Synthesis of cyclic block copolymers with discrete molecular weights
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Cyclic polymers attract interest because of their unique chemical and physical properties arising from their topological constraints of their chain conformations and absence of chain ends. Recently, we reported iterative convergent synthesis of large cyclic polymers with discrete molecular weights. Here, we report the synthesis of discrete linear and cyclic block copolymers. Lactic acid, phenyllactic acid, and chlorolactic acid were used to synthesize discrete homopolymers. The resulting discrete polymers were linked to form block copolymers, followed by functionalization of chain ends for the copper-catalyzed azide-alkyne cycloaddition. The resulting linear and cyclic block copolymers were purified by using preparative size-exclusion chromatography and analyzed by NMR, DSC, MALDI-TOF and SAXS. We describe the effect of molecular weight fractions, molar ratio and topology of the polymer chains on the morphology of the self-assembled structures of these monodisperse block copolymers.