Chain-folded Lamellar Crystals Research Articles

Double-lamella phenomenon of once-folding polymer crystallization raised by chain-end hydrogen-bonding interactions

Poly (ethylene glycol) (PEG) holding molecular weights around 7000 Da exhibits a double-lamella phenomenon on the surface replicas of bulk once-folding crystallization, whose mechanism is still unclear. Concerning to its specific hydrogen-bonding interactions at chain-ends, we performed dynamic Monte Carlo simulations to investigate the effects of specific chain-end interactions on once-folding crystallization of 16-mers. The results showed that the chain-end hydrogen-bonding interactions bring little effects to both kinetics of primary nucleation and lateral growth of chain-folded lamellar crystals but make a more significant terrace at the lateral growth front with a step of metastable once-folding towards the next step of stable chain-extending, raising the double-lamella phenomenon of their surface replicas. We found that the chain-end hydrogen-bonding interactions are rich at the surfaces of once-folded lamellar crystals, which thus enhance their metastability and retard their thickening into the chain-extended crystals. In addition, intra- and inter-molecular secondary nucleation at corresponding chain-folded and extended growth fronts show different growth rate dependences on the specific interaction strengths. Our results revealed the role of specific chain-end interactions in PEG crystallization.

Crystal and molecular structure of V-amylose complexed with butan-1-ol

Chain-folded lamellar V-amylose single crystals were prepared by adding butan-1-ol to hot dilute aqueous solutions of native amylose. The base-plane electron and X-ray diffraction patterns recorded from hydrated specimens agreed with a P212121 space group and an orthorhombic unit cell. A molecular model resulting from an exhaustive search of helix position and restrained structure refinement against diffraction data was proposed. The unit cell contains 4 antiparallel left-handed 6-fold amylose single helices with 1 butan-1-ol molecule located inside each of the helical cavities. In addition, 4 butan-1-ol and 20 water molecules are distributed in the 4 interstitial spaces. The amylose helices form rows along the b-axis that are alternatively shifted by ±b/8 with respect to one another, which validates the geometrical model proposed by Helbert and Chanzy in 1994.

Kinetic Analysis of Quasi-One-Dimensional Growth of Polymer Lamellar Crystals in Dilute Solutions

Flexible polymers are featured with two-dimensional growth of metastable chain-folded lamellar crystals in quiescent dilute solutions. Recently, a massive cylindrical micelle with quasi-one-dimensional (quasi-1D) growth driven by confined crystallization of diblock copolymers in dilute solutions raised a new challenge. We performed dynamic Monte Carlo simulations to investigate the kinetics of quasi-1D growth of lamellar crystals in two typical cases of dilute but not very dilute polymer solutions. We found that in both cases the growth kinetics is dominated by the surface-nucleation-controlled mechanism. Moreover, in the first case corresponding to few and small crystals grown under almost constant polymer concentrations in the huge bulk of solutions, the driving-force term in the kinetic equation dominates a linear concentration dependence of crystal growth rates in the high-concentration region, and the nucleation-barrier term dominates their nonlinear deviation in the low-concentration region. In the second case corresponding to massive crystals grown under depleting polymer concentrations in a limited volume of solutions, the crystal growth rates decay with time, but at the early stage, they follow exactly with the linear-concentration-dependent growth rates of the first case. Therefore, the growth size at the early stage of the second case can be described as an exponential-decay function of time, which provides a theoretical model to the data analysis of corresponding experimental observations.

Photodegradation of ethylene–octene copolymers with different octene contents

The influence of the octene content on the photodegradation behaviour of ethylene–octene copolymers (EOCs) was revealed by investigating the photooxidation of low density polyethylene (LDPE) and EOCs with different octene contents through a series of characterisation methods. LDPE was very sensitive to ultraviolet light and the photostabilities of EOCs decreased with increasing octene concentration. The photodegradation of all samples produced hydroxyl, carbonyl and vinyl groups. The ease of chain crosslinking and scission was increased as the octene content rose. Crosslinking predominated in late irradiation period of LDPE while chain scission was dominant in that of EOCs. Annealing and chain scission promoted the secondary crystallisation of the crystallisable chain segments. Chain scission enhanced the crystallisation ability of the irradiated EOCs while it decreased that of the weathered LDPE. The photostabilities of crystals could be ranked as follows: the chain-folded lamellar crystals > the bundled crystals > the fringed micellar crystals. The thermal stabilities and mechanical properties of samples decreased with increasing irradiation time and the decreasing extent was correlated with the comonomer content.

Crystalline structure of sequential poly(ester amide)s derived from glycolic acid, 1,6-hexanediamine, and even aliphatic dicarboxylic acids

Basic structural data of two sequential poly(ester amide)s derived from glycouc acid, 1,6-nexaneaiamine, ana aaipic acia or aoaecanoaioic acia nave oeen determined by means of X-ray and electron diffraction patterns from fibers and single crystals. Chain-folded lamellar crystals were obtained by isothermal crystallization from diol or glycerine solutions, and the crystalline habit was investigated by real space electron microscopy. Polyethylene decoration techniques were applied to evaluate the regularity of the folding surfaces. Spherulites prepared from evaporation of formic acid solutions were also studied. The two sequential poly(ester amide)s crystallized according to triclinic and monoclinic unit cells, in which the a crystallographic parameter was close to the typical distance between hydrogen-bonded chains. Projections viewed down the chain axis revealed differences in the packing mode since oblique and rectangular cells were found for the adipic acid and dodecanodioic acid derivatives, respectively. Both structures can be envisaged as a stacking of hydrogen-bonded sheets although clear differences concerning the shift between consecutive sheets and the number of layers comprising the unit cell were found. The large unit cells that have been deduced seem to be a consequence of the different packing preferences of the diester and diamide moieties. Both polymers have a molecular conformation that deviates from the all-trans conformation typical of aliphatic polyamides and polyesters with a large number of methylene groups.

Alternating poly(ester amide)s of glycolic acid and ω-amino acids: Crystalline morphology and main crystallographic data

The unit cell parameters of two alternating poly(ester amide)s constituted by glycolic acid and ω-amino acid units have been determined by interpretation of X-ray and electron diffraction patterns. Orthorhombic unit cells containing two chain segments with a nonplanar conformation have been derived. The electron diffraction patterns were rather different from those characteristic of aliphatic polyamides and polyesters with a zig–zag conformation. Chain-folded lamellar crystals have been obtained by isothermal crystallization of dilute diol or glycerine solutions and the crystalline habit has been studied by means of real space electron microscopy. Polyethylene decoration techniques have been applied to evaluate the regularity of the folding surfaces. Diffraction and morphologic data suggest that hydrogen bonds between amide groups were established along a single direction, which coincides with the preferential crystal growth direction. Spherulites prepared from both evaporation of formic acid solutions and melt crystallization have been also studied. Diffraction data indicate that hydrogen bonds are aligned along the spherulite radius. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 815–825, 2007

Crystalline Structure of Poly(hexamethylene adipate). Study on the Morphology and the Enzymatic Degradation of Single Crystals

The crystalline structure of polyester 6 6 was studied by means of X-ray and electron diffraction and real-space electron microscopy. An orthorhombic unit cell containing eight chain segments with a quasi planar zigzag conformation was derived. The chain axis projection could be defined by a small rectangular cell containing only two molecular segments. Simulation of electron diffraction patterns indicates that molecular segments were arranged with azimuthal angles close to +/-46 degrees . X-ray diffraction patterns suggested that the large dimensions of the unit cell were a consequence of a slight shift between neighboring chains that improved the electrostatic interactions. Chain-folded lamellar crystals were obtained by isothermal crystallization of dilute n-hexanol or n-octanol solutions. The crystalline habit was studied, and the influence of temperature was evaluated. A regular folding surface was observed by using polyethylene decoration techniques. Lamellar crystals were easily degraded with different lipases. A preferential enzymatic attack was, in some cases, observed to occur in the crystal edges, giving rise to highly irregular borders with a fringed texture.

Crystal Structure and Morphology of Poly(16‐hexadecalactone) Chain‐folded Lamellar Crystals

Solution-grown, chain-folded lamellar crystals of poly(16-hexadecalactone) (PHDL) were crystallized isothermally from 1-hexanol at 70 degrees C. The morphology of lozenge-shaped crystals was studied by TEM and AFM. The lamellae are ca. 10 nm thick and the chains run orthogonal to the lamellar surface with folding along (110) and (110) planes. The crystal structure of PHDL was determined by XRD and election diffraction of single crystals. The chains are in the 2(1) helix conformation close to all-trans and the structure consists of an orthorhombic unit cell with a P2(1)2(1)2(1) space group with the lattice constants a = 0.746 +/- 0.001 nm, b = 0.504 +/- 0.001 nm, and c (chain axis) = 4.116 +/- 0.003 nm. There are two chains per unit cell, which exist in an antiparallel arrangement. Molecular packing structure has been studied in detail, taking into account both diffraction data and energy calculations. The setting angles, with respect to a axis, were +/-40 degrees for the corner and center chains, respectively. By using the electron and XRD data, the best molecular packing model was refined to R-factors of 0.168 and 0.196, respectively. A brief comparison of chain-packing structure is also made with related polymer structures.

Molecular packing and crystalline morphologies of biodegradable poly(alkylene dicarboxylate)s derived from 1,6-hexanediol

The crystalline structures of two aliphatic polyesters derived from 1,6-hexanediol and suberic or dodecanodioic acid are studied by means of X-ray and electron diffraction and real space electron microscopy. Chain-folded lamellar crystals have been obtained by isothermal crystallization of dilute n-hexanol or n-heptanol solutions and their crystalline habit have been studied. A regular folding habit is deduced from polyethylene decoration techniques. An orthorhombic unit cell containing four chain segments with a planar zig-zag conformation is determined for the two studied polyesters. A P2 1 ab space group symmetry can be assumed taking into account the detected systematic absences and the symmetry of diffraction patterns. In addition, evidence of a second non-orthorhombic structure is found for the suberic acid derivative. The orthorhombic crystal packing of these polymers is characterized by a setting angle close to 45°, showing a similarity with polyethylene. Refinement of the X-ray fiber diffraction pattern of polyester 6-12 allows to determine the c-chain axis shift between the molecular chains, being observed an alignment of the CH 2–O methylene groups with the CH 2–O oxygen atoms of neighbouring chains. Crystallization from the melt renders spherulites with a negative birefringence and a fibrillar texture, whereas banded morphologies constituted by multilayered single crystals can be obtained by evaporation of xylene solutions. Electron diffraction patterns of ultrathin samples allow the spherulitic radial growth direction to be correlated with the crystalline structure.

Crystal structure, thermal behavior and enzymatic degradation of poly(tetramethylene adipate) solution-grown chain-folded lamellar crystals.

Solution-grown chain-folded lamellar single crystals of poly(tetramethylene adipate) (PTMA) were prepared from a dilute solution of 2-methyl-1-propanol by isothermal crystallization. PTMA crystals were hexagonal-shaped and polyethylene decoration of the crystals resulted in a "six cross-sector" surface morphology and showed that the average direction of chain folding is parallel to the crystal growth planes of [110] and [010]. Chain-folded lamellar crystals gave well-resolved electron diffraction diagrams corresponding to all the equatorial reflections of the X-ray fiber diagram obtained from stretched PTMA melt-quenched film (beta structure). The unit cell parameters of the beta structure of PTMA were determined as a = 0.503 nm, b = 0.732 nm and c (fiber axis) = 1.442 nm with an orthorhombic crystal system. The fiber repeat distance is appropriate for an all-trans backbone conformation for the straight stems. The setting angle, with respect to the a axis, is +/-46 degrees for the corner and center chains. Thermal behavior of lamellar crystals has been investigated by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). The lamellar thickness at the edges of the crystal increased after thermal treatment with taking the molecular chains into recrystallization parts; the holes then opened up at the thickening front of the crystal. The morphological changes of lamellar crystals after enzymatic degradation by Lipase type XIII from Pseudomonas sp. and water-soluble products were characterized by TEM, AFM, gel permeation chromatography, high performance liquid chromatography and fast atom bombardment mass spectrometry. The degradation progressed mainly from the edges of the lamellar crystals without decreasing the molecular weights and the lamellar thicknesses. The central portion of single crystals was often degraded by enzymatic attacks. This result combined with thermal behavior indicates that the loosely chain-packing region exists inside the single crystal, and that molecular chains in this region have higher mobility against thermal and enzymatic treatments.

Morphology and Structure of Chain-Folded Lamellar Crystals of Nylons 2 22, 4 22, 6 22, 8 22, 10 22, and 12 22

Chain-folded lamellar crystals of nylons 2 22, 4 22, 6 22, 8 22, 10 22, and 12 22 are grown from 1,4-butanediol solution, and their morphology and crystalline structure are investigated by using transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD). It is found that nylons 4 22, 6 22, 8 22, 10 22, and 12 22 have a similar crystalline structure. All of them crystallize into the triclinic structure of the nylon 6 6 αp phase, and their unit cell parameters are also similar to those of nylon 6 6. On the other hand, nylon 2 22 is special in the crystalline structure compared with other ones. Although nylon 2 22 also adopts the triclinic αp phase, its characteristic signals of diffraction are different from other nylons of this series and nylon 6 6, but similar to those of the nylon 2 Y family. Furthermore, its parameters of the unit cell calculated from the experimental data come to the same conclusion.

Synthesis and crystallization behavior of nylon 12 14. II: Chain‐folded lamellar crystals and crystalline transformation behavior of nylon 12 14

AbstractChain‐folded lamellar crystals of nylon 12 14 have been grown from a dilute 1,4‐butanediol solution with the “self‐seeding” technique. The morphology and structure of nylon 12 14 lamellar crystals were studied by both transmission electron microscopy (TEM) and wide‐angle X‐ray diffraction (WAXD). Two kinds of electron diffraction patterns were detected when different areas were selected for diffraction, which indicates that the α crystal phase and the β crystal phase coexist for nylon 12 14 under the present crystallization conditions. The WAXD diffractograms of the crystal mats confirm the results obtained from electron diffraction (ED). In addition, the changes of the crystal structure as a function of temperature for melt‐crystallized and dilute solution‐crystallized nylon 12 14 were monitored by variable‐temperature WAXD and variable‐temperature infrared spectroscopy (IR). It was found that the melt‐crystallized sample undergoes a Brill transformation at 80°C–90°C, but no Brill temperature can be observed for the dilute solution‐crystallized nylon 12 14.

Structure of 22,12-Polyurethane in Chain-Folded Lamellar Crystals

Aliphatic 22,12-polyurethane has been crystallized directly from the melt and isothermally at 105 °C from N,N-dimethylformamide to give chain-folded lamellae of thickness ≈ 14 nm. The crystals have been investigated using X-ray diffraction, electron microscopy (imaging and diffraction), and computer modeling. The diffraction data was used to establish that the chains crystallize in a single-chain, triclinic unit cell, and the structure bears a strong resemblance to chain-folded lamellar crystals of even−even nylons. The results show that, even for a molecule with relatively long alkane segments, the hydrogen bonds exercise a controlling influence on the crystallization process and crystalline structure. Two models were investigated: one based on an analogy with nylon 6 6 and the other derived using molecular dynamics; they both turned out to be closely related. The model generated using molecular dynamics predicted localized rotations at the termini of the ester−amide coupled units. The resolution of the experimental data was not sufficient to clearly delineate between the two models, but the separate calculations do provide an estimate of the tolerances that can be accepted.

Structure and Morphology of the Aliphatic Polyester Poly-β-propiolactone in Solution-Grown Chain-Folded Lamellar Crystals

Solution-grown, chain-folded lamellar crystals of poly-β-propiolactone (PPL) have been crystallized isothermally from cyclohexanone at 55 °C. The lathlike crystals have been studied by transmission electron microscopy (imaging and diffraction), atomic force microscopy, and X-ray diffraction. A new crystal structure, the γ-structure, has been discovered. Using the experimental diffraction data and computerized modeling the structure has been refined, including the detailed geometry of the adjacent re-entry folds. The chain is in an all-trans or 1-fold helix conformation and the structure consists of a two-chain, C-faced, orthorhombic unit cell with the following parameters: a = 0.700 ± 0.002 nm, b = 0.490 ± 0.002 nm, and c (chain axis) = 0.493 ± 0.002 nm. The setting angles, with respect to the a axis, are ± 51.5° for the corner and center chains, respectively. The lamellae are 5 nm in thickness and the chains run orthogonal to the lamellar surface, although there is evidence for slight c-axis shearing of the chain-folded sheets. The general fold direction is along the a axis (long axis of the crystal) and the chain folds successively in the (110) and (11̄0) planes. Comparisons are made with previous structures for PPL fibers and related chain-folded polymers.

Investigation of solution-grown, chain-folded lamellar crystals of the even-even nylons: 6 6, 8 6, 8 8, 10 6, 10 8, 10 10, 12 6, 12 8, 12 10, and 12 12

Investigation of solution-grown, chain-folded lamellar crystals of the even-even nylons: 6 6, 8 6, 8 8, 10 6, 10 8, 10 10, 12 6, 12 8, 12 10, and 12 12

Investigation of solution-grown, chain-folded lamellar crystals of the even-even nylons: 6 6, 8 6, 8 8, 10 6, 10 8, 10 10, 12 6, 12 8, 12 10, and 12 12

Chain-folded lamellar crystals of the ten even-even nylons: 6 6, 8 6, 8 8, 10 6, 10 8, 10 10, 12 6, 12 8, 12 10, and 12 12 have been grown from solution and their morphologies and structures studied using transmission electron microscopy, both imaging and diffraction. Sedimented mats were examined using X-ray diffraction. The solution-grown crystals are lath-shaped lamellae and diffraction from these crystals, at room temperature, reveals that three crystalline forms are present in differing ratios. The crystals are composed of chain-folded, hydrogen-bonded sheets, the linear hydrogen bonds within which generate a progressive shear of the chains (p-sheets). The sheets are found to stack in two different ways. Some p-sheets stack with a progressive shear, to form the “αp structure”; others sheets stack with an alternate stagger, to form the “βp structure”. Both the αp and βp structures give two strong diffraction signals at spacings of 0.44 nm and 0.37 nm; these signals represent a projected intrasheet interchain distance (actual value 0.48 nm) and the intersheet spacing, respectively. Preparations of nylons 6 6, 8 6, 8 8, 12 6, and 12 8 consisted almost entirely of αp-structure material, with only a trace of βp-structure material being present. In contrast, nylons 10 6, 10 8, 10 10, 12 10, and 12 12 contained substantial quantities of both αp- and βp-structure material, with αp-structure material always being in the majority. Preparations of nylons 10 8, 12 10, and 12 12 also showed an additional diffraction signal at 0.42 nm; this signal is characteristic of the pseudohexagonal (high temperature) structure. The melting temperature of solution-grown lamellae of these even-even nylons decreases with decreasing linear amide density. On heating, the strong diffraction signals (0.44 nm and 0.37 nm) gradually moved together and merge at the Brill temperature to form a single diffraction signal (0.42 nm), characteristic of the pseudohexagonal structure. This single diffraction signal remained until melting. For nylons 6 6, 8 6, 8 8, 10 6, and 12 6, the Brill temperatures were substantially below the respective melting temperatures and the single 0.42 nm diffraction signal was stable over temperature ranges of 14 °C to 56 °C, depending on the nylon. Conversely, nylons 10 8, 10 10, 12 8, 12 10, and 12 12 had coincident melting and extrapolated Brill temperatures. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1209–1221, 2000

Comparison of Structures and Behavior on Heating of Solution-Grown, Chain-Folded Lamellar Crystals of 31 Even−Even Nylons

A wide-ranging and varied group of 31 even−even nylons, in the form of adjacent, re-entry chain-folded lamellar crystals, are compared and contrasted with respect to their room-temperature structures and behavior on heating. In this comparison, various relationships and trends emerge that provide a clearer understanding of the salient features that control the competitive interplay between the nylon chemistry, the crystal structure of the lamellar core, and the nature of the folds. For even−even nylons with differing alkane segment lengths, only one type of hydrogen-bonded sheet is found; for those with equal alkane segment lengths (2N 2(N + 1) nylons), two types of hydrogen-bonded sheet are found and there is direct coupling with the fold chemistry. In some cases the fold chemistry and/or stereochemistry dictate the sheet structure (e.g., nylon 4 6), while in other cases the reverse is true (e.g., nylon 4 4). There is no chain directionality in these even−even nylons, and it transpires that the two disti...

Discovery in nylon-8 chain-folded lamellar crystals of new structure??-structure?with progressive intersheet shear along the chain axis

Structural studies on solution-grown, chain-folded nylon-8 lamellar crystals, using transmission electron microscopy (imaging and diffraction) together with X-ray diffraction from oriented mats, have led to the discovery of a new crystal structure. This has been termed the λ-structure because of its similarity to the recently reported λ-structure found for the nonfolded, monodisperse 5-amide nylon-6 oligomer. In the stable nylon-8 monoclinic α-structure, the flat hydrogen-bonded sheets (ac plane; chain axis c), composed of antiparallel chains, stack via van der Waals interactions with alternating c-axis shear. Thus, in chain-folded lamellae, the chain direction is orthogonal to the lamellar surface. However, in the nylon-8 λ-structure the same hydrogen-bonded sheets stack with severe progressive c-axis intersheet shear (44°), generating an antiparallel two-chain triclinic unit cell with the parameters: a (hydrogen-bonding direction) = 0.980 nm; b = 0.544 nm; c = 2.24 nm; α = 49°; β = 90°; γ = 71.4°. The structure bears a resemblance to the classic, heavily intersheet-sheared (41°) nylon-6 6 α-structure reported by Bunn et al. in 1947. As far as we are aware, this is the first time the λ-structure has been identified in polymeric even nylons and in chain-folded lamellar crystals. Changes to the principal diffraction signal spacings and the unit cell parameters with increasing temperature have been recorded. On heating, the chain-folded hydrogen-bonded sheets remain intact and move apart. Two regimes of intersheet movement have been identified: (1) the low-temperature regime (T 120 °C), where the sheets move along both the b and c directions. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3302–3308, 2000

Polymer Crystallization Studied in Confined Dimensions using Nanocomposites from Polymers and Layered Minerals

ABSTRACTPolymer-layered silicate nanocomposites from polyamide-11 (PA-11) were prepared and the morphology and properties have been investigated in order to link the fundamental research field of polymer crystallization with the technical important field of composite materials. Semi-crystalline polymers are known to crystallize in different phases (e. g. monoclinic, hexagonal) forming chain-folded lamellar crystals. Depending on experimental conditions (e. g. temperature, pressure) the crystal size (lamellar thickness) affects the stability of these phases. The incorporation of layered silicates acting as hard walls into semi-crystalline polymers opens new possibilities to: i) study polymer crystallization in confined dimensions, and ii) provide materials from commodity or engineering polymers with enhanced properties. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The composites are prepared by in situ polycondensation of polyamides and/or blending via melt extrusion. The nanocomposites exhibit a homogeneous distribution of individual silicate layers at low clay contents. The lamellar thickening growth is reduced in polyamide crystallization due to the external constrained of the silicate layers in the host polymer. Furthermore these nanocomposites show a slightly enhanced thermal stability, tensile modulus and an increased elastic behavior over a broader temperature range. No distinct glass transition has been observed at highest clay contents.

Microstructure and Physical Properties of Clay-Polymer Composites

Polymer-layered silicate nanocomposites from polyamide-11 (PA-11) were prepared and the morphology and properties have been investigated in order to link the fundamental research field of polymer crystallization with the technical important field of composite materials. Semi-crystalline polymers are known to crystallize in different phases (e. g. monoclinic, hexagonal) forming chain-folded lamellar crystals. Depending on experimental conditions (e. g. temperature, pressure) the crystal size (lamellar thickness) affects the stability of these phases. The incorporation of layered silicates acting as hard walls into semi-crystalline polymers opens new possibilities to: i) study polymer crystallization in confined dimensions, and ii) provide materials from commodity or engineering polymers with enhanced properties. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The composites are prepared by in situ polycondensation of polyamides and/or blending via melt extrusion. The nanocomposites exhibit a homogeneous distribution of individual silicate layers at low clay contents. The lamellar thickening growth is reduced in polyamide crystallization due to the external constrained of the silicate layers in the host polymer. Furthermore these nanocomposites show a slightly enhanced thermal stability, tensile modulus and an increased elastic behavior over a broader temperature range. No distinct glass transition has been observed at highest clay contents.