TAILORING mESOPOROUS pOLYMERIC mATERIALS FROM sEMI-IPNs AS nANOSTRUCTURED pRECURSORS

D. Grande

Equipe « Systèmes Polymères Complexes », Institut de Chimie et des Matériaux Paris-Est, UMR 7182 CNRS - Université Paris XII, 2 rue Henri Dunant, 94320 Thiais, France (grande / glvt-cnrs.fr)

The utilization of (semi-) Interpenetrating Polymer Networks (IPNs) as nanostructured precursors to porous cross-linked materials has been put forward only by a handful number of research teams. IPNs constitute an intimate combination of two independently cross-linked polymers, at least one of which is synthesized in the immediate presence of the other. Such complex polymer structures are of particular interest when they arise from the association of two components that exhibit a contrasted degradability under specific conditions: indeed, (nano)porous networks can be designed from such IPNs by resorting to selective degradation methods. In this regard, IPNs based on a hydrolyzable polyester, such as poly(D,L-lactide) (PLA) or poly(e-caprolactone) (PCL), and a polymer containing a non-hydrolyzable skeleton, such as poly(methyl methacrylate) (PMMA), can be considered as appropriate precursors.

This contribution discusses the scope and limitations of two complementary routes to mesoporous networks from polyester/PMMA-based semi-IPN and IPN systems. In a first stage, the latter precursory networks have been synthesized by in situ methods by varying different structural parameters, including the cross-linker nature and cross-link density associated with the PMMA sub-network, as well as the nature and molar mass of the oligoester precursor. The kinetics of the cross-linking processes involved in network formation has been monitored by real-time infrared spectroscopy. The microphase separation exhibited by the nanostructured precursors and the average diameters of polyester microdomains have been investigated by Dynamic Mechanical Analysis (DMA) and turbidimetry, respectively. In a second stage, two straightforward and effective approaches that afford (meso)porous methacrylic networks with tunable pore sizes have been envisioned. The first approach applies the extraction of un-cross-linked oligoesters from semi-IPNs, while the second strategy implies the quantitative hydrolysis of the polyester sub-network from IPNs. In this lecture, we will particularly focus our attention on the investigation of the correlations between the multi-scale structure of the precursory networks and the morphology of the resulting porous materials as examined by different techniques, such as Scanning Electron Microscopy (SEM) and thermoporometry using Differential Scanning Calorimetry (DSC).

Acknowledgments. The financial support of the National Agency for Research (programme ANR/PNANO 2005, project POLYNANOCAT "ANR-05-NANO-025") is gratefully acknowledged.

MICROPOROUS, THERMOSENSITIVE ORGANIC-INORGANIC HYBRID HYDROGEL PREPARED BY FREEZING

N. Kato

Department of Applied Chemistry, Faculty of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 JAPAN (katon / cc.utsunomiya-u.ac.jp)

A simple and effective method of microporous gel preparation was developed. By freezing and subsequent re-hydration, a different variety of microporous gels could be conveniently prepared. This technique was suited to widely control the responsive shrinking rates of gels and solute release rates from gels. The microporous properties of organic-inorganic (O-I) hybrid gel could be also altered by freezing.

Basically, formation of microporous structure during the freezing process was determined by nucleation of ice crystals and their growth rates. As the useful way to control the macropore size and stimuli-responsive rates of gels, the honeycomb-like structure could be controlled by adjusting the water content of gels prior to freezing. It appeared that water content was the key factor to control the microporosity and the rates of expelling pore water or solutes. Since the response time of environmentally responsive gels could be drastically reduced by decreasing the characteristic diffusion path length, it is possible to enhance the response rate not simply by reducing the gel size but also by reducing the strut thickness of the pore walls. This freezing method could be applied to control the microporosity of gels of which ingredients were polyacrylamide derivatives, polysaccharides, nucleic acids, or polypeptides.

As the poly(N-isopropylacrylamide), polyNIPA, based O-I networks with polysiloxane structures covalently attached to the polyNIPA, gels were crosslinked by inorganic silsesquioxane-like domains formed by sol-gel process of [3- (methacryloyloxy) propyl]trimethoxysilane (MPTMOS). After gelation, pore water froze in the gel, causing the polymer chains to gather and then condense. The heterogeneous networks could be fixed apparently with hydrophobic interaction between polymer chains even for the O-I networks. The effective diffusion coeficients of thermally responsive shrinking for poly(NIPA/MPTMOS) gel (10^-3cm²/s) increased two orders of magnitude over those gels before freezing (10^-5cm²/s). Furthermore, the cumulative distribution of polyethylene glycols (PEGs) accessible water in gels was determined using the PEGs of 1-38 nm hydrodynamic radii. It is also noticed that the mean pore size of microporous gel was found to decrease after freezing of the gel. Moreover, micron-sized pores were also formed during the freezing process. Polymer concentration at the macropore strut probably increases in a way that leads to decrease the mean radius of nano-sized pores.

ACHIEVING HIGHLY ORDERED NANOSCALE FEATURES AT SURFACES USING SELF-ASSEMBLY OF BLOCK COPOLYMERS

M.A. Morris

Department of Chemistry, University College Cork and Centre for Adaptive Nanostructures and Nanodevices, Trinity College Dublin, Ireland

The self assembly of molecular building blocks (or nanoparticles) is thought to be the only practical and cost-effective means of generating sub-10 nm features at substrates. However, long range periodicity is difficult to achieve with areas of high defect density and ‘mis-alignment’. This is an important problem in generating substrates of precise nanometer dimensioned structures for surface design and in particular as ideal structures to study large molecule interactions.

In Cork, we have developed methods to generate nanoporous and self assembled copolymer systems for application as engineered substrates. Precise geometry and alignment of the nanostructure in a single direction is achieved using engineered substrates. These substrates consist of photo-lithographically topographically defined surfaces consisting of precise channels and grooves in silicon or silica materials. The grooves can be engineered to widths around 100 nm and depths from 30 to 1 um. Typical substrates are shown in figure 1.

The inorganic systems have a rigid backbone and we demonstrate how these can be used to generate a series of ordered nanowire and nanotube arrays at the surface. The polymer systems we have investigated include, polystyrene-polymethylmethacrylate, polystyrene-polyisoprene and polystyrene-polyethylene oxide and these allow the feature size to be changed from 10 to 30 nm. We demonstrate how complex structural motifs equivalent to electronic circuitry might be achieved using suitable polymers and surface engineering. We present the argument that these copolymer systems are the only materials that meet the demands of the electronics industry. We also present some results which demonstrate how the systems can be chemically functionalized to allow materials to be placed on the substrate surface mimicking the exact alignment within the polymer. These methods allow the fabrication of substrates of engineered structure and chemical activity.

POSS grafting on PPgMA by one-step reactive blending

A. Fina, D. Tabuani, G. Camino

Centro di Cultura per l'Ingegneria delle Materie Plastiche - Politecnico di Torino, V.le T. Michel, 5 - 15100 Alessandria

(alberto.fina / polial.polito.it, http://www.cdcmp.it)

The preparation of PPgMA/POSS hybrids by direct POSS grafting during a one-step reactive blending process was successfully explored, taking advantage of the amino-anhydride reaction in the molten state.

The morphology of the obtained hybrid material was studied in details by means of electron microscopy (SEM, TEM) as well as by X-ray diffraction, showing POSS dispersion at the nanoscale, whereas the corresponding non-reactive PPgMA/POSS system presented residual micron-sized aggregates when processed in the same conditions.

The grafting yield, assessed through extraction of non-grafted POSS and FTIR, showed a high efficiency of the reactive blending process.

Thermal, rheological and mechanical properties were studied for POSS-grafted PPgMA and showed advantages in terms of higher thermal stability and improved mechanical properties with respect to the non-reactive PPgMA/POSS system. POSS grafting on PPgMA chains was shown to radically affect the molecular mobility, resulting in a higher melt viscosity and, more interestingly, in a significant stiffness and strength increase.

The effect of grafted POSS on molecular mobility was explained by POSS/POSS interactions, which may lead to the formation of nanoclusters that behave as physical crosslinking points for the flow of PPgMA chains under deformation.

Thanks to POSS versatility, it is proposed that grafting POSS moieties on the polymer backbone by reactive blending can be applied in a number of different systems, representing a very appealing, economic and efficient way to improve polymer properties or to obtain new functionalities.

AMPHIPHILIC GRADIENT COPOLYMERS SHAPE COMPOSITION INFLUENCE ON THE SURFACE/BULK PROPERTIES

K. Karaky, L. Billon

Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux Equipe de Physico-Chimie des Polymères,

IPREM / EPCP CNRS UMR 5254

Hélioparc Pau-Pyrénées, 2 Avenue Angot, 64053 Pau Cedex 09, France

Figure 1. Relationship between the water uptake kinetic and the structured gradient copolymer film.

The rheological properties of gradient copolymers in bulk are also studied and discussed in relation with their local structure. Moreover, thanks to the combination of DMA (hydrophilic monomer) /BuA (monomer having a low T_g) and to the formation of phase segregation observed by AFM, these systems can be used for adhesion in wet media.

1 - K. Karaky et al., Macromolecules, 40, 458, 2007.

2 - K. Karaky et al., Soft Matter, 2, 770, 2006.

3 - K. Karaky et al., New Journal of Chemistry, 30, 698 , 2006.

SYNTHESIS, MOLECULAR AND MORPHOLOGICAL CHARACTERIZATION OF SECOND-GENERATION DENDRITIC HOMOPOLYMERS AND COPOLYMERS OF BUTADIENE AND ISOPRENE WITH DIFFERENT MICROSTRUCTURES

A. Avgeropoulos^*,a,b, S. Rangou^a, V. Krikorian^b, E.L. Thomas^a

^aDepartment of Materials Science & Engineering, University of Ioannina, University Campus, 45110 Ioannina, Greece

^bDepartment of Materials Science & Engineering, and Institute of Soldier Nanotechnologies Massachusetts Institute of Technology, 77 Mass. Ave., 02139 Cambridge, MA, USA

We report the synthesis of 2^nd generation dendritic homopolymers and copolymers (Scheme 1A and 1B) consisting of polybutadiene (PB) of 1,4 microstructure or/and polyisoprene (PI) enriched in 3,4 microstructure (at least 55% PI_3,4). The main aspect was the synthesis of polymers exhibiting high molecular and compositional homogeneity. The preparation of these materials was achieved via anionic polymerization techniques in combination with chlorosilane chemistry potentials. The molecular characterization of the final dendritic materials was accomplished via Size Exclusion Chromatography (SEC), Membrane and Vapor Pressure Osmometries (MO and VPO respectively), Dilute Solution Viscometry and ¹H-Nuclear Magnetic Resonance (NMR) Spectroscopy, leading to the conclusion that they can be considered model polymers. Morphological studies have been conducted to the copolymer samples exhibiting microphase separation between the polydiene segments leading to hexagonally close packed cylinders of the minority phase in the matrix of the majority (Scheme 1C).

Scheme 1. A) Schematic of a 2^nd generation dendritic homopolymer, B) of a 2^nd generation dendritic copolymer and C) hcp cylinders of PI in the PB matrix for a sample of the [(PB)₂PI]₃ type.

Structure, thermal and dielectric properties of LC thiol with azobenzene mesogenic group and comB-like polybutadiene-diols modified with thE thiol

M. Ilavský^a,b, A. Jigounov^a, J. Nedbal^a, P. Pissis^c, J. Baldrian^b, Z. Sedláková^b

^aFaculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 1800 Praha 8, Czech Republic (ilavsky / kmf.troja.mff.cuni.cz)

^bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2,162 06 Praha 6, Czech Republic

^cNationalTechnical University of Athens, 157 80 Athens, Greece

Liquid-crystalline-5-(4-{[4-(octyloxy)phenyl]azo]}phenoxy)pentane-1-thiol (TH1) with azobenzene mesogenic group exhibiting trans/cis isomerization was synthesized and polybutadiene diols (LCPBDs) with the comb-like architecture were prepared by radical reaction of TH1 with double bonds of telechelic HO-terminated polybutadiene (PBD); DSC, polarizing microscopy, WAXS and dielectric behavior of TH1 and LCPBDs has been investigated in a broad temperature and frequency regions. Dielectric spectroscopy of the LCPBDs has revealed both, collective and individual dynamic motions of molecules. Two relaxations, secondary β and segmental α relaxation, were observed in neat PBD. In the LCPBDs two secondary γ and β and two high temperature α and δ relaxations were observed (the last two not in all the compositions) and assigned to specific molecular motions. All relaxations were analyzed and discussed in terms of time scale (Arrhenius diagram), magnitude (relaxation strength) and shape of the response. Characteristic changes of the overall dielectric behavior and of individual relaxations, as well as of conductivity, studied within the ac conductivity and the modulus formalisms, were observed at the phase transition temperatures.

Acknowledgements. Financial support of the Grant Agency the Academy of Sciences of the Czech Republic (grant No. IAA4112401) and of the Ministry of Education, Youth and Sports of the Czech Republic (grant MSM 0021620835) is gratefully acknowledged.

STRUCTURAL CHANGES IN CELLULOSE NANOCOMPOSITES CHARACTERIZED BY IN-SITU X-RAY DIFFRACTION COUPLED WITH CYCLIC TENSILE TESTS

J. Keckes^a, P. Boescke^b, W. Gindl^c

^aDepartment of Materials Physics, University of Leoben, Jahnstrasse 12, A-8700 Leoben, Austria (keckes / unileoben.ac.at, http://www.oeaw.ac.at/esi/)

^bEuropean Synchrotron Radiation Facility, Grenoble, France

^cDepartment of Materials Science and Process Engineering, University of Natural Resources and Applied Life Sciences, Vienna, Austria

Cellulosics represent biodegradable fibrous nanocomposites. In order to understand the structure-property relationship in cellulosics, in-situ synchrotron diffraction studies were combined with tensile tests at the ID01 beamline of the European synchrotron radiation facility (ESRF) in Grenoble, France. By relating the mechanical data with the structural information, it was possible to analyse the deformation processes in the tissues. Upon straining, the tissues exhibited elastic and plastic behaviour depending on the original orientation of the crystallites. The deformation beyond the yield point did not reduce the stiffness of the materials, since the initial modulus was recovered by every increase and decrease of the strain. As determined from the diffraction data, the magnitude of the orientation factors of crystalline cellulose is only the function of the original texture and the applied strain. The results indicate a presence of a dominant recovery mechanism occurring between the interfaces of nanocrystals. The interfaces play a role of slip planes filled by sacrificial bonds. Whenever the straining is interrupted or the strain is reduced, the bonds are recovered and the cellulosics show the original stiffness.

A NOVEL POTENTIAL ECOMATERIALBASED ON POLY(1,4-DIOXANE)-MONTMORILLONITE NANOCOMPOSITE

Y.-Z. Wang^a,b, K.-K. Yang ^b, F.-Y. Huang ^b, Fang-Lu ^b, X.-L. Wang^b

^a Ningbo Institute of Materials Technology and Engineering, The Chinese Academy of Sciences, Ningbo 31520, China (polymers / 126.com, http://chem.scu.edu.cn/polymer/yzwang/)

^b Center for Degradable and Flame-Retardant Polymeric Materials, College of Chemistry, Sichuan Unversity, Chengdu 610064, China

Poly (p-dioxanone) is a useful biomaterial and potential ecomaterial due to its biodegradability and good mechanical properties. Like other aliphatic polyesters, however, it has low crystallization rate and low melt strength, which lead to a difficulty to form thin films by blowing processing. Those problems have been solved successfully by preparing poly(p-dioxanone)/montmorillonite nanocomposites by in situ ring-opening polymerization of p-dioxanone and montmorillonites in this study. The novel biodegradable nanocomposites have a remarkably increased crystallization rate and melt strength, and can be blown to thin films, which have excellent mechanical properties such as a tensile strength of 59.2MPa and elongation at break of 605%. Therefore, this novel nanocomposite can be used to prepare some useful ecomaterials which have a good comprehensive property.

Acknowledgment

This work was supported financially by the National Science Foundation of China (20504022) and the National Science Fund for Distinguished Young Scholars (50525309).

NM-SCALE STRUCTURAL ORIGINS OF MECHANICAL PROPERTIES OF POLYURETHANES

C. Prisacariu^aC.P. Buckley^b,

^aInstitute of Macromolecular Chemistry "Petru Poni", Aleea Grigore Ghica Voda, nr. 41 A, 700487, Iasi, Romania (crispris / icmpp.ro).

^bDepartment of Engineering Science, University of Oxford, Parks Road, OX1 3 PJ,Oxford, UK.

A study has been made of numerous block copolyurethanes (PUs), based on several diisocyanates, macrodiols and chain extenders, with the aim of improving understanding of the relationship between molecular/supramolecular architecture at the nm-scale and macroscopic mechanical properties in such systems. A novel diisocyanate (4,4'-dibenzyl diiscyanate (DBDI)) and a triol chain extender (1,1,1-trimethylol propane (TMP)) were included as well as more widely-used components, in order to widen the range of structures achievable beyond those normally available. A systematic investigation was made of the effects of varying the chemistry of hard and soft segment and chain extender, and the preparation procedures employed, on mechanical response of the PUs. In polymers with diol chain extenders there were tendencies to phase separation, with a characteristic length of ca 20nm, and, when DBDI was employed with certain chain extenders, to crystallization of the hard phase. In polymers prepared with the triol TMP as chain extender a crosslinked system was obtained, preventing phase separation.

The role of the hard segment structure was investigated. When using DBDI, the specific - Ph-CH₂-CH₂-Ph- moiety introduces a variable geometry into the hard segments due to the possibility of internal rotation of this isocyanate around the -CH₂-CH₂- ethylene bridge. This leads to the appearance of both "syn" and "anti" rotational conformations, which coexist in the DBDI based PU macromolecules. As a result, in this latter case the PU macromolecules can adopt a more compact packing which enhances significantly the ability to order in crystalline structures involving predominantly the "anti" form. Thus, new polymers were achieved, with a controlled ordering of copolymer hard segment blocks on the macromolecular chain. Wide angle X-ray diffraction and differential scanning calorimetry (DSC) of the as-moulded polymers revealed the presence of crystallinity in the DBDI-based PU materials. Mechanical tests included load-unload cycles at constant rate of extension, with measurement of hysteresis and strain recovery, and stress relaxation tests. The presence of the flexible DBDI hard segments instead of other conventional rigid isocyanates led systematically to increases in: the input strain energy to a given elongation, hysteresis and residual strain under cyclic loading, and stress relaxation. In large deformation cyclic experiments at room temperature, the degree of hysteresis and stress relaxation were found to be greatly enhanced by hard-phase crystallinity, through its effect of increasing the flow stress. The results from this study provide substantial new insight into the role played by nm-scale structures in determining the mechanical properties of PUs.

NETWORK FORMATION IN PP/LAYERED SILICATE NANOCOMPOSITES: MODELING AND ANALYSIS OF RHEOLOGICAL PROPERTIES

J. Kovács^1,2, Z. Dominkovics^1,2, G. Vörös^2,3, B. Pukánszky^1,2

¹Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, H-1521 Budapest, P.O.Box 91, Hungary

²Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17, Hungary

³Eötvös University Budapest, Department of General Physics, H-1518 Budapest, P.O. Box 32, Hungary

Recently, many attempts are in progress to modify PP with layered silicates to prepare nanocomposites. However, such nanocomposites cannot be produced from an organophilized silicate, mainly montmorillonite (OMMT) and the polymer, the exfoliation of the clay does not take place spontaneously during processing, a functionalized polymer, usually maleinated PP (MAPP) must be added to the composite. The introduction of MAPP leads to intercalated and/or partially exfoliated structures with improved properties. Modulus, strength and some other characteristics often have a maximum as a function of silicate content, which indicates changes in the structure with composition. Layered silicates easily exfoliate in water to individual silicate layers. At large clay content the layers interact with each other in the slurry. Face to face interactions lead to aggregation, while edge to face interactions result in the formation of a network, often referred to as house-of-cards or skeleton structure. Both interactions are claimed to occur also in PP/layered silicate composites. Aggregation obviously deteriorates properties. Relatively little is known about the formation of the network structure and its effect. The exact conditions for network formation are not known either, they must depend on the properties of the components, composition, processing conditions, which all influence the extent of exfoliation and the number of particles dispersed in the matrix. Usually the network is detected either by transmission electron microscopy (TEM) or rheology, or both. The TEM micrographs presented in papers on house-of-cards structures are not very convincing and do not differ much from other pictures taken from PP/layered silicate nanocomposites not having such a morphology.

The formation of the network considerably modifies the rheological properties of nanocomposite melts; usually a yield stress appears at low shear rates. This can be detected on the frequency or shear rate dependence of complex viscosity (h*) or storage modulus (G') as an upward turn in the low shear region. The method is less subjective than TEM, but the changes in the shape of viscoelastic functions might render detection difficult. We used various approaches to analyze the rheological properties of PP/layered silicate nanocomposites. Cole-Cole plots proved to be useful, since they detect the network very sensitively. The frequency dependence of the real part of complex viscosity was described with a series of Maxwel bodies coupled parallel to each other. The relaxation time of the melt changes in the range of 0.0005 and 200 sec. Under certain conditions long relaxation times appear in the spectrum, which indicate the formation of new structural units, probably the silicate network. A certain number of silicate layers are needed to create a house-of-cards structure. A threshold concentration of MAPP exists in the investigated system, which depends on silicate content.

INFLUENCE OF ORGANIC PEROXIDES ON MORPHOLOGY AND PROPERTIES OF EVA-ORGANOCLAY NANOCOMPOSITES

S.B. Mishra, A.K. Mishra, A.S. Luyt*

Department of Chemistry, University of the Free State (Qwaqwa Campus), Private Bag X13, Phuthaditjhaba, 9880, SOUTH AFRICA

Nanocomposites were prepared using an ethylene vinyl acetate copolymer (EVA) and organically modified clay (Cloisite^® 93 A) in the absence and presence of dicumyl peroxide (DCP) and dibenzyl peroxide (DBP) as cross-linking agents. The results clearly show differences in the EVA-clay morphology of nanocomposites prepared in the absence of organic peroxides, and of those prepared in the presence of respectively DCP and DBP. It seems as if DCP may initiate grafting between the polymer and the clay, which results in a complete exfoliated morphology. The presence of clay, however, seems to inhibit the initiation of crosslinking by the DBP free radicals. This leads to hydroxylated edge-edge interaction between the clay layers, which gives rise to a flocculated morphology and reduced polymer-clay interaction. There is a good correlation between these morphologies and the thermal stabilities of the nanocomposites, as studied through TGA, the total crystallinity, as seen from the DSC melting and crystallization enthalpies, and the tensile properties.

* E-mail: luytas / qwa.uovs.ac.za

Melt processing-Property Relationships in multiwalled carbon nanotube-polymer composites

P. Pötschke^a, S. Pegel^a, T. Villmow^a, I. Alig^b, S. Dudkin^b, D. Lellinger^b

^a Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden, Germany (poe / ipfdd.de)

^bDeutsches Kunststoff-Institut Darmstadt, Schlossgartenstraße 6, 64289 Darmstadt, Germany

In context with industrial application of carbon nanotube-polymer composites melt processing is the preferred preparation and shaping method. Melt processing conditions play an important role on the formation of the nanotube network required for electrical conductivity or antistatic discharge behaviour.

In many basic investigations, compounded nanocomposite materials are compression molded to sheets, films, or plates in order to get information about conductivity or mechanical properties. It could be shown for PC-MWNT composites that pressing conditions play an important role on conductivity of the samples. This is related mainly to differences in the nanotube network arrangement which changes with pressing temperature, velocity, time, cooling conditions, and sample shape (thickness). In partially crystalline polymers, i.e. polyamides, in addition the crystallization structures in the presence of the nanotubes and the crystallization conditions may influence the composite conductivity.

Similar effects can be observed in injection molding. The electrical conductivity of samples strongly depends on the processing conditions, but also varies on different locations within the sample. This again is related to differences in the network arrangement of the nanotubes (aggregation, alignment, orientation) within the sample; in addition a depletion of nanotubes at surfaces may not be excluded. Systematic variation in selected injection molding conditions in polycarbonate composites containing 2 and 5 wt% MWNT indicated differences up to 5 decades in electrical surface conductivity of injection molded plates with a fixed sample geometry. The main influencing parameters could be extracted and will be presented.

ALTERNATIVE SYNTHETIC ROUTES TO EPOXY POLYMER-CLAY NANOCOMPOSITES VIA MINIMIZATION OF THE ORGANIC MODIFIER CONTENT IN ORGANOCLAYS

K.S. Triantafyllidis^a,*, P.I. Xidas^a, T.J. Pinnavaia^b

^aDepartment of Chemistry, Aristotle University of Thessaloniki and CPERI/CERTH, 54124 Thessaloniki, Greece (ktrianta / chem.auth.gr, http://www.chem.auth.gr)

^bDepartment of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA (pinnavai / cem.msu.edu, http://www.chemistry.msu.edu/)

Polymer - layered silicate nanocomposites (PLSN) usually exhibit improved physical and performance properties in comparison to pristine polymers and conventional composites, due mainly to their unique phase morphology and the interfacial properties provided by the highly dispersed silicate nanolayers in the polymer matrix. Loadings of only ~5 wt. % exfoliated silicate nanoparticles in PLSN materials result in significant enhancement in mechanical and barrier properties, thermal stability, resistance to solvent swelling and flammability and ablation performance. However, the reinforcement of the polymer matrix is compromised by the presence of the organic modifiers of clays due to the introduction of dangling chains that reduces the degree of polymer crosslinking and weakens interfacial adhesion. In addition, utilization of large quantities of modifiers, which are usually quaternary ammonium ion surfactants, induces economical and environmental issues in the manufacture and the after-use disposal of nanocomposites.

Our approach is based on the utilization of homostructured mixed organic / inorganic cation exchanged smectite clays (e.g., montmorillonite, fluorohectorite) in which both the organic onium ions and the inorganic exchange ions co-occupy the gallery surfaces of the clay, thereby dramatically reducing the amount of organic modifier needed to access the galleries for nanocomposite formation. By the use of long-chain, aliphatic polyoxypropylene diamines (Jeffamines), which can also function as epoxy polymer curing agents, reduction of modifier down to ~35% onium ion exchange can be achieved still leading to highly intercalated / exfoliated nanocomposite structures with enhanced thermomechanical properties. Further improvement has been attempted by the use of triamines in order to benefit both from their large volume/size for efficient clay platelets separation with minimum amount of modifier and from the functionality of the free amino-groups of the triamine which have not been bound to the clay surface. Structure characterization data on the degree of clay layer exfoliation (XRD, TEM), mechanical properties (stress-strain tests, DMA) and thermal stability (TGA) will be reported for the new epoxy nanocomposites in comparison to those of the pristine polymer.

PMMA-EPOXY-CLAY TERNARY BLENDS: SYNTHESIS AND PROPERTIES

M. Hernandez^a, B. Sixou^b, J. Dupuy^a, J. Duchet^a, H. Sautereau^a.

^a Laboratoire des Matériaux Macromoléculaires, UMR IMP CNRS #5223, Institut National des Sciences Appliquées-Bât. Jules Verne 17, Av. Jean Capelle, 69621Villeurbanne Cedex, France

^b MATEIS/INSA, Institut National des Sciences Appliquées-Bât. B. Pascal 7, Av. Jean Capelle, 69621 Villeurbanne Cedex, France

marcelo.hernandez / insa-lyon.fr

The present research reports the preparation, results and analysis of PMMA-epoxy-clay ternary composite. Studies related to ternary blends containing layered silicates at the present time are limited^1,2,3. The importance of this study is to get information concerning the influence of poly (methyl methacrylate) (PMMA), montmorillonite layered silicates (Cloisite30B) and dispersion mechanism on morphology, curing kinetic and mechanical properties of a three phase epoxy nanocomposite. Two processing techniques have been used and compared: one employing melt intercalation and the other using ultrasonic processing. In order to understand the exfoliation mechanisms in ternary blend the dispersion of plates during the curing reaction was followed, as well as the influence of the preparation method on the final morphologies obtained was investigated. Ternary composites were characterized by Wide-angle-X-ray (WAXS), Transmission Electron microscopy (TEM) and Small angle X-ray scattering (SAXS) where these last studies were developed on the cured composites and also during the curing reaction. Organoclay particles were finely dispersed into thermosetting network and predominantly delaminated in ultrasonic-blending, whereas organoclays formed micrometer-sized aggregates in melt-blending. For reacted systems an exfoliation of platelets can occur through the de-aggregation of large agglomerates into smaller particles composed of a few platelets. For in-situ SAXS studies the distribution of the thicknesses of diffusing entities and the evolutions of this distribution with reaction time were followed. The kinetic model showed that the presence of clays does change the reaction rate, but it not changes the conversion at the cloud point, In addition the clay does not have any effect on the reaction induced phase separation phenomenon. The glass transition temperature of the system obtained by ultrasonic dispersion is lower than the sample gotten by met dispersion. Mechanical properties (DMA and fracture) are presented, and discussed with the presence and nature of PMMA and the influence of the different dispersion tools used.

(1) Park, J.H., Jana, S.C. Polymer 2003, 44, 2091

(2) Frolich J, Thomann R, Mulhaupt R. Macromolecules ,2003, 36, 7205-7211

(3) Ratna D., Becker O., Krishnamuthy R., Simon G.P., Varley R.J. Polymer,2003, 44, 7449-7457.

NANOSTRUCTURED POLYMERIC MOLECULAR SIEVES

A.R. Albunia¹, Ch. Daniel¹, C. D'Aniello,¹ P. Rizzo¹, V. Venditto¹, G. Mensitieri², P. Musto³, G. Guerra¹

¹Dipartimento di Chimica, Università di Salerno, via Ponte don Melillo, 84084 Fisciano (Salerno), Italy. E-mail:guerra / unisa.it ² Dipartimento di Ingegneria dei Materiali e della Produzione, Università di Napoli "Federico II". ³ Institute of Chemistry and Technology of Polymers, CNR

The improvement of gas storage, recognition and separation techniques represents a strategic industrial and environmental objective. Some techniques are based on gas absorption on high surface amorphous materials, like e.g. activated carbons, cross­linked polymers or carbon nanotubes. More selective techniques are based on self-assembling of gas-molecules into cavities of crystalline materials leading to molecular complex crystalline phases (generally clathrate phases). The available nanoporous crystalline frameworks can present a large variety of chemical structures. Mostly studied are inorganic frameworks (e.g., zeolites) and, more recently, metal-organic frameworks and organic frameworks.

In this paper we show that the d crystal­line phase of syndiotactic polystyrene (s-PS), presenting a permanent open architecture, ^1,2 can be considered as a first case of polymeric framework. In fact, already at room tem­perature, this polymer crystal phase is able to self-assemble suitable gas-molecules leading to molecular complex crystalline phases.

It is well known that s-PS is a polymer which forms molecular complex crystalline phases (both clathrate and intercalate) with several, mostly aromatic and/or halogenated, guest molecules. By suitable solvent extraction procedures, the guest molecules can be easily removed leading to the nanoporous d form (monoclinic, space group P2₁/a; a = 1.74 nm; b = 1.18 nm; c = 0.77 nm; g =117°; density = 0.98 g/cm³)¹ with a permanent cavity (of 120-160 ų) per 4 monomer units (Figure 1).² This low density crystalline framework rapidly absorbs volatile organic molecules, also if present in traces in air or water, eventually leading to host-guest molecular complex phases and hence is promising for applications in chemical separ­ations,³ molecular senso­rics,^4,5 as well as for advamced optical mate­rials.^6-8

It will be also shown that aerogels including this nanoporous crystalline phase are also particularly suitable for water and air purification from volatile organic compounds.³

Figure 1 - Insert here the Figure and its title bellow in Times New Roman 8)Along c view of two adjacent unit cells of the host d form of s-PS. Suitable crystallization procedures can lead (002), (010) or (`210) crystal planes nearly parallel the film surface. Guest release kinetics can be controlled by these uniplanar crystalline phase orientations.

References

1. De Rosa, C., Guerra, G., Petraccone, V., Pirozzi, B. Macromolecules 1997, 30, 4147.

2. Milano, G., Venditto, V., Guerra, G., Cavallo, L., Ciambelli, P., Sannino, D. Chem. Mater. 2001, 13, 1506.

3. Daniel, C., Alfano, D., Venditto, V., Cardea, S., Reverchon, E., Larobina, D., Mensitieri, G., Guerra, G. Adv. Mater. 2005, 17, 1515.

4. Mensitieri, G., Venditto, V., Guerra, G. Sensors and Actuators B 2003, 92, 255.

5. Giordano, M., Russo, M., Cusano, A., Mensitieri, G., Guerra G. Sensors and Actuators, B 2005, 109, 177.

6. Venditto, V.; Milano, G.; De Girolamo Del Mauro, A.; Guerra, G.; Mochizuki, J.; Itagaki, H. Macromolecules 2005, 38, 3696.

7. Stegmaier, P.; De Girolamo Del Mauro, A.; Venditto, V.; Guerra, G. Adv.Mater. 2005, 17, 1166.

8. Uda, Y.; Kaneko, F.; Tanigaki, N.; Kawaguchi, T. Adv.Mater. 2005, 17, 1846.

AN EFFICIENT SYNTHESIS STRATEGY FOR HIGHLY NONPLANAR OPTO-ELECTRONIC NANOMATERIALS BY BF₃•Eto₂-MEDIATED FRIEDEL-CRAFTS REACTION

Ling-Hai Xie^a, Bao-Min Zhao^b, Lian-Hui Wang^b, Wei Huang^a,*

^aInstitute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210003, China (wei-huang / njupt.edu.cn)

^bInstitute of Advanced Materials, Fudan University, Shanghai 200433, China.

Complicated 9,9-diaryfluorenes (CDAF) is a kind of nonplanar building blocks which can be prepared by BF₃•OEt₂-mediated Friedel-Crafts reaction. A series of nanomaterials based on CDAF building blocks, TPA-terF, and Cz-tetraF with nonplanar multi-dendron and 3-D persistent architectures was designed and constructed. High thermal stability and quantum yield indicate that TPA-terF and Cz-tetraF are potential materials due to unique three-dimensional conformation for opto-electronic application. In addition, the synthetic strategy can help us scale up the synthesis of pure-blue light-emitting dendrimers with terfluorene unit.