Preparation And Characterization Of Fluorescent Comb-copolymers Based On Ethyl Cellulose

Cellulose is a renewable natural biomaterial with very abundant reserves, and has been extensively researched and applied due to its many distinctive properties. Ethyl cellulose (EC) is a kind of cellulose derivatives which can be mass industrialized produced. As the properties of cellulose are kept, EC has excellent biocompatibility, good cold tolerance, high mechanical strength and stability. By graft polymerization from EC, the solubility can be improved, and novel structure and functionality can be achieved. Poly(ε-caprolactone) (PCL) has excellent biodegradability and biocompatibility, and has been widely applied in biomedical field, but with the drawback of high degree of crystallinity and slow degradation rate. If we can combine the advantages of EC and PCL, such material will have more extensive application prospect.The work present here demonstrates the preparation of series of ethyl cellulose-g-poly(ε-caprolactone) (EC-g-PCL) brush copolymers with different graft length via ring-opening polymerization (ROP). FT-IR, NMR, GPC were used for the structure characterization, and differential scanning calorimetric analysis (DSC) was used to study the thermal property.EC-g-PCL copolymers have novel brush structure, and a large number of active reaction sites on the end of brushes which can be further functionalized. This work reports the linkage of fluorescent molecules such as pyrene (Pyr) and rhodamine B (RhB) with the hydroxyl groups at the end of graft chains by esterification with the presence of dicyclohexylcarbodiimide (DCC). Two series of fluorescent brush copolymers, i.e. EC-g-PCL-Pyr and EC-g-PCL-RhB, were prepared by changing the feeding of fluorescent molecules. DSC, atomic force microscope (AFM), UV-vis, and fluorescent spectra were used for the characterization of thermal, crystallographic, and fluorescent properties. The difference in thermal and fluorescent properties of the two kinds of fluorescent brush copolymers was discussed here to get a reasonable explanation.RhB and folic acid (FA), which is famous as a cancer cell-targeted molecule, were linked to the end of graft chains of EC-g-PCL, by DCC-joined esterification, to prepare the bifunctional brush copolymers, EC-g-PCL-RhB/FA, with fluorescence and cancer cell recognition. DSC, UV-vis, and fluorescent spectra were used to study thermal and fluorescent properties. Cancer cell line experiments were designed to research the target behavior and fluorescence of EC-g-PCL-RhB/FA in cancer cells, with EC-g-PCL-RhB as the contrast. The results clarify the obvious enrichment of EC-g-PCL-RhB/FA in cancer cells, and the fluorescence was kept well.These fluorescent brush copolymers prepared here could be applied in fluorescence examination, fluorescence labeling, and fluorescent device. Moreover, fluorescent and cancer cell-targeted bifunctional brush copolymers have great potential in the applications of targeted drug delivery and cancer therapy.