[PDF] Directed Assembly Of Block Copolymer Films Via Surface Energy Tunable Elastomers eBook

Author : Arzu Hayirlioglu
Publisher :
Page : 138 pages
File Size : 23,77 MB
Release : 2014
Category : Block copolymers
ISBN :

GET BOOK

Ordering of block copolymer (BCP) thin films has been great interest for potential applications due to nanometer scale size self-assembly pattern formation. Numerous methods (chemical, physical, etc.) have been developed to create desired alignment and ordering properties in such block copolymer systems. However, the drawback of most current technologies such as brittleness and lack conformability to different surfaces makes them difficult to implement new emerging high-tech flexible technologies. On the other hand, there is a lack of knowledge in block copolymer wettability characteristics and morphological behavior on soft substrates which makes them attractive to explore for further investigations. A notable challenge in this regard is that successful deployment of BCPs for applications requires an understanding of BCP ordering properties on flexible substrate as a function of their surface chemistry, topography including patterning, roughness, stiffness, modulus and thermal conductivity, etc. Therefore, the general purpose of this research is to investigate the thermodynamics and kinetics of directed assembly of cylinder and lamellar forming polystyrene-block-polymethlymethacrylate (PS-b-PMMA) diblock copolymer films on elastomeric polydimethylsiloxane (PDMS) substrates with controlled surface energy and substrate topography. In first part, wettability characteristics of cylinder and lamellae forming PS-b-PMMA thin films versus surface energy of elastomeric PDMS substrates were increasing surface energy of PDMS by tuning with Ultraviolet Ozone (UVO) exposure and elasticity by varying the crosslinking concentration. In this extended wetting regime gradual perpendicular to parallel orientation change was shown for lamellar BCP films unlike cylindrical films where the transition was very sharp, reflecting lamellar BCP intrinsic stability over a wider range of substrate surface energy, consistent with theoretical estimates. In second part of the study, we extended the part on wettability characteristics of polystyrene (PS) homopolymer and PS-b-PMMA block copolymer thin films on flat, periodic and non-periodic nanopatterned elastomeric PDMS substrates. We discovered creating non-periodically nanopatterned surface properties induced retardation of BCP dewetting and mostly eliminate on periodically nanopatterned surface properties without any surface chemistry modification. Time kinetic study results also showed the patterning has a slowing down effect on dewetting mechanism for both homopolymer and block copolymer systems and dewetted droplet shape. In final part of this study, we focused on block copolymer morphology on periodically and non-periodically (rough) patterned elastomeric PDMS substrates with and without tuning the substrate surface energy via UVO exposure. The regular uniform film properties were achieved with parallel or perpendicular microdomain orientation to the substrate at even imcommensurate thicknesses which normally shows island and holes on flat surfaces. In addition to the bottom pattern confinement effect on BCP ordering, uniform size patterned elastomeric top capping layer was also used. Mixed or long range ordered structures were obtained with different annealing conditions.

Author :
Publisher :
Page : 11 pages
File Size : 47,53 MB
Release : 2016
Category :
ISBN :

GET BOOK

Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity ([epsilon]r) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. Lastly, this approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

Author : David Allen Rider
Publisher :
Page : 598 pages
File Size : 47,32 MB
Release : 2007
Category :
ISBN : 9780494527382

GET BOOK

A series of well-defined polystyrene-block-poly(ferrocenylethylmethylsilane) (PS-b-PFEMS) diblock copolymers was synthesized. Both PFEMS and PS- b-PFEMS were shown to be amorphous due to the atactic nature of the PFEMS. As a result, PS- b-PFEMS readily undergo solid-state self-assembly in the bulk producing a spectrum of ordered nanometer sized iron-rich morphologies. When cylinder-forming PS-b-PFEMSs were studied in thin films, well-ordered arrays of hexagonally packed iron-rich cylindrical microdomains oriented either parallel to or normal to the substrate were produced. The orientation was found to depend strongly on the film thickness and/or the conditions of annealing. The etching of these films using (i) reactive plasmas, and (ii) an oxidative chemical wet etch technique were investigated. Using (i), surface-patterned magnetic ceramics were produced as well as a nanotextured silver metal film. The latter was found to dramatically enhance the Raman spectroscopy of an adsorbed analyte molecule. Using (ii), nanoporous polystyrene films were generated by the quantitative elimination of PFEMS domains by exposure to a nucleophilic non-solvent under oxidizing conditions.Thin films of PS-b-PFEMS generated efficient iron nanoparticle catalysts for single-walled carbon nanotube (SWNT) growth via a chemical vapor deposition growth process. The kinetics of the formation of iron catalysts from PS- b-PFEMS and PFEMS were compared. Despite the lower iron content for PS-b -PFEMS films, more active iron sites were produced. Additionally, the tube diameter and density were tunable by adjusting the chain lengths of polyferrocenylsilane- block-polysiloxanes in thin films. Lastly, high-throughput field-effect SWNT transistors have been fabricated with more than 160 individually addressable devices on a chip.The influence of strong 3D confinement on the self-assembly of PS-b-PFEMS was studied. Both silica colloidal crystals and silica inverse colloidal crystals were used for directing the self-assembly. Unusual morphologies, such as concentric shells and branched lamellae, resulted from the interaction of the lamellar-forming PS-b-PFEMS with the high surface area templates. In addition, the control of the 3D confined morphology of cylinder-forming PS-b-PFEMS was demonstrated through mediation of the interfacial interactions within the colloidal crystal.For solution state self-assembly, PS-b -PFEMSs and polystyrene-block-poly(ferrocenylmethylphenylsilanes) (PS-b-PFEMSs) were stoichiometrically oxidized in solution. Due to a redox-induced polarity change for the PFEMS and PFMPS blocks, self-assembly into well-defined spherical micelles occurred. The micelles, composed of a core of partially oxidized PFS segments and a corona of PS, disassembled when treated with a reducing agent and regenerated unassociated free chains.Lastly, the photochemical treatment of metal-containing ferrocenophane monomers with low energy Pyrex-filtered light from a mercury lamp (lambda > 310 nm) or bright sunlight in the presence of an anionic initiator led to living polymerizations in which the conversion and molecular weight of the resulting polymer was controlled by irradiation time. The polymerization proceeded via attack of the initiator or propagating anion on the iron atom of the photoexcited monomer. The formation of functional block copolymer architectures was possible when the light is alternately switched on and off in between the sequential addition of different monomers.

Author : Namita Roy Choudhury
Publisher : Royal Society of Chemistry
Page : 297 pages
File Size : 48,37 MB
Release : 2022-04-20
Category : Science
ISBN : 1839161027

GET BOOK

Elastomeric proteins are ubiquitous in nature, where they have evolved precise structures and properties that are necessary to perform specific biological roles and functions. This book emphasizes the impact of amino acid sequence on modulating protein structure, properties, and function. Examples include conformational ensemble dynamics, environmental responsiveness, self-assembly, physico-mechanical properties, morphology, and properties tailored for biomedical applications. This foundational framework is not only critical to advance scientific understanding and knowledge on elastomeric proteins but also enables the conceptualization, rational design, and development of biosynthetic elastomers and their analogous polypeptides for a variety of applications. Edited and contributed by pioneering researchers in the field, the book provides a timely overview of the materials, along with the synthesis techniques, the unique characteristics of elastomeric proteins, and biomedical and industrial applications. The book will provide a reference for graduate students and researchers interested in designing biomimetic proteins tailored for various functions.

Author : Li-Chen Cheng (Ph.D.)
Publisher :
Page : 188 pages
File Size : 28,61 MB
Release : 2019
Category :
ISBN :

GET BOOK

Self-assembly of block copolymers (BCPs) is emerging as a promising route for numerous technological applications to fabricate a variety of nanoscopic structures. The resulting feature sizes range from a few to several hundred nanometers, and are readily tunable by varying the molecular weights of block copolymers. Directed self-assembly of block copolymer is an effective way to pattern periodic arrays of features with long-range order, to generate complex patterns, and to multiplicatively increase the pattern density and resolution that are far beyond the limit of conventional lithography. Despite of the significant progress in the area of directed self-assembly in recent years, critical research problems regarding the dimension scalability toward sub-10-nm regime and large feature sizes on hundreds of nanometers scale as well as the capability of generating complex device-oriented patterns remain challenging. In this thesis, BCP systems, including high-v BCPs that are capable of self-assembling into extreme small and large feature sizes as well as those with more complex block architectures, are identified and studied in order to understand how those materials may be processed and directed selfassembly to bridge the patterning size spectrum between nano- and micro-fabrication. Another focus is placed on the scientific exploration of directed self-assembly of triblock terpolymers and the investigation on the mechanisms that regulate the scaling and geometry of self-assembled patterns. A comprehensive understanding about self-assembly of BCP thin films will enable developing device-oriented geometries, manipulating BCPs phase behavior, and incorporating new functional materials for a wider range of applications. In the meanwhile, optimizing the processing condition of self-assembly of various BCPs is essential to confirm viability of the directed self-assembly of block copolymers process in manufacturing.