17 research outputs found
Order in Thin Films of Diblock Copolymers by Supramolecular Assembly
Thin membranes with dense periodic arrays of nanoscopic voids were fabricated using the principles of supramolecular assembly and self-organization in polymers. Such nanoporous membranes can be used as templates for synthesis and patterning of various organic and inorganic materials. In this thesis 4-vinylpyridine fragments of polystyrene-block-poly(4-vinylpyridine) (PS-PVP) were associated with the molecules of two different low molar mass additives, 2-(4'-hydroxybenzeneazo)benzoic acid (HABA) and 3-n-pentadecyl phenol (PDP), via hydrogen bonds. The choice of an additive and a solvent is a key factor which influences the morphologies of the PS-PVP+HABA associates (supramolecular assemblies) in thin films. The reversible association via hydrogen bonds allows the amphiphilic molecules of PDP to phase segregate on the free air interface. Unlike, the molecules of HABA remain associated within cylindrical and lamellar domains formed by the PVP block. A solvent used for film deposition influences the orientation of PVP+HABA domains with respect to the confining interfaces. The films deposited from 1,4-dioxane – a good solvent for PS and a bad one for PVP+HABA – demonstrated the perpendicular orientation of PVP+HABA domains. Meanwhile, the preparation of films from a chloroform solution – a good solvent for both PS and PVP+HABA – led to the parallel alignment. The orientation was independent on the film thickness (within the studied range of 20–100 nm) and insensitive to the chemical nature of a substrate. The orientation of the domains was shown to switch upon exposure to vapors of the above mentioned solvents from the parallel to perpendicular orientation and vice versa. Moreover, the swelling of the films in solvent vapors resulted in the significant improvement of the domain ordering. Extraction of HABA with selective solvent transformed of PVP+HABA domains into channels with reactive PVP chains on the walls. The resulted membranes with the perpendicular oriented channels (the diameter about 8 nm, the inter-channel distance 24 nm) were used as a template for the creation of ordered arrays of nanodots from nickel, chromium and gold
Order in Thin Films of Diblock Copolymers by Supramolecular Assembly
Thin membranes with dense periodic arrays of nanoscopic voids were fabricated using the principles of supramolecular assembly and self-organization in polymers. Such nanoporous membranes can be used as templates for synthesis and patterning of various organic and inorganic materials. In this thesis 4-vinylpyridine fragments of polystyrene-block-poly(4-vinylpyridine) (PS-PVP) were associated with the molecules of two different low molar mass additives, 2-(4'-hydroxybenzeneazo)benzoic acid (HABA) and 3-n-pentadecyl phenol (PDP), via hydrogen bonds. The choice of an additive and a solvent is a key factor which influences the morphologies of the PS-PVP+HABA associates (supramolecular assemblies) in thin films. The reversible association via hydrogen bonds allows the amphiphilic molecules of PDP to phase segregate on the free air interface. Unlike, the molecules of HABA remain associated within cylindrical and lamellar domains formed by the PVP block. A solvent used for film deposition influences the orientation of PVP+HABA domains with respect to the confining interfaces. The films deposited from 1,4-dioxane – a good solvent for PS and a bad one for PVP+HABA – demonstrated the perpendicular orientation of PVP+HABA domains. Meanwhile, the preparation of films from a chloroform solution – a good solvent for both PS and PVP+HABA – led to the parallel alignment. The orientation was independent on the film thickness (within the studied range of 20–100 nm) and insensitive to the chemical nature of a substrate. The orientation of the domains was shown to switch upon exposure to vapors of the above mentioned solvents from the parallel to perpendicular orientation and vice versa. Moreover, the swelling of the films in solvent vapors resulted in the significant improvement of the domain ordering. Extraction of HABA with selective solvent transformed of PVP+HABA domains into channels with reactive PVP chains on the walls. The resulted membranes with the perpendicular oriented channels (the diameter about 8 nm, the inter-channel distance 24 nm) were used as a template for the creation of ordered arrays of nanodots from nickel, chromium and gold
Order in Thin Films of Diblock Copolymers by Supramolecular Assembly
Thin membranes with dense periodic arrays of nanoscopic voids were fabricated using the principles of supramolecular assembly and self-organization in polymers. Such nanoporous membranes can be used as templates for synthesis and patterning of various organic and inorganic materials. In this thesis 4-vinylpyridine fragments of polystyrene-block-poly(4-vinylpyridine) (PS-PVP) were associated with the molecules of two different low molar mass additives, 2-(4'-hydroxybenzeneazo)benzoic acid (HABA) and 3-n-pentadecyl phenol (PDP), via hydrogen bonds. The choice of an additive and a solvent is a key factor which influences the morphologies of the PS-PVP+HABA associates (supramolecular assemblies) in thin films. The reversible association via hydrogen bonds allows the amphiphilic molecules of PDP to phase segregate on the free air interface. Unlike, the molecules of HABA remain associated within cylindrical and lamellar domains formed by the PVP block. A solvent used for film deposition influences the orientation of PVP+HABA domains with respect to the confining interfaces. The films deposited from 1,4-dioxane – a good solvent for PS and a bad one for PVP+HABA – demonstrated the perpendicular orientation of PVP+HABA domains. Meanwhile, the preparation of films from a chloroform solution – a good solvent for both PS and PVP+HABA – led to the parallel alignment. The orientation was independent on the film thickness (within the studied range of 20–100 nm) and insensitive to the chemical nature of a substrate. The orientation of the domains was shown to switch upon exposure to vapors of the above mentioned solvents from the parallel to perpendicular orientation and vice versa. Moreover, the swelling of the films in solvent vapors resulted in the significant improvement of the domain ordering. Extraction of HABA with selective solvent transformed of PVP+HABA domains into channels with reactive PVP chains on the walls. The resulted membranes with the perpendicular oriented channels (the diameter about 8 nm, the inter-channel distance 24 nm) were used as a template for the creation of ordered arrays of nanodots from nickel, chromium and gold
Materials with Built-in Logic
Nanostructured signal-responsive materials were coupled with a combination of enzyme-based biocatalytic chemical reactions to yield information-processing responsive hybrid materials with built-in Boolean logic. The combination of enzymatic reactions performed AND/OR logic operations, transducing biochemical input signals into macroscopic structural changes of the materials, thus resulting in the amplification of the biochemical signals. The information-processing hybrid materials could be scaled up to biocomputing networks composed of many logic gates mimicking biological systems and effectively processing complex biochemical information, resulting in reversible changes of macroscopic structures and allowing adaptation of materials to environment changes.Peer reviewe
Plasmonic Nanobiosensor with Chain Reaction Amplification Mechanism
Herein we demonstrate a plasmonic nanobiosensor that explores chain reaction amplification mechanisms to transduce chemical signals released in biocatalytic reactions, turning optical signals into a visual spectral range. The sensor has a very simple design: gold nanoparticles resting in the surface of a grafted P2VP film. Changes in the gold nanoparticles' position causes changes in the plasmon coupling mode. This is detected by means of a maximum absorbance shift.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Superomniphobic Magnetic Microtextures with Remote Wetting Control
Universal remote control of wetting behavior enabling
the transition
from a superomniphobic to an omniphilic wetting state in an external
magnetic field via the alternation of reentrant curvature of a microstructured
surface is demonstrated. This reconfigurable microtexture made of
Ni micronails repels water, water–surfactant solutions, and
practically all organic liquids, whereas it gets wetted by all of
these liquids after a magnetic field pulse is applied
Electrochemically Controlled Drug-Mimicking Protein Release from Iron-Alginate Thin-Films Associated with an Electrode
Novel biocompatible hybrid-material composed of iron-ion-cross-linked
alginate with embedded protein molecules has been designed for the
signal-triggered drug release. Electrochemically controlled oxidation
of Fe<sup>2+</sup> ions in the presence of soluble natural alginate
polymer and drug-mimicking protein (bovine serum albumin, BSA) results
in the formation of an alginate-based thin-film cross-linked by Fe<sup>3+</sup> ions at the electrode interface with the entrapped protein.
The electrochemically generated composite thin-film was characterized
by electrochemistry and atomic force microscopy (AFM). Preliminary
experiments demonstrated that the electrochemically controlled deposition
of the protein-containing thin-film can be performed at microscale
using scanning electrochemical microscopy (SECM) as the deposition
tool producing polymer-patterned spots potentially containing various
entrapped drugs. Application of reductive potentials on the modified
electrode produced Fe<sup>2+</sup> cations which do not keep complexation
with alginate, thus resulting in the electrochemically triggered thin-film
dissolution and the protein release. Different experimental parameters,
such as the film-deposition time, concentrations of compounds and
applied potentials, were varied in order to demonstrate that the electrodepositon
and electrodissolution of the alginate composite film can be tuned
to the optimum performance. A statistical modeling technique was applied
to find optimal conditions for the formation of the composite thin-film
for the maximal encapsulation and release of the drug-mimicking protein
at the lowest possible potential
Field-Directed Self-Assembly with Locking Nanoparticles
A reversible locking mechanism is established for the
generation
of anisotropic nanostructures by a magnetic field pulse in liquid
matrices by balancing the thermal energy, short-range attractive and
long-range repulsive forces, and dipole–dipole interactions
using a specially tailored polymer shell of nanoparticles. The locking
mechanism is used to precisely regulate the dimensions of self-assembled
magnetic nanoparticle chains and to generate and disintegrate three-dimensional
(3D) nanostructured materials in solvents and polymers
Field-Directed Self-Assembly with Locking Nanoparticles
A reversible locking mechanism is established for the
generation
of anisotropic nanostructures by a magnetic field pulse in liquid
matrices by balancing the thermal energy, short-range attractive and
long-range repulsive forces, and dipole–dipole interactions
using a specially tailored polymer shell of nanoparticles. The locking
mechanism is used to precisely regulate the dimensions of self-assembled
magnetic nanoparticle chains and to generate and disintegrate three-dimensional
(3D) nanostructured materials in solvents and polymers