X-ray scattering and calorimetric studies of organoclays obtained by ion-exchange

Structure and thermal behavior of organoclays has important influence on properties of clay-based polymer nanocomposites. Depending on starting materials, i.e. the mineral and amphiphilic compounds, one can obtain organoclays differing in properties. Therefore the careful choice of substrates is the way to predict and tailor ability to accommodate molecules in the interlayer spaces, catalytic activity or thermal stability of these complexes. In this paper, we present results of structural and calorimetric studies of the systems obtained of the synthetic silicate called SOMASIF modified with stoichiometric amounts of three different quaternary alkylammonium salts. SAXS studies clearly indicate that interlayer spacing (d sub(001)) of silicate, calculated from the main diffraction maximum, grows strictly linearly with the length of long aliphatic chains bonded to quaternary nitrogen atoms. Further analysis of the diffractograms leads to the conclusion that the ion exchange results in formation of a mixture of three phases with different values of interlayer spacing (d sub(001)). Results of DSC measurements suggested that, despite being adsorbed on the surface of silicates, quaternary ammonium cations may undergo phase transitions similar to the moieties in the bulk. The temperature range of these transitions was however found to be distinctly shifted towards lower values in comparison to the alkylammonium salts alone. Thermogravimetric analysis (TGA) was applied to estimate thermal stability as well as the coverage of silicate surface with amphiphilic molecules.Original Abstract: Struktura i charakterystyka termiczna organofilizowanych glinokrzemianow warstwowych (rys. 1, tabela 1) ma istotny wplyw na wlasciwosci nanokompozytow polimerowych otrzymanych z udzialem tego typu napemlaczy. Decydujacy wplyw na wlasdwosci takich napelniaczy ma dobor zwiazkow amfifilowych (takich jak czwartorzedowe sole amoniowe) stosowanych do modyfikacji glinokrzemianow. Przedstawiono wyniki badan: termograwimetrycznych, kalorymetrycznych i rentgenograficznych ukladow otrzymanych na drodze organofilizacji syntetycznej fluoromiki o handlowej nazwie SOMASIF, za pomoca trzech homologicznych, czwartorzeowych bromkow alkiloamoniowych. Pomiary SAXS wykazaly, ze wymiana jonowa przeprowadzona przy uzyciu stechiometrycznej (w stosunku do pojemnosci jonowymiennej mineralu) ilosci soli prowadzi do powstania ukladu zlozonego z trzech faz odznaczajacych sie roznymi odleglosciami miezyplaszczyzn