Expandable monomer

Luck, R.M. and Sadhir, R.K., Shrinkage in conventional monomers during polymerization. In Sadhir, R.K. and Luck, R.M. (Eds.), Expanding Monomers, Synthesis. Characterization and Applications. CRC Press, Boca Raton, FL, 1992, p. 5. 

Fig. 7.25. Impacl fracture toughness (O) and interlaminar shear strength (ILSS, ) of unidirectional carbon fiber-epoxy matrix composites as a function of expanding monomer (spiro) content. After Lim...

Cross-linking of another expanding monomer, 1,5,7,11-tetraoxaspiro [5.5] undecane (TOSU), with bisphenol A diglycidyl ether (BADGE) and with bifunctional oxetane (BOXT) was investigated by Holder [124] and Endo [125], respectively (Chart 11.14). The resulted networks are nonshrinking cross-linked materials. 

M.D. Miller, et al., Matrix-assisted laser desorption/ionization time-of-flight analysis of the copolymerization reaction of an expanding monomer with a diepoxide. J. Polym. Sci. A Polym. Chem. 2005, 43(23), 5962-5970. 

Photopolymerizable monomers and oligomers can be classified under four main groups including radical monomers and oligomers, unsaturated polyester resins, thiol-ene systems, and cationic monomers. In addition to these systems, particular photopolymerizable systems are also available such as expanding monomers, liquid crystalline monomers, and some other miscellaneous monomers. 

Table 4 Examples of expanding and liquid crystalline monomers Expanding monomers...

A number of different materials were tested for potential usefulness as expanding monomers. One of the first compounds to be synthesizes and tested as a shrinkage control agent was l,4,6-trioxaspiro[4,4]-nonane. 

An interesting possibility is the formulation of a material with zero coefficient of thermal expansion by adding just enough expanding monomer to counteract the normal shrinkage of the resin. 

An interesting modification involves expandable monomers. These materials, synthesized by Dr. William J. Bailey and coworkers at University of Maryland, are spiro monomers, double rings which open and expand on polymerization. They can be useful in adhesives which are based on polymer/monomer solution, such as structural acrylics, radiation-cured acrylates, etc. These monomers can counteract shrinkage on curing, which is detrimental to adhesion. 

Based on the spirocyclic ether structures, several radically polymerizable cyclic monomers have been designed and synthesized. Such monomers are potentially applicable as volume-expandable monomers that can copolymerize with conventional vinyl monomers to suppress the volume shrinkage. 

Expanding Monomer Diversity 18.4.1 In situ Monomer Strategy... 

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