Polymer Modification Of Nano-materials Surface

This thesis deals with surface modification of two kinds of typicalnano-materials, nano- SiO₂ and multi-walled carbon nanotubes (MWCNTs). Theresults of nano-silica modified with polyethylene glycol (PEG) via direct graftingmethod showed that grafting ratio rose along with the increase of molecular weight ofPEG, but there was little difference in dispersion of SiO₂ grafted with PEG withdifferent molecular weight in butanone. The results of nano-silica modified with PEGvia TDI activation method showed that the extent of reaction decreased along with theincrease of the amount of added TDI, but the number of TDI attached onto the surfaceof nano-silica was almost the same. Grafting ratio increased at first then decreased tothe lowest point, then increased again and decreased afterwards as a function ofPEG/TDI ratio, and the optimum PEG/TDI ratio was 0.9. Grafting ratio obtained viareacting in butanone was higher than that in toluene and DMF. Higher grafting ratiowas obtained by grafting with PEG of higher molecular weight. The best dispersioneffect of nano-silica was got when the molecular weight of PEG was moderate. It wasfound that dispersion effect obtained via TDI activation method was better than thatvia direct grafting method. High grafting ratio can be obtained by functionalizingMWCNTs with polyamidoamine (PAMAM) dendrimer. TEM pictures showed thatgrafting reaction mainly occurred at the end and the bend of the MWCNTs. MWCNTsafter functionalization dispersed well in water, and better dispersion can be obtainedwhen the generation of PAMAM dendrimer was higher.