Hydrophilic And Hydrophobic Modification Of PCL And Preparation Of Microsphere On Cotton Fabric Via Electrospraying

Polycaprolactone is widely used in biological materials,drug release and delivery,tissue engineering,biological scaffolding and other fields,because of its biodegradability,good drug permeability,biocompatibility,and easy access to materials.However,as there is no active group in the PCL chain,most modification of PCL are focused on physical blending.Some chemical modifications of PCL,such as grafting and block polymerization,can only obtain the modified products with low molecular weight.This limited the further application of PCL materials.In this dissertation,aminolysis of high-molecular-weight PCL with alcoholamine provided the PCL chain reaction activity,and followed by hydrophilic modification by embedding PEG segment in PCL chains.This method is also used to introduce fluorine-containing segments into the PCL chain to achieve hydrophobic modification of PCL.Lastly,the modified PCL polymer microspheres were prepared via electrspraying technology and coated on the cotton fabric.Utilizing the superior characteristics of microspheres,special functionalization of cotton fabric has been achieved.Main discussions were as follows:(1)Fabricating PCL/PEG block copolymer and its enzymatic degradationThe ending active sites of hydroxyl groups were introduced by aminolysis with6-amino-1-hexanol of PCL,and terminal carboxyl was formed by reaction with Succinic anhydride(SA).Then,poly(ethylene glycol)(PEG)was bonded to the PCL chain through esterification,thus endowing PCL the hydrophilicity.The prepared PEG-PCL copolymers were characterized by FT-IR,1H NMR,XPS and GPC.Static water contact angles measurement indicated that hydrophilicity of the copolymer films modified by PEG has improved considerably.The degradation of the copolymer disc samples with a certain quality and size,in a phosphate buffer solution containing a type of Lipase(AspergillusOryzae),was observed at different time intervals.The results of weight loss ratio and shape change,during the degradation process,indicated that blocking PEG chains onto the PCL chains can effectively accelerate the process of enzymatic degradation of the resulting copolymer.During the degradation,the copolymers in the films were characterized by1 H NMR,GPC and SEM.The results emphasized that,to compare with PCL,the enzymatic degradation of PCL-PEG copolymers occurred faster by starting from the surface layer of the films.(2)Preparing of PCL/PEG Block Copolymer Microspheres via Eletrospraying and Coating on Cotton FabricsElectrospraying technology was utilized to produce PCL,PCL-PEG400 and PCL-PEG1000(3% wt)microspheres with controlled size and tunable surface morphology by adjusting the procesing parameters,such as flow rate,voltage and collecting distance,and so on.SEM coupled with image analysis software(Image J)was employed to evaluate the structure and the size distribution of microspheres.The results showed that the particle size of the microsphere increases with the increase of the flow rate and collecting distance,while decreases with the increase of the voltage,and the collecting distance was found to be having the least impact.According to the observation and analysis,PCL,PCL-PEG400 and PCL-PEG1000 may form the different microspheres with lots of porous pits,a handful of pits and non-porous wrinkles on the spherical surface,respectively.The preparation process was optimized and then coated the cotton fabrics pre-treated with adhesive directly by electrospraying successfully.(3)Fabricating fluorinated PCL block copolymer and its enzymatic degradationUsing Cu Br/(N,N,N',N',N''-Pentamethyldiethylenetriamine)(PMDETA)as a catalyst system and 2-Hydroxyethyl 2-bromoisobutyrate(HEBi B)as the initiator,Poly(1H,1H,2H,2H-Perfluorooctyl acrylate)(PTFOA)with terminal hydroxyl groups were synthesized by ATRP using 1H,1H,2H,2H-Perfluorooctyl acrylate(TFOA)as monomer.The fluorinated PCL block copolymers with diverse fluorine content were prepared by esterification reaction between terminal carboxyl of the functionalized PCL and the chain-end hydroxyl groups of PTFOA.The structure and composition of the PTFOA modified PCL were characterized by FTIR,1H NMR,19 F NMR,XPS and EDS.The molecular weight and molecular weight distribution of the PCL-PTFOA copolymers was studied by GPC.The results indicated that introducing pre-prepared PTFOA chains into thePCL chains at mild reaction conditions can obtain fluorinated PCL copolymers without decomposition of the PCL main-chain.Contact angle measurements to water and n-hexadecane illustrated that introduction of PTFOA segments can enhance the hydrophobicity of PCL and even obtain the oleophobic performance,while the surface free energy of the membrane is greatly decreased.The results of the enzymatic catalytic degradation to PCL,PCL-PTFOA(2h)and PCL-PTFOA(6h)films showed that the introduction of PTFOA chain lowered the degradation rate of PCL in the early degradation stage,but the modified PCL eventually showed higher weight loss.The surface morphology of the membrane by SEM during the enzymatic degradation process was tested.The enzymatic degradation was found to starts from the surface layer of the films instead of its edge.Meanwhile,in the late degradation,the fluorinated PCL polymer discs appeared missing and became fragmentedly lastly.(4)Preparing of fluorinated PCL block copolymer Microspheres via Eletrospraying and Coating on Cotton FabricsPCL,PCL-PTFOA(2h)and PCL-PTFOA(6h)microspheres were prepared via electrospraying at a concentration of 3 wt%,using chloroform as solvent.The effect of flow rate and voltage on the particle size and surface morphology was studied by SEM coupled with image analysis software(Image J).The results indicated that the particle size of microspheres increased with the increase of flow rate and decreased with the increase of voltage.The diameter of PCL microspheres can be controlled at 6.5-11.0 ?m,the microspheres appeared pits and wrinkles on the surface and showed a golf ball shape.The size of PCL-PTFOA(2h)microspheres can be controlled at 4.4-7.0 ?m and the honeycomb-like structure can be observed on the surface of microspheres,while PCL-PTFOA(6h)microspheres can be controlled at a particle size of 5.6-9.0 ?m,and also exhibited uniform pits and honeycomb-like structure.The microstructure of the modified polymer microspheres and the fluorine content of the wrinkles and pits were investigated by SEM and EDS,respectively.The results confirmed that the fluorine content in the pits is higher than that in the wrinkles.The processes of microspheres were optimized and then coated on cotton fabrics,whose surface was dipped a layer of water-based adhesive,by electrospraying directly.The pre-treated with adhesive can enhance the fastness of microspheres onto the surface of fiber successfully.Static contact angle test showed that the water repellency of cotton fabrics coated by polymeric microsphere was excellent withthe contact angles of 159.5° or 160.0°,from which the “lotus-effect” was obtained.