Synthesis And Applications Of Polysaccharide Derivatives

In this paper,cellulose and dextran were used as the raw material.Aminopyridine functionalized cellulose was coordinated with Pd(OAc)2 to prepare heterogeneous catalyst.Zwitterionic dextran grafted PCL was developed to be drug delivery systems.Details were as follows:1.Aminopyridine functionalized cellulose catalyst was prepared through the SN2 reaction between cellulose tosylate and aminopyridine.Then,functionalized cellulose was coordinated with palladium acetate to obtain the heterogeneous catalyst.It was fully characterized by Inductively coupled plasma atomic emission spectroscopy(ICP-AES),Transmission electron microscope(TEM),Fourier transform infrared spectroscopy(FT-IR),Thermogravimetric analysis(TGA)and X-ray photoelectron spectrometry(XPS).Results indicated the Pd loading was 3.83 mmol/g.The catalytic activity and the recycling performance of this catalyst were tested by Suzuki reaction as a model reaction.The optimum conditions were as follows: 50% ethanol solution as solvent,50 °C as the temperature,0.75 mmol% amount of the catalyst,and potassium carbonate as the base.Based on the optimized reaction conditions,Suzuki reactions of aryl halides with various phenylboronic acids were examined.It was found that almost all the aryl bromides were carried out in excellent yields(66-95%)regardless of electron-rich or electron-deficient.After reaction,it could be easily recycled by simply filtration.Furthermore,the recyclable cellulose-based catalyst had shown a great potential in the water-borne catalyzation of Suzuki reaction.2.Zwitterionic dextrans were prepared via the modification of dextran with carboxybetaine or sulfobetaine.Then,PCL segments were grafted onto the zwitterionic dextran.FT-IR and NMR were used to characterize the dextran-polycaprolactone copolymers.Results showed that the substitution degree of carboxybetaine zwitterionic groups was about 0.3,sulfobetaine zwitterionic groups was about 0.24,and PCL segment was about 0.1.The zwitterionic segments together with dextran showed great performance in protein resistance.The hydrophobic segments made the polymer self-assembled in water,which had great potential for the lipophilic drug loading and delivery.