Unexpected Emission of Poly[(methylenelactide)-co-(2-vinylpyridine)] from Single-chain Luminogen

Non-conjugated luminescent polymers (NCLPs) have attracted great interest due to their novel emission mechanism and potential for applications in a variety of areas. Copolymerization is a facile and effective approach to develop NCLPs from two or more types of non-luminescent comonomers by integrating critical elements that are necessary for inducing intrinsic emissions. In the present work, we report unexpected photoluminescence (PL) of poly[(methylenelactide)-co-(2-vinylpyridine)] random copolymers (PLVPs), which possess intense blue emissions in dilute solution with quantum yield higher than 20 %. The intrinsic PL of PLVPs is attributed to the intra-chain interactions of chains, namely, ‘single-chain luminogen’. As a result, the PL of PLVPs exhibits aggregation-caused quenching (ACQ) feature, which is different from conventional NCLPs based on clustering-triggered emission (CTE). The dependence of emissions on the molecular weights and monomer ratios of PLVPs, as well as excitation wavelength, in both solution and solid states were investigated. This work provides new insight into the design and preparation of NCLPs.