Study On Modification And Properties Of Lignin Hydroxyethylation

Lignin is the second kind of natural polymer next to cellulose,and it is a good substitute for petroleum-based raw materials.The high value utilization of lignin is beneficial to the sustainable development of polymer.The use of lignin can be divided into two main ways.One is that it is directly used on the basis of not particularly destroying the structure of lignin;the other is that lignin can obtain many lignin-derived small molecules through"biorefining",and these small molecules can be reassembled to form new polymers.Whether it is lignin or lignin-derived small molecules,phenolic hydroxyl groups are universally present in the structure.Therefore,the modification based on phenolic hydroxyl groups has broader significance for lignin and lignin-derived phenolic compounds.The activity of phenolic hydroxyl group is lower than that of alcohol hydroxyl group due to the influence of benzene ring.Therefore,the modification of phenolic hydroxyl group into alcohol hydroxyl group is of great significance for the realization of high value utilization of lignin and lignin-derived phenolic compounds.In this work,vinyl carbonate as green hydroxyl alkylation reagent,tetrabutylammonium iodide(TBAI)as high temperature ionic liquid,used as a solvent in the system,at the same time has a catalytic effect,on lignin and lignin-derived phenolic compounds hydroxyethylated modification research.The results showed that the phenolic hydroxyl groups of lignin and lignin-derived phenolic compounds were converted to alcohol hydroxyl groups by hydroxyethyl modification.In addition,the activity comparison experiment before and after hydroxyethylation was carried out with vanillin as a model compound.The experimental results showed that the activity of alcoholic hydroxyl group was higher than that of phenolic hydroxyl group.Polycarbonate is a kind of polymer that has been widely concerned because of its many excellent properties.In this paper,the preparation of polycarbonate is taken as a typical example,and hydroxyethylated eugenol and hydroxyethylated lignin are selected as raw materials to prepare polycarbonate,and the properties of the prepared polycarbonate are studied.Hydroxyethylated eugenol was used in situ to capture and use CO2 in the presence of organic base 1,1,3,3-tetramethylguanidine(TMG),and then bromopropene and 6-bromo-1-hexene were added into the system to prepare two kinds of?-?-diene monomers containing carbonate structure.The polycarbonate with higher molecular weight and better thermal properties was prepared by mild and efficient mercaptoene click polymerization and ADMET polymerization.The molecular weight of the prepared polycarbonate was in the range of 15100-22500 g/mol,and the thermal decomposition temperature of 5%was in the range of 235-340 ~oC.And the polysulfide carbonate and unsaturated polycarbonate are respectively oxidized and hydrogenated.The oxidative modification significantly increases the glass transition temperature of the polymer,and hydrogenation can significantly improve the thermal stability;Hydroxyethylated lignin captures and utilizes carbon dioxide in situ under the action of organic base TMG to prepare polycarbonate polymers containing?,?-polyolefins.The existence of the polyolefin structure provides a platform for the subsequent preparation of lignin-based composites.