Different amine-functionalized poly(diphenylsubstituted acetylenes) from the same precursor

Abstract

A series of poly(diphenyl substituted acetylenes) (PDSAs) were prepared through a post-polymerization modification strategy. Primary amine, tertiary amine and quaternized ammonium functionalities were successfully and efficiently attached onto the skeleton of poly(1,2-diphenylacetylene) via the precursor PDSA (P0) with activated ester moieties. The structures of the derived amine-functionalized PDSAs, the modification processes and the efficiency of the post-polymerization modification were characterized by multiple spectroscopic techniques. With the aid of the protection and de-protection of tert-butyloxyl carbonyl (P1), PDSA bearing terminal primary amine groups (P2) were obtained. The plentiful amine groups on the side-chains helped in grafting P2 onto graphene oxide (GO) and the resultant hybrids not only showed a greatly improved dispersing ability in organic solvents, but also emitted strong yellow-greenish fluorescence. The polymer bearing tertiary amine functionalities on side chains (P3) could be directly derived from reacting P0 with 3-N,N′-dimethyl-1-propylamine under mild conditions and in high yield. P3 showed evident pH-dependent fluorescence emission behaviour. Based on P3, cationic PDSA P4 was readily obtained by the transition of tertiary amine to quaternized ammonium functionalities. This transition afforded a novel fluorescent and polyelectrolytic PDSA. P4 was tried as a water soluble fluorescent probe in calf thymus DNA (ct-DNA) detection. The experimental data indicated that P4 at a low concentration of 0.1 ppm can respond to the existence of 10⁻¹¹ g L⁻¹ct-DNA in aqueous solution. The working mechanism was associated with the aggregation-induced emission enhancement. The present work, together with our previous reports, suggests that the PDSA with an activated ester precursor can be employed as a broad platform to construct different functional PDSAs.