Preparation Of Chitosan/Synthetic Polymer Composite Nanogels And Their CO₂-Responsive Performance

Excessive CO₂ gas emissions in the atmosphere are widely accepted to be the major causes of global warming,the utilization of CO₂ has become a research hotspot.In recent years,CO₂-responsive polymers have attracted more and more attention due to their unique response characteristics.It is an important research approach to design and prepare a new type of CO₂intelligent response material with special functional groups based on natural polymers.Chitosan is the only alkaline polysaccharide in nature,which is rich and easy to gain,renewable,non-toxic,biodegradable,biocompatible and antibacterial.Chitosan contains a large amount of primary amine?-NH₂?and is a potential candidate for CO₂-responsive polymers.In this thesis,it aims to synthesize a series of chitosan/synthetic polymer composite nanogels.Furthermore,the CO₂ responsiveness was studied.Therefore,it lays a foundation for the development of environment-friendly polymer materials with good CO₂ capture performance.The thesis consists of three parts.In chapter 1,it mainly introduces the research progress of"intelligent"polymer in the field of science.Firstly,the classification,structure,response principle and application of various"intelligent"hydrogels are reviewed.Then,the development process,advantages and disadvantages of CO₂ intelligent polymer and its application in various fields are introduced in detail.In the end,some preparation methods of chitosan composite polymer and their applications in CO₂ adsorption materials were reviewed.However,there are few reports on the application of chitosan as the CO₂ intelligent material in this field.In chapter 2,CS/PDMAPMA composite nanogels are fabricated in the solution of chitosan by soap-free emulsion polymerization using N-?3-[dimethylamino]propyl?methacrylamide?DMAPMA?as the monomer,ammonium persulfate?APS?as initiator and N,N-methylenebis?acrylamide??BIS?as the cross-linker.The effects of different mass ratios of CS to DMAPMA and the amount of crosslinking agent on the CO₂ response performance were investigated.A group of composite nanogels with better CO₂ response performance was determined and their response mechanism was further studied.The structures and properties of nanogels were characterized by FTIR,¹HNMR,UV-VIS and SEM.The scanning electron microscope?SEM?results indicate that the nanogels are spherical nanoparticles with a diameter of about 50 nm.After purging with CO₂,the original creamy-white latex becomes a clear solution.While purging with N₂,the clear solution is returned to the original latex state.In additional,the results suggest that the nanogels have good CO₂/N₂ reversible response and morphological switchability.In chapter 3,CS/PDMAPMA/PAA composite nanogel via self-assembly soap-free emulsion polymerization were prepared.DMAPMA was functionally incorporated into the nanogels of CS and PAA using CO₂-responsive 2,2'-azobis-2-methyl-propanimidamide as initiator.Non-covalent forces including of hydrogen bond,hydrophobic and electrostatic interaction caused the stronger physical cross-linking between polymers chains.Nanogels have stronger CO₂ response performance and excellent performance.The effects of AA and DMAPMA content on the stability of composite nanogels and their morphologies were investigated to further explore their effects on CO₂ response performance.CS/PDMAPMA/PAA composite nanogel has the excellent morphological switchability by a shift in the CO₂ and N₂.In addition,it was found that the CO₂ response performance of this nanogel system was faster and more complete than that of CS/PDMAPMA composite nanogels.In conclusion,the nanogel system with excellent response performance was successfully prepared by simple and effective soap-free emulsion polymerization using natural polymer chitosan as the substrate material.The preparation principle and response mechanism of CO₂were studied.It provides a theoretical basis for the further preparation of novel CO₂ smart materials.In addition,based on these advantages,CO₂-responsive chitosan composite nanogel system has broad application prospects as intelligent devices,biosensors,CO₂ adsorbent materials and drug carriers.