Використання лазерних діодів в рейтресінговій аберометрії

Аберометри є найбільш досконалими офтальмологічними приладами, оскільки вони дозволяють оцінювати сумарну аберацію оптичної системи ока. Однак, їх основним недоліком є висока вартість. Одним із чинників, який визначає вартість аберометра, є використання складної оптико-механічної системи керування лазерним променем, який використовують для рейтресінгу – сканування зіниці ока і сітківки

Bicontinuous Ceramics with High Surface Area from Block Copolymer Templates

Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-<i>b</i>-poly­(l-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol–gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol–gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO₂ with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO₂ by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established

Phase Behavior and Color Tuning of Poly(4-vinylpyridine)-<i>b</i>-poly(ε-caprolactone) Complexed with Chromophores

A series of poly(4-vinylpyridine)-<i>b</i>-poly(ε-caprolactone) (P4VP-PCL) diblock copolymers have been synthesized and used for the formation of nanostructures with tunable colors arising from the association of chromophores with P4VP block in P4VP-PCL. The association of chromophores leads to the bathochromical shifts of charge transfer absorption peaks, resulting in the color appearance into the visible region. To achieve the formation of well-defined nanostructured materials, the phase behavior of the mixtures of chromophore/P4VP-PCL was systematically examined. As evidenced by transmission electron microscopy and small-angle X-ray scattering (SAXS), the phase transformation of self-assembled nanostructures can be easily induced by introducing chromophores due to the association of 2-methylidenepropanedinitrile in the chromophores with the lone-pair electron of nitrogen in P4VP block (that is the increase on the effective volume fraction of P4VP, as identified by SAXS experiments through the analysis of one-dimensional correlation function). As a result, by taking advantage of charge transfer and corresponding morphologies from transformation, well-defined nanostructured films resulting from mixing of chromophore and P4VP-PCL offer the possibility to create stimuli-responsive nanomaterials with tunable color

Controlled Ordering of Block Copolymer Gyroid Thin Films by Solvent Annealing

This work presents an approach to achieve controlled ordering of polystyrene-<i>block</i>-poly­(l-lactide) (PS–PLLA) gyroid thin films on a neutral substrate using solvent annealing. Interesting morphological evolution from gyroid to cylinder can be found while using a partially selective solvent for the PS block to anneal the PS–PLLA thin film. To acquire a thin-film sample with thermodynamically stable gyroid morphology, a nonpreferential solvent should be used for solvent annealing to enable controlled ordering of gyroid thin film with the (211)_G plane parallel to the air surface and also the functionalized substrate. By taking advantage of degradable character of the PLLA block, nanoporous PS with well-defined texture can be fabricated by hydrolysis and used as a template for synthesis of various nanohybrids and nanoporous materials

Controlled Self-Assembly of Polystyrene-<i>block</i>-Polydimethylsiloxane for Fabrication of Nanonetwork Silica Monoliths

Herein, this work aims to carry out controlled self-assembly of single-composition block copolymer for the fabrication of various nanonetwork silica monoliths. With the use of lamellae-forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS), nanonetwork-structured films could be fabricated by solvent annealing using a PS-selective solvent (chloroform). By simply tuning the flow rate of nitrogen purge to the PS-selective solvent for the controlled self-assembly of the PS-b-PDMS, gyroid- and diamond-structured monoliths can be formed due to the difference in the effective volume of PS in the PS-b-PDMS during solvent annealing. As a result, well-ordered nanonetwork SiO2 (silica) monoliths can be fabricated by templated sol–gel reaction using hydrofluoric acid etched PS-b-PDMS film as a template followed by the removal of the PS. This bottom-up approach for the fabrication of nanonetwork materials through templated synthesis is appealing to create nanonetwork materials for various applications

Stimuli-Responsive Color Films of Poly(4-vinylpyridine)‑<i>b</i>‑Poly(ε-caprolactone) Complexed with Cyano-Capped Chromophores

Here, we develop a method to fabricate stimuli-responsive color films using block copolymer, poly­(4-vinylpyridine)-<i>b</i>-poly­(ε-caprolactone) (P4VP-PCL), as a template complexed with functionalized chromophores. The P4VP block in the P4VP-PCL can be associated with a cyano end-capped chromophore via charge transfer, which is a noncovalent interaction that can be conveniently manipulated by external stimuli, giving a specific color. The color of the film can be switched by tuning the charge transfer interaction between the chromophore and P4VP with controlled environmental conditions, such as pH, temperature, and moisture, while maintaining high transmittance for visible light due to the formation of the nanostructure of chromophore/P4VP-PCL complex. However, the association/dissociation process between chromophore and P4VP is diffusion-dominated, which may limit the kinetic response time for color change. A way to create quick and reversible color switching can be achieved by a combination of stimuli. The contrasting color change of the responsive chromophore/P4VP-PCL thin films which exhibit RGB primary colors can provide a sensor film that is flexible, fast-responsive, and convenient

Morphological Evolution of Gyroid-Forming Block Copolymer Thin Films with Varying Solvent Evaporation Rate

In this study, we aim to examine the morphological evolution of block copolymer (BCP) nanostructured thin films through solvent evaporation at different rates for solvent swollen polystyrene-<i>block</i>-poly­(l-lactide) (PS–PLLA). Interesting phase transitions from disorder to perpendicular cylinder and then gyroid can be found while using a partially selective solvent for PS to swell PS–PLLA thin film followed by solvent evaporation. During the transitions, gyroid-forming BCP thin film with characteristic crystallographic planes of (111)_G, (110)_G, and (211)_G parallel to air surface can be observed, and will gradually transform into coexisting (110)_G and (211)_G planes, and finally transforms to (211)_G plane due to the preferential segregation of constituted block to the surface (i.e., the thermodynamic origin for self-assembly) that affects the relative amount of each component at the air surface. With the decrease on the evaporation rate, the disorder phase will transform to parallel cylinder and then directly to (211)_G without transition to perpendicular cylinder phase. Most importantly, the morphological evolution of PS–PLLA thin films is strongly dependent upon the solvent removal rate only in the initial stage of the evaporation process due to the anisotropy of cylinder structure. Once the morphology is transformed back to the isotropic gyroid structure after long evaporation, the morphological evolution will only relate to the variation of the surface composition. Similar phase transitions at the substrate can also be obtained by controlling the ratio of PLLA–OH to PS–OH homopolymers to functionalize the substrate. As a result, the fabrication of well-defined nanostructured thin films with controlled orientation can be achieved by simple swelling and deswelling with controlled evaporation rate

Functionalized Nanoporous Gyroid SiO₂ with Double-Stimuli-Responsive Properties as Environment-Selective Delivery Systems

Herein, we aim to fabricate nanoporous gyroid SiO₂ from templated sol–gel reaction using degradable block copolymer with gyroid-forming nanostructure as a template and then to functionalize the nanoporous materials using “smart” polymer, poly­(2-(dimethylamino)­ethyl methacrylate) (PDMAEMA), brushes via the “grafting from” method to give double-stimuli-responsive properties. By taking advantage of the responses to environmental stimuli, both thermal and pH, the pore features can be well-defined by the stretching and recoiling of PDMAEMA brushes because of their adjustable chain conformations with reversible character. The responsive properties with respect to environmental stimuli can be successfully traced by temperature-resolved small-angle X-ray scattering (SAXS) in aqueous environment. Owing to the high specific surface area and porosity, 3D pore network, biocompatibility, and environmental responses, the functionalized nanoporous gyroid SiO₂ is further demonstrated as a stimuli-responsive controlled release system

A Facile Method To Fabricate Double Gyroid as a Polymer Template for Nanohybrids

Here, we suggest a facile method to acquire double gyroid (DG) phase from the self-assembly of chiral block copolymers (BCPs*), polystyrene-<i>b</i>-poly­(l-lactide) (PS–PLLA). A wide region for the formation of DG can be found in the phase diagram of the BCPs*, suggesting that helical phase (H*) from the self-assembly of BCPs* can serve as a stepping stone for the formation of the DG due to an easy path for order–order transition from two-dimensional to three-dimensional (network) structure. Moreover, the order–order transition from metastable H* to stable DG can be expedited by blending the PS–PLLA with compatible entity. Unlike the conventional way for blending BCP with homopolymer, PS–PLLA blends are prepared by using styrene oligomer (S) to fine-tune the morphologies of the blends at which the molecular weight ratio of the S and compatible PS block (<i>r</i>) is less than 0.1. Owing to the use of the low-molecular-weight oligomer, the increase of BCP chain mobility in the blends significantly reduces the transformation time for the order–order transition from H* to DG. Consequently, by taking advantage of degradable character of the PLLA, nanoporous gyroid SiO₂ can be fabricated using hydrolyzed PS–PLLA blends as a template for sol–gel reaction followed by removal of the PS matrix