A climate responsive urban design tool: a platform to improve energy efficiency in a dry hot climate

In the Middle East and North Africa (MENA) region, new urban developments should address the climatic conditions to improve outdoor comfort and to reduce the energy consumption of buildings. This article describes a design tool that supports climate responsive design for a dry hot climate. The approach takes the climate as an initiator for the conceptual urban form with a more energy-efficient urban morphology. The methodology relates the different passive strategies suitable for major climate conditions in MENA region (dry-hot) to design parameters that create the urban form. This parametric design approach is the basis for a tool that generates conceptual climate responsive urban forms so as to assist the urban designer early in the design process. Various conceptual scenarios, generated by a computational model, are the results of the proposed platform. A practical application of the approach is conducted on a New Urban Community in Aswan (Egypt), showing the economic feasibility of the resulting urban form and morphology, and the proposed tool.     

Synthesis and swelling characteristics of responsive carboxybetaine gel

A polyimminium gel, Dimedone‐[N, N′ melaminium] butyrocarboxylate copolymer, comprising of zwitterionic carboxybetaine repeat units was synthesized via a catalyst free facile polycondensation approach. The polymer was studied for its photoluminescence, thermal, and swelling behavior. Swelling behavior was investigated in different solvent mixtures as well as in pure solvents. The extent of swelling was dictated by solvent composition, such as dielectric constant, pH, ionic strength, and other variables for instance, temperature and crosslinking density. Gel was soluble in alkali and could be regenerated on treatment with an acid. This pH responsive behavior could find various industrial applications, especially in wastewater treatment. A preliminary study on sorption of dyes was also carried out. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Evaluation of redox-responsive disulfide cross-linked poly(hydroxyethyl methacrylate) hydrogels

Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels were prepared with a disulfide containing cross-linker bis(2-methacryloxyethyl) disulfide (DSDMA) that exhibited enhanced release in the presence of glutathione (GSH), a biologically available reducing agent. Varying concentrations of the DSDMA cross-linker were incorporated into the prepolymer before the radical polymerization, enabling the cross-link density to be easily tuned. Dye release studies were performed using rhodamine B and rhodamine 6G dyes, and the UV response of the dyes released into the supernatant measured with the addition of GSH. Using ether-based cross-linkers as a control, the disulfide cross-linkers exhibited a substantial increase in release rates, confirming the responsive nature of the hydrogels to biological reducing agents. The polymers were also tested in a cell culture system for their ability to release the anti-fibroproliferative agent, mitomycin C (MMC). Polymers cross-linked with DSDMA delivered MMC over a slightly longer time period than control polymers prepared with a conventional ether cross-linker.     

pH‐responsive hydrogel microparticles as intelligent delivery carriers for α‐MSH antagonists

For a first step in the development of an intelligent delivery system for a nonapeptide as an α‐MSH antagonist, pH‐responsive P(MAA‐co‐EGMA) hydrogel microparticles were prepared and their feasibility as intelligent delivery carriers was evaluated. There was a drastic change in the swelling ratio of P(MAA‐co‐EGMA) microparticles at a pH of around 5 and as the MAA amount in the hydrogel increased, the swelling ratio increased at a pH above 5. The loading efficiency of the nonapeptide at pH 7 increased with the amount of Methacrylic acid (MAA) in the hydrogel and at pH 2, where the electrostatic attraction was greatest, a high loading efficiency was not obtained because of the low swelling ratio of the hydrogel. The P(MAA‐co‐EGMA) microparticles demonstrated a pH‐sensitive release behavior for the nonapeptide. In addition, the P(MAA‐co‐EGMA) microparticles showed a protective ability for the nonapeptide and preserved the stability of the nonapeptide. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Recent developments in polypseudorotaxanes and polyrotaxanes

This review highlights developments since 2008 in the field of polypseudorotaxanes and polyrotaxanes. Progress in synthetic polyrotaxane chemistry has resulted in the preparation of numerous functionalized polymers for various applications in areas such as molecular machines, stimuli responsive materials, supramolecular gels and molecular sensors. This new genre of supramolecular polymers is advancing rapidly with several groups developing novel materials with unique characteristics.     

Dual-responsive polymer–drug nanoparticles for drug delivery

A well-defined, dual temperature- and pH-responsive drug carrier was synthesized through the radical copolymerization of methacrylic acid, N-isopropylacrylamide, and an N-(methacryloyl)glycylglycine 4-nitrophenyl ester. When the anticancer agent gemcitabine or antibiotic sulfamethoxazole was conjugated with a polymer and heated beyond its low critical solution temperature (40 °C), a dual temperature- and pH-induced phase transition was observed. This temperature was considered ideal for activating drug aggregation under hyperthermic and acidic conditions. The structure and properties of polymer drugs were investigated using nuclear magnetic resonance, Fourier transform infrared spectrometry, ultraviolet–visible absorption, transmission electron microscopy, and gel permeation chromatography. At a critical micelle concentration of 1 mg/mL, both polymer drugs formed micellar structures with diameters ranging from 50 nm to 150 nm, based on TEM image. These micelles exhibited higher pharmacological efficacy than the free drug alone did, and the cytotoxicity at the target site was substantially enhanced compared with that of the polymer–drug conjugate formed under normal physiological conditions.