Cyclic macromonomer from a multifunctional atom transfer radical polymerization initiator via sulfoxide-based vinyl protection

A novel synthetic approach to vinyl-functionalized cyclic macromolecules via sulfoxide chemistry is reported. We prepared a multifunctional atom transfer radical polymerization (ATRP) initiator with alkyne and vinyl groups, which were protected by silyl and sulfoxide groups, respectively. ATRP was performed using a styrene monomer, followed by azidation of the halogen chain-end and deprotection of the silyl and sulfoxide groups. This afforded a polymer with trifunctional azide, alkyne, and vinyl groups. Subsequently, cyclization via Cu(i)-catalyzed azide-alkyne cycloaddition was performed to yield a polymer with vinyl functionality. The vinyl-functionalized cyclic polymers were characterized using H-1 NMR spectroscopy, Fourier-transform infrared spectroscopy, size-exclusion chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and their structure and properties were confirmed. We also used the vinyl-functionalized cyclic polymers as co-monomers to prepare linear polymers with cyclic pendant polymers. The unique topology of the ring-grafted polymers was investigated and comparisons were drawn with their linear counterparts. We demonstrated that the multifunctional ATRP initiator facilitated the facile synthesis of the ring-grafted polymer. The vinyl-functionalized cyclic polymers have potential applications in various fields due to their novel structure and functionality.