Chemical Structure Of Samples Research Articles

Characteristic comparison of lignocellulose nanofibrils from wheat straw having different mechanical pretreatments

AbstractWheat straw (WS) was considered the most abundant agricultural residue in China. Therefore, it was meaningful to explore the effective utilization of WS. Thus far, WS has been considered a potential raw material to produce lignocellulose nanofibrils (LCNFs) with the rapid development of nanotechnology. Unfortunately, the existing methods of LCNFs preparation directly from WS still faced some hurdles. Herein, screw extrusion and ball milling considered the common mechanical pretreatments were employed to directly prepare LCNFs from WS. The different impacts of screw extrusion and ball milling pretreatments on the properties of LCNFs were revealed by systematically comparing physicochemical analyses. The results showed that the crystalline and chemical structure of samples was little affected by the mechanical pretreatment. However, the mechanical pretreatment caused a change in the morphology, yield, and chemical composition of LCNFs. LCNFs prepared by screw extrusion with a high yield of 73% had the narrowest diameter distribution (0 ~ 80 nm), the most cellulose content (51.1%), and the maximum crystallinity degree (44.7%). LCNF samples all exhibited good thermal stability. This work could not only offer theoretical guidance on the preparation of LCNFs by mechanical pretreatments but also expand the high‐value application of WS in polymer composites.

Facile construction of superhydrophobic polydopamine-based film and its impressive anti-corrosion performance on zinc surface

Under weakly alkaline conditions, polydopamine (PDA) has strong adhesion to the surface of metal materials and chelate adsorption to nanoparticles. According to this characteristic, polydopamine (PDA) was formed by spontaneous polymerization of dopamine (DA), and then modified with octadecylamine (ODA) and 1H,1H,2H, 2H-perfluoro-decyl mercaptan (PFDT) to form a dense and uniform superhydrophobic film on the surface of zinc material. SEM, XPS, FTIR, SVET, electrochemical measurement (polarization curve and impedance spectroscopy) and other methods were used to characterize the surface morphology and chemical structures of samples before and after modification. The water contact angle (WCA) were further used to analyze the wettability of the superhydrophobic film. The experimental results show that the zinc surface with superhydrophobic PDA film exhibits higher corrosion resistance and lower corrosion current density than control groups, and the modification effect of PFDT is better. Moreover, the corrosion resistance of pure zinc can be significantly improved by the modification treatment, which is the effect of “micro nano structure air valley” formed by the superhydrophobic film layer and the enhancement of adhesion.

Preparation and Characterization of Polyimide/TiO2 Nano-composites for Non-lethal Weapon

A series of Polyimide/TiO2 (PI/TiO2) nano-composites were successfully prepared by incorporating different nano-sized TiO2 contents into PI which derived from pyromellitic dianhydride (PMDA) and a flexible diamine 4,4-bis(3-aminophenoxy)biphenyl (4,3-BAPOBP) via in-situ polymerization and a thermal imidization method. The micromorphology, chemical structure of samples were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR). The SEM results show that when the content of nano-TiO2 is lower, the nano-TiO2 can be distributed uniformly in the matrix by the method of this experiment scheme, and signs of agglomeration have begun to appear when the TiO2 content is 12 wt.%. XRD patterns reveal the crystal structure of TiO2 remains unchanged and stable after being doped into PI matrix, and the TiO2 nano-particles have good compatibility with PI matrix

Multi-responsive poly(amidoamine)-initiated dendritic-star supramolecular structures containing UV cross-linkable coumarin groups for smart drug delivery

Dendritic-star supramolecular structure of poly(amidoamine)-g-[polystyrene-b-(2-(dimethylamino)ethyl methacrylate-co-11-((4-methyl-2-oxo-2H-chromen-7-yl)oxy)undecyl acrylate)] (PAMAM-g-P(St-b-(DMAEMA-co-CuA))) was synthesized via grafting-from atom transfer radical polymerization (ATRP) by using PAMAM-initiator as smart drug carrier. This structure consisted of multi-responsive unites of hydrophilic PDMAEMA regarding to pH change, temperature, and CO2 gas and the coumarin molecule as photocrosslinking agent. Photocrosslinking agent is efficient for controlling DOX release after dimerization under UV light. The chemical structure of samples was confirmed by proton nuclear magnetic resonance (1H NMR) and their molecular weight was studied by gel permeation chromatography (GPC). The change of hydrophilic length of PDMAEMA and pH media resulted in various morphologies including hollow sphere, snowman- and dumbbell-like particles. The morphology of supramolecular assemblies was not changed after photocrosslinking, which confirmed the structure stabilization under UV light irradiation of 365 nm. Fluorescence microscopy was confirmed the presence of fluoresce segments in self-assembled supramolecular structures. Dynamic light scattering (DLS) indicated that the size of supramolecular assemblies was changed through the response to external stimuli such as pH, temperature, and CO2 gas. The DOX release behavior was investigated in different conditions such as pH, temperature, and after photocrosslinking under UV light of 365 nm.

The effect of plasma polymerization of silicon compounds on the properties of biaxially oriented polypropylene (BOPP)

In this study, hexamethyldisiloxane was polymerized on the biaxially oriented polypropylene films by low-pressure radio frequency (RF) plasma. The samples were polymerized by using RF plasma in the frequency range of 13.56 MHz at the different polymerization times. The surface properties and chemical structure of samples were examined by contact angle measurement, atomic force microscopy, scanning electron microscopy and Fourier transformation infrared (FTIR). Also, the scratch behavior and the mechanical properties of samples were evaluated by using SPM lithography. In this work, some distinguishing changes were observed in properties of polymerized samples in comparison with raw sample. Results showed that the scratch resistance increased by prolonging polymerization time, whereas the surface energy decreased dramatically. It can be inferred from SPM and FTIR data that there is a direct relationship between scratch resistance and chemical composition of samples. Scratch resistance is mostly affected by silicon compounds deposited on the samples. Plasma polymerization causes changes in the chemical structure and surface properties of samples.

Visible-Light Induced Photodegradation of Methyl Orange via Palladium Nanoparticles Anchored to Chrome and Nitrogen Doped TiO2 Nanoparticles

The Cr/N–TiO2 and Pd/Cr/N–TiO2 were synthesized via sol–gel and photoreduction techniques respectively. Subsequently, optimized samples were utilized as photocatalyst agent to degradation of methyl orange under visible light. Tetraisopropyl orthotitanate, chromium nitrate Cr(NO3)3·9H2O, palladium nitrate Pd(NO3)2 and triethylamine was used as precursors. The crystalline structure, morphology, particle size, absorbance, band-gap and chemical structure of samples were characterized by X-ray diffraction, diffuse reflectance spectra, scanning electron microscopy, energy dispersive spectrometry and Fourier transform infrared (FT-IR) techniques, respectively. Results demonstrate that nature and amount of dopant affect photocatalytic activity. For degradation of methyl orange, optimum concentration of Cr3+ and Pd was obtained 2% and 10% respectively. After 240 min, under visible light, photocatalytic efficiency of 2%Cr/2%N–TiO2 was obtained 97.59%. Also, after 75 min, under ultra violet light, photocatalytic efficiency of 10%Pd/2%Cr/2%N–TiO2 was obtained 97.56%.

A Novel Stimuli-Responsive Magnetite Nanocomposite as De Novo Drug Delivery System

ABSTRACTA novel stimuli-responsive magnetite nanocomposite as de novo drug delivery system for cancer chemotherapy is developed successfully through the incorporation of magnetite nanoparticles into PEG-b-(PNIPAAm-b-PAA)2 copolymer. The chemical structures of samples were characterized using FTIR and 1H NMR spectroscopies. Furthermore, thermal property, morphology, size, and magnetic properties of the nanocomposite were investigated. The DOX loading and encapsulation efficiencies as well as stimuli-responsive drug release ability of the nanosystem were studied. As results, at pH 5.3 and temperature of 41°C the nanocomposite exhibited higher drug release values, which qualified it for cancer chemotherapy according to especial features of cancerous tissue.

Synthesis and characterization of novel environmentally friendly shape memory polyurethanes based on poly(epsilon-caprolactone) diol/castor oil mixtures

A new category of polyurethane plastics (PUs) was obtained from poly (e-caprolactone) diol/castor oil mixture as a dual-component of their soft segment and hexamethylene diisocyanate (HDI) as the hard segment. The main aim of this study was to explore the effect of castor oil on content chemical structure, dynamic and mechanical properties and low temperature heat induced shape memory of the obtained polyurethane system. The chemical structure of samples was confirmed by Fourier transforms infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC) was carried out to study thermal transitions of synthesized polyurethanes. At 50 mol % of oil, the polyurethane showed the highest enhancement in tensile strength (54%) and Young’s modulus (23%) compared to PU-0. The PU containing 50 mol % of oil was nearly recovered by 99%.

Structural, thermal, mechanical, swelling, drug release, antibacterial and cytotoxic properties of P(HEA/IA)/PVP semi-IPN hydrogels

The aim of this work was to synthesize a series of semi-interpenetrating polymer networks (semi-IPNs) of 2-hydroxyethyl acrylate and itaconic acid, in the presence of poly(N-vinylpyrrolidone). Samples were synthesized by free radical copolymerization with constant PVP and variable IA content and characterized for structural, morphological, thermal, swelling, drug release, antibacterial and cytotoxic properties. The chemical structure of samples was confirmed by Fourier-transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) was used to examine morphology of samples and glass transition temperatures were determined by differential scanning calorimetry (DCS). The pH and temperature sensitivity was confirmed by measuring the dependence of the degree of swelling on pH and temperature. All samples show volume phase transition temperature (VPTT) around 47°C. Drug release profiles were investigated using vitamin B3 as a model drug. The vitamin B3 transport mechanism was studied by fitting experimental data to five different model equations and calculating the corresponding parameters. It was also observed that IA content has a marked influence on the release profiles of vitamin B3, so the rate of drug release can be designed by changing the HEA/IA ratio. Cell viability, performed using MTT test, was high for all samples and all concentration of extract used. The antibacterial activity of hydrogels was determined against Pseudomonas aeruginosa. It turns out that IA content and time of exposure have an influence on the antibacterial potential. All samples showed satisfied cell viability. Due to these characteristics, P(HEA/IA)/PVP semi-IPNs represent interesting biomaterials for biomedical applications.

Chemical and electrochemical grafting of polyaniline onto poly(vinyl chloride): synthesis, characterization, and materials properties

We have designed and developed a new strategy for the chemical and electrochemical graft copolymerization of aniline onto poly(vinyl chloride). For this purpose, first phenylamine groups were incorporated into poly(vinyl chloride) via a nucleophilic substitution reaction in the presence of a solvent composed of 4-aminophenol, potassium carbonate, and dry N,N-dimethylformamide at room temperature, in order to avoid cross-linking. The macromonomer obtained was used in chemical and electrochemical oxidation copolymerization with aniline monomer to yield a poly(vinyl chloride)-g-polyaniline (PVC-g-PANI) graft copolymer. The chemical structures of samples as representatives were characterized by means of Fourier transform infrared and 1H nuclear magnetic resonance spectroscopies. The electroactivity behaviors of the synthesized samples were verified under cyclic voltammetric conditions. The electrical conductivity and electroactivity measurements showed that the PVC-g-PANI graft copolymer has lower electrical conductivity as well as electroactivity than those of the pure PANI. However, the lower electrical conductivity and electroactivity levels in this material can be improved at the price of solubility and processability. Moreover, the thermal behavior and chemical composition of the synthesized graft copolymer were investigated. Copyright © 2016 John Wiley & Sons, Ltd.

A facile and effective immobilization of glucose oxidase on tannic acid modified CoFe2O4 magnetic nanoparticles

This article presents a study of glucose oxidase (GOx) immobilization by employing tannic acid (TA) modified-CoFe2O4 (CFO) magnetic nanoparticles which demonstrates novel aspect for enzyme immobilization. By using the strong protein and tannic acid binding, GOx immobilization was carried out via physical adsorption in a simpler way compared with the other immobilization methods which require various chemicals and complicated procedures which is difficult, expensive, time-consuming, and destructive to the enzyme structure. CFO was synthesized by hydrothermal synthesis and modified with TA to immobilize GOx. The immobilized GOx demonstrated maximum catalytic activity at pH 6.5 and 45°C. The samples were characterized by vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), zeta potential, and fourier transform infrared spectroscopy (FTIR), all of which confirm the surface modification of CFO and GOx immobilization. Also, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were performed to demonstrate the surface morphology and chemical structure of samples. According to the Lineweaver–Burk plot, GOx possessed lower affinity to glucose after immobilization, and the Michelis–Menten constant (KM) of immobilized and free GOx were found to be 50.05mM and 28.00mM, respectively. The immobilized GOx showed excellent reusability, and even after 8 consecutive activity assay runs, the immobilized GOx maintained ca. 60% of its initial activity.

Study on the Micro-Phase Structure of Hydrophilic Polyurethane with Mixed Polyester and Polyether Soft Segments

Polyether-polyester nonionic hydrophilic polyurethanes with amorphous soft segment phase are prepared from 4,4’- diphenylmethane diisocyanate (MDI), polybutylene adipate glycol 2000 (PBA2000) and polyethylene glycol 1000 (PEG1000) with 1,4-butanediol (BDO) as chain extender. Further more, the relationships between micro-phase structure and chemical structure of samples is investigated. The studies show that the chemical structure has remarkable effects on the micro-phase structure of hydrophilic polyurethane and micro-phase separation degree of the mixed soft domains.

In situ solvothermal synthesis and characterization of transparent epoxy/TiO2 nanocomposites

AbstractA solvothermal process was developed to in situ prepare epoxy (EP)/TiO2 hybrid precursors. The chemical structure of samples was confirmed by X‐ray and Fourier transformed infrared spectroscopy. Field emission scanning electron microscope micrographs of cured EP/TiO2 hybrid composites showed that well‐dispersed TiO2 nanoparticles were successfully in situ formed in epoxy matrix through the solvothermal process. The thermogravimetic analysis, DSC, and gel content measurements showed that EP/TiO2 hybrid precursors were fully cured with the glass transition temperature decreasing gradually. The effect of TiO2 contents on optical and surface properties was investigated in detail. The results indicated that epoxy/TiO2 nanocomposites exhibited excellent UV shielding effect and high visible light transparency. The contact angle of EP/TiO2 nanocomposites, when the content of silane‐coupling agent (KH560) was 5 g and the content of tetrabutyl titanate (TBT) was 3 g, can reach as high as 101°, which was 36° higher than that of pure EP, representing for the increase of hydrophobicity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012