Conventional fluorophore-free dual pH- and thermo-responsive luminescent alternating copolymer

• Published in: Polymer chemistry Vol. 7; no. 45; pp. 6895 - 6900
• Main Authors: Saha, Biswajit, Bauri, Kamal, Bag, Arijit, Ghorai, Pradip K., De, Priyadarsi
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Copolymerization; Copolymers; Expulsion; Fluorescence; Monomers; Rings (mathematics); Solvents; Synthesis (chemistry)
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/C6PY01738J

Herein, we report the synthesis of a new class of traditional fluorophore-free dual pH- and thermo-responsive fluorescent copolymer through sequence-controlled copolymerization of rationally designed monomers. The N -substituted maleimide monomer bearing a diethylene oxide side-chain, ( N -(methoxy diethylene glycol) maleimide, M1), was copolymerized with a tert -butyl carbamate (Boc)-protected leucine appended styrenic monomer (M2) to obtain well-defined copolymers with perfectly alternating sequences of M1 and M2. The as-synthesized copolymers displayed bright-blue fluorescence in organic solvents. After Boc-group expulsion, the copolymers showed dual pH- and thermo-responsiveness, they retained their luminescence properties in organic solvents, and also showed pH/thermo-tunable fluorescence activity in water. The origin of the fluorescence in the copolymers was ascertained using density functional theory (DFT), where we observed that the “through-space” π–π interaction between the benzene ring and the neighbouring carbonyl group of the maleimide unit is responsible for the unexpected fluorescence in the alternating copolymer.