Preparation And Properties Of Modified Chitosan And Composites Based On Chitosan Oligosaccharide And Polyurethane

Part ?:Chitosan?CS?and its derivatives are developing rapidly and getting more and more attention because of its widely available and excellent performance.The alkylation of CS can improve the hemostatic performance of CS,and hope to be applied in the field of clinical medicine.In the work,different substitution degree?S.D?of N-alkylated chitosan?N-ACS?was synthesized by reaction of caprylic aldehyde or dodecyl aldehyde with chitosan,which will be introduced octyl and dodecyl to the amino of CS.The chemical structures were characterized by Fourier transform infrared spectroscopy?FT-IR?and the S.D was determined by elemental analysis.The crystalline and thermal stability was measured by X-Ray diffraction?XRD?and thermogravimetric analysis?TGA?.The results of contact angle measurements indicated that the hydrophobicity of N-ACS increased with the increase of the S.D.The hemostatic experiments were carried out with the powder of N-ACS?300 mesh size?,the results showed that the N-ACS could form a flexible film on the blood surface,which could cover the blood completely and meaned the faster haemostasis than CS.Part ?:O-carboxymethyl chitosan?O-CMC?and polyethylene glycol?PEG?/polyethylene glycol monomethyl ether?mPEG?grafted O-CMC?PEG-O-CMC/mPEG-O-CMC?,which have security,non-toxic,environmental protection and other excellent performance,can be used widely,such as medicine,food packaging.In this paper,O-CMC was firstly synthesized by introducing the carboxymethyl to hydroxyl at C6 position of CS,and then the mPEG/PEG with different molecular weight were grafted into the amino group of O-CMC to obtain the PEG-O-CMC/mPEG-O-CMC.The corresponding membranes were prepared by solvent evaporation method.The chemical structures were characterized by FT-IR and the properties were measured through XRD,TGA and differential thermal analysis?DSC?.By grafting the hydrophilic PEG chain to the CMC,the hydrophilicity,toughness and film-forming properties increased obviously.The results of permeability test?CO₂and O₂?showed that the penetration rate of CO₂ and O₂ in 6 h was very low and tended to be stable.Due to the smaller molecular radius of CO₂ than that of O₂,CO₂ is easier to penetrate than O₂.The gas penetration rate decreased with the increase of grafting degree,and the gas penetration rate of PEG-O-CMC membrane is lower than that of mPEG-O-CMC,which meaned that the PEG-O-CMC membrane was beneficial to the preservation of fruits and vegetables.Therefore,the grafted CMC material could be expected to be applied to the packaging field of fruits and vegetables.Part ?:Due to the high molecular weight and high degree of crystallinity,CS is hard to dissolve in organic solvent,which makes it difficult to prepare the uniform composite of polyurethane?PU?and CS.As the degradation and deacetylation product of chitin,chitosan oligosaccharide?COS?consisting of 2-10 glucosamine units can be dissolved in some organic solvents.Using COS to prepare the COS/PU composite?PCU?can improve the PU biocompatibility and biodegradability,and the preparation method is simple,which can be widely used in medical field.The PU and CHO were dissolved in N,N-dimethylformamide to get a homogenous solution,then the composite films were obtained by solvent evaporation method.The structure was characterized by FT-IR,XRD and TGA.The mechanical performance test results show that when the content of COS increased from 5 wt%to 25 wt%,the ultimate tension stress and elongation at break decreased gradually to 18.5 MPa and 890%.However,the ultimate tension stress and elongation at break decreased relatively sharply when the amount of COS increased to an amount over 25 wt%.As a result,the COS content in the composites should be controlled no more than 25 wt%in order to maintain the mechanical properties to meet the requirement of biomaterials.In vitro degradation tests showed that the degradation rate of PCU gradually increased with the increase of COS content,so the degradation rate and time could be controlled by changing the content of COS in PCU.It was found that that biocompatibility and blood compatibility of PCU surface were study by protein adsorption and platelet adhesion.As the content of COS increased,the amount of protein adsorption decrease from 27.6 ug/cm² to 11.6ug/cm²,and the adsorption amount of platelets decreased significantly,which showed that PCU had a high biocompatibility and it will be a biological material for the human body.