Exploring Microstructures and Interphase Properties of Surface- Grafted Diblock Copolymers in a Homopolymer Melt by Self-Consistent Field Theory Simulations

Polymeric self-consistent field theory is used to investigate microstructures and interphase properties of diblock copolymers grafted onto solid surfaces in a homopolymer melt. The calculations show that the grafted diblock copolymers can self-assemble into hemispherical microstructures at low grafting densities of the diblock copolymers. The morphology transforms into hemicylinder-like and sandwich-like lamellar microstructures with an increase in the chain-grafting density. The effective thickness of the grafted block layer and the interphase width between the homopolymer melt and the grafted copolymers strongly depend on the physicochemical parameters of the system, such as the composition of the grafted copolymer, the chemical incompatibility between the different components, the length ratio of grafted copolymer to homopolymer, and the grafting density of the diblock copolymers. In addition, the above computational results of microphase-separated structures and interphase properties are qualitatively compared with our previous experimental observations. The comparison indicates that our theoretical results not only reproduce the general feature of the experimental observations, but also elucidate the internal structural information and complement the findings in the region of high grafting densities of diblock copolymers.     

Predicting Polymorphism of Electrospun Polyvinylidene Fluoride Membranes by Their Morphologies

Although electrospinning of polyvinylidene fluoride (PVDF) has been studied for more than 10 years, the crystalline phase differentiation of the electrospun mats is still normally through the combination of different characterization techniques, and the relationship between polymorphism and morphology of the fibers in electrospun PVDF membranes has never been reported. Here, we show their close relationships by conducting room-temperature electrospinning experiments on various polymer/solvent systems. The electrospun membranes full of bead-free fibers have a very high fraction of β-phase, F(β), over 90%, and high orientation, whereas the membranes comprising beads and/or a large number of beaded fibers most often result in a low fraction of β-phase (F(β) normally below 50%) and low orientation. On the other hand, electrospun membranes consisting of both bead-free fibers and a very limited number of beaded fibers showed a medium high fraction of β-phase, F(β) more than 70% but less than 90%. These findings suggest the feasibility of intuitively predicting the crystalline phase of electrospun PVDF membranes directly by their morphologies, which is obviously simple, inexpensive and convenient for future investigations.     

New complexity analysis of a full-Newton step feasible interior-point algorithm for $$P_*(\kappa )$$-LCP

In this paper, we consider a full-Newton step feasible interior-point algorithm for \(P_*(\kappa )\)-linear complementarity problem. The perturbed complementarity equation \(xs=\mu e\) is transformed by using a strictly increasing function, i.e., replacing \(xs=\mu e\) by \(\psi (xs)=\psi (\mu e)\) with \(\psi (t)=\sqrt{t}\), and the proposed interior-point algorithm is based on that algebraic equivalent transformation. Furthermore, we establish the currently best known iteration bound for \(P_*(\kappa )\)-linear complementarity problem, namely, \(O((1+4\kappa )\sqrt{n}\log \frac{n}{\varepsilon })\), which almost coincides with the bound derived for linear optimization, except that the iteration bound in the \(P_{*}(\kappa )\)-linear complementarity problem case is multiplied with the factor \((1+4\kappa )\).     

Preparation and Characterization of PVC-based Photoresponsive Polymers Containing Azo-chromophores

New strategy was developed for the preparation of the photoresponsive polymers containing azo-chromophores as side-groups from the active chlorine atoms of polyvinyl chloride (PVC). The anilinated polyvinyl chloride precursors, anilinated polyvinyl chloride (PVC-An) and o-chloroanilinated polyvinyl chloride (PVC-oClAn), synthesized chemically by reacting PVC with sodium aniline (o-chloroaniline) salt. Then the two novel PVC-based polymers functionalized with azo-chromophores (PVC-AZ-An and PVC-o-AZ-NP) were synthesized via the azo-coupling reactions of the anilinated polyvinyl chloride precursors (PVC-An and PVC-oClAn) with the diazonium salts of aniline and alpha naphthylamine, respectively. The structures of polymers were confirmed by FTIR and ¹H–NMR. The UV-Vis spectra of the obtained polymer in THF solution showed that the π ?π ? absorption band of PVC-o-AZ-NP shifted to longer wavelength (red-shifted) due to the influence of auxochrome (-Cl) compared to the π ?π ? absorption band of PVC-AZ-An.     

Effects of Ultra-sonification Assisting Polyethylene Glycol Pre-treatment on the Crystallinity and Accessibility of Cellulose Fiber

In order to prepare the advanced cellulosic super-absorbent polymer with high grafting level, we tried the novel ultrasound wave assisting polyethylene glycol (PEG) pre-treatment method to decrease the crystallinity and increase the accessibility of cellulose fiber. The effects of ultrasonification assisting PEG method on the crystallinity and swelling capacity of cellulose fiber were investigated. To optimize the experimental condition, the Taguchi method was employed in the treatment process. The influence factors such as ultrasonic wave power, ultrasonic wave time and PEG molecular weight relative to the crystallinity of cellulose fiber were studied systematically. The degree of crystallinity of cellulose fiber was measured by wide-angle X-ray diffraction (WAXD). The morphology of cellulose fiber was observed by environment scanning electron microscopy (ESEM). The effects of pre-treatment variables on the water absorbency and water retention values of cellulose fiber were also investigated. The research results revealed that, under the optimal experimental condition (ultrasonic powder, 500 W; ultrasonic time, 150 s; PEG molecular weight, 600 g/mol), the crystallinity of cellulose fiber decreased from 72.16 to 42.95%. Accordingly, the absorbency of cellulose fiber increased from 1.436 to 2.063 g/g, and the water retention value increased from 47.21 to 113.4%. However, the morphology of cellulose fiber did not change thoroughly compared with the original cellulose fiber. It can be hypothesized that the original inter- and intra-macromolecular hydrogen bonds in cellulose network were weakened, resulting from the high level dispersion of PEG within cellulose network without breaking the surface morphology of fiber.     

Fast naked-eye detection of amines with viologen derivatives

Three viologen derivatives with the ability to detect amines were synthesised. Upon interacting with amines, a rapid colour change caused by electron transfer and charge transfer between viologen derivatives and amines can be directly observed by naked eyes. With fluorine substituents, the detection sensitivity of these viologen derivatives for amines is remarkably enhanced to reach the level of ppm.     

The Effects of Intramolecular Hydrogen Bonding on the Reaction of Phenols with Epoxide in the Presence of Nano Calcium Carbonate

The reaction of phenols and dihydroxybenzenes with epoxide in the presence of nano CaCO₃ was studied. Catechol could react with epoxide and gave monochlorohydrin derivative; other dihydroxybenzenes and monomeric phenols had no reaction under the same conditions. The reaction of catechol with epoxide did not occur when nano CaCO₃ was replaced by a normal one. These were attributed to the strong interaction between nano CaCO₃ and the substrate as catechol possessed intrahydrogen bond and excess active hydrogen, which can induce the intramolecular proton transfer via the intramolecular hydrogen bond and promote the reaction of hydroxyl and epoxide. This is an example revealing the unique role of the hydrogen bond played in chemical reactions.     

Two Thiourea-based Colorimetric Sensors for Anions: Structure and Binding Study

Two colorimetric thiourea-based chemsensors with two relatively rigid arms, 2A and 2B, were synthesized. Their binding abilities with halide anions, AcO^?, [Formula: See Text] were studied by UV-Vis spectroscopy in DMSO. The two sensors showed a notable selective color response to F^? anion from colorless to green-yellow in recognition. The structures of the two sensors and their binding behaviors are discussed. The association constants were calculated by nonlinear fittings of 1:1, 1:2 or 1:1 to 1:2.     

UFLC–MS/MS method for simultaneous determination of six lignans of Schisandra chinensis (Turcz.) Baill. in normal and insomniac rats brain microdialysates and homogenate samples: towards an in‐depth study for its sedative‐hypnotic activity

Schisandra chinensis (Turcz.) Baill., a traditional Chinese medicine, has been clinically used for the treatment of insomnia for centuries. The insomnia mechanism and the possible active ingredients of S. chinensis remain largely unknown. The objective of this study was to develop a method to detect its components which could pass through the blood brain barrier (BBB) by determining the brain microdialysate and brain tissue homogenate samples and then obtain the pharmacokinetic profile in brain for comprehensive understanding of its hypnotic clinical efficacy. Therefore, an efficient, sensitive and selective ultra fast liquid chromatography/tandem mass spectrometry method for the simultaneous determination of six sedative and hypnotic lignans (schisandrin, schisandrol B, schisantherin A, deoxyshisandrin, γ‐schisandrin and gomisin N) of Schisandra chinensis (Turcz.) Baill. in rat brain tissue homogenate and brain microdialysates has been developed and validated. The analysis was performed on a Shim‐pack XR‐ODS column (75 mm × 3.0 mm, 2.2 µm) using gradient elution with the mobile phase consisting of acetonitrile and 0.1% formic acid water. The method was validated in brain homogenate and microdialysate samples, which all showed good linearity over a wide concentration range (r² > 0.99), and the obtained lower limit of quantification was 0.1 ng · ml^?1 for the analytes in brain microdialysate samples. The intra‐ and inter‐day assay variability was less than 15% for all analytes. The study proved the six lignans, as sedative and hypnotic ingredients, could pass through the BBB with brain targeting, distributed mainly in the hypothalamus and possessed complete pharmacokinetics process in brain. The results also indicated that significant difference in pharmacokinetic parameters of the analytes was observed between two groups, while absorptions of these analytes in insomniac group were significantly better than those in normal group. Copyright © 2013 John Wiley & Sons, Ltd.