Study On Bio-based Polymers Incorporated With Azobenzene Structures: Preparation And Performance

Bio-based polymeric materials derived from renewable resources have the potential to reduce or even eliminate environmental concerns and oil crises,favoring sustainable development.It has been attracting much research attention from all around the world since the initial concept emerged twenty years ago.The area of bio-based polymers is going through two stages,that is,the synthesis and usage of bio-based monomers and high-performance bio-based polymers for replacing oil-based polymers.Functionalizing bio-based polymers enables to enhance their competition in market,whereas it has not attracted much attention yet.This dissertation starts with functionalizing the polyesters.We prepared photoresponsive copolymers from azobenzene and bioresource-derived dimethyl furan-2,5-dicarboxylate by a melt-polymerization approach.The measurements of nuclear magnetic resonance(NMR),Fourier transform infrared spectroscopy(FTIR),and mass spectrometry(MS)identify the chemical structure and azo-containing polyester structures.Characterizations of gel permeation chromatography(GPC),dynamic mechanical analysis(DMA),tensile tests,and thermogravimetric analysis(TGA)show the molecular weight and dispersity and thermo-mechanical properties.Furthermore,we used differential scanning calorimetry(DSC),polarizing microscopy(POM),ultraviolet-visible spectroscopy(UV-vis)and two-dimensional x-ray powered diffraction(2D-XRD)characterizations to study the liquid crystal behaviors and photoinduced isomerization.It reveals the content of azo-compounds can affect the photoresponse actions with the same light power density.We further used in-situ FTIR,XRD,and DMA analysis to monitor the change in condensed matter(crystallinity,intermolecular force,and interplanar distance)of polyesters of D5 and D10,which were sequentially processed by tensile tests,ultraviolet illumination,and visible light illumination.D10 polyesters with higher amounts of azobenzene moieties have stronger inter-chains interaction and different condensed matter properties,which results in the stronger ability of shape-persistence than that of D5 polyesters.We then conducted density-functional theory(DFT)calculation with statistical models to build up structures of D5 and D10 polyesters.It sheds light on the correlation between condensed matter and photoresponsivity,providing a strategy of tuning the condensed matter to control the photoresponsive behavior of polyesters.This dissertation also successfully grafted azobenzene onto itaconic acid-epoxy thermoset resins to achieve photochromic coatings derived from bio-resources.We used NMR,FTIR,and MS analysis to confirm the chemical structures.Results from FTIR and DSC tests show the success of the thermal-and light-curing process between azo-compounds and itaconic acid epoxy resin.Tensile tests were conducted to analyze the effect of the content of azo-compounds on the thermo-mechanical performance of epoxy thermoset resin.We find that 5% of azo-compounds have the most excellent performance.We then prepared chromatic ink made by azo-doped itaconic acid polymers and coated it onto the surface of polyesters,glass,and steel by thermal-and light-curing processes.The azo-containing thermoset resin have excellent adherent properties(5B),hardness(5H)and photochromic performance,showing its potential application in information storage.