Synthesis and characterization of benzocyclobuten-4-yl acrylate monomer and its radical polymerization

 A benzocyclobuten-4-yl acrylate (1) monomer was prepared by esterification of 4-hydroxybenzocyclobutene with acryloyl chloride. The radical homopolymerization of 1 and copolymerization of 1 with styrene or n-butyl acrylate were carried out to produce linear polymers 2a, 2b and 2c. Heating of these linear polymers under thermal initiation gave corresponding cross-linked polymers 3a, 3b and 3c. The ring-opening reaction in the cross-linking process was confirmed by on-line infrared spectra. Differential scanning calorimetry showed that the glass transition temperatures of linear polymers 2a and 2b were 83.2°C and 68.1°C, respectively. Thermogravimetric analysis of the cross-linked polymers showed that they all exhibited good thermal stability.