Effect of synthesis method and buffer composition on the LCST of a smart copolymer of N‐isopropylacrylamide and acrylic acid

Responsive polymers have been the focus of many studies during the past decade because of their ability to change according to environmental stimuli. In this paper, we report on the development of a method to synthesize a pH/temperature‐sensitive linear copolymer, poly(N‐isopropylacrylamide‐ co‐acrylic acid)(poly(NIPAAm‐co‐AAc)), with a molecular weight of about 10⁶–10⁵ Da in water using azobisisobutyronitrile (AIBN) as the initiator. The effects of the following on the lower critical solution temperature (LCST) of the copolymer and homopolymer of NIPAAm were investigated: the type of buffer salts and pH changes of test solutions, molecular weight and concentration of homopolymer/copolymer solutions, and AAc monomer molar feed ratio (mol%). The effects of different synthesis methods on the molecular weight and on the AAc content were also evaluated. The mechanism of action in environments with different pH values is discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Magnetic recyclable eggshell-based mesoporous catalyst for biodiesel production from crude neem oil: Process optimization by central composite design and artificial neural network

A magnetically recyclable eggshell-based catalyst (MKEC) was synthesized to circumvent saponification during the conversion of neem, Jatropha, and waste cooking oils (free fatty acid, 2.3–6.6%) to biodiesel. The characterization results indicated that MKEC had a mesoporous structure with the pore width of 3.24 nm, a specific surface area of 128 m²/g, and a pore volume of 0.045 cm³/g. The results confirmed that the MKEC is more tolerant to fatty acid poisoning than calcined eggshell. The effects of process parameters for maximum fatty acid methyl ester (FAME) content were evaluated by central composite design (CCD) and artificial neural network (ANN). The experimental FAME content of 94.5% was achieved for neem oil with a standard deviation (SD) of 0.68, which was in reasonable agreement with predicted values (CCD, 96.9%; ANN, 95.9%; SD, 0.73). The reusability studies showed that the mesoporous catalyst can be reused efficiently for five cycles without much deterioration in its activity.     

Characterisation of microporous sol-gel films for optical device applications

This paper describes progress towards a silica-on-silicon integrated optics technology based on sol-gel. In particular, the aim of this work is to use porous sol-gel films as a host for semiconductor microcrystallites, in order to achieve optical Kerr effect devices. Control of crystallite size is important to maximize the nonlinear effect, and also has a strong influence on band-gap, and thus the wavelength of operation. We are examining the control of pore size distribution, via sol-gel process parameters, as a means of setting crystallite size, and for this reason have developed a technique for the measurement of micropore distributions in films. Results of this technique are presented; these give the first detailed measurements of pores below 10 Å in diameter. The fabrication and measurement of initial doped films is described, giving strong evidence for quantum confinement.     

Ciprofloxacin Loaded Alginate/Chitosan and Solid Lipid Nanoparticles,Preparation, and Characterization

The aim of the present study was to develop controlled drug delivery systems based on nanotechnology. Two different nanocarriers were selected, chitosan-alginate nanoparticles as hydrophilic and solid lipid nanoparticles as lipophilic carriers. Nanoparticles were prepared and characterized by evaluating particle size, zeta potential, SEM pictures, DSC thermograms, percentage of drug loading efficiency, and drug release profile. The particle size of SLNs and Chi/Alg nanoparticles was 291 ± 5 and 520 ± 16. Drug loading efficiency of Chi/Alg and SLN particles were 68.98 ± 5.5% and 88 ± 4.5%. The drug release was sustained with chitosan-alginate system for about 45 hours whereas for SLNs >98% of the drug was released in 2 hours. Release profile did not change significantly after freeze drying of particles using cryoprotector. Results suggest that under in vitro condition chitosan/alginate systems can act as promising carriers for ciprofloxacin and may be used as an alternative system in sustained delivery of ciprofloxacin.     

Refractive Indices, Viscosities, and Densities for L-Cysteine Hydrochloride Monohydrate + D-Sorbitol + Water, and Glycerol + D-Sorbitol + Water in the Temperature Range between T=303.15 K and T=323.15 K

Viscosities, refractive indices, and densities for ternary systems of (L-cysteine hydrochloride monohydrate [LCHCMH] + D-sorbitol + water) and (glycerol + D-sorbitol + water) and binary systems of ([LCHCMH] + water) and (D-sorbitol + water) have been measured at several temperatures (between T=303.15 K and T=323.15 K) and mass fractions (0.1 to 0.8) at atmospheric pressure. For these mixtures, the experimental values of density were correlated with an experimental equation and the experimental values of viscosity were correlated with the Jones-Dole equation.     

Solgel grating waveguides for distributed Bragg reflector lasers

Solgel grating waveguides and their application to the fabrication of external-cavity distributed Bragg reflector (DBR) lasers are demonstrated. A new composition of aluminosilicate material is developed for the fabrication of single-mode waveguides and Bragg reflectors. An average loss of <0.2 dB/cm is measured in the single-mode waveguides at 1550 nm. The reflectors show filtering greater than 97% near 1530 nm, with a bandwidth of ~0.6 nm . The Bragg reflectors are used as feedback resonators for DBR lasers. Single-mode lasing with a sidemode suppression of better than 25 dB is demonstrated.     

Compliance switching for adhesion control

Climbing lizards display numerous advanced features in their locomotion, notably a method to quickly switch between a state of low and high adhesive force capacity. Inspired by the gecko's adhesive switching, a method of mechanically switching between low and high adhesive states is reported. In particular, the first switching of an adhesive system using only a change in system compliance is demonstrated. Mechanical clamping and a novel magnetic clamping system are used to switch an iron/PDMS composite adhesive between a soft and rigid state. The switch in compliance directly influences the maximum load of the adhesive as measured in lap‐shear. Notably, contact area and the contact chemistry remain unaltered despite significant changes in force capacity. The demonstration of a compliance‐only switching mechanism has broad implications for understanding natural adhesive systems—especially in organisms that can dynamically alter their rigidity (e.g. cells). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 48–57     

Thermodynamic properties of dimethyl phthalate + vinyl acetate, diethyl phthalate + vinyl acetate or bromocyclohexane, and dibutyl phthalate + vinyl acetate or 1,2-dichlorobenzene at T = 298.15–308.15 K

Thermodynamic properties (densities and viscosities) of binary mixtures of diethyl phthalate (DEP) + bromocyclohexane, dibutyl phthalate (DBP) + 1,2-dichlorobenzene, and vinyl acetate (1) + dimethyl phthalate (DMP) (2), + diethyl phthalate (2), or + dibutyl phthalate (2) were measured over the whole range of mole fractions at atmospheric pressure and different temperatures (T = 298.15 K to 308.15 K). For these mixtures, their excess molar volumes (V ^E) and viscosity deviations (Δη) were calculated from the experimental data. These results were correlated with the Redlich-Kister polynomial equation to derive the coefficients and standard errors.     

Introducing a Linear Empirical Correlation for Predicting the Mass Heat Capacity of Biomaterials

This study correlated biomass heat capacity (Cp) with the chemistry (sulfur and ash content), crystallinity index, and temperature of various samples. A five-parameter linear correlation predicted 576 biomass Cp samples from four different origins with the absolute average relative deviation (AARD%) of ~1.1%. The proportional reduction in error (REE) approved that ash and sulfur contents only enlarge the correlation and have little effect on the accuracy. Furthermore, the REE showed that the temperature effect on biomass heat capacity was stronger than on the crystallinity index. Consequently, a new three-parameter correlation utilizing crystallinity index and temperature was developed. This model was more straightforward than the five-parameter correlation and provided better predictions (AARD = 0.98%). The proposed three-parameter correlation predicted the heat capacity of four different biomass classes with residual errors between −0.02 to 0.02 J/g∙K. The literature related biomass Cp to temperature using quadratic and linear correlations, and ignored the effect of the chemistry of the samples. These quadratic and linear correlations predicted the biomass Cp of the available database with an AARD of 39.19% and 1.29%, respectively. Our proposed model was the first work incorporating sample chemistry in biomass Cp estimation.