We theoretically studied the reversible adsorption of polymers onto selective mixed brushes. Mixed brushes are recently developed self-adoptive materials that reversibly change their morphology in response to altering external stimuli. The above changes in the morphology result in the reversible formation of different patterns on the outer surface of the brush. It is shown that thus achieved patterning of the adsorbing surface of the mixed brush can dramatically enhance the adsorption of polymers onto this brush, as compared to the adsorption onto the homogeneous brush surface. By making use of the developed self-consistent field theory we calculate the surface excesses of homo- and co-polymers adsorbed on the binary mixed brush for the two different morphologies (`ripple' and random). The interplay between the depletion effect caused by the loss of the polymer entropy in the interior of the brush and binding interactions is shown to lead to a rich adsorption-desorption behavior. The surface excess of the adsorbed polymers is calculated as a function of the relation between the radius of gyration of the adsorbed polymers and characteristic size of the surface pattern. Shorter (relative to the size of the pattern) polymers are shown to better adsorb onto the regular patterned brush surface, as compared to the random brush surface.

We present an off-lattice numerical algorithm based upon pure diffusion to construct two-dimensional star-branched polymers with one, three, six and twelve branches. We built up structures with a total of up to 30,000 monomer units. For each one of them averages over one hundred independent configurations were taken. From a finite size analysis the scaling properties of the pair correlation function as well as the radius of gyration were obtained. Our findings indicate that the fractal dimension of the structures are: df=1.21 (0.03) for a linear polymer, df==1.21(0.02), for three branches, df==1.23 (0.02) for six branches and df=1.26 (0.03) for twelve branches.

Macroporous crosslinked polymer gels have been prepared via TEMPO-mediated living radical polymerization of divinylbenzene (DVB) in a solvent with a counter polymer. Incorporating a counter polymer, poly(dimethylsiloxane) (PDMS), induced macroscopic spinodal-type phase separation during the course of polymerization of DVB while suppressing the segregation of DVB-derived particles from the solution by living polymerization. Well-defined macroporous morphologies comprising continuous DVB-derived skeletons have thus obtained. Macropore volume and diameter were independently controlled by altering the concentrations of PDMS and the solvent. Since the present polymer gels are prepared using only the multifunctional “crosslinker”, mechanical durability against bending and compression was found to be as high as inorganic ceramics with similar morphologies and porosities.

Ag particles were generated on Ag+-doped polyimide film by ion exchanging, followed by copper deposition using metallic silver particles as seeds. The Cu layers were coated on the surface of polyimide films by electroless plating method. The surface image and morphology of Cu layers on the polyimide films were characterized with scanning electron microscopy (SEM), and atomic force microscopy (AFM). The chemical composition on the PI film was investigated energy dispersive X-ray (EDX) spectrometer.

Particles of sizes within the nano region have attracted many applications in different fields of science. In this study, the self assembly property in a selective solvent of block copolymers has been used for the preparation of polystyrene nanospheres. Sulfonated Styrene-Butadiene-Styrene (SSBS) tri block copolymer was used as a polymeric surfactant for synthesis of uniformly sized polystyrene nanoparticles using emulsion polymerization. The effects of initiator, monomer and block copolymer concentration to the molecular weight distribution and size distribution were investigated. Uniformly sized nanoparticles with a polydispersity index of 1.004 and diameter of 112.9nm was verified by Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM), respectively. Using a mixed continuous phase solution of water and methanol, it was found out that the particle size decreased relative to the increase of methanol added to the reaction solution. Associating behavior of the polyelectrolyte block copolymer in the binary solvent environment regarding size of micelle formed was reflected on the properties of the nanospheres. Nanoparticles prepared with greater methanol concentration were observed to be less than 100 nm. Size distribution was also observed to be narrower in proportion to MeOH concentration.

We compare water adsorption and desorption on ferroelectric copolymer poly(vinylidene fluoride-trifluoroethylene), and the dipole ordered polymer poly(methylvinylidene cyanide). The angle-resolved thermal desorption spectra prove that the absorbed water species interacts more strongly with poly(vinylidene fluoride-trifluoroethylene) than with poly(methylvinylidene cyanide). The angle resolved thermal desorption spectra shows large deviations from the cosine distribution for light illuminated poly(vinylidene fluoride-trifluoroethylene). Water desorption from poly(methylvinylidene cyanide) deviates from the cosine distribution without illumination.

The friction between the polymer network and the solvent water was measured by a newly designed simple apparatus where the hydrogel was mechanically constrained in a glass microcapillary. The water-flow through the hydrogel could be continuously controlled by more than ten times only by adjusting the temperature in the vicinity of the transition temperature (around the human body temperature). The concentration of polymer network and cross-linker as well as the inhomogeneity of polymer networks introduced at gelation was found to determine the overall flow velocity and the amount of change during the phase transition could be controlled by the temperature change. The principle to control the solvent flow will be discussed on the basis of the material parameters and the experimental conditions.

A novel associative polymer network with tunable rheological properties is developed based on cyclodextrin-hydrophobe inclusion. The network is formed from mixtures of two polyacrylic acid (PAA) backbone polymers, one with pendant cyclodextrin groups and one with pendant hydrophobic alkyl groups. The lifetime of the cyclodextrin-hydrophobe inclusion can be well controlled by the length of alkyl chains inserted into the cyclodextrins; also, the binary nature of cyclodextrin-hydrophobe inclusion prevents hydrophobes from forming non-stoichiometric multiple associations. This system can serve as a model associative polymer network to test associative polymers theories. Dynamic rheological properties of this mixture solution can be tuned by adding free cyclodextrins or sodium dodecylsulfate (SDS) to displace polymer to polymer associations. Dynamic moduli change three orders of magnitude from a gel state to a sol state. This polyelectrolyte system is also pH sensitive, salt sensitive and temperature sensitive. The phase behavior of this mixture solution is experimentally studied by light scattering measurements and rheology. The thermodynamics of the cyclodextrin-hydrophobe interaction is independently studied using isothermal titration calorimetry and surface plasmon resonance study.

High resolution pattern transfers in the nano-scale regime have been considerable challenges in ‘soft lithography’ to achieve nanodevices with enhanced performances. In this technology, the resolution of pattern integrations is significantly rely on the materials' properties of polydimethylsiloxane (PDMS) stamps. Since commercial PDMS stamps have shown limitations in nano-scale resolution soft lithography due to their low physical toughness and high thermal expansion coefficients, we developed stiffer, photocured PDMS silicon elastomers designed, specifically for nano-sized soft lithography and photopatternable nanofabrications.

Incorporation of ligands and metals into polymers by controlled methods yields multifunctional responsive materials. Dibenzoylmethane (dbm) is a beta-diketone ligand that binds metal and metalloid ions such as boron, iron or europium in a bidentate fashion producing complexes with one or more dbm chelates. Modification of dbm with biocompatible poly(lactic acid) (PLA) allows materials processing and leads to responsive metallobiomaterials. This is accomplished by modification of dbm with hydroxyl groups (e.g. dbmOH), that serve as initiators for lactide polymerization. Improved control is noted when dbm is protected as iron or boron complexes, namely Fe(dbmOH)3 or BF2(dbmOH). Furthermore, the iron center in iron tris(dbmOH) also functions as a catalyst for the polymerization; no tin catalyst is required. Redorange iron-centered three arm star polymers, Fe tris(dbmPLA), are obtained. Acid sensitivity of these materials provides a method for dbm ligand dissociation, demetalation and production of dbmPLA macroligands for coordination to other metals such as Eu. Currently, dbmPLA and its polymeric iron complexes are being fabricated as nanoparticles. Light emitting B and Eu dbm complexes are also under investigation. Progress in the synthesis, characterization and nanoscale fabrication of dbm ligand and metal based polymeric biomaterials is reported.

Dispersion and stability of single walled nanotubes (SWNT) is one of the inhibiting factors affecting their tailorability for various electronic, chemical and mechanical applications . The realization of these applications depends on dispersing the SWNTs in aqueous media by inducing high forces of repulsion among the nanotubes. Steric repulsions are induced to the nanotubes by attaching polyelectrolytes, like poly styrene sulfonate (PSS) and poly allyl amine hydrochloride (PAH). In this work, Self Assembly technique is employed to attach polyelectrolytes, and thereby enhance the dispersion of SWNTs in aqueous media. The steric forces produced by the attached polyelectrolytes overcome the high van der waals force of attraction between the nanotubes and aid in the nanotubes dispersion. Characterization of the dispersions with UV-Vis Spectrophotometric method in kinetic mode revealed that nanotubes treated at pH 3 are seen to be more stable than the ones treated at pH 7. The effect of pH of the polyelectrolyte solutions in the assembly and its consequence on dispersion stability is also studied with zeta potential measurements. The morphology of the films produced by drying the nanotubes in vacuum on a silicon substrate is characterized by field emission scanning electron microscopy (FESEM).

Adsorbate molecules usually carry electric dipole moments, and the magnitude can be engineered by adding polar groups. This paper investigates the dynamic domain pattern formation of multilayer dipolar molecules on a substrate under the guidance of external electric fields. The simulations reveal self-alignment, pattern conformation and the reduction of feature size in multilayer systems. A novel approach of transporting molecules on a substrate surface by reconfigurable molecular vehicles and embedded electrodes is proposed.

Nonmagnetic microspheres dispersed in a ferrofluid are denoted magnetic holes. When the spheres are confined to a monolayer between two plane, parallel plates and subjected to AC magnetic fields, they show a variety of dynamical behaviors and assemblages. The magnetic interactions between the particles and their dynamical behavior are influenced by the boundaries and the degree of confinement. We have derived analytical results for the pair-wise competing interactions, and these compare favorably with experimental results.

It is also possible to characterize the self-assembly and dynamics of the spheres by the theory of braids. It involves classifying different ways of tracing curves in space. The essentially two-dimensional motion of a sphere can be represented as a curve in a three-dimensional space-time diagram, and so several spheres in motion produce a set of braided curves. The dynamical modes can then be described in terms of braid-words. We also present a few other examples on how this system can be used to study dynamical processes.

Dilute electrostatically–Vstabilized aqueous solutions of hexa-acylated (C14) lipid A-diphosphate from Escherichia coli were prepared with low polydispersities in shape, size and charge. A high degree of ordering was exhibited for volume fractions between Φ ≅ 1.5 × 10−4 and 3.5 × 10−4. The structure factor S(Q) was strongly dependent on the particle number density, the nature of ions, e.g. Ca2+, Mg2+, K+, Na+ and H+, the effective colloidal charge (Z*), and the Debye screening length, k. The magnitude and position of the S(Q) peaks vary not only with counterions, e.g. Ca2+ or Mg2+, and concentration (nM to μM), but also with the order of their addition to the lipid A-dispersions. Different types of colloidal-crystal structures were obtained for Φ ≅ 3.5 × 10−4. The Ca2+ and K+ salts exhibited FCC type-lattices with a = 56.3 nm and 55.9 nm, whereas the Na+ and Mg2+ salts of lipid A-diphosphate formed BCC type-lattices with a = 41.5 nm and 45.5 nm, respectively.

Multiple techniques have been developed to assemble micro- or nanostructured materials into well-defined patterns. These techniques are, however, often dependent on the size, shape, composition and/or surface chemistry of the structures being patterned. We have developed a general approach to pattern materials with a wide range of physical and chemical characteristics. We are able to assemble these materials into isolated or interconnected patterns covering areas up to ∼1 mm2.

We report the integration of single wall carbon nanotube ensembles into micro-mechanical systems to realize a new carbon nanotube micro-optomechanical system (CNT-MOMS). CNT-MOM grippers were fabricated with CMOS compatible techniques involving nanotube film formation, wafer bonding, photo-lithography, plasma etching and dry release. MOM-grippers displacement of ∼24μm was obtained from a gripper of 430μm in length under infra-red laser stimulus and continuous operation of more than 100,000 cycles was acquired. The optical power consumption of the gripper operation was estimated to be as small as ∼240μW. This study is a good example of how nano-materials could be integrated into CMOS compatible techniques for applications in high performance MEMS and nanoscale actuation technologies.

3D micro-molded PDMS (polydimethylsiloxane) elastomer is widely used in MEMS. However, traditional PDMS is non-conductive and as a result is used in mostly structural applications. It is difficult to embed elastomeric, “stretchy” conductors and transduction elements in molded PDMS matrix. We report general methods for monolithic fabrication of multi-layer PDMS structures with embedded conductive and non-conductive elastomer elements. Conductive PDMS parts, made of carbon-nanotube-filled composite PDMS, can form internal elastomer wires, electrodes, heaters, and sensors. The process uses a series of PDMS patterning, micromolding, and bonding techniques. In this work we demonstrate elastomer strain gauges, capacitive pressure sensors, as well as microfluidic channels with integrated heaters and sensors.