J.-P. Pascault
Laboratoire des Matériaux Macromoléculaires/Ingénierie des Matériaux Polymères, UMR CNRS 5223, Bât. Jules Verne, INSA-Lyon, 69621 Villeurbanne Cedex, France (Jean-Pierre.Pascault / insa-lyon.fr)
Nanostructured thermosets, TS may be obtained by the self-assembly of amphiphilic block copolymers, BCP in a reactive solvent and fixation of the resulting morphologies by the cross-linking reaction. In particular, BCP self-assembled into vesicles and micelles can significantly increase the fracture resistance of cured epoxies with a minimum impact on Tg and modulus. BCP used for these purposes are composed of one block that is immiscible in the TS precursors and at least another one that is initially miscible and does not phase separate during the network formation. In this way the self-assembled structure is fixed by the cross-linking reaction. Various immiscible blocks have been employed to generate stable nanostructures in epoxies cured with different hardeners. The election of the miscible block is strongly dependent on the hardener selected to perform the cure. Examples of miscible blocks are: PEO, PMMA and PCL.
The search of a miscible block for a specific epoxy-hardener combination is not a trivial task due to the variety of mechanisms of network formation involving different types of hardeners. PMMA may be a convenient selection as a miscible block because it is soluble with epoxy in all proportions. However, for most hardeners it becomes phase separated during polymerization well before gelation. On the other hand, poly(N,N-dimethylacrylamide) (PDMA) is miscible both in non-polar solvents such as cyclohexane and in highly-polar solvents such as water, methanol and ethanol. Therefore, the family of random copolymers poly(MMA-co-DMA), with different proportions of both monomers, should be a useful choice as a "universal" miscible block for the synthesis of nanostructured epoxies. Examples of nanostructured epoxies and other TS like polyurethanes or unsaturated polyesters, and some rules to control processing and properties will be given in this presentation.
C. Sanchez
Laboratoire de Chimie de la Matière Condensée, Université Pierre et Marie Curie. 4, Place Jussieu, Tour 54, 5e. 75252, Paris, Cedex 05, France. * clems / ccr.jussieu.fr
Hybrid nano-composites materials can be obtained either through hydrolysis and condensation reactions of functional metal alkoxides or chlorides or through the assembly of well defined nanobuilding blocks. The properties that can be expected for such materials of course depend on the chemical nature of their components but also on the extend and the nature of their interface. This interface can also be tuned with or without templates to built nano-structured hybrids or even nanostructured metallic oxides. The control of the surface properties of the inorganic nano-building bricks by using nucleophilic groups carried by texturing agents triggers the obtention of a given nano-phase. Considerable effort is being currently directed to the obtention of nanostructured oxides. The use of ordered lyotropic phases as templating agents (surfactants, organogels, bio-polymers), leading to a mesoscopically ordered hybrid precursor allow the obtention of long-range nanostructured hybrid or metal oxide phases shaped as bulks or films. Some examples concerning the design of hybrid materials made by using, metal alkoxides precursors or nano-building bricks, to create mesoscopically ordered phases will be presented together with some of our results concerning materials having hierarchical structures. Hybrid Meroporous sensors, photocatalysts and catalysts, new solar and fuell cells and new mesoporous films made of nanocrystalline multimetallic metal oxides will be also described.
C.Sanchez and F. Ribot, New Journal of Chemistry, 18, (1994),1007., G. Soler-Illia, L. Rozes, M.K. Boggiano, C. Sanchez, C-O. Turrin, A-M. Caminade, J-P. Majoral, Angewandte Chemie, 39,23 (2000), 4249. C. Sanchez and B. Lebeau, MRS Bulletin, (2001), 26 (5), 377. D. Grosso, G. Soler-Illia, F. Babonneau, C. Sanchez, PA Albouy , A. Brunet, A.R. Balkenende, Adv. Mater., 2001, 13,1085..C. Sanchez, G. Soler-Illia,F. Ribot, T. Lalot, C. Mayer, V. Cabuil, Chem. Mater., October 2001, 13, 10.G. Soler-Illia, C. Sanchez, B.Lebeau, J. Patarin, Chem. Rev., Nov 2002., D. Grosso, E. Crepaldi,G. Soler-Illia, B. Charleux and C. Sanchez, Adv. Funct. mater, 2003,13,37.
E. Crepaldi,G. Soler-Illia, D. Grosso, A. Bouchara and C. Sanchez, Angew. Chemie, 2003, 42,347.
C.Sanchez, G. Soler-Illia, F. Ribot, D. Grosso Comptes-Rendus Acad Science Chimie, 2003, 8, 109.
E. Crepaldi,G. Soler-Illia, D. Grosso, F. Ribot, F. Cagnol and C. Sanchez, JACS, 2003.
C. Sanchez et al ; Nature Materials 2004, 2006, 2005, and Chem mater 2004, Advanced Functional Materials 2004., *Special Issue on Functional Hybrids : J. Mater Chemistry, 2005, vol 15, N°35-36.C. Sanchez Guest Editor, ,
* Functionnal Hybrid Materials, P. Gomez Romero and C. Sanchez, Wiley-VCH, ISBN 3-527-90484-3, 2004
U. Schubert
Institute of
Materials Chemistry, Vienna University of Technology, Getreidemarkt 9,
A-1060 Wien, Austria (uschuber /
mail.zserv.tuwien.ac.at,
http://www.imc.tuwien.ac.at)
Carboxylate-substituted metal oxide/alkoxide clusters of the general formula MxOy(OH/OR)v(OOCR)w with various compositions, structures, diameters and shapes were obtained either by reacting metal alkoxides with unsaturated carboxylic acids or by ligand exchange reactions. In each case, the metal oxide cluster core - with dimensions between 0.7 and 1.8 nm - is capped by a variable number of carboxylate ligands, which are fully accessible for polymerization reactions.
The carboxylate-substituted metal oxo clusters not only exhibit interesting coordination chemistry, they are also very versatile nanosized building blocks for the preparation of inorganic-organic hybrid polymers. Ring-opening metathesis or free radical polymerization of small proportions of the clusters with organic co-monomers (methylmethacrylate, acrylic acid, styrene, norbornene, etc.) resulted in hybrid polymers in which the clusters crosslink the polymer chains.
Cluster-reinforced organic polymers constitute a new class of inorganic-organic hybrid materials with interesting materials properties. Swelling behavior in organic solvents, thermal stability and mechanical properties of the cluster-crosslinked polymers are distinctly different to that of the parent polymers. The materials properties depend on the polymerization conditions, the cluster proportion in the polymer and - to some extent - also on the kind of cluster; they originate from a combination of nanofiller and crosslinking effects.
R.M. Laine, M. Roll, M. Asuncion, C. Brick, S. Sulaimann, R. Tamaki
Depts. of Materials Science and Engineering, Chemistry,and Macromolecular Science and Eng., University of Michigan, Ann Arbor, MI. 48109-2136, U.S.A.
talsdad / umich.edu
Octafunctional cubic silsesquioxanes [RSiO1.5]8 are unique molecules wherein the body diagonal of the single crystal silica core is 0.5 nm and each functional group attached to the vertices of these cores occupies a different octant in Cartesian space. These materials are easily accessible in high yields from simple starting materials including rice hull ash. Furthermore, an extensive variety of functional groups can be introduced. Consequently, these materials offer unique opportunities to engineer new nanobuilding blocks and polyfunctional materials. The nanobuilding blocks provide the tools for creating novel nanocomposites nanometer by nanometer in 1-, 2- or 3- dimensions. The polyfunctional materials have unique properties in their own right.
We describe here methods of making and processing highly imperfect, slightly imperfect and perfect nanostructures from Q8 [RSiMe2SiO4]8, [RPhSiO1.5]8 (ROPS) and [RPhSiO1.5]12 , (RDPS) systems and some of their properties including unusual photoluminescence behavior.
ab c
Figure 1. Cubic silsesquioxanes. a. Q8 (Q= SiO4) R= H, vinyl, epoxy, alcohol, amine, halide, isocyanate, acrylate, etc. b. ROPS, R = Br, NH2, alkyl, alkene, acetylene, acyl, azo, etc. R = same or mixed. c. typical sizes/volumes. d. DPS
For example, both the OPS
and DPS can be halogenated
to give BrxOPS
and Brx,yDPS
and IxOPS and Ix,yDPS (x = 8, y
= 12). The iodo compounds are >90% para
substituted. Using both Heck and Suzuki coupling reactions we have
learned make materials that offer unique photoluminescence behavior
that suggests some semiconducting behavior.
References
1. R.M. Laine, "Nano-building blocks based on the [OSiO1.5]8 silsesquioxanes," J. Mater. Chem., 15, 3725 - 44 (2005).
2. C.M. Brick, Y. Ouchi, Y. Chujo, R.M. Laine, "Robust Polyaromatic Octasilsesquioxanes from Polybromophenylsilsesquioxanes, BrxOPS, via Suzuki Coupling," Macromol. 38, 4661-5 (2005).
3. C. Brick, R. Tamaki, S-G. Kim, M. Asuncion, M. Roll, T. Nemoto, R.M. Laine, Spherical, Polyfunctional Molecules Using Polybromooctaphenylsilsesquioxanes as Nanoconstruction Sites," Macromol. Macromol. 38, 4655-60 (2005).
J.D. Lichtenhan1*, B. Fu1, P. Wheeler1, R. Misra2, S. E. Morgan2
1Hybrid Plastics Inc., Hattiesburg, MS USA 39401
2Department of Polymer Science, University of Southern Mississippi, Hattiesburg, MS 39406
The use of polyhedral oligomeric silsesquioxanes (POSS) for modification of surface properties of engineering thermoplastics offers low-cost alternative to fluoropolymers and silicones while maintaining the processing advantages of an engineering polymer. POSS® masterbatches in PP, PE, and PA are prepared via twin screw compounding and can be let-down via single screw extrusion. A 60% reduction in nanoscale surface friction coefficient relative to base polymer is observed in PP by incorporating of 10% POSS® into the polymer. Changes in the surface topography have been characterized by SEM and nanoprobe atomic force microscopy (AFM) and will be discussed with respect to the reduction of friction and improvement of hydrophobicity. Applications for the POSS masterbatches as low friction textiles, and in sporting goods will be presented.
M. Shibayama
Institute for Solid State Physics, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
The structure of poly(N-isopropylacrylamide) (PNIPA)-clay nanocomposite gels (NC gel) was investigated in terms of small-angle neutron scattering (SANS). The NC gels were prepared by radical polymerization of PNIPA in the presence of clay platelets. The gelation dynamics was also investigated by time-resolved dynamic light scattering. It allowed us to determine the percolation threshold and to monitor the critical dynamics. Contrast-matching as well as contrast-variation methods were employed to elucidate the local structure of NC gels. It was found that PNIPA chains are condensed near clay platelets with a thickness of a few nm. SANS of deformed NC gels revealed that NC gels consist of long PNIPA chains tied by clay platelets. This unique structure is responsible for large deformability and high toughness of NC gels.
Department of Materials Science & Engineering, University of Arizona, Tucson, Arizona 85721-0012
Polysilsesquioxanes are widely used as coupling agents and surface modifiers due to their hybrid organic-inorganic nature. There have been a number of groups focusing on developing electrolyte membranes based on polysilsesquioxanes for fuel cell applications. In this presentation, I will provide a brief review of these efforts and describe our own efforts to prepare highly functionalized materials using tetrasulfide bridged polysilsesquioxanes for fuel cell membranes and for metal ion adsorbents. Each tetrasulfide linkage serves as a template for either two sulfonic acid groups or two thiol groups. These groups are automatically positioned adjacent to one another for proton conduction or metal chelation. For fuel cell membranes we focused on non-porous membranes in which the tetrasulfide groups were oxidized to sulfonic acid groups. Ion conductivity experiments revealed that the resulting membranes did conduct protons (0.002 S/cm), but that the membranes were more brittle than desirable. In the metal adsorbent studies, it was important to retain as much porosity as possible in the materials. Our best efforts here utilized surfactant templating to maintain mesoporosity. The result was high surface area materials with high platinum ion capacity. However, we were surprised to find that the tetrasulfide bridged precursor was almost as good as the reductively cleaved system at scavenging chalcophilic metals.
Institute of Materials Science and Technology, University of Mar del Plata and National Research Council, J. B. Justo 4302, 7600 Mar del Plata, Argentina (williams / fi.mdp.edu.ar)
Monofunctional polyhedral oligomeric silsesquioxanes (POSS) have been used to modify different types of polymer networks. In most cases, a polymerization-induced phase separation takes place leading to a dispersion of a POSS-rich phase in the polymer network. We will show that the nature of the organic inert group and the pre-reaction of the functional group can be used to control morphologies generated in POSS-modified epoxies. An example where large amounts of a monofunctional POSS can be introduced to an acrylic formulation without any evidence of phase separation will be discussed. Mechanical and thermal properties of the resulting hybrid materials will be analyzed.
Narrow distributions of POSS can be synthesized in one step starting from organotrialkoxysilanes bearing hydroxyl groups in beta position with respect to tertiary amines. When this precursor is co-condensed with tetraethoxysilane (TEOS), soluble functionalized-silica can be obtained. This product can be covalently bonded to the surface of silica and the resulting modified-silica used as a support of a metallocene catalyst. The activity of the supported catalyst for ethylene polymerization was similar than the activity found in the homogeneous reaction.
Bridged silsesquioxanes can be synthesized by the hydrolysis and condensation of monomers containing an organic bridging group joining two trialkoxysilyl groups. When the organic bridge contains urea groups, the material exhibits photoluminescence arising from processes taking place both in inorganic and organic domains. We will show that the photoluminescence spectra can be varied by controlling the relative rates between the self-assembly of organic bridges and the inorganic polycondensation. Specific dies can be covalently bonded to the structure during the synthesis producing a significant variation of the emission spectra.
When bulky pendant groups are present in the organic bridge, a nanostructuration at different levels takes place due to the need to accommodate the bulky group in the structure. We will discuss examples of the nanostructures obtained when the pendant group is a dodecyl chain or a cyclohexyl ring.
M. Matsuo, Y. Xi, Q. Chen, Y. Bin
Faculty of Human Life and Environment, Nara Women's University,
Nara, 630-8506 Japan (m-matsuo / cc.nara-wu.ac.jp)
Conductive polymer composites were obtained by adding conductive fillers like carbon black (CB), carbon fibers (CFs) or multi-wall carbon nanotubes (MWNTs) to polymer matrix. The composites by admixing common conductive fillers were characterized by a percolation threshold or a critical value at which the electrical conductivity starts to increase as a function of filler contents. For ultra-high molecular weight polyethylene (UHMWPE), its high melting viscosity, limited the use of the melt processing method. The gelation/crystallization from solution was proven to be more effective than the other methods to disperse carbon fillers in the UHMWPE matrix. This talk deals with two contents.
1) UHMWPE and MWNT composites were prepared using either decalin or paraffin as solvents. Electrical conductivity measurements were performed for the original and heat-treated composites. The drastic increase in conductivity occurred at low MWNT content for the composite prepared in paraffin, while the conductivity of the composite prepared in decalin increased slightly up to 10wt% MWNT content. Scanning electron microscopy observations revealed that the MWNTs within the composite prepared in decalin were covered by UHMWPE, and their average diameters were much greater than those of the original MWNTs, while the average diameter of the MWNTs within the composite prepared in paraffin was similar to the diameter of the original MWNTs. Such different morphologies were found to be due to the different crystallizations.
2) Some of UHMWPE-carbon filler composites showed a sharp increase in electrical resistivity at elevated temperature close to the polymer melting point, which is known as positive temperature coefficient (PTC) effect. A simple resistor-capacitor circuit model was proposed to explore the alternating current (AC) conductivity and dielectric permittivity behavior of UHMWPE-CF composites. The composites were considered as a system composed of random arrays of closely spaced conductors dispersed in an insulating UHMWPE matrix and broad frequency measurements were carried out to probe the conducting paths and the space gaps to show the experimental evidence for explaining PTC.