A New Method Of Organic Acid Anion Intercalation Hydrotalcite And Its Modification On Hydrogel

Organic-inorganic hybrid LDHs is a type of hydrotalcite-based composite derivative material,which combines the respective characteristics of inorganic hydrotalcite and organic matter,and shows great potential in the fields of healthcare,polymer composites,environment,catalysis and energy generation.So the development of organic-inorganic hybrid LDHs materials has important practical significance.It is known that most organic substances enter the hydrotalcite layer in the form of their acid ion,and the development of the preparation method of organic acid anion intercalated hydrotalcite is very important for studying organic-inorganic hybrid LDHs materials.In this paper,we propose a new preparation method to realize the intercalation of hydrotalcite with various organic acid anions.At the same time,the mechanism of the method is verified,and the scope of the method is extended.Later,we have successfully applied this method to the preparation of nanocomposite hydrogels.By this method,acetate Tris-LDHs is prepared,which is added to the hydrogel system as a crosslinking agent to obtain hydrogels with structural stability and enhanced performance.The internal interaction force of the gel is studied,and the hydrogel morphology,mechanical properties,and swelling properties is experimentally characterized.The specific content of this paper is as follows:(1)Aiming at the shortcomings of the current preparation method of organic acid anion intercalated hydrotalcite,such as long time consumption,high energy consumption and complicated operation,a new preparation method is proposed.This method is to directly combine the organic acid and carbonate hydrotalcite in methanol medium During the reaction,the organic acid slowly dissociates in methanol,and the generated hydrogen ions combine with the carbonate between the hydrotalcite layers to form carbon dioxide and water.At the same time,the organic acid anion enters the hydrotalcite layer to replace the carbonate,carbonate hydrotalcite reacts with organic acid in a "strong acid sets weak acid" reaction.At the same time,the substrate expansion experiment found that the method is suitable for different sizes(50-80 nm,250-500 nm,2-3?m)and different types(CO32--Zn2Al-LDHs,CO32--Co2Al-LDHs,CO32--Ni2Fe-LDHs).It is also suitable for aliphatic monocarboxylic acid,aliphatic dicarboxylic acid,aromatic carboxylic acid,organic sulfonic acid,phosphonic acid and organic photofunctional acid.This work provides an efficient method for preparing organic-inorganic hybrid LDHs.(2)Aiming at the problem of poor mechanical properties,swelling performance and biocompatibility of traditional chemical cross-linked hydrogels,we introduce acetate Tris-LDHs and oxidized dextran into the hydrogel system to build an enhanced structure nanocomposite hydrogel.Tris-LDHs modified by acetate can swell in water and be stripped into a single layer of hydrotalcite nanosheets.The Van der Waals force exists between the hydrotalcite nanosheets and the polymer chain,and at the same time,the amino group on the hydrotalcite layer and the aldehyde group of oxidized dextran form a Schiff base bond.This multiple interaction makes the three-dimensional network of the nanocomposite hydrogel more uniform,the structure more stable,the mechanical properties of the hydrogel are more excellent,and the swelling performance has been significantly improved.At the same time,the use of hydrotalcite instead of organic small molecule cross-linking agents and the use of oxidized dextran have enhanced the biocompatibility of hydrogels.Our experimental results show that the fracture strain energy of the hydrogel reaches 1523%,the fracture stress is 591 kPa,and the toughness is as high as 3338.94 kJ/m3.The equilibrium swelling rate of the hydrogel reaches 50 g/g,and the water content is as high as 97.82%.This work provides a foundation for expanding the application of hydrogel functions.