Studies On Structure And Properties Of Biopolymer Composite Materials Based On Carbon Nanotubes

As a new member of carbon material family,carbon nanotubes(CNTs) have become the subject of intense investigation because of their unique structural, electrical and mechanical properties.In recent years,increasing studies are focused on exploring CNTs' properties for biological applications both at molecular and at cellular levels.In order to develop some new potential application of CNTs in the field of biological applications,we have studied lots and the details will be reviewed in this thesis within three part.Firstly,through the process of ultrasonic,three types of carbon nanutubes (MWCNT,MWCNT- NH₂ and MWCNT-OH) were dispersed in theε-Caprolactone monomer.Then viain-situ polymerization,the PCL/MWCNT,PCL/MWCNT- NH₂ and PCL/MWCNT-OH composite was prepared.The disperse configuration of carbon nanotubes was studied via SEM and TEM.Then we studied the thermal properties, mechanical properties and electric properties.The result showed that the carbon nanotubes with no functional groups were dispersed well into the composite,the mechanical property of the composite was best when the content of MWCNT was 3%, of which the Peak Stress,Strain at Break and Modulus were enhanced 11.6%,11.3% and 10.4%respectively.Compared with PCL/MWCNT composites,PCL/MWCNT-NH₂ and PCL/MWCNT-OH composites did not showed the better properties as expectation,which maybe attributed to two reason.One is the wave absorbability of MWCNT,the other is the active groups which were too activity to increase the PCL segment.Secondly,In order to improve the mechanical strength and the stability of the alginate hydrogel,MWCNT and SWCNT were introduced into calcium alginate hydrogel system use the method of solution blending.Then in order to prepare a controlled release of carbon nanotube hybrid alginate microspheres,the small molecule drug theophylline were loaded into the compound AL/SWCNT-0 and AL/MWCNT-0.Then FTIR,XRD and the rheological behavior test methods were used to study the structure of the carbon nanotubes hybrid microspheres.The characterization test results showed that the addition of carbon nanotubes into alginate hydrogen highly improved the strength.The method of MTT have used to complete the cytotoxicity test,the initially result showed that this carbon nanotube material has a good biocompatibility.The drug encapsulation efficiency was advance from 76.5 percent to 91.3 percent,the release time also continued from 4 hours to 10 hours.Just as expectation,in the condition of simulated gastric juice drug release in a small speed, but tardiness in the fluid of intestines for a long time and totally drug free.Thirdly,well-dispersed single-walled carbon nanotubes(SWCNT) were successfully incorporated into a supramolecular hydrogel through combining dual roles of Pluronic copolymer in dispersing SWCNT and forming inclusion complexes withα-cyclodextrin(α-CD).Such hydrogel hybridized with SWCNT was prepared by mixing an aqueous solution ofα-CD with an aqueous dispersion of SWCNT stabilized by Pluronic copolymer.The structure and properties of the supramolecular hydrogels were studied in detail by means of a variety of characterization methods.The results obtained from X-ray diffraction(XRD),(FTIR) and scanning electron microscopy (SEM) showed that the SWCNT were well dispersed had no obvious influence on the structure and morphology but changed gelation mechanism comparing with that of the native hydrogel.The resultant hybrid hydrogel retained the basic characters of supramolecular hydrogel,especially the shear-thinning and reversible temperature-responsive properties.It is noteworthy that the introduction of SWCNT accelerated the gel formation obviously.Last but not the least,the cytotoxicity test proving that the hybrid supramolecular hydrogels have very good safety as drug delivery materials,and also the hybrid hydrogel has a better performance of bacteria resistance than the native hydrogel.