Rozprawy doktorskie na temat „Ordered Nanocomposite”

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 260-280).
Nanocomposites, materials of heterogeneous composition with at least one of the phases having dimensions between 1-100 nm, can be produced with unique properties dependent on their composition and geometric configuration. However, it is a major challenge to precisely and simultaneously design the structure of synthetic nanocomposites at the nanoscale, microscale, and macroscale. To create advanced nanocomposites in which both structure and composition can be programmed across these disparate size regimes, we have developed a new nanoparticle-based building block, the Nanocomposite Tecton (NCT). An NCT consists of an inorganic nanoparticle core and a polymeric shell, with each chain terminating in a supramolecular binding group at the periphery of the NCT.
As each NCT contains both an inorganic nanoparticle and a polymer phase, each building block is itself a nanocomposite, and the incorporation of supramolecular binding groups allows for the directed assembly of NCTs that contain complementary binding groups. These reversible supramolecular interactions enable the assembly of NCTs into ordered arrays, and the collective behavior of the binding groups can be regulated by the dynamics of the polymer chains. The NCTs are capable of rapidly self-assembling into several different crystalline phases that are determined by the design of the building block, and are resilient against dispersity in the molecular weight of the polymer brush and the diameter of the nanoparticle cores. NCTs have been synthesized with both gold and iron oxide nanoparticle cores, indicating the ability to produce NCTs at reasonable scales.
Moreover, the incorporation of multiple nanoparticle compositions allows for the synthesis of NCT-based materials with plasmonic and magnetic properties that can affect, as well as be affected by, the assembly process. We further demonstrate that the crystallization kinetics can be modulated to induce the assembly of NCTs into faceted crystallites with micron-sized diameters, and the resulting NCT crystallites can be post-processed into bulk solids with arbitrary macroscopic shape and controlled grain size. The NCT design concept is therefore a highly modular and versatile building block capable of fabricating materials with controlled structures at the levels of atomic composition and molecular geometry, nanoscale organization, microstructure, and macroscopic form.
by Peter J. Santos.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

Chemistry
Ph.D.
This dissertation reports a simple route to synthesis nanostructured composites by immobilizing colloidal crystals (CCs) of monodisperse SiO2 spheres in crosslinked polymer network. The resulting ordered nanocomposites exhibited the highest modulus reported yet, to the best of our knowledge, for similar materials. The ordered nanocomposites were optically active and the Bragg diffracted light in a NIR region and wavelength of the Bragg peak could be tuned simply by changing the silica concentration in the composite. They also exhibited intense angle dependent iridescence.
Temple University--Theses

Block copolymers exhibit a wealth of morphologies that continue to find ubiquitous use in a diverse variety of mature and emergent (nano)technologies, such as photonic crystals, integrated circuits, pharmaceutical encapsulents, fuel cells and separation membranes. While numerous studies have explored the effects of molecular confinement on such copolymers, relatively few have examined the sub-microdomain structure that develops upon modification of copolymer molecular architecture or physical incorporation of nanoscale objects. This work will address two relevant topics in this vein: (i) bidisperse brushes formed by single block copolymer molecules and (ii) copolymer nanocomposites formed by addition of molecular or nanoscale additives. In the first case, an isomorphic series of asymmetric poly(styrene-b-isoprene-b-styrene) (S1IS2) triblock copolymers of systematically varied chain length has been synthesized from a parent SI diblock copolymer. Small-angle x-ray scattering, coupled with dynamic rheology and self-consistent field theory (SCFT), reveals that the progressively grown S2 block initially resides in the I-rich matrix and effectively reduces the copolymer incompatibility until a critical length is reached. At this length, the S2 block co-locates with the S1 block so that the two blocks generate a bidisperse brush (insofar as the S1 and S2 lengths differ). This single-molecule analog to binary block copolymer blends affords unique opportunities for materials design at sub-microdomain length scales and provides insight into the transition from diblock to triblock copolymer (and thermoplastic elastomeric nature). In the second case, I explore the distribution of molecular and nanoscale additives in microphase-ordered block copolymers and demonstrate via SCFT that an interfacial excess, which depends strongly on additive concentration, selectivity and relative size, develops. These predictions are in agreement with experimental findings. Moreover, using a poly(styrene-b-methyl methacrylate) (SM) diblock copolymer with an order-disorder transition temperature (TODT) of 186°C, we find that the addition of clustered and discrete nanoparticles of varying size and surface selectivity can cause TODT to generally decrease, but occasionally increase. Also experimenting with a poly(styrene-b-isoprene) (SI) diblock copolymer with an TODT of 116°C, we find that the addition of smaller nanoparticles at small volume fractions effect the TODT more profoundly. The latter unexpected results are likewise predicted by SCFT and provide a unique strategy by which to improve the nanostructure stability of block copolymers by physical means.

Within the field of modern technology, nanomatrials, such as nanoparticles (NP), nanorods (NR), quantum dots (QD) etc. are, probably, the most prominent and promising candidates for current and future technological applications. The interest in nanomaterials arise not only form the continuous tendency towards dimensions minimisation of electronic devices, but also due to the fact, that new and, often, unique properties are acquired by the matter at the length scale between 1 and 100 nm. The ability to organize nanoparticles into ordered arrays extends the range of useful NP-based systems that can be fabricated and the diversity of functionalities they can serve. However, in order to successfully exploit nanoparticle assemblies in technological applications and to ensure efficient scale-up, a high level of direction and control is required. Recently, block copolymers (BCP) have attracted much attention as a powerful and very promising tool for creation of nanoscale ordered structures owing to their self-assembling properties. In addition, these systems offer the possibility to fabricate nanostructured composite materials via incorporation of certain nanoadditives (i.e. NPs). The concept is that by selective inclusion of the nanoparticles into one of the blocks of a self-assembling copolymer, the nanoparticles are forced into a defined spatial arrangement determined by the phase morphology of the block copolymer. In present work self-assembling phenomena of block copolymers was exploited to fabricate binary (NP/BCP) and ternary (NP1/NP2/BCP) composites, filled with pre-synthesized nanoparticles of various nature. Polystyrene-block-polyvinylpyridine block copolymers (PS-b-PVP) of various composition and molecular weight were used for fabrication of nanocomposites. The first part of the thesis focuses on fabrication of functional BCP-based composites containing magnetic nanoparticles (MNP), selectively assembled within one of the blocks of BCP matrix. Magnetic nanoparticles (MNPs) were selected among others since, as for today, there is the least number of successful results reported in literature on their selective incorporation into one of the phases of a BCP matrix. From the application point of view fabrication of periodic arrays of “magnetic domains” with periodicity on nanometer scale is also of interest for potential use in high-density magnetic data storage devices. For this purpose, ferrite-type MNP (Fe3O4, CoFe2O4) having apparent affinity toward polyvinylpyridine (PVP) phase were prepared using simple one-pot synthesis. Highly selective nanoparticles segregation into PVP domains of BCP was achieved owing to the presence of sparse stabilizing organic shell on the nanoparticles surface. Importantly, as-prepared MNPs did not require any additional surface modification step to acquire affinity towards PVP phase. Appropriate selection of annealing conditions allowed to produce patterns of nearly perfect degree of lateral order over relatively large surface large area (more than 4 sq µm). The second task of present work was fabrication of ternary NP1/NP2/BCP hybrid composites with two different types of nanoparticles being selectively localized in different microdomains of phase segregated block copolymer matrix. So far as only few studies have been reported on developing of approaches toward ternary composites, creation of alternative and straight forward routes toward such systems is still a challenge. In the frame of this part of present work, silver nanoparticles (AgNPs) covered with polystyrene shell were prepared, with the purpose to be incorporated into polystarene phase of phase separated PS-b-PVP block copolymer matrix. Two different approaches were tested to achieve desired three-component system. First, supposed simple blending of block copolymer and two kinds of nanoparticles having specific affinity toward different blocks of BCP in common solvent. After preparation of MNP/AgNP/BCP composite thin film and subsequent solvent vapour annealing, different domains of microphase segregated PS-b-PVP BCP were filled with different type of nanoparticles. Alternatively, step-wise approach for nanoparticles incorporation was developed and implemented for successful selective nanoparticles incorporation. For this purpose polystyrene stabilized AgNPs (i.e. NP1) were initially mixed with PS-b-PVP BCP to produce composite thin films having nanoparticles selectively located within PS microdomains, while citrate-stabilized second type nanoparticles (i.e NP2) were deposited from their aqueous solutions into PVP domains of AgNP/PS-b-PVP composites. By partition of nanoparticles incorporation procedure into two distinct steps it was also possible to increase effective loading of each type of NPs into BCP matrix.

Organic-inorganic nanostructured composites are nowadays integrated in the field of material science and technology. They are used as advanced materials directly or as precursors to novel composites with potential applications in optics, mechanics, energy, catalysis and medicine. Many properties of these complex materials depend on conformational rearrangements in their inherently dynamic organic parts. The focus of this thesis is on the study of the molecular mobility in ordered nanostructured composites and lyotropic mesophases and also on the development of relevant solid-state NMR methodologies. In this work, a number of new experimental approaches were proposed for dipolar NMR spectroscopy for characterizing molecular dynamics with atomic-level resolution in complex solids and liquids. A new acquisition scheme for two-dimensional dipolar spectroscopy has been developed in order to expand the spectral window in the indirect dimension while using limited radio-frequency power. Selective decoupling of spin-1 nuclei for sign-sensitive determination of the heteronuclear dipolar coupling has been described. A new dipolar recoupling technique for rotating samples has been developed to achieve high dipolar resolution in a wide range of dipolar coupling strength. The experimental techniques developed herein are capable of delivering detailed model-independent information on molecular motional parameters that can be directly compared in different composites and their bulk analogs. Solid-state NMR has been applied to study the local molecular dynamics of surfactant molecules in nanostructured organic-inorganic composites of different morphologies. On the basis of the experimental profiles of local order parameters, physical motional models for the confined surfactant molecules were put forward. In layered materials, a number of motional modes of surfactant molecules were observed depending on sample composition. These modes ranged from essentially immobilized rigid states to highly flexible and anisotropically tumbling states. In ordered hexagonal silica, highly dynamic conformationally disordered chains with restricted motion of the segments close to the head group have been found. The results presented in this thesis provide a step towards the comprehensive characterization of the molecular states and understanding the great variability of the molecular assemblies in advanced nanostructured organic−inorganic composite materials.

QC 20150225

Magnetic nano-particles dispersed in a non-magnetic matrix is promising for storage technology. Additionally, such magnetic nano composite (MNC) materials have potential applications in the field of telecommunication, nano-capacitors, high frequency filters and bio-medical domains. Conventionally, Nano composite (NC) material comprises of sub 100 nm particles randomly distributed in a matrix material. The shape, size and distribution of the particles play an important role in determining the physical properties. The aim of this work is to develop ordered and aligned magnetic nanocomposite and explain composite behaviors in terms of behaviors of single nanowire. Hence, ordered and aligned ferromagnetic Nickel nanophase homogeneously dispersed in alumina matrix is developed. The matrix phase separates the magnetic nanophase and modifies the magnetic interaction, electrical transport and mechanical strength. Anodization of aluminum is used to fabricate nano-porous alumina matrix. Under certain controlled electrochemical conditions, anodization of aluminum results in a highly ordered hexagonal porous structure. Nickel is electrochemically deposited into these pores resulting in uniformly distributed magnetic nanowires of high aspect ratio. This ordered MNC is characterized for its mechanical, electrical, magnetic and tribological properties to explore the possibility of using for various possible applications with the focus to study the feasibility for magnetic storage application. Ordered porous alumina is formed by a two-step anodization process. By optimizing the anodization conditions, the thickness and the pore size of the porous alumina layer is controlled. The interface between the porous structure and aluminum substrate comprise of thick and non-conducting barrier oxide layer. However, to deposit metal into the pores using electrodeposition technique, a conducting path should be established through this barrier layer. Hence, the barrier layer is thinned by reducing the anodizing voltage in steps and subsequent chemical etching. The pores are filled with Ni by pulsed electro-deposition. Uniform deposition is achieved by optimizing the pulse duty cycle. From electrical resistance measurements, the resistance of single nanowire is found to vary between 400 Ω to 700 Ω. Whereas, the composite resistance is measured to be about few ohms. The resistivity of the Ni within composite is 2.9 × 10-7 Ω-m, which is two orders higher than the bulk Ni, confirming larger scattering events at smaller scale. Electrical resistivity further gave information on structural details of the as developed MNC. It is found that during low frequency measurements only a fraction of nanowires take part in conduction. Rest of the nanowires are not conducting as a capacitive barrier layer separates Ni nanowire from base aluminum. Also, magneto-capacitance response at high carrier frequency is observed. Magnetic response of the nanocomposite is measured using magnetic force microscopy and magnetoresistance measurement. It is found that neighboring magnetic domains are dipole coupled which makes it difficult to change magnetization state of the composite compared to single Ni nanowire. This has important implication for magnetic storage application. Mechanical hardness and elastic modulus of the single suspended nanostructure are characterized using atomic force microscopy (AFM) based indentation technique. Using nanoindentation it is found that for the MNC, inclusion of ductile metal improves the hardness of the brittle matrix by 40%. Finally, a macro scale experiment is designed to mimic magnetic read / write operation by allowing electrical current to flow from probe to sample under static load and dynamic load conditions. These experiments helped us to understand the effect of static and frictional force on the electrical response. Static and reciprocating electrical contact resistance measurement tool is developed. Monitoring contact resistance helps to understand, evolution of the real contact area, which affects both the electrical and tribological behaviors. It is observed that, the high electrical field increases wear rate of the composite. Subsequent chemical etching. The pores are filled with Ni by pulsed electro-deposition. Uniform deposition is achieved by optimizing the pulse duty cycle. From electrical resistance measurements, the resistance of single nanowire is found to vary between 400 Ω to 700 Ω. Whereas, the composite resistance is measured to be about few ohms. The resistivity of the Ni within composite is 2.9 × 10-7 Ω-m, which is two orders higher than the bulk Ni, confirming larger scattering events at smaller scale. Electrical resistivity further gave information on structural details of the as developed MNC. It is found that during low frequency measurements only a fraction of nanowires take part in conduction. Rest of the nanowires are not conducting as a capacitive barrier layer separates Ni nanowire from base aluminum. Also, magneto-capacitance response at high carrier frequency is observed. Magnetic response of the nanocomposite is measured using magnetic force microscopy and magnetoresistance measurement. It is found that neighboring magnetic domains are dipole coupled which makes it difficult to change magnetization state of the composite compared to single Ni nanowire. This has important implication for magnetic storage application. Mechanical hardness and elastic modulus of the single suspended nanostructure are characterized using atomic force microscopy (AFM) based indentation technique. Using nanoindentation it is found that for the MNC, inclusion of ductile metal improves the hardness of the brittle matrix by 40%. Finally, a macro scale experiment is designed to mimic magnetic read / write operation by allowing electrical current to flow from probe to sample under static load and dynamic load conditions. These experiments helped us to understand the effect of static and frictional force on the electrical response. Static and reciprocating electrical contact resistance measurement tool is developed. Monitoring contact resistance helps to understand, evolution of the real contact area, which affects both the electrical and tribological behavior. It is observed that, the high electrical field increases wear rate of the composite.

Over the past few decades there has been great interest in exploring alternatives to conventional separation methods due to their high cost and energy requirements. Membranes offer a potentially attractive alternative as they potentially address both of these points. The overarching theme of this dissertation is to design nanocomposite membranes for processes where existing separation schemes are inadequate. This dissertation focuses on three challenges: 1) designing organic-inorganic hybrid membranes for reverse-selective removal of alkanes from light gases, 2) defect-free inorganic nanocomposite membranes that have uniform pores, and 3) nanocomposite membranes for minimizing protein fouling in microfiltration applications. Reverse-selective gas separations that preferentially permeate larger/heavier molecular species based on their greater solubility have attracted considerable recent attention due to both economic and environmental concerns. In this study, dendrimer-ceramic hybrid membranes showed exceptionally high propane/nitrogen selectivities. This result was ascribed to the presence of stable residual solvent that affects the solubility of hydrocarbon species. Mesoporous silica-ceramic nanocomposite membranes have been fabricated to provide defectless mesoporous membranes. As mesoporous silica is iteratively synthesized in the ceramic macropores, the coating method and the surfactant removal step significantly affected permeance and selectivity. It was also shown that support layers can cause a lower selectivity than Knudsen limit. Membrane fouling which results from deposition and nonspecific adsorption of proteins on the membrane surface is irreversible in nature, and results in a significant decrease in the membrane performance. To address this problem, two approaches were explored: 1) control of the surface chemistry tethering alumina membranes with organic components and 2) development of a novel photocatalytic membrane that exhibits hydrophilicity and can be easily regenerated. Both approaches can offer a viable route to the synthesis of attractive membranes, in that 1) the density of protein-resistant organic groups such as PEG is controllable by changing scaffolds or synthesis conditions and 2) the photocatalytic nanocomposite membranes can open the way for a new regeneration method that is environmentally benign.

Anodisation is a surface treatment process, commonly used to form a protective oxide coating on the surface of metals like aluminium. Anodised coatings, being grown out of the base metal have excellent interface strength but are porous and brittle. Porosity of the coating reduces the hardness and the brittle nature of the oxide induces cracking. In practice, the pores are typically filled with organic dye and sealed. Under certain controlled electrochemical conditions, anodisation results in a highly ordered hexagonal porous structure in pure aluminium. In this work, we explore the possibility of using this ordered porous alumina to form a novel metal nanocomposite as a tribological coating. By optimizing the nonporous structure and tuning the electrodeposition process, we uniformly filled the ordered pores with copper. We have measured the hardness of the resulting ordered and aligned nanocomposite. We explore the possibility of using this composite coating for tribological applications by carrying out some preliminary reciprocating wear test. Ordered porous alumina layer is formed by a two-step anodisation process. By optimizing the anodisation conditions, we control the thickness of the coating and the pore size. The interface of the porous structure and aluminium substrate is defined by a non-conducting dense barrier oxide layer. However, to deposit metal into the pores, a conducting path should be established through the barrier layer. One possibility is to etch out the bottom of the pores at the cost of the interface strength and losing out on the main advantage of anodised coatings. To be able to fill metal without this sacrifice, we utilised the dendritic structure in the barrier layer formed by a step-wise reduction of voltage towards the end of anodisation process. Optimisation of this dendritic structure led to uniform deposition of metal into pores, achieved by pulsed electrodeposition. In pulse lectrodeposition, a positive pulse is applied to remove accumulated charge near to the bottom of pores, followed by a negative pulse to deposit metal and a delay to allow diffusion of ions. By optimising the pulse shape and duration, we have achieved uniform growth of metal into pores. Further, monitoring the deposition current helped us to identify and control different phases of growth of the nanowire. The properties of the porous alumina and the nanocomposite were measured by nanoindentation. The deformation characteristics were obtained by observing the indents in a FE-SEM. We find that dendritic modification of interface has very little effect on the hardness of the porous alumina layer. We also found that the porous alumina deformed either by compaction or by forming circumferential and radial cracks. When copper is filled in the nano pores, the hardness increased by 50% and no circumferential cracks were found up to the load of 10 mN for a film thickness of about 1 µm. Coefficient of friction of the coating reciprocated against steel in dry condition is found to be around 0.4. Minimal wear was observed from the SEM images of wear track. In summary, a novel nanocomposite coating with ordered porous alumina as matrix embedded with aligned metal nano rods has been developed. This was achieved by optimally modifying the barrier layer without sacrificing the interfacial strength. Uniform coating has been achieved over an area of 10 mm x 10 mm. The coating is found to have high hardness and high wear resistance.

Anodisation is a surface treatment process, commonly used to form a protective oxide coating on the surface of metals like aluminium. Anodised coatings, being grown out of the base metal have excellent interface strength but are porous and brittle. Porosity of the coating reduces the hardness and the brittle nature of the oxide induces cracking. In practice, the pores are typically filled with organic dye and sealed. Under certain controlled electrochemical conditions, anodisation results in a highly ordered hexagonal porous structure in pure aluminium. In this work, we explore the possibility of using this ordered porous alumina to form a novel metal nanocomposite as a tribological coating. By optimizing the nonporous structure and tuning the electrodeposition process, we uniformly filled the ordered pores with copper. We have measured the hardness of the resulting ordered and aligned nanocomposite. We explore the possibility of using this composite coating for tribological applications by carrying out some preliminary reciprocating wear test. Ordered porous alumina layer is formed by a two-step anodisation process. By optimizing the anodisation conditions, we control the thickness of the coating and the pore size. The interface of the porous structure and aluminium substrate is defined by a non-conducting dense barrier oxide layer. However, to deposit metal into the pores, a conducting path should be established through the barrier layer. One possibility is to etch out the bottom of the pores at the cost of the interface strength and losing out on the main advantage of anodised coatings. To be able to fill metal without this sacrifice, we utilised the dendritic structure in the barrier layer formed by a step-wise reduction of voltage towards the end of anodisation process. Optimisation of this dendritic structure led to uniform deposition of metal into pores, achieved by pulsed electrodeposition. In pulse lectrodeposition, a positive pulse is applied to remove accumulated charge near to the bottom of pores, followed by a negative pulse to deposit metal and a delay to allow diffusion of ions. By optimising the pulse shape and duration, we have achieved uniform growth of metal into pores. Further, monitoring the deposition current helped us to identify and control different phases of growth of the nanowire. The properties of the porous alumina and the nanocomposite were measured by nanoindentation. The deformation characteristics were obtained by observing the indents in a FE-SEM. We find that dendritic modification of interface has very little effect on the hardness of the porous alumina layer. We also found that the porous alumina deformed either by compaction or by forming circumferential and radial cracks. When copper is filled in the nano pores, the hardness increased by 50% and no circumferential cracks were found up to the load of 10 mN for a film thickness of about 1 µm. Coefficient of friction of the coating reciprocated against steel in dry condition is found to be around 0.4. Minimal wear was observed from the SEM images of wear track. In summary, a novel nanocomposite coating with ordered porous alumina as matrix embedded with aligned metal nano rods has been developed. This was achieved by optimally modifying the barrier layer without sacrificing the interfacial strength. Uniform coating has been achieved over an area of 10 mm x 10 mm. The coating is found to have high hardness and high wear resistance.

This research aims to control the configuration and properties of functional, conjugated polymer systems by tuning the composite nanostructure and molecular interactions. This is accomplished by self-assembly of specific organic and inorganic building blocks. New nanocomposite synthesis schemes are demonstrated for poly(2,5-thienylene ethynylene) (PTE) and polydiacetylene (PDA) that focus on the combination of amphiphiles with hydrophobic and hydrophilic components. The weak molecular interactions between these building blocks result in spontaneous organization into highly ordered amorphous and crystalline structures. Emulsion polymerization, simultaneous monomer incorporation during self-assembly, and PDA supramolecular assembly synthesis paradigms will be discussed. By controlling the interactions, synthesis conditions, and building blocks; this research tunes the structure, molecular conformation, and therefore the optical properties of the resultant composites. Notable results include control of PTE particle size; direction of PTE/silica nanocomposite mesostructure; synthesis of free-standing mesoporous PTE; completely reversible thermochromatic and structural transitions in PDA assemblies; chemical and solvent sensing with PDA; and tunable mechanochromatic response with PDA composites. The synthesis schemes developed in this dissertation research program provide a general route to prepare functional materials with beneficial properties such as thermally controlled optical adsorption, self-healing mesostructure, molecular recognition, and mechanically induced color changes for the detection of damage in plastic composites
acase@tulane.edu

碩士
國立中央大學
化學系
85
In this investigation, we prepared more ordered polyaniline in the interlayer space of the layer materials and synthesized organic-inorganic nanocomposites by host-guest reactions. Infrared spectra and X-ray diffraction patterns showed that the organic guests are indeed insertedin the interlayer space of layer materials. The intercalation of anilinein HNbTiO5 and HNb3O8 results in two layers of aniline molecules in the interlayer space. When aniline was poly-merized to polyaniline, single layer polymer was formed. From the thermogravimetric analysis, we estimated the stoichiometries of these compounds are (C6H5NH3)0.31NbTiO5 , (C6H5NH3)0.72Nb3O8 , (PANI)0.17NbTiO5 and (PANI)0.14Nb3O8 .When V2O5 xerogel was reacted with furfuryl alcohol, PPV precursor and water-soluble poly-aniline, the interlayer space of V2O5 host increased 4 ~ 5 angstrom. The results implied that the aromatic rings of organic guests were parallel to the layer of the host. When V2O5 reacted with o-phenylenediamine, the guest molecules were polymerized to poly-o-phenylenediamine, and the resulting product was a biphasic structure. Some of the poly-o- phenylenediamine chains have their aromatic rings parallel to the layer of the host and some are perpendicular to the host layer. The shift of Infrared absorption peaks of guest moleculeinside the host is an additional evidence to prove that these organic guests are confined inthe restricted space. The stoichiometry of these nanocomposites is (FA)0.16V2O5 0.39H2O,( PDA)0.20V2O5 0.4H2O,(PPV precursor)0.28V2O5 1.2H2O and (PAPSANaH)0.13V2O5 0.79H2O respectively. The conductivity of these nanocomposites was quite different, ranged from 0.001 to 1 S/cm.

Nanocomposites are of interest for numerous applications such as catalysis, photonic band gap materials, and waveguides. Ionomers and diblock copolymers have previously been used as templates for ordered nanocomposites. However, these processes have been limited to reactions within thin films or coprecipitation methods from solution due to mass transport limitations of ceramic and metallic precursors within the solid templates. This issue has been addressed by fabricating ordered nanocomposites using phase selective deposition of precursors into supercritical carbon dioxide (SC-CO2) swollen polymeric templates. SCCO2 is an effective plasticizing agent for most polymers and enhances mass transport of the precursors into polymeric templates while preserving the initial template morphology. By proper choice of template material, the precursor can be selectively bound within one phase of the template and reacted to produce the desired material. The resulting composite contains nanoparticles arranged in an ordered morphology dictated by the template over bulk dimensions. Polymer/ceramic and polymer/metal nanocomposites have been successfully synthesized using this technique.

Hierarchically structured inorganic materials are everywhere in nature. From unicellular aquatic algae such as diatoms to the bones and/or cartilage that comprise the skeletal systems of vertebrates. Complex mechanisms involving site-specific chemistries and precision kinetics are responsible for the formation of such structures. In the synthetic realm, reproduction of even the most basic hierarchical structure effortlessly produced in nature is difficult. However, through the utilization of self-assembling structures or "templates", such as polymers or amphiphilic surfactants, combined with some favorable interaction between a chosen inorganic, the potential exists to imprint an inorganic material with a morphology dictated via synthetic molecular self-assembly. In doing so, a very basic hierarchical structure is formed on the angstrom and nanometer scales. The work presented herein utilizes the self-assembly of either surfactants or block copolymers with the desired inorganic or inorganic precursor to form templated inorganic structures. Specifically, mesoporous silica spheres and copolymer directed calcium phosphate-polymer composites were formed through the co-assembly of an organic template and a precursor to form the desired mesostructured inorganic. For the case of the mesoporous silica spheres, a silica precursor was mixed with cetyltrimethylammonium bromide and cysteamine, a highly effective biomimetic catalyst for the conversion of alkoxysilanes to silica. Through charge-based interactions between anionic silica species and the micelle-forming cationic surfactant, ordered silica structures resulted. The incorporation of a novel, effective catalyst was found to form highly condensed silica spheres for potential application as catalyst supports or an encapsulation media. Ordered calcium phosphate-polymer composites were formed using two routes. Both routes take advantage of hydrogen bonding and ionic interactions between the calcium and phosphate precursors and the self-assembling copolymer template. Some evidence suggests that the copolymer morphology remained in the composite despite the known tendency for calcium phosphates to form highly elongated crystalline structures with time, as is commonly the case for synthetic hydroxyapatites. Such materials have obvious application as bone grafts and bone coatings due, in part, to the osteoconductive nature of calcium phosphate as well as to the mesoporosity generated through the cooperative assembly of the block copolymer and the inorganic. Future work, including potential experiments to determine osteoconductivity of as-prepared composites, is also presented herein.

Hierarchically structured inorganic materials are everywhere in nature. From unicellular aquatic algae such as diatoms to the bones and/or cartilage that comprise the skeletal systems of vertebrates. Complex mechanisms involving site-specific chemistries and precision kinetics are responsible for the formation of such structures. In the synthetic realm, reproduction of even the most basic hierarchical structure effortlessly produced in nature is difficult. However, through the utilization of self-assembling structures or "templates", such as polymers or amphiphilic surfactants, combined with some favorable interaction between a chosen inorganic, the potential exists to imprint an inorganic material with a morphology dictated via synthetic molecular self-assembly. In doing so, a very basic hierarchical structure is formed on the angstrom and nanometer scales. The work presented herein utilizes the self-assembly of either surfactants or block copolymers with the desired inorganic or inorganic precursor to form templated inorganic structures. Specifically, mesoporous silica spheres and copolymer directed calcium phosphate-polymer composites were formed through the co-assembly of an organic template and a precursor to form the desired mesostructured inorganic. For the case of the mesoporous silica spheres, a silica precursor was mixed with cetyltrimethylammonium bromide and cysteamine, a highly effective biomimetic catalyst for the conversion of alkoxysilanes to silica. Through charge-based interactions between anionic silica species and the micelle-forming cationic surfactant, ordered silica structures resulted. The incorporation of a novel, effective catalyst was found to form highly condensed silica spheres for potential application as catalyst supports or an encapsulation media. Ordered calcium phosphate-polymer composites were formed using two routes. Both routes take advantage of hydrogen bonding and ionic interactions between the calcium and phosphate precursors and the self-assembling copolymer template. Some evidence suggests that the copolymer morphology remained in the composite despite the known tendency for calcium phosphates to form highly elongated crystalline structures with time, as is commonly the case for synthetic hydroxyapatites. Such materials have obvious application as bone grafts and bone coatings due, in part, to the osteoconductive nature of calcium phosphate as well as to the mesoporosity generated through the cooperative assembly of the block copolymer and the inorganic. Future work, including potential experiments to determine osteoconductivity of as-prepared composites, is also presented herein

The fractional–order capacitors add an additional degree of freedom over conventional capacitors in circuit design and facilitate circuit configurations that would be impractical or impossible to implement with conventional capacitors. We propose a generic strategy for fractional-order capacitor fabrication that integrates layers of conductive, semiconductor and ferroelectric polymer materials to create a composite with significantly improved constant phase angle, constant phase zone, and phase angle variation performance. Our approach involves a combination of dissolving the polymer powders, mixing distinct phases and making a film and capacitor of it. The resulting stack consisting of ferroelectric polymer-based composites shows constant phase angle over a broad range of frequencies. To prove the viability of this method, we have successfully fabricated fractional-order capacitors with the following: nanoparticles such as multiwall carbon nanotube (MWCNT), Molybdenum sulfide (MoS2) inserted ferroelectric polymers and PVDF based ferroelectric polymer blends. They show better performance in terms of fabrication cost and dynamic range of constant phase angle compared to fractional order capacitor from graphene percolated polymer composites. These results can be explained by a universal percolation model, where the combination of electron transport in fillers and the dielectric relaxation time distribution of the permanent dipoles of ferroelectric polymers increase the constant phase angle level and constant phase zone of fractional-order capacitors. This approach opens up a new avenue in fabricating fractional capacitors involving a variety of heterostructures combining the different fillers and different matrixes.