Fabrication And Evaluation Of POSS-based Organic-inorganic Hybrid Silica Hydrophilic Monolith

Polyhedral oligomeric silsesquioxane(POSS)have a stable inorganic core composed of Si-O bonds and a three-dimensional distribution of functional groups,which consiste of multiple active sites and stable structure.Todate,POSS-based hybrid silica monoliths with many merits including simple preparation,a wide tolerant range of pH and good solvent resistance,has gained attention of numerous researchers and lighted a new direction of monolith research.Fabricating novel POSS-based organic-silica hybrid monoliths,and then developing a new mode to prepare functional monoliths,has an important scientific significance in the application of capillary monolithic column to microchromatography.In this paper,the preparation basing on the epoxy-amino ring-opening reaction and characterization of the resultant POSS-based hydrophilic hybrid silica monolith were described.The main contents are shown as follows:In chapter 1,literature review.The introduction of the development and application of organic-inorganic hybrid silica column was presented.The preparing methods,development,and application of organic-inorganic hybrid silica monolithic column were also summarized,and the topic selection and scheme design of this paper are put forward.In chapter 2,A POSS-based organic-inorganic hybrid silica hydrophilic column was prepared by "one-pot" cross-linking polymerization by using octa-glycidyl dimethylsilyl grafted polycyclic oligomeric silsesquioxane(POSS-epoxy)and polyethylenimine(PEI)as polymer monomer.Various factors including polymer composition,structure,permeability and efficiency of the monolithic column were investigated.The mechanical stability and reproducibility of the poly(POSS-epoxy-PEI)hybrid silica monolithic column are also explored,and the mechanism of chromatographic retention are also studied.The structure of the obtained monolithic column is homogeneous,and possess of obvious merits such as good stability,low swelling coeff-icient and high hydrophilicity.Applied to phenolic compounds,basic nucleobase and encephalin,a good retention and high separation efficiency for these compounds were obtained.In Chapter 3,in order to enhance the hydrophilic properties,chitooligosaccharides(COS)were introduced into poly(POSS-epoxy-PEI)hybrid silica monolith to obtain a novel chitosan oligosaccharide functionalized hybrid silica monolith.The conditions for chitooligosaccharide derivatization have been optimized.Structure morphology,electroosmotic flow,mechanical stability,swelling property,and retention mechanism of poly(POSS-epoxy-PEI-co-COS)hybrid silica column were investigated.By introducing COS into poly(POSS-epoxy-PEI)monolith,the hydrophilicity of the column was improved.A variety of retention modes such as hydrophilic interaction,hydrogen bonding and anion exchange were observed poly(POSS-epoxy-PEI-co-COS)hybrid silica monolith.Applied to different electrical properties(electro-neutral phenols,positively charged nucleobases and negatively charged benzoic acids),the separation efficiencies of polar compounds were significantly improved,and could raise up to 49,600 plate/m and 82,300 plate/m for benzoic acid compounds and nucleoside bases,respectively.