Packing Behaviors of Structurally Different Polyhedral Oligomeric Silsesquioxane-Imidazolium Surfactants in Clay

Abstract

This paper reports the packing structures of two types of polyhedral oligomeric silsesquioxane (POSS)-imidazolium surfactants with different molecular rigidity in the intergalleries of montmorillonite clay. Wide-angle X-ray scattering (WAXS) and molecular modeling studies suggest that the POSS-imidazolium cations have a bilayer packing structure in clay with the long axes of the molecules largely tilted with respect to the basal plane. Direct evidence for the bilayer structure is provided by transmission electron microscopy (TEM). WAXS and differential scanning calorimetry (DSC) results indicate that the relatively flexible POSS-imidazolium cation is able to form a two-dimensionally ordered structure in the clay intergalleries, while the relatively rigid one exhibits a disordered structure in clay. Furthermore, with reducing surfactant loading, the clay modified with the rigid surfactant exhibits increased interlayer d-spacings probably because the surfactant is able to take more extended conformation at lower loadings. With its low organic content and disordered surfactant packing structure, the clay modified with the rigid surfactant also exhibits excellent thermal and thermo-oxidative stabilities.

Architecture, Assembly, and Emerging Applications of Branched Functional Polyelectrolytes and Poly(ionic liquid)s

“…147,148,149,150,151,152,153,154,155,156,157,158,159,160 Based on the range of molecular masses involved, these compounds can be regarded as OIL compounds. Their molecular weight depends on the length of the spacer and the type of the ionic group and starts from 1338 g/mol for derivatives with one arm 147 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 temperature of 172°C.…”

“…The IL-groups are represented by terminal aliphatic tertiary amines with various lengths of the aliphatic substituent at the nitrogen atom,147,148,149,151,156,158 and also 1-substituted imidazole groups 150,153,154,155,159,161,162. The classical anionic groups are usually used as counterions (Figure 2).The charge density is regulated either by synthesis of monosubstituted POSS with varied spacer lengths, or by the degree of quaternization of these amino-containing substituents in the case of octasubstituted POSS 147,149,153,154,155. The variation of nitrogen substitution in the ionic group, the counterion structure, and the charge density have a dramatic effect on the properties of POSS-IL compounds.…”

Thermoplastic polymer nanocomposites based on polydopamine-coated clay : preparation, structures and properties

“…33 Recently, Toh et al has successfully synthesized a rigid POSS-imidazolium-modified montmorillonite which exhibited superior high thermal stability and large interlayer spacing. 47 On the other hand, Naveau et al has invented a greener clay modification process in which clay was modified in supercritical carbon dioxide (scCO 2 ) environment without using any solvents. 48 When the two components are totally immiscible, the polymer chains are unable to diffuse into the interlayer spacing between clays and hence large clay tactoids are observed in micron size, a conventional phase-separated microcomposite forms.…”

Studies of anhydride-cured epoxy networks with bonded and unbonded polyhedral oligomeric silsesquioxane (POSS)

“…The attractiveness of this approach resides in the large interlayer d-spacing brought about by the bulky POSS cages, which may help to improve clay intercalation/exfoliation in the polymer matrices, and the potential to impart synergistic effects of POSS and clay on property improvements. A number of research groups have studied POSS as clay modifiers and the properties of resultant POSS-clay/polymer nanocomposites [6][7][8][9][10][11][12][13][14].…”

“…POSS have been applied to numerous polymeric matrices such as polystyrenes, polypropylenes, poly methyl methacrylates, polyimides, polyurethanes, and epoxies [1][2][3][4][5]. More recently, POSS have also been used as clay intercalating agents for preparing polymer/clay nanocomposites [6][7][8][9][10][11][12][13][14].…”