Immobilization of RAFT agents on silica nanoparticles utilizing an alternative functional group and subsequent surface‐initiated RAFT polymerization

Silica–polystyrene core‐shell particles were successfully prepared by surface‐mediated reversible addition fragmentation chain transfer (RAFT) polymerization of styrene monomer from the surfaces of the silica‐supported RAFT agents. Initially, macro‐RAFT agents were synthesized by RAFT polymerization of γ‐methacryloxypropyltrimethoxysilane (MPS) in the presence of chain transfer agents (CTAs). Immobilization of CTAs onto the silica surfaces was then performed by reacting silica with macro‐RAFT agents via a silane coupling. Grafting of polymer onto silica forms core‐shell nanostructures and shows a sharp contrast between silica core and polymer shell in the phase composition. The thickness of grafted‐polymer shell and the diameter of core‐shell particles increase with the increasing ratio of monomer to silica. A control experiment was carried out by conventional free radical emulsion copolymerization of MPS‐grafted silica and styrene under comparable conditions. The resulting data provide further insight into the chemical composition of grafted‐polymers that are grown from the silica surface through RAFT process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 467–484, 2009     

Preparation and drug controlled-release of polyion complex micelles as drug delivery systems

Block copolymers, poly(N-vinylprrolidone)-block-poly(styrene-alter-maleic anhydride) (PVP-b-PSMA) and poly(N-vinylprrolidone)-block-poly(N,N-dimethylaminoethyl methacrylate) (PVP-b-PDMAEMA), were synthesized by reversible addition- fragmentation chain transfer (RAFT) polymerization. In aqueous media, this a pair of oppositely-charged diblock copolymers could self-assemble into stable and narrow distribution polyion complex micelles (PICMs). Transmission electron micrographs (TEM) and dynamic light scattering (DLS) analysis showed that the micelles to be spherically shaped with mean hydrodynamic diameter around 70 nm. In addition, the PICMs display ability to response to external stimuli. All of theses features are quite feasible for utilizing it as a novel intelligent drug delivery system. In order to assess its application in biomedical area, release profiles of coenzyme A (Co A) from PICMs were studied under both simulated gastric and intestinal pH conditions. The release was much quicker in pH 7.4 buffer than in pH 2.0 solution. Based on these results, these PICMs could be a potential pH-sensitive carrier for colon-specific drug delivery system.     

Monolithic Integration of Diffractive Microlens Arrays and Infrared Focal Plane Arrays

Monolithic integration method has been demonstrated to increase the fill factor of the infrared focal plane arrays (IRFPA). Which is consists of 256×256 Pt-Si schottky barrier charge coupled devices(CCD) operation in 3-5m IR region. The relative silicon 256×256 element diffractive microlens arrays have been fabricated on the back side of the substrate of the IRFPA using binary optics technology. The aligning process between IRFPA and microlens arrays on each side of the substrate has been completed by IR mask aligner. The testing results show that the imaging quality is very good and the average optical response of the IR FPA is increased by a factor of 3.0, which is improved by about 25% compared with the hybrid integration method in the previous work.     

Super‐Hydrophobic PDMS Surface with Ultra‐Low Adhesive Force

Summary: Rough polydimethylsiloxane (PDMS) surface containing micro‐, submicro‐ and nano‐composite structures was fabricated using a facile one‐step laser etching method. Such surface shows a super‐hydrophobic character with contact angle higher than 160° and sliding angle lower than 5°, i.e. self‐cleaning effect like lotus leaf. The wettabilities of the rough PDMS surfaces can be tunable by simply controlling the size of etched microstructures. The adhesive force between etched PDMS surface and water droplet is evaluated, and the structure effect is deduced by comparing it with those own a single nano‐ or micro‐scale structures. This super‐hydrophobic PDMS surface can be widely applied to many areas such as liquid transportation without loss, and micro‐pump (creating pushing‐force) needless micro‐fluidic devices.

Etched PDMS surface containing micro‐, submicro‐, and nano‐composite structures shows a self‐cleaning effect with water CA as high as 162° and SA lower than 5°.     

A highly sensitive “test paper” for Hg2+ ions based on polyurethane membrane

Heavy metals have caused a lot of serious problems to human beings. A reusable, highly sensitive metal sensor based on polyurethane membrane, which can detect and remove Hg²⁺ ions, was prepared and tested in this work. A sensor with hydroxyl (?OH) group was grafted to polyurethane, and the heavy metal sensitive membrane was synthesized accordingly. Upon addition of Hg²⁺ ion solution to the as‐prepared membrane, the color change occurred instantly. Moreover, different colors appeared with different concentration of the Hg²⁺ ions, which could make the membrane be employed as a heavy metal “test paper”. In addition, the membrane sensor could be recycled after the interaction with Hg²⁺ ions by treating the used membrane with dilute ethylenediaminetetraacetic acid 2Na solution. This efficient and easily prepared membrane‐based sensor has a promising application in environmental science. Copyright © 2013 John Wiley & Sons, Ltd.     

Emergence of a Radical‐Stabilizing Metal–Organic Framework as a Radio‐photoluminescence Dosimeter

Radio‐photoluminescence (RPL) materials display a distinct radiation‐induced permanent luminescence center, and therefore find application in the detection of ionizing radiation. The current inventory of RPL materials, which were discovered by serendipity, has been limited to a small number of metal‐ion‐doped inorganic materials. Here we document the RPL of a metal–organic framework (MOF) for the first time: X‐ray induced free radicals are accumulated on the organic linker and are subsequently stabilized in the conjugated fragment in the structure, while the metal center acts as the X‐ray attenuator. These radicals afford new emission features in both UV‐excited and X‐ray excited luminescence spectra, making it possible to establish linear relationships between the radiation dose and the normalized intensity of the new emission feature. The MOF‐based RPL materials exhibit advantages in terms of the dose detection range, reusability, emission stability, and energy threshold. Based on a comprehensive electronic structure and energy diagram study, the rational design and a substantial expansion of candidate RPL materials can be anticipated.     

Coaxial Electrospinning Method for the Preparation of TiO2@CdS/PVA Composite Nanofiber Mat and Investigation on its Photodegradation Catalysis

TiO₂/PVA composite nanofiber mat was prepared via an electrospinning technology. SH‐TiO₂‐SiO₂ hybrid particles and PVA solution were injected through a coaxial syringe, yielding a composite nanofiber mat. The as‐prepared SH‐TiO₂‐SiO₂/PVA composite nanofiber mat was immersed in Cd²⁺ cation solution and S^2? anion solution in turn. Thus, yellow TiO₂@CdS/PVA composite nanofiber mats were prepared. By adjusting the number of times a mat was immersed in the Cd²⁺ and S^2? solutions, different amounts of CdS particles attaching to the mats were obtained. Both SH‐TiO₂‐SiO₂/PVA and TiO₂@CdS/PVA composite nanofiber mats were employed to catalyze the photodegradation of a model dye, methylene blue. The photodegradation performance could be greatly enhanced by the introduction of CdS particles anchoring onto TiO₂ particles. The photodegradation efficiency reached 99.2% within 180 min. Also, the nanofiber mat could be recycled and reused at least 10 times. The photodegradation efficiency of TiO₂@CdS/PVA composite nanofiber mats remained 68.8% for 10 cycles.     

Synthesis of photosensitive polyimide for liquid crystal alignment under non-polarised UV ageing lamp irradiation and a study on the possible mechanism of alignment

ABSTRACT

A new photosensitive polyimide (PI) was successfully synthesised via esterification of PI containing hydroxyl groups with cinnamoyl chloride (CL). The cinnamate (CA) group contents of the PI was up to 90%. The PI films could induce uniform parallel alignment of liquid crystal (LC) molecules after the non-polarised ultraviolet ageing lamp exposure, which reduce the cost significantly compared with polarised ultraviolet light equipment. In addition, the PI exhibited good thermal stability. Meanwhile, the possible mechanism of PI alignment films induced by NPUVL was discussed in some detail.     

Emergence of a Radical-Stabilizing Metal–Organic Framework as a Radio-photoluminescence Dosimeter

Radio-photoluminescence (RPL) materials display a distinct radiation-induced permanent luminescence center, and therefore find application in the detection of ionizing radiation. The current inventory of RPL materials, which were discovered by serendipity, has been limited to a small number of metal-ion-doped inorganic materials. Here we document the RPL of a metal–organic framework (MOF) for the first time: X-ray induced free radicals are accumulated on the organic linker and are subsequently stabilized in the conjugated fragment in the structure, while the metal center acts as the X-ray attenuator. These radicals afford new emission features in both UV-excited and X-ray excited luminescence spectra, making it possible to establish linear relationships between the radiation dose and the normalized intensity of the new emission feature. The MOF-based RPL materials exhibit advantages in terms of the dose detection range, reusability, emission stability, and energy threshold. Based on a comprehensive electronic structure and energy diagram study, the rational design and a substantial expansion of candidate RPL materials can be anticipated.