Photoinduces Free Radical Ring Opening Copolymerization in Acceptor / Donor Systems

The total electron density as well as the distribution within the carbon-carbon double bond in the
donor monomer will strongly influence the preference and ratio of "reactivity" towards alternating
co-polymerization, homo-polymerization and cyclo-addition reactions in typical acceptor (A) / donor (D) combinations. Furthermore, the rate of co-polymerization will also be influenced by the donor structure. The relative rates in the alternating co-polymerization of conventional alkenyl ethers, Nvinyl amides and vinyl esters have been investigated and compared to exomethylenic dioxolanes, such as 4-methylene-1 ,3-dioxolanes using RTFTIR and Photo-DSC. The mechanistic differences in initiation and propagation between the various donors have been examined and evaluated by Ml triplet quenching using Laser-Flash-Photolysis. The influence of structural modifications to increase the electron density in the vinylic C=C bond was shown to promote higher rates of copolymerization. A comparison between vinyl ethers and exomethylenic dioxolanes showed increased "reactivity" for the dioxolane monomers. In addition, the temperature controlled ringopening of the dioxolane monomer was monitored. The importance of aryl substituents in the 2- position in order to improve the radical stability at lower temperatures has been exemplified by the FTRTIR recordings of ring opening versus 1,2 vinyl additions.