Thermoresponsive helical dendronized poly(arylacetylene)s: modulating the dynamic chirality

Abstract

Helical poly(arylacetylene)s have formed an intriguing class of polymers, whose chiralities are dynamic and liable to external stimuli. By combining dendronized polymer topology with dendritic oligoethylene glycols (OEGs), we here report on synthesis of a homologous series of thermoresponsive dendronized poly(arylacetylene)s with either poly(phenyl acetylene) or poly (naphthalene acetylene) as the backbones, and investigate tunability of their helical conformations. These polymers carry dendritic OEG pendants with either methoxyl- or ethoxyl-terminals to tune their unprecedent thermoresponsive behaviors, and at the same time, dendritic shielding plays an important role in mediating their thermal phase transition temperatures. Helicity of these polymers is originated from the chiral alanine or phenylalanine moieties within the dendritic pendants, which can be tailored through manipulating solvation in different organic solvents or via thermal dehydration and collapse in water. Furthermore, achiral additives such as linear or dendritic OEGs and benzene derivatives can act similarly as thermal dehydration to induce chirality transitions of these polymers in aqueous phase through interplay competitions between the additives and the polymers against their hydration.