Double ring-opening

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 difficult to characterize. Some monomers with potential for double ring-opening are reported in fable 4.8. 

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. 

Systems with substituents on the aeelal ring254 or with larger acetal rings may give double ring-opening (e.g. Scheme 4.39).202,203... 

Table 4.8 Extent of Double Ring-Opening During Polymerization of Polycyclic...

Finally, the unsaturated spiro ortho carbonates were been shown to undergo double ring opening in a free radical polymerization to introduce a carbonate group in the backbone of an addition polymer (19). 

Apparently, the driving force for the ring opening is the relief of the strain in the spiro system and the formation of the stable carbonate double bond. The double ring opening is probably a concerted process from the initial radical addition product to the open-chain radical. Even though the spiro compound XI is an allyl monomer, it does copolymerize with a wide variety of comonomers. 

Double rings Opening and Small sheets Isoroerizlng (480 A) aligning of filaments... 

North and Banti observed double-ring-opening metathesis of dialkynylcycloalkenes and obtained a tricyclic compound from a norbornene derivative shown in Equation (16)." " ... 

At temperatures higher than 80 C, polyethers (83) having pendant formate moieties were produced by double ring-opening in the polymerization of 80. 

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). 

Double Ring-Opening in Free Badical Polymerization... 

When this monomer was treated with peroxide, it underwent double ring opening by the following mechanism ... 

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. 

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