Present a new scanning-probe-based data-storage concept called the "millipede" that combines ultrahigh density, terabit capacity, small form factor, and high data rate. Ultrahigh storage density has been demonstrated by a new thermomechanical local-probe technique to store, read back, and erase data in very thin polymer films. With this new technique, nanometer-sized bit indentations and pitch sizes have been made by a single cantilever/tip into thin polymer layers, resulting in a data storage densities of up to 1 Tb/in/sup 2/. High data rates are achieved by parallel operation of large two-dimensional (2-D) atomic force microscope (AFM) arrays that have been batch-fabricated by silicon surface-micromachining techniques. The very large-scale integration (VLSI) of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2-D array of 32/spl times/32 (1024) AFM cantilevers with integrated write/read/erase storage functionality ever built. Time-multiplexed electronics control the functional storage cycles for parallel operation of the millipede array chip. Initial areal densities of 100-200 Gb/in/sup 2/ have been achieved with the 32/spl times/32 array chip.

The "millipede" - nanotechnology entering data storage

http://documents.irevues.inist.fr/bitstream/handle/2042/37333/693.pdf

Morphology and rheology of immiscible polymer blends filled with silica nanoparticles

Melt blending of polylactide and linear low-density polyethylene (LLDPE) was performed in an effort to toughen polylactide. In addition, two model polylactide-polyethylene (PLLA-PE) block copolymers were investigated as compatibilizers. The LLDPE particle size and the impact resistance of binary and ternary blends were measured to determine the extent of compatibilization. For the amorphous polylactide (PLA), toughening was achieved only when a PLLA-PE block copolymer was used as a compatibilizer. For the semicrystalline polylactide (PLLA), toughening was achieved in the absence of block copolymer. To decrease the variability in the impact resistance of the PLLA/LLDPE binary blend, as little as 0.5 wt % of a PLLA–;PE block copolymer was effective. The differences that were seen between the PLA and PLLA binary blends were investigated with adhesion testing. The semicrystalline PLLA did show significantly better adhesion to the LLDPE. We propose that tacticty effects on the entanglement molecular weight or miscibility of polylactide allow for the improved adhesion between the PLLA and LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3757–3768, 2003

Toughening of polylactide by melt blending with linear low‐density polyethylene

25.1 Chain Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 25.2 Chain Entanglement and Tube Diameter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 25.3 Critical Molecular Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 25.4 Temperature Dependence of Chain Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

Chain Dimensions and Entanglement Spacings

Alumina/poly(methyl methacrylate) (PMMA) nanocomposites were synthesized by an in situ free-radical polymerization process with 38 and 17 nm diameter γ-alumina nanoparticles. At extremely low filler weight fractions (<1.0 wt % of 38 nm fillers or < 0.5 wt % of 17 nm fillers) the glass-transition temperature (Tg) of the nanocomposites drops by 25 °C when compared to the neat polymer. Further additions of filler (up to 10 wt %) do not lead to additional Tg reductions. The thermal behavior is shown to vary with particle size, but this dependence can be normalized with respect to a specific surface area. The nanocomposite Tg phenomenon is hypothesized to be because of nonadhering nanoparticles that serve as templates for a porous system with many internal interfaces that break up the percolating structure of dynamically heterogeneous domains recently suggested by Long, D.; and Lequeux, F. Eur Phys J E 2001, 4, 371 to be responsible for the Tg reductions in polymer ultrathin films. The results also point to a far field effect of the nanoparticle surface on the bulk matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4371–4383, 2004

Glass-transition temperature behavior of alumina/PMMA nanocomposites

The viscoelastic properties of two series of poly(methyl methacrylates) (PMMA) with different tacticities and very narrow molecular weight distributions were measured in the molten state at different temperatures by means of oscillatory rheometry. Zero-shear viscosity η0, steady-state shear compliance Je°, and plateau modulus GN° were obtained from the resulting master curves for the storage modulus G‘ and loss modulus G‘‘. Relaxation time spectra h(τ) were calculated by a nonlinear regularization method and could be used to determine the terminal relaxation time τ0. The molecular weight and polydispersity dependence of these parameters agrees with existing empirical rules for linear amorphous polymers. Stereoregularity, however, has a great influence on η0 and τ0. The entanglement molecular weight Me and the critical molecular weight Mc seem to vary with the tacticity as well. These results are possible explanations for some contradicting or inconsistent literature data concerning PMMA.

Viscoelastic Properties of Narrow-Distribution Poly(methyl methacrylates)

We have analyzed the influence of different amounts ω be of two diblock copolymers, poly(styrene-b-methyl methacrylate) (sm blend series) and poly(cyclohexyl methacrylate-b-methyl methacrylate) (cm blend series), on the morphological and rheological characteristics of a blend containing w = 7.5 wt % polystyrene in poly(methyl methacrylate) matrix. The morphological analysis is based on the sphere size distribution function, which was determined from the image analysis of the transmission electron micrographs. Using this function and assuming that all block copolymers are located at the interface, the interfacial area per copolymer joint, Σ, was calculated. From its hyperbolic dependence on ω bc the value at the critical micelle concentration, Σ cmc , was found to be about 10 nm 2 for both systems. The rheological analysis reveals that in addition to the form relaxation process, well-known for polymer blends, a new relaxation process is observed for these systems. Its relaxation time, τ β , has been studied in dependence on the amount of added block copolymers. The observed phenomena for each blend series, i.e. constant blend viscosity, slight shift of the form relaxation times τ 1 , and systematic shift of the interface governed relaxation time τ β (τ β > τ 1 ), have been interpreted quantitatively. In contrast to τ 1 , τ β is less influenced by the interfacial tension but is mainly governed by an additional contribution, the interfacial shear modulus. Formulas were derived from an expanded version of the Palierne emulsion model which allows the determination of the proposed interfacial properties from rheological measurements. In general, the interfacial tension decreases with increasing amount of block copolymer, and the decrease is more pronounced for the cm blend series. The interfacial shear modulus increases during compatibilization from 0 to amounts which are in the range of 20-30% of the interfacial tension. The decrease of interfacial tension is in good agreement with predictions from Leibler's brush model extended by Dai et al. In conclusion, it was found that the Palierne model with an nonisotropical interfacial stress state is quantitatively correct to describe the observed phenomena for those blends.

Chr. Friedrich

Papers

Viscoelastic Properties of Narrow-Distribution Poly(methyl methacrylates)

Interpretation of a New Interface-Governed Relaxation Process in Compatibilized Polymer Blends