Ceiling temperature cyclic acetals

The polymer has a relatively low ceiling temperature (119 °C), but this is the highest of all the formaldehyde polymers. The lack of success at polymerizing other monomers was due to the low ceiling temperatures (e.g. —39 C for acetaldehyde) (Odian, 1991). Aldol condensation can be a side reaction competing with polymerization for these monomers. There are other routes, such as cationic ring-opening polymerization of cyclic acetals, to achieve the same polymer (Penczek and Kubisa, 1989). 

Some cyclic acetals may have a low ceiling temperature and polymerization may ensue at a lower temperature than applied. We recall here the polymerization of 4-phenyl-1,3-dioxolane (considered earlier nonpolymerizable) at —20 °C by Elias et al. 6). The Tc of 4-phenyl-1,3-dioxolane is 20 °C 6). 

Though useful polymers can be made by these reactions, their low ceiling temperatures (see p. 599) and consequent tendency to undergo facile depolymerization by an unzipping mechanism pose serious limitations. To overcome this problem the technique of end-capping or end-blocking may be used. Thus poly-oxymethylene (polyacetal), an engineering plastic, prepared from the cyclic acetal... 

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