Photonic crystals in biology - NanoTR-VI

Poster Session, Thursday, June 17Theme F686 - N1123Effect of Both Silane-Grafted and Ion-Exchanged Organophilic Clay in Structural, Thermal andMechanical Properties of Unsaturated Polyester NanocompositesSinan enDepartment of Polymer Engineering, Yalova University, 77100 Yalova, Turkey /Advanced Technologies Research and Development Center, Bogazici University, 34342 stanbul, Turkey.Abstract— Unsaturated polyester (UPE) resin including styrene monomer was mixed with montmorillonite (MMT) claywhich was modified with cetyl trimethly ammonium bromide and trimethoxy vinyl silane. The exfoliated nanocompositestructure having better thermal and dynamic mechanical properties was obtained when the MMT clay was modified in thepresence of both modifiers.Polymer-clay nanocomposites have attracted anincreasing attention due to impressive enhancements ofmaterial properties due to nanometer size of filler dispersioncompared to pure or conventionally filled polymers. There aretwo types of polymer-clay nanocomposite structures, namelyintercalates, where polymer chains intercalate between thelayers and exfoliates, where silicate layers are completelydelaminated in the polymer matrix [1]. Since improvements inmany properties depend on the degree of dispersion of thenanoparticles, exfoliated nanocomposites are generally thetarget of many nanocomposite studies. In situ polymerizationwas the first method used to synthesize polymer-claynanocomposites. The thermoset-clay nanocompositesincluding phenol resins [2], epoxy resins [3] and unsaturatedpolyester resins [4] as polymer matrices were obtained by insituintercalative polymerization method in which polymerresin, dissolved in a polymerizable monomer such as styrene,is intercalated between clay layers and then followed bycrosslinking reaction.In this study, UPE - MMT clay nanocomposites havebeen synthesized by in situ method. The MMT clay wasorganically modified with cetyl trimethyl ammonium bromideand also with trimethoxy vinyl silane. These modificationagents were used both individually and together. The cetyltrimethyl ammonium bromide is expected to intercalatebetween the clay layers through ion-exchange reaction whilethe silane agent grafts onto edge and surface hydroxyl groupsin montmorillonite clay. Thereby, for “double” modifiedMMT clay, reactive double bond in vinyl silane couplingagent can participate in the polymerization reaction from bothsurface and edges of ammonium ion-intercalated clay layers,which may lead to a completely exfoliated nanocompositesstructure. Differences in dynamic mechanical and thermalproperties as well as the morphology of the resultantnanocomposites were all discussed by paying attention to theMMT modification mechanisms.XRD analysis gave the values of the interlayer spacing ord-spacing of the NaMMT and the modified clays which wereobtained from the peak position of the d 001 reflection in thediffraction patterns The XRD result showing a decrease ofdiffracting angle which in turn increase in interlayer distanceproved succesful intercalation of MMT clay layers with cetylammonium salt through the ion-exchange reaction. In the caseof the ‘double-modifed’ clay-containing nanocomposite,UPECetViSiM-C, an exfoliated structure was obtained withthe absence of any d 001 reflection in the XRD region. Thisresult may be attributed to the good swelling of CetViSiMMTin UPE resin and homogeneous and fine dispersion of it in thematrix, as well as promotion of polymerization both betweensilica layers, and from surfaces and edges of the clay with thehelp of reactive double bond present in the ViSi modifier. Themorphology of the exfoliated nanocomposite was alsoinvestigated by AFM analysis showing that very thindispersion of CetViSiMMT clay platelets were oriented in allpossible directions to one another in the matrix as aconfirmation of XRD peak disappearance. Accordingly, theexfoliated UPECetViSiM-C nanocomposite was found to havethe highest thermal stability and better dynamic mechanicalproperties (Table 1), even with a clay content as low as 3 wt%.Table 1. DMA data for neat UPE and UPE nanocompositesMaterials E’ at 60°C(MPa)E’ at 80°C(MPa)Neat UPE 1458 204UPECetM-C 1625 247UPEViSiM-C 1743 259UPECetViSiM-C 1840 390Fracture surfaces of UPE and its nanocomposites wereinvestigated by scanning electron microscopy (SEM) usingbackscattered imaging (Fig. 1). SEM images of the fracturesurfaces showed that presence of CetViSiMMT clay with ahomogeneous and nano-sized dispersion in the polymermatrix, led to crack propagation along a more ‘rougher’ path.On the other hand, the UPECetM-C exhibited a heterogenousfracture surface, which may be probably due to its intercalatedstructure.Figure 1: SEM micrographs of the fracture surfaces of (a) neatUPE; (b) UPECetM-C; (c) UPECetViSiM-C and (d) UPEViSiM-C.*Corresponding author: sinans@yalova.edu.tr[1]. S.S. Ray, and M. Okamoto, Prog. Polym. Sci., 28, 1539 (2003).[2]. T. Lan, P.D. Kaviratna, and T.J. Pinnavaia, Chem. Mater., 7, 2144 (1995).[3]. D.C. Lee, and L.W. Jang, J. App. Polym. Sci., 68, 1997 (1998).[4]. D.J. Suh, Y.T Lim, and O.O. Park, Polymer, 41, 8557 (2000).6th Nanoscience and Nanotechnology Conference, zmir, 2010 752