Next to cellulose, lignin is the second most abundant biopolymer, and the main source of aromatic structures on earth. It is a phenolic macromolecule, with a complex structure which considerably varies depending on the plant species and the isolation process. Lignin has long been obtained as a by-product of cellulose in the paper pulp production, but had rather low added-value applications. Changes in the paper market have however stimulated the need to focus on other applications for lignins. In addition, the emergence of biorefinery projects to develop biofuels, bio-based materials and chemicals from carbohydrate polymers should also generate large amounts of lignin with the potential for value addition. These developments have brought about renewed interest in the last decade for lignin and its potential use in polymer materials. This review covers both the topics of the direct use of lignin in polymer applications, and of the chemical modifications of lignin, in a polymer chemistry perspective. The future trend toward micro- and nanostructured lignin-based materials is then addressed.
This review describes the design of polymeric micelles from block copolymers and their performances as nano-scale drug delivery systems, with emphasis on our recent work. The basic drug delivery system platform developed by our group consists of polymeric micelles comprising a core–shell structure with a versatile drug-loading hydrophobic core and biocompatible hydrophilic shell, and are several tens to one hundred nanometer in size. These characteristics are preferable to bypass both renal clearance and entrapment by the reticuloendothelial system, thus allowing subsequent accumulation within tumor tissues by the enhanced permeability and retention effect. Furthermore, polymeric micelles may be designed for enhanced biological performance by modification of the block copolymers to contain chemistries that can sense a specific biological environment. These “smart” micelles allow for target site-triggered drug release by reversible stabilization of the micelle structure and controlled intracellular trafficking (efficient endosomal release). Smart micelles designed with responsive features have demonstrated the utility in many cases compared to controls lacking such functionality. Additionally, the ability to control the size of polymeric micelles in the range of several tens to hundreds of nanometer significantly affects their longevity in the blood stream and efficiency of tumor tissue accumulation and penetration. In hypovascular tumor tissues, smaller polymeric micelles are more effective for tissue accumulation/penetration, bringing about stronger anti-tumor activity. All together, fine-tuning the structure of block copolymers enables preparation of polymeric micelles with versatile functions for treatment of many diseases including intractable cancer.
Of late, the most bountiful natural biopolymer chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However applications of chitin are limited due to its inherent insoluble and intractable nature. Chitosan, alkaline hydrolytic derivative of chitin has better solubility profile, less crystallinity and is amenable to chemical modifications due to presence of functional groups as hydroxyl, acetamido, and amine. The chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. In view of rapidly growing interest in chitosan its chemical aspects and chemical modification studies is reviewed. The several chemical modifications such as oligomerization, alkylation, acylation, quternization, hydroxyalkylation, carboxyalkylation, thiolation, sulfation, phosphorylation, enzymatic modifications and graft copolymerization along with many assorted modifications have been carried out. The chemical modification affords a wide range of derivatives with modified properties for specific end use applications in diversified areas mainly of pharmaceutical, biomedical and biotechnological fields. Assorted modifications including chitosan hybrids with sugars, cyclodextrin, dendrimers, and crown ethers have also emerged as interesting multifunctional macromolecules. The versatility in possible modifications and applications of chitosan derivatives presents a great challenge to scientific community and to industry. The successful acceptance of this challenge will change the role of chitosan from being a molecule in waiting to a lead player.
Selective recognition of metal ions is a real challenge for a large range of applications in the analytical field (from extraction to detection and quantification). For that purpose, ion-imprinted polymers (IIPs) have been increasingly developed during the last 15 years on the principle of molecularly imprinted polymers (MIPs). Those imprinted materials are designed to mimic the binding sites of biological entities and assure an improved recognition of the template species. The aim of this review is to give the current state of the art in the conception of IIPs from the components to the polymerization process. Some applications of those materials will be also discussed.
Additive manufacturing (or 3D printing) involves the process of fabricating a part by layer-by-layer assembly of materials with processes such as extrusion, binding, melting, and photopolymerization. It is transforming how we assemble our prototypes and, in the future, manufacture our products. There have been a number of materials that can be utilized for this technology, however, high performance polymer nanocomposites are a very important class of material that is just recently being used in additive manufacturing. High performance polymer is a group of polymer materials that are known to retain its desirable mechanical, thermal, and chemical properties when subjected to harsh environment such as high temperature, high pressure, and corrosive chemicals. When mixed with nanofillers such as carbon nanotube, nanoclay, and graphene, these polymers can have improved mechanical properties and sometimes acquire properties that were not present initially like thermal and electrical conductivity. This review article aims to summarize available additive manufacturing techniques, high performance polymers and nanofillers available, and research efforts on its use for additive manufacturing.
Mucoadhesion, the state in which two materials, amongst which one is biological in nature, adhere to each other for extended periods of time with the help of interfacial forces, provides an attractive strategy to overcome the hurdles of conventional drug delivery systems including first pass metabolism, and localized delivery of biomolecules including proteins, peptides and oligonucleotides. Mucoadhesion provides great opportunities for the delivery of a variety of compounds different routes of administration ocular, nasal, vaginal and buccal. In addition mucoadhesion also makes it possible to obtain prolonged, local or systemic drug action. In this review we discussed about potential applications of mucoadhesion and mucoadhesive polymers in drug delivery along with the mechanism of mucoadhesion and the methods for evaluation of mucoadhesive drug delivery systems.
Polyimides comprising high polarized moieties and electron-withdrawing groups usually exhibit high refractive index and good transparency with great potential for optoelectronic devices. Particularly, the incorporation of hydroxyl groups on the backbones of polyimides is an important strategy to enhance the solubility and provide reactive sites for organic-inorganic bonding. Composites prepared from organic polymer binder and inorganic fillers have recently attracted considerable interests due to their enhanced mechanical, thermal, optical and electrical properties compared to the corresponding polymer or inorganic component. Moreover, the inorganic components in hybrid films can also serve as electron acceptors for stabilizing the charge transfer complex thus result in electrically programmable digital memory properties. In addition, the high performance polyimides can further served as substrate and protector for the AgNWs-polyimide conductive hybrid films, exhibiting good adhesive property, high bendability, and excellent thermal stability. Owing to the high glass transition temperature ( ) of polyimides, the resulted AgNWs-polyimide electrode can maintain its conducting performance at high temperature operation. Thus, the hybrid electrode provided extremely high potential to operate at harsh working environment or further post processing. By the excellent combination of transparent polyimides and inorganic materials, the resulting polyimide hybrids showing promising potential are indispensable to optical and electrical applications.
Advances in biotechnology have produced therapeutically active proteins on a commercial scale, and therapeutic proteins are now extensively applied in medical practices to treat various diseases. Oral delivery of protein drugs is a highly attractive approach, and, naturally, numerous attempts have been made to develop such formulations. Despite various attempts, however, no clinically useful oral formulations have been developed, and this is mainly due to extremely low bioavailability of protein drugs. The effective oral protein delivery needs to overcome barriers related to poor absorption, poor permeation, and degradation in the gastrointestinal tract. Various strategies have been explored for enhancing the bioavailability of orally administered proteins. They include chemical modification of protein drugs, use of enzyme inhibitors, and exploration of special formulation ingredients, such as absorption enhancers and mucoadhesive polymers. This article examines the current technologies under development for oral protein delivery.
The increasing scientific and industrial interest for starch nanoparticles (SNP) has led to the development of numerous methods for preparing sub-micron starch fillers for nanocomposites applications. Starch nanocrystals (SNC), which constitute the focus of this review, are one type of SNP with crystalline property and platelet like morphology. SNC can be extracted from various starch botanical sources, allowing to obtain a large range of amylose content, shape, viscosity in suspension, surface reactivity and thermal resistance. To date, the most common method for extracting SNC remains the mild acid hydrolysis of the amorphous parts of native granular starch. So far, alternative methods render much lower yield. Since first publications on SNC, the principal aim is to use them as reinforcement in polymer matrices. Thanks to the reactive nature of starch, SNC surface can be modified by grafting or cross-linking which renders them more readily dispersible in the polymer matrix. The present review focus on the reinforcing effect and mechanisms of SNC, as well as on their impact of barrier properties of polymers.
The synthesis of isocyanate free polyurethanes is a major concern. This paper first reports the synthesis of new biobased isosorbide dicyclocarbonates from isosorbide. Then polyhydroxyurethanes (PHUs) were synthesized by a cyclocarbonate–amine step growth polyaddition with four commercial diamines (e.g. jeffamine D-400, 1,10 diaminodecane, diethylenetriamine and isophoronediamine). These unprecedented products, obtained with high yield, were characterized by H NMR, FTIR, DSC, SEC and TGA analyses. PHUs exhibited glass transition temperatures from −8 °C to 59 °C, and degradation temperatures (Td 5%) between 234 °C and 255 °C. Last but not least, the compounds produced during the degradation of these PHUs were analyzed by ATG-IR technique and showed that carbon dioxide and secondary amines are released.
Quaternary ammonium chitosan- -poly(acrylic acid- -acrylamide) superabsorbent hydrogels were successfully synthesized from acrylic acid (AA), acrylamide (AM) and quaternary ammonium chitosan with high substitution degree. They were prepared using potassium persulfate (KPS) as an initiator and , ′-methylenebisacrylamide (MBA) as a crosslinker respectively. The structure and morphology of the superabsorbent hydrogel were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The water absorbency and antibacterial activities of the superabsorbent hydrogels against ( ) and ( ) were investigated. The introduction of quaternary ammonium chitosan made the antibacterial activity improve. The crosslinker, initiator and AM contents had certain influences on the water absorbency as well as the antibacterial activity against . The AM could enhance the hydrogel strength apparently. In addition, the AM (the content was 10 wt%) could increase the water absorbency in 0.9 wt% NaCl solution obviously. The superabsorbent hydrogel also had pH sensitive property.
This review analyses the progress in the field of shape memory epoxy resins (SMEPs). Partial crystallisation and vitrification are the basis of shape memory effect in SMEPs. Several synthetic approaches for SMEPs, their composites and foams have been reviewed. Strategically incorporated thermally reversible segments induce the shape memory effect in epoxy resins. By varying the nature and concentration of shape memory segments, wide range of shape memory properties and transition temperatures (shape memory temperatures) can be achieved. Triple shape memory, self-healability and electroactive capability are some of the additional features that can be created in SMEPs. Among the thermoset resins, shape memory epoxies are the most attractive systems because of the ease of processability, composite forming properties and dimensional stability. Shape memory epoxy polymers that can be processed into elastic memory composites are candidate materials in the processing of many smart engineering systems. In this background, a review consolidating the progress in SMEP has contemporary relevance. The present article takes a stock of the trend in SMEP with a view to assess the direction of future initiatives in this area. It is concluded that there is tremendous scope for research leading to technological evolution in the field of SMEP.
Chitosan (CHI) is a biopolymer that can be used on complexation and adsorption of heavy metals in water. Chitosan can be chemically functionalized to modulate the pH range of solubility and favoring the complexation and adsorption processes with metal ions. Thus, in this study, it was investigated the synthesis and characterization of carboxymethyl-chitosan (CMC) as well as its application for the complexation and adsorption of Cd(II) and Cr(VI) ions at different pH conditions and compared to pristine chitosan. The properties of the synthesized derivative were extensively characterized by potentiometric titration, Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–vis) spectroscopy. The complexation and adsorption behaviors of CHI and CMC were assessed using atomic absorption spectrometer (AAS) and zeta potential analysis. The results demonstrated that carboxymethylation of chitosan has occurred with a degree of functionalization higher than 50% leading to the formation of CMC soluble in alkaline medium. In addition, the effective incorporation of carboxylic groups in the chitosan chain (CMC) has significantly altered the complexation and adsorption responses towards heavy metal cations (Cd ) and anions (chromates) as compared to CHI. Therefore, these systems offer an attractive alternative as biosorbents for the removal of heavy metal pollutants from the wastewater.
The synthesis of 3-, 5- and 8-arm dimethylaminoethyl methacrylate star polymers are reported, final (PDI) = 12.2 K (1.09), 18.9K (1.10) and 38.4 K (1.11), respectively. The synthesis of 3-arm methyl methacrylate and dimethylaminoethyl methacrylate block co-polymer stars is also described. Living polymerisation occurred in all cases providing well defined stars with predictable molecular weights and narrow polydispersity. A fluorescent tag, 2-(8-methacryloyloy-3,6-dioxaoctyl)thioxantheno[2,1,9-dej]isoquinoline-1,3-dione, derived from a commercially available pigment, was incorporated into the star polymers. The fluorescence spectra of the polymers prepared were recorded over a range of pH and the peak emission frequency and intensity have been reported, = 462 nm. All of the multi-arm polymers exhibit fluorescence across a broad pH range with maximum emission at pH 4. A 3-arm star polymer has been demonstrated to show good bioadhesion in rat tissue. A reduced adhesion in epithelial tissues not covered by a viscoelastic mucus gel indicates an increased tendency for mucoadhesion over bioadhesion.
This review summarizes recent developments in the preparation and characterization of grafting of poly(lactic acid) or polylactide (PLA). PLA is the most expansively researched and utilized biodegradable, biocompatible, compostable, recyclable and renewable thermoplastic polyester. The graft copolymers of PLA have been synthesized and characterized by different spectroscopic techniques, including FTIR spectra and NMR data. The graft copolymers of PLA have been analyzed critically by taking different monomers/polymers; such as chitosan, cellulose, starch, polyethylene glycol, vinyl based polymers, lignin, dextran, methyl methacrylate, maleic anhydride and graphene oxide. In the first part of this review, the grafting of PLA and applications of grafted PLA has been discussed briefly. The second part, the major objective of this paper, focuses on the synthesis and characterization of different PLA based graft copolymers. For few cases, where useful properties, such as high molecular weight, narrow PDI, or stereocontrol, have been observed, a more detailed examination of the graft copolymers is provided.
Recent progress in the recycling and recovery of polyurethane and polyurethane composites is reviewed. The various types of polyurethane waste products, consisting of either old recycled parts or production waste, are generally reduced to a more usable form, such as flakes, powder or pellets, depending on the particular type of polyurethane that is being recycled. The various recycling technologies for material and chemical recycling of PU materials have greatly contributed to improve the overall image regarding the recyclability of polyurethanes in recent years, by far the most important being regrinding and glycolysis. These technologies open an emerging, effective and economic route for recycling polyurethane rigid foams and composite. Polyurethane foam in automotive seating has been successfully recycled using regrind technology. Glycolysis of polyurethanes can be economically acceptable, but still requires more development in order to tolerate more contamination in the post-consumer material. Current technologies can recover the inherent energy value of polyurethanes and reduce fossil fuel consumption. Energy recovery is considered the only suitable disposal method for recovered material for which no markets exist or can be created. Increasing waste-to-energy and other thermal processing activities involving gasification, pyrolysis and two-stage combustion has contributed for the disposal of significant amounts of scrap PU without many difficulties. It is concluded that many of the plastic feedstock recycling processes appear to be technically feasible and robust enough to warrant further development in the future.
The paper evaluates accumulated information about the apparent inner surface area ( ), pore volume ( ), pore size (diameter, ), and pore size distribution (PSD) of the single-phase hypercrosslinked polystyrene networks prepared by an intensive post-crosslinking of either dissolved linear polystyrene or swollen gel-type styrene–divinylbenzene copolymers. Critical analysis of data obtained by conventional physical methods used for the characterization of porous solids (low temperature adsorption of nitrogen or argon, mercury intrusion porosimetry, inversed size exclusion chromatography, electronic microscopy, positronium annihilation) reveals the most trustworthy porosity parameters of the above hypercrosslinked polystyrene resins as ⩾ 1000 m /g, in the range of 0.3–0.5 cm /g, in dry networks from 4–5 to 30 Å and only slightly increasing in swollen samples. The hypercrosslinked networks thus present first basically microporous polymeric material that exhibits narrow PSD resulting from a statistically uniform distribution of crosslinks.
Electrospinning has been recognized as a simple and efficient technique for the fabrication of ultrathin fibers from a variety of materials including polymers, composite and ceramics. Significant progress has been made throughout the past years in electrospinning and the resulting fibrous structures have been exploited in a wide range of potential applications. This article reviews the state-of-art of electrospinning to prepare fibrous electrode materials and polymer electrolytes based on electrospun membranes in the view of their physical and electrochemical properties for the application in lithium batteries. The review covers the electrospinning process, the governing parameters and their influence on fiber or membrane morphology. After a brief discussion of some potential applications associated with the remarkable features of electrospun membranes, we highlight the exploitation of this cutting edge technology in lithium batteries. Finally the article is concluded with some personal perspectives on the future directions in the fascinating field of energy storage.
Recently, we have demonstrated the use of wood-derived nanocellulose papers, herein termed nanopapers, for organic solvent nanofiltration applications. In this study, we extend the use of these nanopapers to tight ultrafiltration (UF) membranes. The feasibility of such nanopaper-based UF membranes intended for use in water purification is shown. Four types of nanocelluloses, namely bacterial cellulose, wood-derived nanocellulose, TEMPO-oxidized cellulose nanofibrils and cellulose nanocrystals, were used as raw materials for the production of these nanopaper-based membranes. The resulting nanopapers exhibit a transmembrane permeance in the range of commercially available tight UF membranes with molecular weight cut-offs ranging from 6 to 25 kDa, which depends on the type of nanocellulose used. These molecular weight cut-offs correspond to average pore sizes of a few nanometres. The rejection performance of the nanopapers is on the border of nanofiltration and UF. We demonstrate that the pore size of the nanopapers can be controlled by using different types of nanocellulose fibrils.
This work provides an overview of the most common polymeric corrosion inhibitors for the oil and gas industry. Exploration, production and transportation of petroleum and natural gas products constantly deal with highly corrosive environments due to oxygen, acid stimulation, CO and H S contamination. Therefore, versatile materials are required in order to keep corrosion rates in control. Unlike small molecule corrosion inhibitors, polymers possess multi-functionality and better film-forming capabilities, which could significantly improve protective barrier properties. In this article, polymeric architectures tested in relevant oil and gas media are compiled in order to highlight certain moieties capable of complex formation with the metal surface or chelation on corrosive agents resulting to improved corrosion inhibition.