Preparation And Modification Of Poly(Methyl/Phenyl) Silicone Xerogel Monoliths

Because of its Si-O-Si main chain structure and abundant porous structure,polysiloxane porous materials have great potential for application as high temperature insulation materials,but the high brittleness and higher demand for thermal stability inhibit the widespread use.Therefore,this thesis aims to modify the polysiloxane matrix from the point of molecular design,by introducing phenyltriethoxysilane(PTES)and diphenyldiethoxysilane(DPDES)into the structure.Synthesis of polysiloxane containing side groups of methyl and phenyl groups has been conducted.This thesis focuses on the effect of monomer ratio and catalyst concentration on structure and properties,as well as modification of poly(methyl/phenyl)siloxane porous material using carbon nanotubes(CNTs)an d trimethylethoxysilane(TMES).First,the influence of catalyst concentration on the pore structure was investigated by scanning electro microscopy(SEM).The results showed that the higher the catalyst concentration,the shorter the gelation time.SEM images showed the structure was tailored by changing catalyst c oncentration.Then the effect of monomer ratio on thermal performance was investigated by FT-IR,TG and 29Si-NMR analysis.The results showed that the sample with phenyl and diphenyl monomer had enhanced heat resistance,and the lowest mass loss rate was 18.8% at 1000? in a nitrogen atmosphere.TG-MS analysis showed that the decomposition process of silicone resin under oxygen conditions was divided into two parts: the oxidation decomposition of the side group at 300~620? and the degradation of the main chain at 310~480?.Then,CNTs modified poly(methyl-phenyl)siloxane porous materials were studied.After addition of 2% CNTs,the specific surface area of the xerogel monolith was 323.7 m2/g.Additionally,the heat resistance increased,and the final mass loss of TG analysis was 15.1%.Then the effect of TMES on the surf ace modification of poly(methyl-phenyl)silicon porous materials was investigated by 29Si-NMR and contact angle tests.29Si-NMR spectrum showed that after the TMES modification,((CH3)3Si O-)structure appeared,which proved that the TMES was successfully grafted to the surface of the material.The contact angle also increased from 147.0° before modification to 154.7°.The experiments of oil-water separation and adsorption of organic liquids showed th at the TMES-modified poly(methyl-phenyl)siloxane porous material has the ability to adsorb organic substances while being hydrophobic,and its adsorption rate to soybean oil is 580%.Cyclic adsorption-desorption experiments confirmed that the TMES-modified poly(methyl-phenyl)siloxane porous material can be reused for many times without the weakening of adsorption capacity and has a potential in the relative application field.