Double ring-opening polymerization

It should also be noted that for many of the applications where volume expansion is required (adhesives, composites, etc.) a crosslinked product is desirable and some monomers have been designed with this in mind. This does, however, make the products difllcult to characterize. Some monomers with potential for double ring-opening are reported in I able 4.8. 

The vinyleyelopropane derivatives substituted with a five- or six-membered 

The spiro monomers 57-59 are reported to give single ring-opening. Solution polymerization of 57 products. 

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Various methylene derivatives of spiroorthocarbonates and spiroorthocstcrs have been reported to give double ring-opening polymerization e.g. Scheme 4.36). Like the parent monocyclic systems, these monomers can be sluggish to polymerize and reactivity ratios are such that they do not undergo ready copolymerization with acrylic and styrenic monomers. Copolymerizations with VAc have been reported.170 These monomers, like other acetals, show marked acid sensitivity. 

This reaction is thermodynamically controlled, because the polymer containing 1,3-dioxolane rings converts itself to a polyether when allowed to stand at room temperature for several days or heated at 80 °C for a few hours in the presence of an acid catalyst. Similar double ring-opening polymerizations were observed for 2,6,7-trioxabicyclo[2.2.2]octane and its derivatives [86, 87] and for spiro orthoesters and spiro orthocarbonates as well (see Sects. 6 and 7). 

J.H. Ge, M. Trujillo-Lemon, and J.W. Stansbury, A mechanistic and kinetic study of the photoinitiated cationic double ring-opening polymerization of 2-methylene-7-phenyl-l,4,6,9-tetraoxa-spiro[4.4]nonane. Macromolecules 2006, 39(26), 8968-8976. 

Scheme 2.5 Unsaturated polyester formation with low volume shrinkage by radical initiated double ring-opening polymerization [23].

The driving force for the double ring-opening polymerization apparently is the relief of the strain at the central splro atom. 

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