Characterization of an amylose-graft-poly(n-butyl methacrylate) copolymer obtained by click chemistry by EPR and SS-NMR spectroscopies

Abstract

We present an investigation of the main chemical and physico-chemical properties of a graft copolymer of amylose and poly(n-butyl methacrylate), Am-g-PBMA, amphiphilic and able to self-assemble in water, prepared by coupling end azide-functionalized PBMA and alkyne-functionalized amylose under convenient click conditions. A deep knowledge of these properties is necessary in the perspective of real applications of the copolymer. To this aim we combined a basic characterization through FT-IR, TGA, ICP-OES and SEM with an extensive EPR and Solid State NMR investigation. It was possible to characterize the main structural and dynamic properties of Am-g-PBMA and highlight the presence of residual copper (Cu(II)) from the catalyst, even after an extensive purification procedure. We could identify two main species of Cu(II): Cu(II) complexes coordinated to the N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) ligand from the catalyst and to the copolymer triazole nitrogens and multi-nuclear or clustered Cu(II) species likely coordinated to amylose hydroxyl groups.

Keywords: Amylose; Click chemistry; Graft copolymers; MAS NMR; Nuclear relaxation times; PBMA.