Synthesis And Performance Of A Novel Fluorescent Poly (Caprolactone)-Type Polyurethane

In recent years,polyurethane fluorescent materials have attracted more and more researchers’ attention,because of their unique structural characteristics such as excellent dispersion properties,environmental advantages and potential optical applications.In addition,polyurethane has excellent mechanical strength,abrasion resistance,weatherability,thermal stability and processability and its molecular structure can design freedom and meet different application requirements.There are many researches about fluorescent polyurethane and most of them used fluorescent dyes containing amino or hydroxyl functional groups attached to the polyurethane chain to obtain the corresponding fluorescent polyurethane materials.Due to the limitations of fluorescent dyes,the potential value of fluorescent polyurethane is not high.In this paper,a series of fluorescent polyurethanes were synthesized by a new method,and their structures and properties were preliminarily explored.Because of its unique photophysics,electrochemistry,catalysis and magnetism,terpyridine and its complexes have been extensively studied in potential applications involving light to electrical conversion,such as luminescent electrochemical cells(LEC),organic Light-emitting diodes and non-linear optics.At the same time,in the polymer science,optoelectronic devices,pharmaceutical chemistry,nanotechnology and molecular catalysis and other emerging areas,the terpyridine-based materials have a good application prospect.Polycaprolactone(PCL)has good solubility,low melting point and good mixing compatibility,so that its potential applications in the field of biomedicine is widely studied,and it provides a hope to solve the global problem of organ and tissue shortage.In addition,fluorescent PCL polymers can track the degradation of cells and tissues under physiological conditions and can be used as an optical probe for in vitro and in vivo tissue engineering applications with the ability to optically image and the use for drug delivery.It can be seen if we can prepare terpyridine-based PCL/PU fluorescent biodegradable composite materials,It has potential application value in biomedical field such as biological imaging,cell detection,drug delivery,cell physiology research.In the first,a-N,N-dihydroxyethyl-aniline-terpyridines(TPYOH)containing two hydroxyl groups was used as fluorescent monomer to complex with tin,zinc,magnesium,aluminum and manganese metal ions.Then a series of different fluorescent polycaprolactones were synthesized by the polymerization of caprolactone which used the terpyridine metal ion complexes as the catalysts.Finally,a series of fluorescent polyurethanes were synthesized by using fluorescent polycaprolactone as soft segment.The polymer structure were characterized by FTIR and NMR,the molecular weight were measured by GPC,and the crystallinity was investigated by XRD and DSC.In addition,the fluorescence properties of a series of polymers were tested and compared by UV spectroscopy,fluorescence spectroscopy,fluorescence lifetime and quantum yield.Finally,the thermal stability of terpipyridine complexes and a series of polymers were tested by TG.The results showed that the novel fluorescent polycaprolactone type polyurethane had been successfully synthesized.It can be seen that FPU1,FPU2,FPU3,FPU4 and FPU5 had a diffusion peak of urethane when 2θ was 18.9°.In addition,there were two distinct crystal diffraction peaks in the vicinity when 2θwere 21.3° and 23.6°,respectively.Compared with PCL,the crystalline of polyurethane was obviously weakened.In the solid state,the fluorescence intensity of the fluorescent polyurethane was stronger than TPYOH.Solid fluorescence of FPU2 was the strongest,but the fluorescence of FPU5 was weaker than TPYOH and close to quenching.The fluorescence lifetime of FPU1 was improved and the fluorescence lifetime of FPU3 was also improved compared with TPYOH.And the quantum yields of FPU 1 and FPU2 were increased fivefold,the quantum yields of FPU3 and FPU4 increased nearly three times.TG test showed that compared with the fluorescent polycaprolactone,the thermal stability of polyurethane was improved obviously.This will lay the experimental foundation for the preparation of fluorescent PCL/PU composite nanomaterials and the application on biomedicine.