane monomers or oligomers are used as the basis of the monomer system. The main deficiencies of current resin composites are polymerization shrinkage and insufficient wear resistance under high masticatory forces. Both factors are highly influenced by the monomer system, and considerable efforts are being made around the world to reduce or eliminate these undesirable properties. The use of fluoride-releasing monomer systems, some of which are under investigation, has been suggested to mitigate the negative effects of marginal gaps formed in consequence of polymerization shrinkage. The very crux of the problem has also been approached with the synthesis of potentially low-shrinking/non-shrinking resin composites involving ring opening or cyclopolymerizable monomers. By the use of additives with a supposed chain transfer agent function, monomer systems have been formulated that improve the degree of conversion of methacrylate double bonds and mechanical properties. Many promising monomer systems have been devised, the implementation of which may be expected to improve the longevity of resin composite fillings and expand the indications for resin composites.

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Section: Non-shrinking Monomersmentioning

confidence: 99%

Resin composites in dentistry: the monomer systems

Peutzfeldt

1997

European J Oral Sciences

805

485

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“…An important advantage of such counterion crosslinked vesicles is that the vesicular bilayer is only electrostatically bound to the crosslinked network and is therefore likely to maintain its fluid nature, unlike the case of most reported polymerized vesicles. One important difference between our counterion crosslinkable vesicles and those reported by Regen and coworkers31 is that our system is truly crosslinkable, whereas Regen's systems used diallyl ammonium counterions, which are known to undergo cyclopolymerization,32 possibly leading to the formation of linear rather than crosslinked polymers. Thus, our system might well represent a truer example of a vesicular assembly with a crosslinked polymeric net encasing it.…”

Section: Discussionmentioning

confidence: 83%

“…Thus, the enhanced stability is gained without a significant loss of fluidity of the bilayer components. One potential drawback with the Regen systems is that the diallylammonium counterions are known to undergo cyclopolymerization to produce linear rather than crosslinked systems,32 and, hence, the extent of crosslinking in their vesicles, if any, might have been rather limited.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and vesicular polymerization of novel counter‐ion polymerizable/crosslinkable surfactants

Paul

Indi

Ramakrishnan

2004

J. Polym. Sci. A Polym. Chem.

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Two novel two-tail surfactants, dicetyldimethylammonium 4-vinyl benzoate (DDVB) and dicetyldimethylammonium 3,5-divinyl benzoate (DDDB), were synthesized by neutralizing the corresponding quaternary ammonium hydroxide with the appropriate benzoic acid. As expected, these surfactants formed both homo and mixedvesicles, which were readily polymerized with a suitable radical photo-initiator. The polymerization process was followed by UV-vis spectroscopy and also reconfirmed by NMR and IR spectroscopy. Polymerization of vesicles prepared from DDVB, unlike the more commonly polymerized vesicles, in which the polymerizable group forms an integral part of the surfactant, leads to the formation of a linear polyelectrolyte chain that is only electrostatically bound to the lipid bilayer. On the other hand, polymerization of DDDB vesicles leads to the formation of a crosslinked shell (or net) that encases the vesicle bilayer. Such counterion crosslinked vesicles were shown to be resistant to destabilization both by lysis as well as in the presence of a fairly high volume fraction of an organic solvent, such as ethanol. However, although the simple polymerized (linearly) vesicles, formed from DDVB, exhibit enhanced stability toward lysis when compared to their unpolymerized counterparts, they are readily destabilized in the presence of ethanol, leading to precipitation. This sharp contrast in the behavior of linearly polymerized and crosslinked systems suggests that crosslinking is essential to arrest conformational reorganization of the polyelectrolyte chains induced by a change in the solvent medium, which in turn leads to precipitation. Such counterion crosslinked vesicular systems also have an added advantage; they may retain the fluidityof the lipid bilayer while at the same time possess enhanced stability.

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“…The possibility of competing acid catalysed, carbocation mediated linear polymerization was considered to be unlikely because the linear polymerization of a difunctional monomer to such high molecular weights would be expected to yield a highly crosslinked, insoluble polymer. Consequently, carbocation mediated cyclopolymerization 5 was suspected. However, the NMR spectrum of poly (3) did not provide an unambiguous structural assignment for these polymer linkages.…”

Section: Resultsmentioning

confidence: 99%