Enzymatic polymerizations using surfactant microstructures and the preparation of polymer-ferrite composites

Applied Biochemistry and Biotechnology - Horseradish peroxidase has been used as a biocatalyst to synthesize a polymeric material from alkyl-substituted phenols. The synthesis is carried out in a...     

Redox polymerization of methyl methacrylate with allyl alcohol 1,2-butoxylate-block-ethoxylate initiated by Ce(IV)/HNO3 redox system

Redox initiated free-radical polymerization of methyl methacrylate (MMA) with allyl alcohol 1,2-butoxylate-block-ethoxylate (AABE) was carried out using cerium(IV) ammonium nitrate/nitric acid (HNO₃) redox system to yield AABE-b-PMMA copolymers. The effects of MMA, AABE, Ce(IV) and HNO₃ concentrations on the polymerization rate and polymer yield were investigated. The effect of temperature on the rate of polymerization and polymer yield was also investigated in the temperature range of 25-70 °C. Copolymers were characterized using GPC, FT-IR, ¹H NMR and viscometry methods.     

Plasma Induced Graft Polymerization of Three Hydrophilic Monomers on Nylon 6,6 Fabrics for Enhancing Antistatic Property

In this study, three hydrophilic monomers; 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxyethyl methacrylate, diallyldimethylammonium chloride (DADMAC) were selected and their performance as an antistatic finish on nylon 6,6 fabrics was investigated. A non-thermal, high density atmospheric pressure plasma was used to graft polymerize the monomers on nylon 6,6 fabrics. Fabrics were first treated with solutions of monomer in water, air dried and then treated with helium plasma to graft polymerize the monomer on the fiber surface. Surface resistivity values were measured before and after soxhlet extraction with water. Results showed that the DADMAC monomer provided better antistatic properties to fabrics. Further studies with DADMAC monomer were made; effects of plasma post exposure time, plasma pre-exposure time, plasma power, concentration of the monomer and existence of a crosslinker were investigated. Higher plasma power, higher concentration of the monomer and longer post exposure times all gave better antistatic properties to the nylon 6,6 fabrics. Acid dye staining, UV–Vis and FT-IR measurements were conducted and results confirmed a grafted poly-DADMAC layer on the fabric surface.     

Localizing Binding Sites on Bioconjugated Hydrogen-Bonded Organic Semiconductors at the Nanoscale

Hydrogen-bonded organic semiconductors are extraordinarily stable organic solids forming stable, large crystallites with the ability to preserve favorable electrical properties upon bioconjugation. Lately, tremendous efforts have been made to use these bioconjugated semiconductors as platforms for stable multifunctional bioelectronics devices, yet the detailed characterization of bio-active binding sites (orientation, density, etc.) at the nanoscale has not been achieved yet. The presented work investigates the bioconjugation of epindolidione and quinacridone, two representative semiconductors, with respect to their exposed amine-functionalities. Relying on the biotin-avidin lock-and-key system and applying the atomic force microscopy (AFM) derivative topography and recognition (TREC) imaging, we used activated biotin to flag crystal-faces with exposed amine functional groups. Contrary to previous studies, biotin bonds were found to be stable towards removal by autolysis. The resolution strength and clear recognition capability makes TREC-AFM a valuable tool in the investigation of bio-conjugated, hydrogen-bonded semiconductors.     

Synthesis,Characterization and Electrorheological Properties of Polyindene/Kaolinite Composites

In this study, synthesis, characterization and electrorheological (ER) properties of polyindene (PIN) and polyindene/kaolinite composites were carried out by cationic radical polymerization using FeCl₃ as the oxidizing agent. The homopolymer and composites, containing different amounts of PIN were characterized by FTIR spectroscopy, thermo‐gravimetric (TGA) analyses, scanning electron microscopy (SEM) and dynamic light scattering (DLS) methods. The conductivity and dielectric properties of PIN and PIN/kaolinite composites were determined. Suspensions of PIN and PIN/kaolinite composites were prepared in silicone oil (SO), at a series of concentrations (c=5–25 m/m %). The effects of concentration, shear rate, electric field strength, frequency, temperature and promoter on ER activities of suspensions were investigated.     

A self-tuning heuristic for the design of communication networks

This paper addresses the design of communication networks that has a large application area. The problem is to design a minimum cost network subject to a given reliability level. Complexity of the problem is twofold: (1) finding a minimum-cost network topology that every pair of nodes can communicate with each other and (2) computing overall reliability to provide the reliability constraint. Over the last two decades, metaheuristic algorithms have been widely applied to solve this problem due to its NP-hardness. In this study, a self-tuning heuristic (STH), which is a new approach free from parameter tuning, is applied to the design of communication networks. Extensive computational results confirm that STH generates superior solutions to the problem in comparison to some well-known local search metaheuristics, and also more sophisticated metaheuristics proposed in the literature. The practical advantage of STH lies in both its effectiveness and simplicity in application to the design problem.     

Star polymers with POSS via azide–alkyne click reaction

Azidopropyl‐heptaisobutyl‐substituted polyhedral oligomeric silsesquioxane (POSS‐N₃) was reacted with 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane ( 1 ) and poly(ethylene glycol) (PEG)‐b‐poly(methyl methacrylate) (PMMA) copolymer with alkyne at its center (PEG‐PMMA‐alkyne) affording the first time synthesis of 3‐arm star POSS and PEG‐PMMA‐POSS 3‐miktoarm star terpolymer, respectively, in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst and N,N‐dimethylformamide/tetrahydrofuran as solvent at room temperature. The precursors and the target star polymers were characterized comprehensively by ¹H NMR, GPC, and DSC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5947–5953, 2009     

A New Hybrid Iteration Method for I-Asymptotically Nonexpansive Mappings

In this article, convergence theorems are established for a new hybrid iteration for a finite family of I-asymptotically nonexpansive mappings. Our results extend, generalize, and unify various known results in the existing literature.     

Polyurethane Films for Wound Dressing Applications

Polyurethane films based on renewable sources were prepared as an alternative to petroleum-based polyurethane. The effects of the structure and ratio of diisocyanate components on polymer properties were investigated. Hexamethylene diisocyanate (HMDI) and diphenylmethylene diisocyanate (MDI) were chosen as the diisocyanate components in polymer synthesis. Membranes were prepared by casting-evaporation technique and characterized for their gas permeability, film and mechanical properties. The oil-based membranes were found to be suitable for wound dressing applications.