Free-radical copolymerization behavior of 5,6-benzo-2-methylene-1,3-dioxepane and methacrylic acid via the in situ generation of 3-methyl-1,5-dihydrobenzo[e][1,3]dioxepin-3-yl methacrylate and 2-(acetoxymethyl)benzyl methacrylate

The copolymerization of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) with methacrylic acid (MAA) using free radical initiator like di-tert-butylperoxide resulted in different copolymer structures depending on the monomer feed ratio. The copolymerization proceeded in an unconventional way, i.e., by in situ formation of a new vinyl monomer on mixing BMDO and MAA. In this work, we found a new route to copolymerization by first adding MAA to the doul ble bond of BMDO generating a new vinyl monomer (3-methyl- 1,5-dihydrobenzo[e][1,3]dioxepin-3-yl methacrylate) with a double bond and retaining the seven membered ring of BMDO intact. The new structure is stable at 25 degrees C but underwent ring-opening at higher temperatures like 120 degrees C, generating further a different vinyl monomer with ester linkages in the side chain (2-(acetoxymethyl)benzyl methacrylate). The resulting new monomer can. copolymerize with both MAA and BMDO depending on the monomer feed ratio. The structure of the new monomers and copolymers were characterized using 1D and 2D NMR techniques.