Synthesis of Flower-Like Polybutadiene
Résumé
Synthesis of complex macromolecular architectures exhibiting no chain ends such as flower-like polymers is still of interest in the aim of investigating their physicochemical properties. For this purpose, poly(3,4-dimethyl maleic imidoethyl acrylate)-block-polybutadiene-block-poly(3,4-dimethyl maleic imidoethyl acrylate) triblock copolymer is synthesized in a convergent manner using a combination of living polymerization (anionic polymerization), reversible deactivation radical polymerization, and click chemistry. This copolymer is self-assembled in a selective solvent (heptane/THF mixture) of the polybutadiene block leading to the formation of flower-like micelles in thermodynamic equilibrium in dilute solution. These resulting transient architectures are fixed by covalently crosslinking the micelles core by inducing [2+2] cyclodimerization of the 3,4-dimethyl maleic imidoethyl groups borne by the short solvophobic blocks under UV irradiation. Single flowers are isolated from residual non-crosslinked chains by semipreparative size exclusion chromatography (SEC) and characterized by H-1 NMR, SEC, dynamic light scattering (DLS), and transmission electron microscopy (TEM).