The largest commercial application of carbon nanotubes (CNT) are their polymer nanocomposites (PNCs). This motivates detailed studies of the interactions between CNTs and polymers and the ways the CNTs influence the crystallization behavior and structure of PNCs. We have chosen isotactic polypropylene (iPP) as one of the best model systems because of its ability to form a smectic liquid crystal phase. We studied iPP/CNT nanocomposites with CNT concentrations ranging from 0.01 to 5% per weight. We prepared films by compression molding and quenching in a mixture of isopropyl alcohol and dry ice. Some of the formed smectic liquid crystalline (LC) phase of iPP/CNT PNCs persisted to temperatures higher than the last melting temperature for iPP crystals. By means of differential scanning calorimetry we corroborated the existence of the LC phase in the nanocomposites and studied the impact of multi-walled carbon nanotubes on its melting and re-crystallization. We used a polarizing optical microscopy to reconfirm our DSC data.

There is widespread interest in developing efficient solar cells derived from conjugated polymers and TiO2. The conjugated polymer can act as a light harvesting dye as well as a hole transport material, and can potentially replace both the ruthenium dye and the I3-/I- couple in the DSSCs. Herein, we report a novel and facile approach of using conjugated polymer nanoparticles to make conjugated polymer:TiO2 nanocomposite based solar cell. Nanoparticles from poly(3-hexylthiophene) (P3HT) were made using mini-emulsion technique. In this work we report on incorporation of these P3HT nanoparticles into nanoporous titania. Device characteristics made using P3HT nanoparticle sensitized solar cells were measured. These devices showed a short-circuit current density (Jsc) of 0.207 mA/cm2, open-circuit voltage (Voc) of 0.62 V and 0.07% (η) efficiency.

The facile bottom-up fabrication of a perfect preferentially-oriented MOF nanofilm, NAFS-1 on a solid surface, which is endowed with highly crystalline order both in the out-of-plane and in-plane orientations to the substrate, as determined by synchrotron X-ray surface crystallography, was achieved by the unique combination of a layer-by-layer growth technique coupled with the Langmuir-Blodgett (LB) method.

Our overall approach is based on developing a photocrosslinkable polymer network with a favorable shape-memory response, using polymer chemistry and crosslinking density to control thermo-mechanical properties. Three polymer networks were created and thermo-mechanically tested, each from tert-Butyl acrylate linear builder co-polymerized with a poly(ethylene glycol) dimethacrylate cross-linker. By systematically altering the molecular weight and the weight fraction of the cross-linker, it was possible to create three polymers that exhibited the same glass transition temperature, but varied by almost an order of magnitude in rubbery modulus. Therefore, the mechanical stiffness could be tailored to suit a given application. Recovery behavior of the polymers was characterized over a range of deformation temperatures. It has been implicitly assumed a linear relationship between Free-Strain (i.e. no actuation force) and Fixed-Stress (i.e. maximum actuation force), however, this has never been confirmed experimentally. The energy per unit volume performed by the shape-memory polymer was quantified, and observed to be a function of strain recovered. The maximum recoverable work was shown to increase with cross-linking density, although the overall efficiency is similar for all materials tested.

Dielectric elastomer actuators (DEAs) have been demonstrated to represent today a high-performance technology for electromechanical transducers based on electroactive polymers. As a means to improve versatility and safety of DEAs for several fields of application, so-called ‘hydrostatically coupled’ DEAs (HC-DEAs) have recently been described. HC-DEAs are based on an incompressible fluid that mechanically couples a DE-based active part to a passive part interfaced to the load, so as to enable hydrostatic transmission. This paper presents ongoing developments of bubble-like HC-DEAs and their promising potential application in the field of haptics. In particular, the first part of the paper describes a static and dynamic characterization of a prototype actuator made of two pre-stretched membranes (20 mm wide, 1.8 mm high, and 60 μm thick) of 3M VHB acrylic elastomer, coupled via silicone grease. The actuator exhibited a maximum stress of 1.3 kPa at 4.4 kV, a relative displacement of -80% at 4.4 kV, a -3dB bandwidth of 3 Hz, and a resonance frequency of 160 Hz. The second part of the paper presents possible applications of the tested actuator configuration for haptic interfaces. Two specific examples are considered. The first deals with a wearable tactile/haptic display used to provide users with tactile feedback during electronic navigation in virtual environments. The display consists of HC-DEAs arranged in contact with finger tips. As a second example of usage, an up-scaled prototype version of an 8-dots refreshable cell for dynamic Braille displays is shown. Each Braille pin consists of a miniature HC-DEA, with a diameter lower than 2 mm. Both types of applications clearly show the potential of the new technology and the prospective opportunities for haptics.

In this paper, we present the possibility of nano-scale patterning on surfaces of 3-D micro structures by means of block copolymer self assembly. We succeeded in forming vertical cylinders on the surfaces of the 3-D micro structures using dip-coat process with Au deposition instead of random copolymers. The material of 3-D structures fabricated by FIB-CVD was diamond-like carbon (DLC) due to selecting phenanthrene as a gas source. Since the surface energy of DLC is low, instead of PS-r-PMMA polymer brush, 100 nm-thick Au films were coated on the surfaces of 3-D structures. PS-b-PMMA (PS:PMMA = 50 kg/mol:21 kg/mol) was dip-coated on the Au coated surfaces and annealed. First, we prepared DLC 60° angled slope with size of 2.5 by 3 μm2. As a result, the vertical cylinders were formed in a similar way regardless of the places, i.e., top, middle and bottom on the slopes. vertical cylinders were formed regularly and densely on the entire slope. In order to investigate the effect of slope angle, we prepared 3-D micro structures with different angled slopes such as 70, 80 and 90°. There was no slope angle specific difference, and vertical cylinders were also formed on each slope.

Acrylic based films containing thermo-chemically synthesized magnetite nanoparticles (NPs) were prepared by UV-curing. A stable dispersion of Fe3O4 NPs in n-hexane was added to polyethylene glycol diacrylate (PEGDA) oligomer or to hexanediol diacrylate (HDDA) oligomer, producing a blend whose viscosity matches the processing requirements for inkjet printing technology. Morphologic characterization is provided by means of Field Effect SEM on a representative nanocomposite section.

By real-time FT-IR analysis it was shown that Fe3O4 NPs are able to initiate radical chain-grown polymerization under UV light, for what concerns the HDDA matrix. Tight cross-linked transparent polymeric films were obtained after 1 minute of UV irradiation.

The magnetic properties of the produced films were studied by means of an Alternating-Gradient Force Magnetometer (AGFM) in the temperature range 10 – 300 K and up to 18 kOe. The isothermal magnetization curves of both HDDA and PEGDA -based nanocomposites showed that these hybrid systems must be described as interacting superparamagnets (ISP) characterized by inter-particle magnetic interactions dominating over intra-particle effects.

Thermo-responsive actuation (thermomechanical effects) based on nematic liquid crystal elastomers (LCEs) have become a research priority in the preparation of soft actuators. Nematic LCEs combine the anisotropic features of liquid crystal phases with the rubber elasticity of polymer network. When heated at nematic to isotropic phase transition temperature (N-to-I temp.), a uniaxial thermomechanical deformation of LCEs will undergo at nearly constant volume due to a change of LC director order. Recently, an array of the micro-sized LCE pillars related to such thermomechanical effects have been successfully constructed through a soft lithography technology (i.e., replica molding). The prepared LCE pillars are mono-dispersive and micro-sized. They also possess N-to-I temp. higher than 100°C, largely limiting the available application. By contrast, the present study will report a hexagonal array of nano-sized thermo-responsive pillar actuators that are able to contract and expand in response to temperature changes around a lower N-to-I temp. is manufactured via using reactive rod-like liquid crystal and ultraviolet nanoimprinting technology. According to atomic force microscope (AFM) observation, a hexagonal array of pillars can be easily constructed by nanoimprinting and a responsive surface with a thermo-stimuli-driven roughness change is achieved. The room-temperature AFM scans quantitatively represent the single pillar shows a diameter of ca. 270 nm and 140 nm in depth, and the pitch meaning the averaged inter-pillar distance is measured as ca. 425 nm, thus lying in a nano-sized range. Furthermore, temperature-variable AFM is also utilized to demonstrate the pillar behaves as a thermally-stimulated nano-sized actuator. In our case, when heated above N-to-I phase transition temperature (ca. 65°C), it is clearly observed that the pillar diameter is expanded in the order of over 12-15 % and then reversibly contracted in response to temperature drop.

Besides energy density, the electric loss at high electric fields is another major concern for many capacitor applications. This paper presents recent works in developing high energy density low loss polymer capacitors. In order to reduce the dielectric loss while maintaining high energy density in poly(vinylidene fluoride-hexafluoropropylene) P(VDF-HFP) and P(VDF-CTFE) (CTFE: Chlorotrifluoroethylene) based polymers, a polymer blend approach was investigated. We show that by blending P(VDF-CTFE) with a proper low loss polymer such as poly(ethylene- chlorotrifluoroethylene) (ECTFE) can lead to marked improvement in the loss of dielectric films. In this study, P(VDF-CTFE) blends films with different wt% of ECTFE have been examined to find a balance between dielectric constant and the loss. In addition, crosslink in the blends has been employed to further improve the dielectric performance of the blends. The results indicate that these blends exhibit an excellent performance: relatively high dielectric constant (~ 6~7) and low loss (~ 0.01) at 1 kHz. For the crosslink blend films, the high field loss is reduced to below 5% with a discharged energy density 4.3 J/cm3 under a field of 300 MV/m.

In this paper, we present layer-by-layer stacking method to fabricate self-assembled structures of block copolymers (BCP) toward the out-of-plane direction. Layer-by-layer stacking is realized by transferring a BCP film on one substrate to another. Specifically, a water-soluble polymer film is coated on the former substrate, which is placed and fixed in contact with a target substrate. Consequently, the BCP film is released from the substrate and transferred to the target substrate when immersed in de-ionized water. In our experiment, PS-b-PMMA is used to form and transfer self-assembled structures, and polyvinyl alcohol is used as a water-soluble polymer. We prepared two kinds of target substrates; one has horizontal cylindrical structures by BCP self assembly, and the other has groove structures by EB lithography. In the case of BCP patterned substrate, BCP film with vertical cylindrical structures is transferred onto the line structures of BCP. In the case of EB lithography patterned substrate, BCP film with vertical cylindrical structures is transferred in a doubly suspended condition. Furthermore, vertical and horizontal cylindrical structures are also observed to align along the grooves.

Hydrogels with their tunable properties are attractive candidates for developing tissue engineering scaffolds for various applications (including bone and cartilage). The current work involved studying the synergistic effect of basic fibroblast growth factor (bFGF) and platelet derived growth factor BB (PDGF-BB) entrapped within injectable porous gels for bone regeneration applications. An in situ gelling system was developed using bacterial polysaccharides gellan and xanthan gum by temperature and ionic gelation with Ca+2. After the initial characterization of the hydrogels, a dual growth factor release system was developed wherein growth factors were encapsulated within chitosan nanoparticles embedded in the gels as well as directly within the gel. The hydrogel structure was characterized by SEM and TEM and in vitro growth factor release studies showed a slow release profile in PBS. Further, human fetal osteoblasts were entrapped within the hydrogel and a 21 day osteoblast differentiation study was conducted. An improvement in osteoblast total protein synthesis and collagen content was observed by day 21 compared to control gels without growth factors. Although further evaluation regarding mechanical properties and expression of osteogenic differentiation marker genes will be necessary, the present study suggests that injectable scaffolds can be used for the delivery of multiple growth promoting agents to support osteoblast differentiation.

We show evidence of electrical and thermal conductivity percolation in polymer based carbon nanotube (CNT) composites, which follow power law variations with respect to the CNT concentrations in the matrix. The experimentally obtained percolation thresholds, i.e., ~ 0.074 vol % for single walled CNTs and ~ 2.0 vol % for multi-walled CNTs, were found to be aspect ratio dependent and in accordance with those determined theoretically from excluded volume percolation theory. A much greater enhancement, over 10 orders of magnitude, was obtained in the electrical conductivity at the percolation threshold, while a smaller increase of ~ 100 % was obtained in the thermal conductivity values. Such a difference is qualitatively explained on the basis of the respective conductivity contrast between the CNT filler and the polymer matrix.

We report preliminary studies on the preparation of carbon nanoparticles (CNPs) of ~ 20 nm in diameter derived from asphaltenes under mild conditions. This transformation occurred upon heating a thin film of asphaltenes cast on a carbon coated copper grid under both nitrogen and oxygen atmosphere. The resulting CNPs were characterized by thermogravimetric analysis (TGA), scanning/transmission electron microscopy (SEM/STEM), transmission electron microscopy (TEM), elemental analysis (EA) and Auger electron spectroscopy (AES). The findings point towards asphaltenes, a crude oil by-product, as a potential source for carbon nanomaterials.

Multilayered films comprising alternating layers of polycarbonate (PC) and poly(vinylidene fluoride-hexafluoropropylene) (P[VDF-HFP]) show an enhanced dielectric strength (E B> 750 kV/mm) and an increased energy storage density (U d ~ 13.5 J/cm3) compared to monolithic PC and P[VDF-HFP] films. Here the role of electromechanical effects in the breakdown of multilayer films is explored both by imaging the changes in the layer structure caused by electrical fields below the breakdown field and by a direct measurement of the strain in multilayer PC/ P[VDF-HFP] films subjected to similar fields. Focused Ion Beam (FIB)/ Scanning Electron Microscopy (SEM) images of the layer structure in films subjected to repeated cycles at near-breakdown fields showed local changes in the thickness of individual layers, suggesting that mechanical forces arising from field-induced compression may play a role in the steps preceding the breakdown. The directly measured field induced strain showed evidence for both an elastic and a flow component to the strain. The mechanical responses of films with ≤ 50 vol% P[VDF-HFP] were modeled as simply the sum of an elastic and viscous flow. The observed electromechanical properties vary with the layer structure. This suggests that multilayering polymers may provide a means to mitigate deleterious electromechanical effects in low modulus, high dielectric materials.

Selective laser sintering (SLS) process was used to obtain nanostructured porous 3D objects consisting of Ni or/and Cu nanoclusters enveloped with a polycarbonate (PC) matrix for M/NEMS applications. The liquid phase SLS process was performed in air or Ar. The powder mixtures of Ni + PC in proportions 1:1, 1:2 (Ni particle size ranged from 27 to 184 nm) and Cu + PC = 1:9, 1:4, 3:7 (Cu particle size ranged from 76 to 90 nm) and a cw YAG:Nd+3 laser (P = 4–10 W) with defocused laser beam were used. Optimal regimes of laser treatment as monolayer as layerwise 3D part manufacturing in above mention nano compositions were determined. The scanning electronic microscopy (SEM) equipped EDX and qualitative XRD analysis showed that content and size of nanoparticles are remained unaffected after the liquid-phase sintering. It was shown a principle possibility of functional graded 3D parts fabrication via the interleaving of the metal - polymer powdered compositions with Ni and/or Cu additives, which ensures the nano particle sizes conservation. Proposed approach is opened a new way by deliberated M/NEMS device synthesis. Alternation of ferromagnetic and non-magnetic layers with Ni and/or Cu core – polymer shell structures was provided the interesting electro-physical properties of such devices.

Polyaniline is one of the most studied conducting polymers and its properties have been used in many sensor applications including gas sensors and pH sensors. In this work, we present a method that is able to embed a conducting polyaniline film in a desired pattern onto a nonconducting polymer matrix. We have developed an embedded polyaniline film on a polydimethylsiloxane (PDMS) matrix using a cast molding technique. The polyaniline film was grown by electrochemically polymerizing polyaniline from an electrolyte containing sulfuric acid and aniline monomer. A three-electrode cell system was used with a standard Ag/AgCl reference electrode, a gold auxiliary electrode, and a patterned gold working electrode. After the polyaniline film was formed on the patterned working electrode, PDMS was poured atop and cured. Cured PDMS was then debonded along with the polyaniline film embedded on the PDMS layer or block. The gold layer of the working electrode can be patterned using a photolithography steps so that the designed pattern can be transferred by the polyaniline growth on the working electrode. The greenish color of the polyaniline film indicated that the embedded polyaniline was in the conducting state (emeraldine salt form) and the conductivity of the polyaniline has also been verified by applying a DC voltage across the film and measuring the current through the polyaniline layer. The measured conductivity of the PANi layer at room temperature was in the range of 4.5 ~ 4.6 S/m. The advantage of this technique is that the PDMS matrix holds the polyaniline in place while allowing the polyaniline film to undergo reversible doping/dedoping chemistry when electrolyte solution comes into contact with the surface of the film. The developed technology can be used for various chemical sensor applications, for example, a pH sensor or gas sensors where a flexible and all-polymer apparatus is needed.

It is investigated how figures of merits of nanocomposites are affected by structural and interaction length scales. Aside from macroscopic effects without characteristic lengths scales and atomic-scale quantum-mechanical interactions there are nanoscale interactions that reflect a competition between different energy contributions. We consider three systems, namely dielectric media, carbon-black reinforced rubbers and magnetic composites. In all cases, it is relatively easy to determine effective materials constants, which do not involve specific length scales. Nucleation and breakdown phenomena tend to occur on a nanoscale and yield a logarithmic dependence of figures of merit on the macroscopic system size. Essential system-specific differences arise because figures of merits are generally nonlinear energy integrals. Furthermore, different physical interactions yield different length scales. For example, the interaction in magnetic hard-soft composites reflects the competition between relativistic anisotropy and nonrelativistic exchange interactions, but such hierarchies of interactions are more difficult to establish in mechanical polymer composites and dielectrics.

The actuation of ionic polymer actuators is mainly caused by the ion transport and excess ions storage in the membrane and electrodes. To quantify the charge transport behavior, a time domain method based on Poisson-Nernst-Planck equations was applied. The time domain transient current in response to a step voltage can provide insights on the charge transport and storage behaviors in the membranes. In this study, we investigate the charge transport behavior of Aquivion ionomer with different uptakes of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf). A critical uptake and voltage independent of charge transport behavior were observed. The results also show that bending actuations of the Aquivion membrane with 40wt% EMI-Tf is much larger than that of Nafion, indicating that the shorter flexible side chain ionomer possesses a better electromechanical coupling between the excess ions and the membrane backbones, while not affect the actuation speed.

Polyacrylamide- Multiwalled carbonnanotube (PAM- MWNT) composites were prepared via free radical crosslinking copolymerization with different amounts of MWNT varying in the range between 0.1 and 15 wt. %. PAM- MWNT composite gels were characterized by fluorescence, dielectric spectroscopy and the tensile testing technique. A small content of doped nanotubes dramatically changed gelation time, conductivity and young modulus, respectively. The gel fraction exponent, β of PAM- MWNT composite gels were measured for various monomer and MWNT concentrations and observed that the gel fraction exponent β agrees best with the percolation theory for various amounts of PAM- MWNT. These polymer systems which are initially of an isolator character are doped with carbon nanotubes of nano dimensions and when the amount of this addition exceeds a critical value (0.3 wt. % MWNT) known as the percolation threshold, then composite gel systems with carbon nanotubes become electrically conducting structures with a critical exponent around r=2 which is close to the theoretical prediction of this value in 3D percolated system as known random resistor network. The observed elasticities are decreased above 3 wt. %MWNT with critical exponent around y=0.72 which is indicative of a transition from liquid-like to solid-like viscoelastic behavior.

Well-controlled fluorinated star-shaped polymers with oxyethylene units were designed and synthesized by living cationic polymerization. These fluorinated star-shaped polymers were prepared using successive fluorinated initiators to generate fluorinated, end-functionalized and hydrophilic segments with oxyethylene. Poly(vinyl ether)s with oxyethylene units are known to be thermo-responsive polymers that exhibit a lower critical solution temperature (LCST) in aqueous solutions. These novel fluorine-containing star-shaped polymers with oxyethylene were also thermo-responsive, as expected. In addition, the hetero-fluorinated star-shaped polymers with oxyethylene segments and different fluorine compositions were synthesized with various bifunctional initiators by living cationic polymerization having narrow molecular weight distributions (Mw/Mn=1.23−1.29) and contained very little, if any, presence of the linear homopolymer precursor, as evidenced by GPC. The LCST of this polymer depended on the end group fluorine composition and significant changes in cloud points were observed in water, as confirmed by static light scattering (SLS) measurements. As an example, aqueous solutions the star-shaped polymers without fluorine terminal groups showed no cloud point below up to 60 ºC in aqueous solution. After the fluoro-functionality was incorporated into the terminal groups, the cloud point of the aqueous solutions decreased to almost 20 ºC.