Polymer Science, Series A最新文献

Poly(N-vinyl succinimides) synthesized by classical radical polymerization are studied by the methods of molecular hydrodynamics in dilute solutions in dimethylformamide within a 40-fold MM range. The molecular characteristics and scaling ratios of poly(N-vinyl succinimide) molecules are determined, and their equilibrium rigidity is estimated.

Bio composites of acrylonitrile butadiene rubber (NBR) reinforced with chitosan were prepared using dicumyl peroxide (DCP) as a curing agent. Composites with two types of chitosan with different degrees of deacetylation (DD) were studied i.e., Chitosan with 85% DD and 75% DD. The cure characteristics of composites were studied. The mechanical properties of NBR were found to be improved by the incorporation of chitosan. The composite containing 20 phr chitosan has the best balance of mechanical properties. The swelling behavior of the composites in non-polar solvents such as petrol, diesel, kerosene, toluene, and hexane were analyzed for the swelling coefficient values which supports the results of mechanical properties. Antimicrobial properties of the composites were studied by inoculating the composites with Aspergillus niger (A. niger) fungus on a potato dextrose agar media and incubated for 60 days at room temperature. It is found that presence of chitosan resist the microbial action on the composite samples compared to the gum sample. It is believed that the outcome obtained from the present study is to develop environment-friendly composites for various applications such as oil seals, hoses, automobile bushes, etc.

The spatial distribution of filler particles and their agglomeration depending on concentration and size was studied. In all cases, silica particles served as filler. The particle size varied over a wide range, from nanoparticles to glass beads, and therefore the filler particles have the same nature. An amorphous polymer (polysulfone) and a crystallizing polymer (polypropylene) were chosen as a matrix for comparison. The filler concentration over the cross-section of the samples was determined visually and by electronic chemical analysis. It was shown that with increasing particle size, the tendency to redistribute the concentration increases in such a way that the near-wall region becomes depleted of filler. This effect is more pronounced for high filler concentrations and for a crystallizing polymer compared to an amorphous one.

Due to wide application of biomaterials in drug delivery systems for wound healing, this research work is focused on the development and characterization of a Gelatin/Glycerol composite film for delivering the antibiotic Erythromycin. The aim was preparing gelatin/glycerol films loaded with erythromycin suitable for a future application as a patch for skin wound healing application. A set of films were prepared with various gelatin to glycerol weight ratio and the impact of glycerol content on the mechanical, physicochemical and thermal behavior of film evaluated. Erythromycin was loaded into the film and the antibacterial activity evaluated versus E.coli and S.aureus. Results demonstrate a correlation between the content of glycerol and the physico-chemical properties of the film. The Ge/GY films containing the drug show good antibacterial effects only against Staphylococcus aureus bacteria. TGA and DSC of Ge/ GY thin films showed thermal stability until 110°C, however, the complete decomposition occurred at 350°C.

Dual-modal fluorescent/magnetic resonance imaging attracts more and more attentions in biomedical applications. Herein, star-shaped poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) amphiphilic copolymer with a tetrakis-(4-amino)-terminated tetraphenylethylene core was synthesized. Then, dual-functional nano micelles were achieved via a facile self-assembly of the star copolymer and in situ encapsulation of iron oxide nanoparticles. The fluorescent characteristic of the tetraphenylethylene moiety and encapsulation of iron oxide endowed the resultant dual-functional micelles with bright fluorescence and superparamagnetic properties, which indicated that the PCL segments coated on magnetic nanoparticles is effective at separating the conjugated core from iron oxide nanoparticles to minimize fluorescence quenching. The obtained micelles were found to have a good colloidal and fluorescent stability in different environment. In vitro studies revealed that these dual-functional micelles could serve as an effective fluorescent probe to achieve imaging of MCF-7 cells without obvious cytotoxicity. Thus, this work provides a facile strategy to fabricate fluorescent-magnetic dual-functional micelles for dual-modal imaging applications.

To study the effects of graphene oxide (GO) dimension on the mechanical and dielectric performance of epoxy resin (EP), two kinds of GO with different dimensions were selected and characterized by Fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The results showed that the two kinds of GO had similar chemical structure, but different average particle sizes of 190.1 nm (SGO) and 1510 nm (MGO), respectively. The mechanical properties, dynamic mechanical properties, and dielectric properties of the EP/GO composites are analyzed using electronic universal testing machine, Rockwell hardness tester, dynamic mechanical analysis (DMA) and broadband dielectric impedance relaxation spectrometer. Results revealed that the GO dimension plays important role in determining the dispersion of the filler in EP matrix, and further determines the mechanical properties and dielectric performance of the composites. EP/SGO with better dispersion of GO in the EP matrix exhibits better mechanical properties, higher glass transition temperature, higher dielectric constant. Related mechanism has been proposed.

Biodegradable poly(ɛ-caprolactone) (PCL), which is used in bioengineering applications thanks to its mechanical and biodegradable properties, it used as a polymer matrix in this study. The nanocomposite of PCL reinforced with recycled red mill scale PCL/RS has been prepared via ultrasonic mixing by solution casting technique at different amounts of RS (1, 5, 10, and 20 wt %), while virgin PCL was also produced for comparison. The structural, thermal, mechanical, and optical behaviors of PCL/RS nanocomposite films have been investigated. Raman spectroscopy shows that small amounts of particles ≤10 wt % may act as nucleation sites for the growth of polymer crystallites; While large amounts of particles will destroy crystallization zones. Blue shifts in spectrum Raman might be caused by the electronic interactions associated with charge transfer between PCL and RS nanoparticles. The XRD results is in good agreement with the Raman results that the crystallinity of esters increases in PCL/RS 10 wt % film. The melting temperature T_m of the nanocomposites is in the order of PCL/RS 1 wt % (71.1°C) > PCL/RS 5 wt % (71°C) > PCL/RS 10 wt % (70.3°C). We note that it has a resemblance in the values established by DRX and DSC, the crystallinity rate increases with the increase in the filler content 45 < 47 < 69 < 74.5. The nanocomposite materials prepared have UV-protective properties. Tensile results increase with an slight increase in RS filler at 5 wt % is 2 MPa, in comparison with PCL/RS 10 wt % (~1 MPa this result yields flexibility of the film and indicates good dispersion of RS in nanocomposite, resulting better interfacial adhesion.

The effect of ZrO₂ nanoparticles on the structural, electrical, and dielectric properties of polyaniline was studied. ZrO₂ nanoparticles with an average size of 8 nm were synthesized by a simple precipitation method and their tetragonal and monoclinic crystalline phase was confirmed. Polyaniline and its nanocomposite with ZrO₂ have been synthesized by chemical oxidation method using CH₃COOH as a doping agent and APS as an oxidant. The synthesized composites were analyzed by infrared spectroscopy, X-ray diffraction, scanning electronic microscopy, AC conductivity, dielectric and impedance spectroscopy. In Nyquist plots, systematic decrement in the semicircle size was observed with growth of ZrO₂ content. The dielectric constant in the PANI/ZrO₂ composite has been increased with an increase in weight content of ZrO₂ in PANI matrix and exhibited the Maxwell–Wagner–Sillars effect.

The cross-linking of bacterial cellulose (BC), hydroxypropyl methylcellulose (HPMC), and hyaluronic acid (HA) accomplished with the Copper (I) catalyzed azide-alkyne cycloaddition (CuAAC) click reaction was investigated to obtain the multicomponent hydrogels that allow selective control of material properties. Click chemistry is one of many design methodologies that can be used to create hydrogels for multi-component systems. BC, HPMC, and HA are the most preferred and suitable natural polymers for tissue engineering studies. However, in order to combine their properties in a synergistic way, they must be functionalized to interact with each other. In this study, azide-functional HA was achieved by the reaction of hyaluronic acid with 1-azido-2,3-epoxypropane. To obtain multicomponent hydrogel alkyne-terminated cellulose is also prepared. The cellulose and hyaluronic acid functionalization was confirmed by using FTIR and NMR analysis. The crosslinking reaction took place at ambient conditions for 24 h. It was observed that the swelling capacity of the multi-component hydrogel declined with the increasing amount of BC due to its high crosslinking degree. In addition, the porous morphology of hydrogels makes them suitable for wound dressing applications. SEM results revealed that pore size and porosity decreased with increasing BC concentration. MTT assay demonstrated that the hydrogels promote cell proliferation and adhesion for 3T3 cells. In vitro cell culturing within the hydrogel demonstrated good cell spreading.

In the present investigation synthesis of Xanthan Gum (XG-g-PAAcoAM), Lignosulphonate sodium salt (LS-g-PAAcoAM), and their combination (XG/LS-g-PAAcoAM) based hydrogels by grafting them onto acrylic acid and acrylamide for efficient removal of Methylene Blue dye have been reported. The results were found to be reliable with a removal rate exceeding 91% when administered at a dosage of 0.2 g in a 20 mL solution of Methylene blue dye over a period of 7 h. The hydrogels have been characterized by various techniques using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction analysis. Among the three commonly used isotherms (Langmuir, Freundlich, and Temkin), the Freundlich isotherm model exhibits the highest level of fit for the dye adsorption as evident with the R² value of 0.99. This study provides a meaningful comparative insight towards using these natural polymers i.e., XG and LS as feedstock for hydrogel synthesis and efficient adsorbent for wastewater treatment applications.