Hydrogen-Bonding-Induced Clusteroluminescence and UCST-Type Thermoresponsiveness of Nonconjugated Copolymers

Stimuli-responsive light-emitting polymers (SRLEPs) have many promising applications. However, the synthesis of SRLEPs from nonconjugated and water-soluble monomers remains a challenge. Herein, for the first time, nonconjugated luminescent polymers with an upper critical solution temperature (UCST) in aqueous solution are reported. The polymer is synthesized through copolymerization of a strong hydrogen-donating monomer, acrylic acid (AAc), and a strong hydrogen-accepting monomer, N-vinylcaprolactam (NVCL). The polymer–polymer hydrogen-bonding rigidifies the chain conformation and enhances the clustering of the heteroatoms and carbonyl groups, resulting in an improved clusteroluminescence. Meanwhile, the polymer–polymer hydrogen bonding also brings in dynamic chain association that can be switched with temperature, yielding a UCST-type thermoresponsiveness in aqueous solution. This work demonstrates a novel and facile method of designing SRLEPs through tailoring the hydrogen bonds in the polymer. The properties of clusteroluminescence and thermoresponsiveness of the AAc–NVCL copolymers may render themselves with applications as temperature-sensitive biosensing.