Synthesis and characterization of polymer-layered silicate nanocomposites

Vinylbenzyl n-alkyldimethylammonium (VDAC for n = 12, VOAC for n = 18) chloride cationic surfactants were synthesized for functionalization of clay. VDAC can form copolymer with styrene. Polystyrene hydrogels were synthesized by polymerization of VDAC/water/styrene oil-in-water microemulsions.; Organoclays were prepared by ion exchange of montmorillonite (MMT) with cationic surfactants. The swellability of organoclays was compared by wettability, contact angle, X-ray diffraction (XRD) and rheology measurements. Lattice based statistical thermodynamic model was developed to calculate the entropy and enthalpy change of styrene intercalation in organoclay gallery.; Polystyrene (PS)-clay nanocomposites were prepared by bulk polymerization. Intercalated and exfoliated nanocomposites were formed depending on the surfactant used for functionalization of clay. Hexadecyltrimethylammonium bromide and octadecylamine functionalized clay led to intercalated polystyrene-clay nanocomposites, while VDAC exchanged clay formed exfoliated polystyrene-clay nanocomposites. PS-VDAC-MMT nanocomposites have higher modulus and higher thermal degradation temperature compared with pure polystyrene.; PS-clay nanocomposites were also prepared by one-step and two-step emulsion polymerization methods. The one-step method requires that surfactant concentration is less than cationic exchange capacity of clay in order to avoid clay flocculation. PS-VDAC-MMT nanocomposites were synthesized by two-step emulsion polymerization. The polymer extracted from nanocomposites was found to consist of polystyrene homopolymer and a copolymer of styrene and VDAC units. The glass transition temperature of the nanocomposites increases as the percentage of organophilic clay increases, while the average molecular weight of the polymer matrix decreases.; Unsaturated polyester nanocomposites were prepared by bulk polymerization in the presence of VDAC-MMT or VOAC-MMT organoclays. The wetting and swelling kinetics of VDAC-MMT were much slower in unsaturated polyester than in styrene. VOAC-MMT has better swellability in unsaturated polyester than VDAC-MMT. Polyester clay nanocomposites have higher dynamic modulus than pure polyester.; Resole type liquid and powder phenolic resins were used to prepare polymer-clay nanocomposites. Tyramine and benzalkonium chloride bearing a phenol group or benzyl ring functionalized MMT were identified to have better intercalation of phenolic resin. XRD measurements indicated the formation of intercalated phenolic-clay nanocomposites. Scanning electron microscopy did not reveal clay aggregates.