Use Of Polymers Research Articles

Solubility of solvents in polyethylene below the melt temperature

Polyethylene, the most ubiquitous polymer in use, is a semi-crystalline material. Solvents enter only the amorphous phase. The solubility in that phase, however, cannot be characterized by the amorphous solubility found above the melt temperature. The polymer chains that have ends attached to the crystalline structure but extend into the amorphous phase are referred to as tie chains, and they affect the overall solvent solubility. Six different polyethylenes covering a range of densities were studied. Below the melt temperature all the samples exhibited an increase in solubility with increasing temperature. The solubility of the penetrants, however, is not the same for different types of polyethylene. A model which incorporates an elasticity factor that accounts for the stress effects on the solubility in the tie chains was found to be valuable. When incorporated into a version of the UNIFAC free-volume model there was good correlation between of the solubilities. The present work indicates that the tie chain fraction, f, tends to increase with density.

In-situ modification of carbon fibers with hyperbranched polyglycerol via anionic ring-opening polymerization for use in high-performance composites

In this study, hyperbranched polyglycerol (HPG) is chemically bound onto carbon fiber (CF) surface by anionic ring-opening polymerization for linking fiber and matrix to release interior and exterior applied forces. To explore the optimal conditions for the successful hyperbranched polymerization of glycidol on the carbon fiber, various characterization techniques were employed. The atomic force microscope quantitative nanomechanical mapping results reveal that the HPG can significantly improve interfacial status between carbon fiber and epoxy matrix. Compared with the mechanical properties of desized fiber based composites, both interfacial shear strength and interlaminar shear strength of HPG grafted fiber/epoxy composites increase by 90.69% and 49.83%, respectively. The adjustable size of HPG grafted on CF endorse the CF modification strategy with the unique characteristic, which can design the optimized interface between CF and resin to meet various scientific and technical demands.

Amino group in Leptothrix sheath skeleton is responsible for direct deposition of Fe(III) minerals onto the sheaths

Leptothrix species produce microtubular organic–inorganic materials that encase the bacterial cells. The skeleton of an immature sheath, consisting of organic exopolymer fibrils of bacterial origin, is formed first, then the sheath becomes encrusted with inorganic material. Functional carboxyl groups of polysaccharides in these fibrils are considered to attract and bind metal cations, including Fe(III) and Fe(III)-mineral phases onto the fibrils, but the detailed mechanism remains elusive. Here we show that NH2 of the amino-sugar-enriched exopolymer fibrils is involved in interactions with abiotically generated Fe(III) minerals. NH2-specific staining of L. cholodnii OUMS1 detected a terminal NH2 on its sheath skeleton. Masking NH2 with specific reagents abrogated deposition of Fe(III) minerals onto fibrils. Fe(III) minerals were adsorbed on chitosan and NH2-coated polystyrene beads but not on cellulose and beads coated with an acetamide group. X-ray photoelectron spectroscopy at the N1s edge revealed that the terminal NH2 of OUMS1 sheaths, chitosan and NH2-coated beads binds to Fe(III)-mineral phases, indicating interaction between the Fe(III) minerals and terminal NH2. Thus, the terminal NH2 in the exopolymer fibrils seems critical for Fe encrustation of Leptothrix sheaths. These insights should inform artificial synthesis of highly reactive NH2-rich polymers for use as absorbents, catalysts and so on.

A boosting skin vaccination with dissolving microneedle patch encapsulating M2e vaccine broadens the protective efficacy of conventional influenza vaccines

The biodegradable microneedle patch (MNP) is a novel technology for vaccine delivery that could improve the immunogenicity of vaccines. To broaden the protective efficiency of conventional influenza vaccines, a new 4M2e-tFliC fusion protein construct containing M2e sequences from different subtypes was generated. Purified fusion protein was encapsulate into MNPs with a biocompatible polymer for use as a boosting vaccine. The results demonstrated that mice receiving a conventional inactivated vaccine followed by a skin-applied dissolving 4M2e-tFliC MNP boost could better maintain the humoral antibody response than that by the conventional vaccine-prime alone. Compared with an intramuscular injection boost, mice receiving the MNP boost showed significantly enhanced cellular immune responses, hemagglutination-inhibition (HAI) titers, and neutralization titers. Increased frequency of antigen-specific plasma cells and long-lived bone marrow plasma cells was detected in the MNP boosted group as well, indicating that skin vaccination with 4M2e-tFliC facilitated a long-term antibody-mediated immunity. The 4M2e-tFliC MNP-boosted group also possessed enhanced protection against high lethal dose challenges against homologous A/PR/8/34 and A/Aichi/2/68 viruses and protection for a majority of immunized mice against a heterologous A/California/07/2009 H1N1 virus. High levels of M2e specific immune responses were observed in the 4M2e-tFliC MNP-boosted group as well. These results demonstrate that a skin-applied 4M2e-tFliC MNP boosting immunization to seasonal vaccine recipients may be a rapid approach for increasing the protective efficacy of seasonal vaccines in response to a significant drift seen in circulating viruses. The results also provide a new perspective for future exploration of universal influenza vaccines.

Linker Effects in Porphyrin Polymeric Donor Materials for Photovoltaic Devices

The electronic properties of porphyrin-based polymers for use in organic photovoltaic devices were studied using density functional theory and oligomeric model systems. A number of unique linkers are used to form porphyrin oligomers from monomers. We have calculated the molecular orbitals and energy gap between the HOMO and LUMO of the oligomers, seeking to optimize the gap between the HOMO and the LUMO to increase the wavelength range the devices can absorb and thus increase their efficiency. We have also calculated electron transmission through some of the oligomeric systems to establish which oligomers allow effective charge transport. It is found that linkers that form planar oligomers that extend the delocalization of the molecular orbitals tend to have smaller HOMO/LUMO gaps and enhanced transmission.

Facile control of nanoporosity in Cellulose Acetate using Nickel(II) nitrate additive and water pressure treatment for highly efficient battery gel separators

We succeed in fabricating nearly straight nanopores in cellulose acetate (CA) polymers for use as battery gel separators by utilizing an inorganic hexahydrate (Ni(NO3)2·6H2O) complex and isostatic water pressure treatment. The continuous nanopores are generated when the polymer film is exposed to isostatic water pressure after complexing the nickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O) with the CA. These results can be attributed to the manner in which the polymer chains are weakened because of the plasticization effect of the Ni(NO3)2·6H2O that is incorporated into the CA. Furthermore, we performed extensive molecular dynamics simulation for confirming the interaction between electrolyte and CA separator. The well controlled CA membrane after water pressure treatment enables fabrication of highly reliable cell by utilizing 2032-type coin cell structure. The resulting cell performance exhibits not only the effect of the physical morphology of CA separator, but also the chemical interaction of electrolyte with CA polymer which facilitates the Li-ion in the cell.

Thermo-reversible MWCNTs/epoxy polymer for use in self-healing and recyclable epoxy adhesive

A self-healing and recyclable carbon tube/epoxy adhesive was prepared by epoxy monomer with Diels-Alder (DA) bonds, diethylenetriamine and polyethyleneimine modified multi-wall carbon nanotubes (MWCNTs). The self-healing and recyclable ability was attained by thermally reversible Diels-Alder reaction between furan and maleimide in the epoxy monomer. By controlling the molar ratio of furfuryl glycidyl ether and 4,4′-methylenebis(N-phenylmaleimide), the glass transition temperature and mechanical properties of MWCNTs/epoxy adhesives were varied. The self-healing properties of MWCNTs/epoxy polymers were evaluated by lap shear experiment and the results showed that the MWCNTs/epoxy adhesives exhibited enhanced mechanical properties and excellent self-healing ability under heat stimulus. The healing efficiency was related to the molecule mobility and the conversion of DA reaction between furan and maleimide. The MWCNTs/epoxy adhesives also displayed excellent recyclable ability by transforming into soluble polymer under heating. These materials offer a wide range of possibilities to produce materials with healing and recyclable ability and have the potential to bring great benefits to our daily lives by enhancing the safety, performance, and lifetime of products.

Bithiazole: An Intriguing Electron‐Deficient Building for Plastic Electronic Applications

The heterocyclic thiazole unit has been extensively used as electron-deficient building block in π-conjugated materials over the last decade. Its incorporation into organic semiconducting materials is particularly interesting due to its structural resemblance to the more commonly used thiophene building block, thus allowing the optoelectronic properties of a material to be tuned without significantly perturbing its molecular structure. Here, we discuss the structural differences between thiazole- and thiophene-based organic semiconductors, and the effects on the physical properties of the materials. An overview of thiazole-based polymers is provided, which have emerged over the past decade for organic electronic applications and it is discussed how the incorporation of thiazole has affected the device performance of organic solar cells and organic field-effect transistors. Finally, in conclusion, an outlook is presented on how thiazole-based polymers can be incorporated into all-electron deficient polymers in order to obtain high-performance acceptor polymers for use in bulk-heterojunction solar cells and as organic field-effect transistors. Computational methods are used to discuss some newly designed acceptor building blocks that have the potential to be polymerized with a fused bithiazole moiety, hence propelling the advancement of air-stable n-type organic semiconductors.

Immobilization of 2-Deoxy-d-ribose-5-phosphate Aldolase in Polymeric Thin Films via the Langmuir-Schaefer Technique.

A synthetic protocol for the fabrication of ultrathin polymeric films containing the enzyme 2-deoxy-d-ribose-5-phosphate aldolase from Escherichia coli (DERAEC) is presented. Ultrathin enzymatically active films are useful for applications in which only small quantities of active material are needed and at the same time quick response and contact times without diffusion limitation are wanted. We show how DERA as an exemplary enzyme can be immobilized in a thin polymer layer at the air-water interface and transferred to a suitable support by the Langmuir-Schaefer technique under full conservation of enzymatic activity. The polymer in use is a poly(N-isopropylacrylamide-co-N-2-thiolactone acrylamide) (P(NIPAAm-co-TlaAm)) statistical copolymer in which the thiolactone units serve a multitude of purposes including hydrophobization of the polymer, covalent binding of the enzyme and the support and finally cross-linking of the polymer matrix. The application of this type of polymer keeps the whole approach simple as additional cocomponents such as cross-linkers are avoided.

PH-Triggered Drug Release of Monodispersed P(St-co-DMAEMA) Nanoparticles: Effects of Swelling, Polymer Chain Flexibility and Drug-Polymer Interactions

Monodispersed pH-sensitive poly(styrene-co-N,N′-dimethylaminoethyl methacrylate) (P(St-co- DMAEMA)) nanoparticles (NPs) were synthesized by emulsion polymerization for use in potential applications in targeted drug delivery to the tumor microenvironment. pH-Sensitive volume swelling and drug release of the NPs with varied St/DMAEMA molar ratios, crosslinking degrees and model drug coumarin-6 loading were explored in vitro to elucidate the pH-sensitive drug release mechanisms. The swelling of the NPs, which accounts for the electrostatic repulsion of protonated tertiary amine groups under acidic conditions, reaches maximum at low pH, low crosslinking density and high DMAEMA content. The NPs undergo a pH-triggered drug release, and under the condition of pH 5 and pH 2, the average release rate during 24 h is 1.5-fold and 3-fold higher than that at physiological pH, respectively. The pH-triggered drug release is related to pH-sensitive swelling, polymer chain flexibility and drug-polymer interaction, and is significantly impacted by the St/DMAEMA molar ratio, degree of crosslinking and drug loading.

Investigation of the biocompatibility and cytotoxicity associated with ROP initiator and its role in bulk polymerization of l-lactide

Poly (l-lactide) (PLLA) is one of the most attractive polymers for use in biomedical applications. In such applications it is necessary to reduce the use of toxic chemicals and catalysts used in PLLA synthesis, to minimize any adverse effects. In view of this, we have performed ring opening polymerization (ROP) of l-lactide (LA) using biocompatible initiator, namely, Zinc l-Proline (ZnP) in bulk. High molecular weight PLLA (Mw up to 1.45 × 105 Da) was obtained using the ZnP complex. The ZnP complex is safe, easy to prepare, store and handle. 1H and 13C NMR spectra of PLLA were used to determine the extent of monomer conversion and stereo sequence respectively. Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC) were used to determine thermal properties, Mn, Mw and polydispersity index respectively. The mechanism of ROP of LA in the presence of ZnP was studied using Density Functional Theory (DFT) which was in good agreement with results from 1H NMR and Matrix-Assisted Laser Desorption/Ionization Spectrometry (MALDI-TOF). Biocompatibility/non toxicity of PLLA prepared using ZnP was studied in-vitro using MTT assay by examining the proliferation rate of mouse myoblast C2C12 cell line. Escherichia coli and Staphylococcus aureus were used for the study of antibacterial activity of PLLA.

Anti-biofilm Activity of Solvent-Cast and Electrospun Polyhydroxyalkanoate Membranes Treated with Lysozyme

Biofilms consist of groups of microorganisms that adhere to surfaces, such as wound and implant surfaces, making it difficult to prevent or remove their formation by antibiotic treatment, due to the innate resistance of the biofilm. Effective treatments of medical biofilms are limited. Polyhydroxyalkanoate (PHA) is a biodegradable and biocompatible polymer that is a suitable alternative to petroleum based polymers for use as a raw material for medical applications. In this study, membranes of the copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB-co-HHx)] containing different HHx monomer contents were used due to its porosity and flexibility, and different sheets were prepared by solvent-casting and electrospinning methods. The sheets were loaded with lysozyme in order to measure the maximum amount of protein adsorption and to examine the ability of immobilized enzyme to inhibit biofilm formation and detach previously established biofilms. Our results have shown maximum loading of 16.1 µg enzyme per 9.5 mm3 discs, and these sheets are effective for inhibiting biofilm formation. Also, lysozyme loaded, eletrospun sheets were observed to more effectively inhibit biofilm formation, as compared to solvent-cast sheets. Based on this study, P(HB-co-HHx) sheets are a suitable material for being used as a potential raw material for fabrication of wound dressings to be used in anti-biofilm treatments.

Preparation of zirconium and hafnium complexes containing chiral N atoms from asymmetric tertiary amine ligands, and their catalytic properties for polymerization of rac-lactide

Preparation of Zr and Hf complexes containing chiral N atoms, and their use in polymerization of rac-lactide.

Cyano substituted benzotriazole based polymers for use in organic solar cells

A new synthetic route to the electron accepting di-cyano substituted benzo[d][1,2,3]triazole (BTz) monomer 2-(2-butyloctyl)-4,7-di(thiophen-2-yl)-2H-benzotriazole-5,6-dicarbonitrile (dTdCNBTz) is reported.

Anticorrosion and physical properties of organic coatings containing perovskites surface modified by polyaniline or polypyrrole phosphates

The work describes the properties of perovskites pigments subjected to surface treatment with conductive polymers for use in protective coatings. The perovskites (XYO3; X = Zn, Ca, Sr; Y = Ti, Mn) were synthesised by high-temperature solid-phase reaction, and their surface was modified with a conductive polymer, specifically polyaniline phosphate (PANI) or polypyrrole phosphate (PPy), by chemical oxidative polymerisation. Conductive polymers are currently attracting considerable interest in a number of sectors, among them the paint industry owing to their non-toxicity and high stability. Paints consisting of a solvent-based epoxy-ester resin as the binder and the above-mentioned perovskite/PANI/PPy pigments were formulated. Corrosion resistance of the coatings was evaluated in dependence on the type of particle surface treatment with the conductive polymer, chemical composition of the pigment, and pigment volume concentration (PVC) in simulated corrosive atmospheres. The effect of the surface-treated inorganic composite pigments on the corrosion rate was investigated using electrochemical tests and accelerated corrosion tests.

27P Pectin-Chitosan conjugates novel biomaterial as platform for colon cancer drug delivery

Background In comparison to injectable, oral delivery of chemotherapeutic agents, especially in the form of a colon specific delivery system is expected to increase drug bioavailability at target site, reduce drug dose and systemic adverse effects. Pectin (PEC) and Chitosan (CS) are suitable and well documented independently drug delivery polymers for use as colon specific drug delivery as it is selectively digested by colonic microflora to release drug with minimal degradation in upper gastrointestinal tract. Pectin chitosan bioconjugate has not been synthesized and well studied for their suitability in colon cancer drug delivery applications; hence we have attempted to synthesize PEC-CS conjugate system. Methods Pectin-chitosan conjugate system was developed by conjugating the free carboxyl group of moiety of pectin and primary amine group of CS. Synthesized material was characterized by FTIR, XRD, DSC, TGA and SEM. Cancer cell toxicity study of the synthesized material were done in HT29 colon adeno- carcinoma cell lines using MTT assay. Results Pectin reacts with -NHS to form an ester in presence of DCC in anhydrous conditions along with the side product dicyclohexylurea, and finally CS reacts with this mixture replacing NHS to form the conjugate. The peaks in the region 1709 cm-1 and 1641 cm-1 corresponds to weak carbonyl stretch due to H-bonding and the amide-I band of the formed conjugate. Also seen in the FTIR spectrais the peak belongingt o amide-II band of secondary amides at 1554 cm-1 and C-C ring stretch at 1509 cm-2. The conjugate showed significantly low weight loss till 300 C (23.6%) as comparedto PEC.TheaboveresultopinedthatPEC-CSexhibitedhighthermalstabilityascompared to its native precursor. The plain PEC showed its Tgat69.55 C, while in PEC-CS itwas observed at55.13 C. This result confirmsthat movementof molecule in PEC-CS is unhindered as compared to in PEC. The conjugation was confirmed by FTIR, and XRD. TheDSCandTGAanalysisexhibitedformationofamorethermostablematerialas compared to its native precursors. The conjugated material did not exhibit any cytotoxicity in HT29 cells. Conclusions The results showed a potential to be used this novel conjugate material for colon cancer drug delivery application. Legal entity responsible for the study Akhilesh Vikram Singh Funding UGC-MHRD, New Delhi, India Disclosure A.V.Singh: The presented work is purely academic research and funded by Government of India (UGC-MHRD,NewDelhi).

Macromolecular design of specialty polylactides by means of controlled copolymerization and stereocomplexation

AbstractAmong the biobased polymers developed, poly‐l‐lactide (PLLA) has been the most widely used in many fields because of its excellent cost − property balance. However, the properties and functionalities ofPLLAcannot easily be controlled like the conventional petroleum‐based polymers, retarding the progress of its manufacturing on a large scale. One approach to obtain high‐performance and specialty polylactides is to use stereocomplex‐type polylactides (sc‐PLA) that can be obtained by mixingPLLAand its enantiomer poly‐d‐lactide. The other approach is to use copolymers consisting of polylactides (PLA) and other types of macromolecular chains. Here we demonstrate how such high‐performance and specialtyPLApolymers can be designed and synthesized. These macromolecular designs and synthetic methodologies are highly effective for controlling the structure and properties ofPLApolymers for use as biomedical and high‐end industrial materials. © 2016 Society of Chemical Industry

Development of High-Energy Li-S Batteries Based on Commercial Materials and Water-Soluble Functional Binders

The lithium-sulfur (Li-S) battery has seen a resurgence of interest in recent years, with hundreds of journal articles now published every year. Significant advances have been made towards tackling the long-standing issues of poor efficiency and cycle life, most of which derive from the well-known polysulfide redox shuttle. Optimisation of the structure of the positive electrode, to improve contact to insulating solid particles and control the diffusion of soluble intermediates, has been one of the most intensely explored areas within this field. However, much of the published research involves increasingly exotic materials synthesis techniques which may not prove suitable when scaled up to the order of tons, which would be required if the system is to break into consumer applications. Our group has previously investigated the use of functional polymers for use as binders in this system, particularly polyethers, such as PEO, and amide/lactam-containing polymers such as PVP. These water-soluble commodity polymers can actively improve active material utilisation, efficiency, and rate capability, depending on the materials chosen. Recently, we have investigated the compatibility of these materials with commercially available carbon materials suited towards electrodes with higher energy densities (e.g., highly porous carbon blacks). In this way, electrodes have been prepared from water-based processes with sulfur loadings of 65% and higher and areal capacities up to 4 mAh/cm2, with reversible sulfur utilisations in excess of 1000 mAh/g. Such figures are among the highest reported for this system. This presentation will summarise our work in optimising positive electrodes based on porous carbon blacks and functional binders. New results on previously unreported materials will also be presented, as well as the results of electrochemical characterisation of cells employing these electrodes where other cell components have been further optimised towards high-energy: particularly the electrolyte volume and the excess of the lithium-metal anode.

Polymer surface modification using UV treatment for attachment of natamycin and the potential applications for conventional food cling wrap (LDPE)

The purpose of this study was to develop an active non-migratory antifungal Low Density Polyethylene (LDPE) polymer for use in food packaged applications. The functional acrylic acid monomer was grafted on the LDPE film surface by photo-initiated graft polymerization using Ultra Violet light irradiation (from 0 to 5min). Natamycin, an antifungal agent, was applied to the treated film to bind with the pendent functional groups and were evaluated its performance against mold and yeast. The grafted amounts were determined by gravimetric measurement and dye absorbance. Attenuated Total Reflectance/Fourier Transfer Infrared Spectroscopy, scanning electron microscopy, mechanical strength test was used to characterize film properties. The antifungal efficacy of the film was evaluated with Saccharomyces cerevisiae and Penicillium chrysogenum on growth media and fresh cut cantaloupe. The amounts of the grafted group were increased with the longer ultraviolet exposure time. The amount of the grafted natamycin on the treated film was up to 49.87μg/cm2, and the film inhibited mycelium formation of P. chrysogenum spores by over 60%. Due to the thickness of the film (less than 12.25μm), long time UV exposure decrease the film’s mechanical strength. The application of such non-migratory active packaging film represents a promising approach to maintaining food quality with reduced additive.

Microwave-assisted synthesis and high-performance anhydrous electrorheological characteristic of monodisperse poly(ionic liquid) particles with different size of cation/anion parts

Abstract Monodisperse poly(ionic liquid) particles with a styrenic backbone and different size of quaternary ammonium/fluorinated imide ion parts were synthesized by microwave-assisted dispersion polymerization for use as high-performance anhydrous polyelectrolyte-based smart electrorheological materials. The morphology and structure of particles were characterized by SEM, NMR, FT-IR, and TGA. The electrorheological effect of poly(ionic liquid) particles in silicone oil was investigated by rheometer under electric fields. It showed that, different from classic polyelectrolytes, the poly(ionic liquid) particles possess strong electrorheological effect in dry state and the electrorheological effect depends on the size of cation/anion parts. The poly(ionic liquid) particles having smaller cation/anion parts possess stronger electrorheological effect. Dielectric analysis indicated that the local ion motion-induced interfacial polarization is responsible for the strong electrorheological effect of poly(ionic liquid) particles and the dependence of electrorheological effect on the size of cation/anion is related to the change of interfacial polarizability with the size of cation/anion parts.