Spiro orthoesters/orthocarbonates

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). 

Patent Synthesis of Spiro Orthoesters, Spiro Orthocarbonates, and... 

The review will be limited to atom- and bond-bridged bicyclic monomers. The important work of Bailey on the polymerization of spiro bicyclo orthoesters and spiro bicyclic orthocarbonates has been adequately described elsewhere 0 1 60 3. The outstanding and systematic body of work by Schu-erch2 3> and others on the ring opening polymerization of bicyclic acetals derived from carbohydrate precursors will also not be covered here. 

Figure 2. Structures of an alternate spiro orthoester methacrylate (2) and the Spiro orthocarbonate methacrylate (SOCM, 3) monomer.

In a program to develop monomers that expand on polymerization, we had prepared a series of spiro orthoesters, spiro orthocarbonates, trioxabicyclooctanes, and ketal lactones that could be polymerized with ring-opening by ionic catalysts to give either no change in volume or slight expansion... 

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