Controlled Synthesis And Study On Rheological Properties Of Bottlebrushes Bearing Helical Polyisocyanide

The reported bottlebrush polymers were usually prepared by incorporating a brush onto every two or more backbone atoms.In this work,we report the precise synthesis of densely grafted bottlebrushes bearing helical polyisocyanide on almost all the backbone atom.First,a series of C1 polymers,polyisocyanides bearing active pentafluorophenol ester pendants were prepared which were then installed with a Pd(II)-catalyst on each backbone carbon via transesterification.All the Pd(II)-catalyst pendants can efficiently catalyze living polymerization of isocyanide monomers,lead to the formation of well-defined bottlebrush polymers.The grafting density of the bottlebrushes was extremely high since it carrying side polyisocyanide chain on almost all the backbone atom as revealed by detailed NMR analyses.Moreover,the grafting density can be facilely tuned through the variation on the content of Pd(II)-pendants.Both the backbone and the side chain were synthesized via living chain-growth polymerizations,thus a variety of bottlebrush polymers and core-shell bottlebrushes with different compositions and controlled structures were facilely prepared.Interestingly,the synthetic bottlebrush polymers showed distinctively enhanced viscosity and modulus which can be further regulated by the grafting density.