► Alginates can be crosslinked with various cations to modify the characteristics of the resultant matrices for different applications. ► New strategies have been successfully employed to improve the ...gelation mechanism of alginates. ► Innovative wound dressings with haemostatic, absorbent and antimicrobial properties have been developed. ► A number of patents involving alginate formulations for cell transplant have emerged. ► Alginates can be employed for rapid, as well as prolonged delivery of bioactive compounds.
This review outlines the role of alginates in microencapsulation and therapeutic applications. It focuses on the physicochemical properties of alginates (e.g. viscosity, thermo-stability, sol–gel transformation and drug release) to gain better insight into their potential medical applications, particularly for wound care and therapeutics. In order to understand how alginates can be optimized as a useful delivery system for therapeutic applications, various factors that impact drug release from alginate matrices (e.g. types of cations used in cross-linking, porosity of alginate matrices, pH effect, alginate composition, molecular weight of encapsulated drugs and modification of the functional groups in alginates) are also discussed. More specifically, practical applications of the cross-linking mechanism and sol–gel transformation property of alginates are explored to assess their potential to improve the mechanical properties of alginate dressings, to impart anti-microbial properties for treating wound infections and to develop products for tissue repair and wound healing. Innovative processes of developing alginate carriers and delivery systems and their recent applications are also discussed. Strategies employed to improve gelation of alginates commonly target the formulation by the inclusion of non-gelling cations or sequestrants during cross-linking. The application of other strategies, such as hot-made alginate gel method,
in situ gelation method, crystal gun method, acoustic excitation method, and the use of extrusion devices with improved design are reviewed.
A high‐molar‐mass cylindrical brush polymer with a main chain degree of polymerization of Pw = 1047 is synthesized by free‐radical polymerization of a poly‐2‐isopropyloxazoline macromonomer with Pn = ...28. The polymerization is conducted above the lower phase transition temperature of the macromonomer, i.e., in the phase‐separated regime, which provides a sufficiently concentrated macromonomer phase mandatory to obtain high‐molar‐mass cylindrical brushes. Upon heating to the phase transition temperature, the hydrodynamic radius is observed to shrink from 34 to 27 nm. Further increase in temperature resulted in aggregated chains which were observed to coexist with single chains until eventually only aggregates of μm size were detectable.
Free‐radical polymerization of poly‐2‐ isopropyl‐oxazoline macromonomers in the phase‐separated regime yields cylindrical brush polymers with several hundred nanometers in length and a large Kuhn statistical segment length of lk = 110 nm. Upon polymerization, the cloud point temperature is suppressed by approximately 20 °C.
Non‐biodegradable petroleum‐based plastic wastes have become a leading environmental concern, and new efforts are underway to prepare biobased and biodegradable replacements. We have explored the ...preparation of adhesives suitable for use in consumer products, and here we report the development of waterborne, biodegradable adhesives from biobased monomers resulting in adhesives exceeding 70% biocontent. Using water as the polymer medium, viscosity challenges and the use of volatile organic solvents are avoided. Material properties of the polyurethane dispersions, resulting films, and laminates produced showed Mw ranging between 56,000 and 124,000. Lastly, the biodegradability of films and laminates was evaluated. The resulting metrics indicate that the adhesives produced meet the desired mechanical and biodegradability targets, indicating that high renewability content solvent‐free polyurethane dispersions are a viable solution for lamination adhesives.
Synthesis was carried out of waterborne polyurethane‐urea dispersions for composite adhesive applications with high biocontent. The composites showed strong mechanical properties and rapid biodegradation in compost conditions. The resulting dispersions were found to be drop‐in candidates for industrial applications.
Natural fiber-based composites are applied in many structural engineered products from civil constructions to automobile manufacturing due to the properties such as low density, high aspect ratio, ...biodegradability and ease to work. During the past decades such composites have been thoroughly studied for their mechanical properties and failure behavior and their properties compared with those of synthetic fiber-based composites. Other properties, such as the thermal behavior of natural fibers and composites, have also been studied because they determine the performance of their products possible. It deals with the effect of temperature on adhesive curing, effect of high temperature and fire damage during fabrication. Further, the thermal properties have equal importance in structural applications such as temperature transfer from end to end, load capacity at specific temperature, material behavior and dimensional stability at high temperature. In this respect the isothermal and non-isothermal thermogravimatric analyses are discussed and the improtance of glass transition temperature is studied during prepapration of composites to ensure their ultimate properties. Although there are several works that have been done on thermal behavior, especially thermogravimetric analysis of natural fibers and their composites, there is no review article available specially focused on natural fiber-based composites, hybrid composites, and nanocomposites. The aim of this review was to focus on the advances in the comprehension of thermogravimetric behavior of natural fibers and compare the effect of natural fibers as reinforced materials in polymer composites.
At present, most synthetic organic materials are produced from fossil carbon feedstock that is regenerated over time scales of millions of years. Biobased alternatives can be rapidly renewed in ...cradle-to-cradle cycles (1-10 years). Such materials extend landfill life and decrease undesirable impacts due to material persistence. This work develops a LCA for synthesis of polyhydroxybutyrate (PHB) from methane with subsequent biodegradation of PHB back to biogas (40-70% methane, 30-60% carbon dioxide). The parameters for this cradle-to-cradle cycle for PHB production are developed and used as the basis for a cradle-to-gate LCA. PHB production from biogas methane is shown to be preferable to its production from cultivated feedstock due to the energy and land required for the feedstock cultivation and fermentation. For the PHB-methane cycle, the major challenges are PHB recovery and demands for energy. Some or all of the energy requirements can be satisfied using renewable energy, such as a portion of the collected biogas methane. Oxidation of 18-26% of the methane in a biogas stream can meet the energy demands for aeration and agitation, and recovery of PHB synthesized from the remaining 74-82%. Effective coupling of waste-to-energy technologies could thus conceivably enable PHB production without imported carbon and energy.
Cancer represents one of the most dangerous diseases, with 1.8 million deaths worldwide. Despite remarkable advances in conventional therapies, these treatments are not effective to completely ...eradicate cancer. Nanotechnology offers potential cancer treatment based on formulations of several nanoparticles (NPs). Liposomes and polymeric nanoparticle are the most investigated and effective drug delivery systems (DDS) for cancer treatment. Liposomes represent potential DDS due to their distinct properties, including high-drug entrapment efficacy, biocompatibility, low cost, and scalability. However, their use is restricted by susceptibility to lipid peroxidation, instability, burst release of drugs, and the limited surface modification. Similarly, polymeric nanoparticles show several chemical modifications with polymers, good stability, and controlled release, but their drawbacks for biological applications include limited drug loading, polymer toxicity, and difficulties in scaling up. Therefore, polymeric nanoparticles and liposomes are combined to form polymer-lipid hybrid nanoparticles (PLHNPs), with the positive attributes of both components such as high biocompatibility and stability, improved drug payload, controlled drug release, longer circulation time, and superior in vivo efficacy. In this review, we have focused on the prominent strategies used to develop tumor targeting PLHNPs and discuss their advantages and unique properties contributing to an ideal DDS.
•A molecularly imprinted conducting polymer-based electrochemical sensor was developed to determine 2,4-DCP.•Hydrogen bonding of analyte to conducting polymer was utilized for imprinting and the ...template was electrochemically removed.•MIP-PEDOT/CFP has exhibited high selectivity towards 2,4-DCP.•Effective sensor with nanomolar-level detection of 2,4-DCP in real water samples.
A highly selective electrochemical sensor has been developed for the determination of the pesticide molecule, 2,4-dichlorophenol (2,4-DCP) using molecularly imprinted conducting polymer. 2,4-dichlorophenol imprinted polymer films were prepared by electropolymerising 3,4-ethylenedioxythiophene (EDOT) on surface of carbon fiber paper electrode (CFP) in presence of 2,4-dichlorophenol. Electrochemical over-oxidation was carried out for the controlled release of 2,4-DCP templates and to generate definite imprinting sites. Surface morphology of the imprinted electrode was analysed by Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, Fourier Transform Infrared and Raman spectroscopy. In optimized conditions, the voltammetric sensor gave a linear response in the range of 0.21 nM – 300 nM. The significantly low detection limit (0.07 nM) demonstrates the ultra-low sensitivity of the method. The imprinted sensor displayed higher affinity and selectivity towards the target 2,4-DCP over similar structural analogical interference than the non-imprinted sensor. MIP sensor was efficaciously employed for the selective determination of 2,4-DCP in real samples of water.
Two thermally cross‐linkable hole transport polymers that contain phenoxazine and triphenylamine moieties, X‐P1 and X‐P2, are developed for use in solution‐processed multi‐stack organic ...light‐emitting diodes (OLEDs). Both X‐P1 and X‐P2 exhibit satisfactory cross‐linking and optoelectronic properties. The highest occupied molecular orbital (HOMO) levels of X‐P1 and X‐P2 are −5.24 and −5.16 eV, respectively. Solution‐processed super yellow polymer devices (ITO/X‐P1 or X‐P2/PDY‐132/LiF/Al) with X‐P1 or X‐P2 hole transport layers of various thicknesses are fabricated with the aim of optimizing the device characteristics. The fabricated multi‐stack yellow devices containing the newly synthesized hole transport polymers exhibit satisfactory currents and power efficiencies. The optimized X‐P2 device exhibits a device efficiency that is dramatically improved by more than 66% over that of a reference device without an HTL.
The synthesis and characterization of two new cross‐linkable HTL polymers, X‐P1 and X‐P2, are described. The current efficiency of a solution‐processed multi‐stack OLED device with X‐P2 is found to be approximately 1.5 times higher than that of the reference device.
Nitroxide-mediated polymerization enabled the synthesis of cationic, imidazolium-containing triblock copolymers as a membrane for an electromechanical transducer. Nitroxide-mediated polymerization ...afforded poly(styrene-b-1-ethyl-3-(4-vinylbenzyl)imidazolium bis(trifluoromethane sulfonyl)imide)-b-styrene) in a controlled fashion as confirmed using aqueous size exclusion chromatography and 1H NMR spectroscopy. Dynamic mechanical analysis revealed a modulus of approximately 100 MPa for the triblock copolymer at 23 °C, which was suitable for fabrication of an electromechanical actuator. Evaluation of electromechanical actuators revealed device curvatures over twice the curvatures for Nafion® in both the presence and absence of a conductive network composite. Addition of the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethane sulfonate selectively reduced the glass transition temperature (Tg) of the central block and increased overall ionic conductivity. Normalizing temperature with the central block Tg caused the ionic conductivity for the IL-incorporated polymers to collapse onto a single curve, which was an order of magnitude higher than the block copolymer in the absence of added IL.
Display omitted
PDF
