Synthesis of AB3‐type miktoarm star polymers with steroid core via a combination of “Click” chemistry and ring opening polymerization techniques

Well‐defined AB₃‐type miktoarm star‐shaped polymers with cholic acid (CA) core were fabricated with a combination of “click” chemistry and ring opening polymerization (ROP) methods. Firstly, azide end‐functional poly(ethylene glycol) (mPEG), poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(ε‐caprolactone) (PCL) polymers were prepared via controlled polymerization and chemical modification methods. Then, CA moieties containing three OH groups were introduced to these polymers as the end groups via Cu(I)‐catalyzed click reaction between azide end‐functional groups of the polymers ( mPEG‐N₃ , PMMA‐N₃ , PS‐N₃ , and PCL‐N₃ ) and ethynyl‐functional CA under ambient conditions, yielding CA end‐functional polymers ( mPEG‐Cholic , PMMA‐Cholic , PS‐Cholic , and PCL‐Cholic ). Finally, the obtained CA end‐capped polymers were employed as the macroinitiators in the ROP of ε‐caprolactone (ε‐CL) yielding AB₃‐type miktoarm star polymers ( mPEG‐Cholic‐PCL₃ , PMMA‐Cholic‐PCL₃ , and PS‐Cholic‐PCL₃ ) and asymmetric star polymer [ Cholic‐(PCL)₄ ]. The chemical structures of the obtained intermediates and polymers were confirmed via Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopic techniques. Thermal decomposition behaviors and phase transitions were studied in detail using thermogravimetric analysis and differential scanning calorimetry experiments. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3390–3399     

Synthesis,characterization, electrochromic properties,and electrochromic device application of a novel star polymer consisting of thiophene end‐capped poly(ε‐caprolactone) arms emanating from a hexafunctional cyclotriphosphazene core

Hexa‐armed and thiophene (Thi) end‐capped poly(ε‐caprolactone) star polymer (N₃P₃‐(PCL‐Thi)₆), containing cyclotriphosphazene core, was prepared in a four‐step reaction sequence. Ring‐opening polymerization (ROP) and “click chemistry” techniques were employed in the first and final steps, respectively. Hexa‐armed PCL star polymer (N₃P₃‐(PCL‐OH)₆) was successfully synthesized via ROP of ε‐caprolactone (ε‐CL) by using hekzakis(p‐(hydroxymethyl)phenoxy) cyclotriphosphazene as the multisite initiator and tin(II) 2‐ethylhexanoate (Sn(Oct₂)) as the catalyst in bulk at 115 °C. Further modifications of the N₃P₃‐(PCL‐OH)₆ were accomplished by derivatization of the hydroxyl‐functional chain ends. The obtained N₃P₃‐(PCL‐OH)₆ was then reacted with 2‐bromo‐2‐methylpropanoyl bromide, and this led to a star polymer with bromide end groups, N₃P₃‐(PCL‐Br)₆. In the third step, N₃P₃‐(PCL‐Br)₆ was azidified with sodium azide (NaN₃) in DMF affording N₃P₃‐(PCL‐N₃)₆. Conversion of the azide chain end groups into Thi was quantitatively accomplished via the “click reaction” between N₃P₃‐(PCL‐N₃)₆ and prop‐2‐yn‐1‐yl 3‐thienyl acetate in the final step. Subsequently, the star polymer with six Thi chain ends (N₃P₃‐(PCL‐Thi)₆) was employed in electrochemical copolymerization with both pyrrole and Thi. Electrochromic properties and electrochromic device application of N₃P₃‐(PCL‐Thi)₆/PThi were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3668–3682, 2010     

Synthesis and characterization of sulfonated homo‐ and co‐polyimides based on 2,4 and 2,5‐diaminobenzenesulfonic acid for proton exchange membranes

A series of sulfonated homo‐ and random co‐polyimides (co‐SPI) based on 2,4‐diaminobenzenesulfonic acid (2,4‐DABS) and 2,5‐diaminobenzenesulfonic acid (2,5‐DABS) has been synthesized via conventional two‐step polyimidization method. 2,4‐DABS and 2,5‐DABS were used as sulfonated diamine compounds, 4,4′‐oxydianiline (ODA) and 4,4′‐diaminodiphenyl sulfone (DDS) were used as non‐sulfonated diamine compounds. Mixtures of sulfonated and non‐sulfonated diamine compounds were reacted with benzophenonetetracarboxylic dianhydride (BTDA) to obtain co‐SPI membranes. Molar ratios of sulfonated to non‐sulfonated diamine were systematically varied to produce copolymers of controlled compositions. The co‐SPIs were evaluated for thermal oxidative stability, ion exchange capacity (IEC), water uptake, proton conductivity, solubility, and hydrolytic stability. Proton conductivity and hydrolytic stability of the co‐SPIs were compared with the fully aromatic polyimide, homo‐SPIs (BTDA/2,4‐DABS and BTDA/2,5‐DABS). Regarding thermogravimetric analysis (TGA) analysis, it is concluded that desulfonation temperature in the range of 200–350°C suggests high stability of sulfonic acid groups. co‐SPIs with 40 mol% of 2,4‐DABS showed similar or higher proton conductivity than Nafion® 117 in water. Proton conductivity values of the co‐SPIs were mainly a function of IEC and water uptake. Consequently, the optimum concentration of 2,4‐DABS was found to be in the range of 30–40 mol% from the viewpoint of proton conductivity, IEC, and hydrolytic stability. Copyright © 2008 John Wiley & Sons, Ltd.     

Control of transient flow in irrigation canals using Lyapunov fuzzy filter‐based Gaussian regulator

An optimal fuzzy filter was applied to solve the state estimation problem of the controlled irrigation canals. Using linearized finite‐difference model of the open‐channel flow, a canal operation problem was formulated as an optimal control problem and an algorithm for gate openings in the presence of unknown external disturbances was derived. A fuzzy filter was designed to estimate the state variables at the intermediate nodes based upon measured values of depth at the points in the canal. A Lyapunov function was utilized as a performance index to formulate the fuzzy interference rules of the optimal fuzzy filter. A linear quadratic Gaussian (LQG) optimal controller for a multi‐pool irrigation canal was considered as an example. The state estimation problem in the controller was simulated using two techniques: Kalman estimator and the proposed fuzzy filter. The performance of the fuzzy state estimator designed using the Lyapunov fuzzy technique was compared with the results obtained using the Kalman estimator technique. The obvious advantages of the fuzzy filter were the lower computational costs and ease of implementation. The results of this study demonstrated that proposed Lyapunov‐type fuzzy filter provides both good stability and simplicity in the control of irrigation canals more than a Kalman filter. Copyright © 2005 John Wiley & Sons, Ltd.     

A Dual Simplex Algorithm for Piecewise-Linear Programming

This paper presents a dual piecewise-linear simplex algorithm for minimizing convex separable piecewise-linear functions subject to linear constraints. It is an extension of Fourier's work on piecewise-linear programming to the dual piecewise-linear simplex algorithm. This algorithm has advantages over indirect methods which solve equivalent linear programs augmented by additional variables and/or constraints. Computational experience is presented which demonstrates the efficiency these advantages contribute.     

Modal Control of Cantilever Beam Using a Gyrostabilizer

In this paper, an experimental model of a horizontal cantilever beam with a rotating/oscillating attached to the shaker for harmonic excitation at the one end and a gyrostabilizer at the other end is built to verify the equations of the Lagrangian model. The primary focus of the study was to investigate the parameters of excitation amplitude, natural frequency, rotating mass (disk mass), and disk speed of gyro that would minimize the amplitude of the beam to identify these effects. Numerical and experimental results indicate that the angular momentum of the gyrostabilizer is the most effective parameter in the reduction of beam displacement.     

Synthesis,Spectral Characterization and Antimicrobial Activity of Some Transition Metal Complexes of 1,3‐Bis(1H‐benzimidazol‐2‐yl)‐2‐oxapropane

1,3‐Bis(1H‐benzimidazol‐2‐yl)‐2‐oxapropane ( L ) complexes with Fe(NO₃)₃, CoCl₂, Co(NO₃)₂, Ni(NO₃)₂, CuCl₂, Cu(ClO₄)₂, PdCl₂, CdI₂, Hg(NO₃)₂ were synthesized and characterized by elemental analysis, molar conductivity, magnetic moment, TGA, FT‐IR, NMR, ESI‐MS, fluorescence spectroscopy. Also, the crystal structure of 1,3‐bis(1H‐benzimidazol‐2‐yl)‐2‐oxapropane]dichlorocobalt(II), [Co( L )Cl₂], complex is reported that it has distorted trigonal bipyramidal geometry. Antibacterial activities of the compounds were evaluated using the disk diffusion method against six bacteria and Candida albicans. The Hg(II) complex shows superior activity toward S. epidermidis and E. coli whereas the other complexes are ineffective except the Co(NO₃)₂ complex: it showed weak activity toward all of the microorganisms.     

The Use of 2,2,2-Trichloro-1-Arylethanones as Benzoylating Agents

The preparation of several amides and hydrazides from the reaction of the title compounds with different nitrogen nucleophiles is shown to be a general high-yield conversion of synthetic utility.     

TN approximation to neutron transport equation and application to critical slab problem

The critical slab problem has been studied in one-speed neutron transport equation with isotropic scattering by using the T_N method. T_N moment criticality solutions are obtained for the uniform finite slab using Mark and Marshak type vacuum boundary conditions. Results obtained by T_N method, using the two type boundary conditions mentioned above, were presented in the Tables and also the Tables included the results obtained by P_N method for the comparisons.     

Parallel computation of intertemporal multicommodity spatial price equilibria in the presence of quotas

An intertemporal, spatial price equilibrium is determined for multiple commodities where the net import of each commodity in a given time period is a linear function of the prices of all commodities in that region and time period. Temporal and spatial flows are subject to fixed unit costs, and quotas in the form of upper bounds. A parallel decomposition scheme exploits characteristics of equilibria.