Clusterization-triggered emission of poly(vinyl amine)-based ampholytic block and random copolymers.

Nonconventional stimuli-responsive luminescent polymers without aromatic units have garnered considerable attention. In this study, luminescent ampholytic block copolymer (BCP) and random copolymer (RCP) consisting of nonconjugated vinyl amine (VAm) and N -acryloyl-L-threonine (AThrOH) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequent deprotection. The ampholytic BCP and RCP display concentration-enhanced emissions, which are apparently higher than those of the VAm homopolymer and polyion complex, and wavelength-dependent emissions, thus validating clusterization-triggered emission (CTE). The intrinsic photoluminescence properties of the primary amine-containing ampholytic copolymers and corresponding polyion complexes were investigated in aqueous solution in response to the change in pH. Two noncovalent interactions, which involve electrostatic interactions between cationic VAm and anionic AThrOH units and hydrogen bonds (e.g., the amino group in VAm/hydroxyl and amide groups in AThrOH), contribute to the achievement of unique self-assembled structures and stimuli-responsive and fluorescent properties of VAm-containing BCP and RCP, which were verified by dynamic light scattering, circular dichroism, and fluorescence measurements. The ability of the copolymers to form clusterized states of the VAm unit can be governed by the comonomer sequence and external stimuli (e.g., pH change, the addition of salt and urea), leading to the manipulation of the assembled structures with CTE features. [Display omitted] • Luminescent ampholytic block and random copolymers without aromatic units were developed. • Copolymers consisting of vinyl amine (VAm) and N -acryloyl-L-threonine were synthesized by RAFT polymerization. • The ampholytic copolymers exhibited concentration-enhanced emissions and wavelength-dependent emissions. • Unique assembled structures and VAm-based clusterization-triggered emission (CTE) were confirmed. • The comonomer sequence and external stimuli led to the manipulation of the assembled structures with CTE features. [ABSTRACT FROM AUTHOR]