Supramolecular assembly of H-bonded copolymers/complexes/nanocomposites and fluorescence quenching effects of surface-modified gold nanoparticles on fluorescent copolymers containing pyridyl H-acceptors and acid H-donors

Abstract

A series of photoluminescent (PL) and liquid crystalline (LC) self-H-bonded side-chain copolymers (P1-P3) consisting of pyridyl H-acceptors and isomeric acid H-donors (i.e., para-, meta-, and orthobenzoic acids) were synthesized. Supramolecular H-bonded complexes were also obtained by mixing the photoluminescent H-acceptor homopolymer PBT1 (containing pyridyl pendants) with isomeric H-donor homopolymers P7-P9. The formation of H-bonds was confirmed by FTIR, DSC, and XRD measurements. Moreover, PL and LC properties of the H-bonded copolymers and complexes were affected not only by the H-bonding effect of the supramolecular structures but also by the acid-substituted positions of isomeric H-donors. In combination with different functionalized gold nanoparticles (which bear acid or acid-free surfactants), the emission intensities of nanocomposites containing self-H-bonded copolymer P1 (bearing both H-acceptor and H-donor moieties) and non-self-H-bonded copolymer P4 (bearing acid-protected moieties), were quenched to different extents by varying the concentration of gold nanoparticles. The copolymeric H-acceptors and surface-modified gold nanoparticles demonstrated diverse morphological and PL quenching effects on the supramolecular architectures of the nanocomposites, which result from competition between the H-donors from the acid pendants on copolymers and the acid surfactants on the gold nanoparticles.