•An efficient method is developed to obtain CDs with strong and stable photoluminescence.•Fluorescent carbon dots (CDs) were attached to CDs@PCL hybrids with excellent biocompatibility and biodegradability.•The CDs@PCL hybrids have a promising future in biomedicine, photocatalyst, bioimaging, and environmental analysis.In this paper, the environment-friendly, water-soluble carbon dots (CDs) with stable photoluminescence (PL) have been prepared via the one-step pyrolysis of lotus leaf. Then the as-prepared CDs containing abundant hydroxylic and carboxylic groups were employed as cocatalyst with tartaric acid (TA) in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The low-toxic organic acid TA, as main catalyst, was used to catalyze the ROP of ε-CL efficiently. The fluorescent CDs@PCL hybrids were obviously hydrophobic and they exhibited an excellent biocompatibility, and biodegradability due to the existence of PCL. Therefore the hydrophobic, biodegradable and multi-color fluorescent CDs@PCL hybrids may have potential applications in biomedicine, photocatalyst, bioimaging, and environmental analysis. Furthermore the application of CDs in catalyzing and initiating polymerization reaction will exemplify the versatility of CDs in the most unexpected fields.

•The copolymer poly(CL-co-DMAEMA) was obtained by one-pot copolymerization.•The biodegradable copolymer can self-assemble into micelles.•The pyrene solubilization capacity of zwitterionic copolymer is good.•The copolymers possess good antifouling and low cell cytotoxicity.A novel biocompatible and biodegradable copolymer was synthesized by one-step hybrid copolymerization of ε-caprolactone (CL) and 2-(N,N-dimethylamino) ethyl methacrylate (DMAEMA) employing (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) as a catalyst. The as-synthesized copolymer was betainizated resulting in a zwitterionic copolymer poly(CL-co-zDMAEMA) and the structure of the zwitterionic copolymer was confirmed by the FT-IR, NMR, and XPS measurements. The results of dynamic light scattering (DLS) show that this zwitterionic copolymer can self-assemble into stable micelles. The results of quartz crystal microbalance with dissipation (QCM-D) analysis and MTT measurement suggest that this zwitterionic copolymer possess better protein resistance and lower cell cytotoxicity in vitro in comparison with the cationic copolymer. The pyrene solubilization measurement of copolymers poly(CL-co-zDMAEMA) indicates an excellent pyrene solubilization capacity. These zwitterionic polymer micelles can release drugs in response to specific signals, such as temperature, pH, and enzymes and have a potential application in drug delivery and gene therapy due to their good antifouling, low cytotoxicity and high pyrene solubilization.