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Geomembranes are low-permeable liners used to control the molecular migration in many proven applications. Landfills is most common application in the field of civil and environmental engineering. Geomembrane is the main component in lining system which works as hydraulic barrier. The polyolefins are the basic materials of liner and more commonly polypropylene and polyethylene are preferred. Commercial manufacturing process involves extrusion techniques viz cast extrusion and blown extrusion process. The individual process is designed for multiple layered structures which are then coextruded to lead into a single liner. Typical structure comprises, high to low-density polyethylene (PE) resin, processing aids, stabilisers to retard the degradation through ultra-violet rays, photo-oxidation, and thermal oxidation. The stabilizer is usually used in smaller dosses to avoid degradations which includes, 2 to 3% carbon-black (CB), 0.5 to 1% antioxidants (AO), and plasticizing additives to introduce the flexibility. During the process, components are homogenised in specially designed screws of feeding and mixing zones. The formulated melt is co-extruded through specially designed die of multi-layered structures. The subsequent melt enters in circular die with a certain pressure which leads to bubbled shaped films. The variation in the surface morphology layer structure and layer number are the important technical aspects to alter the required end application. Finally, manufactured geomembrane is qualified as per the international specifications which are governed by geosynthetic research institute (GSI/GRI).

The functional conjugations with natural polyphenols could be a working strategy for accomplishing the degradation resistance of hyaluronic acids (HA). Herein, a series of HA conjugates with four different polyphenols with wide ranges in the degree of substitution were systematically prepared. The degradation rate could be retarded in a wide range without crosslinking: The conjugates having polyphenolic aglycone (catechin or quercetin) maintained their structures, as identified by viscosity, for up to 7 weeks in the presence of hyaluronidase. This retardation was outstanding compared to those reported from previous studies, and the physical mixtures of HA and polyphenols still showed significantly more retarded degradation than pristine HA. The degradation resistance could be controlled by varying the feed ratio of polyphenols. This conjugation method of polyphenols could open up new application areas of HA with the outstanding degradation resistance.

In recent years, the challenge of efficient oil-water separation has become the subject of immense fundamental research, with significant impact in the development of industrial applications. This article reviews the recent progress in the fabrication of porous polydimethylsiloxane (PDMS) materials, which are the most widely investigated materials for oil-water separation. Various strategies for the fabrication of porous PDMS have produced a diversity of bulk and surface structures, where these structures in turn determine the performance of the materials for oil-water separation. Understanding the interrelationship governing the fabrication strategy, structure, and performance is essential for the development of future selective oil absorbents with improved commercial potential. The separation of organic contaminants from industrially produced wastewater is a serious environmental challenge, and the preparation of superior oil absorbents is critical for overcoming this challenge. To address the issues in the development of promising candidates as oil absorbents, the current strategies for the design of low-surface energy coatings of three-dimensionally (3-D) interconnected porous materials are also discussed. The reusability, surface roughness, and superhydrophobic properties are discussed as vital parameters.

Recent advances in hydrogel chemistry have led to the development of various soft materials capable of self-healing. Nevertheless, their self-healing capabilities are primitive compared to the responsive and adaptive strategies of blood clotting and wound healing in the human body. We developed a novel microgel system that mimics the process of blood clotting. Electrospun polylactic acid (PLA) fibers were entrapped inside the microgels of a hyaluronic acid conjugate with hesperidin side groups crosslinked by Fe ions; the resulting hydrogels showed fast self-healing and magnetic responsive properties. By applying an external magnetic field, which mimicked blood flow, the microgels successfully aggregated at target sites, like platelets. The aggregates were stable, as demonstrated by resistance to sonication for 30 min, and their moduli spanned tens to hundreds of kPa, demonstrating the mechanical integrity of the artificial clots. Like fibrin, the PLA fibers successfully strengthened the aggregates due to formation of uniform fiber-reinforced hydrogels; the artificial clots containing fibers had a 300% improved modulus and 50% increased hardness relative to the hydrogels without fibers. This unique intelligent system can be utilized in future self-healing systems, delivery systems, and devices with microfluidic channels.

Multi-functionality plays a decisive role in tuning and improving fundamental properties of active molecules, and grafting polymerization/conjugation development imparts properties of active molecules to the backbones. Recently, metal-polyphenol coordination networks have attracted a great deal of attention. A variety of transition metal ions can freely combine with catechol/keto-enol containing polyphenols to form metal-polyphenol networks. Herein, the recently studied conjugated polyphenols were summarized and compared to dopamine-conjugated polymers with evaluation of their properties and gelation behaviors. The biomimetic understanding of bioinspired adhesion, metal ion coordination of hydroxyl groups, and their rearrangement within aglycone could expand the ability for the development of biomimetic, eco-friendly, and biocompatible polymers.

Polyphenols are naturally occurring compounds found in fruits and vegetables. They are bulky molecules comprising of hydroxyl groups in the forms of catechol and other phenolic groups. The catechol functionality is believed to be responsible for the adhesive and cross-linking characteristics. Natural polyphenols were grafted onto hyaluronic acid (HA) using epichlorohydrin chemistry, and the successful preparation of novel HA conjugates were confirmed. The reduction potential of polyphenols was inversely related to the DPPH radical scavenging activity of the conjugates, which in turn was linearly related to the adhesion strength of the conjugates. Although polypropylene had no site for hydrogen bonding, the adhesion strength of the conjugates onto polypropylene reflected the numbers of hydroxyl and catechol groups in general. The adhesive strength of the conjugates increased by 20-fold compared to that of the native HA. Although, hesperidin has no catechol groups, it still improved the adhesion strength. Reversible coordination with metal ions facilitated ionic gelation and self-healing properties. Adhesive, antioxidant, gelation, and self-healing properties were successfully achieved simultaneously. These functional properties could make the natural conjugates promising candidates for biomedical applications and environmentally safe materials.

Natural hydrophilic polymers have been utilized for a variety of applications, ranging from the food industry to the coatings industry. However, recent social needs have demanded rapid progress with regard to medical and environmental applications. Natural hydrophilic polymers have attracted considerable interest due to their physicochemical properties and useful functions. This report explores recent findings made in medical, environmental, and food applications of natural hydrophilic polymers and their modified polymers. Applications of these materials are based on their intrinsic biocompatibility, biodegradability, and non-toxicity. Advances in the chemical modification of natural polymers as well as new source developments are overcoming the physicochemical property limits and high costs of these materials, opening up new opportunities for the development of future applications.

Natural polyphenols have been used in foods, cosmetics, and medicines to exploit their functional properties, including antioxidant, anti-inflammatory, antiviral, antidepressant, analgesic, anti-mutation, and antitumor activities. Because of their protective property against reactive oxygen species in the human body, which are associated with aging-related chronic diseases, polyphenols have been considered as useful building blocks for biomaterials development. Here, recent studies on common polyphenols are summarized and their structural implications are discussed, providing insights into their molecular structure and related properties and evaluating the effect of structural modifications such as functional rearrangements, substitution reactions, and polymeric conjugations. The fundamental understanding of the chemical structure of polyphenols could diversify the strategy for the development of biomimetic, eco-friendly, and biocompatible materials.

The development of antioxidant polymers through the chemical conjugation of natural polyphenols onto polysaccharides has important applications in biomedical, pharmaceutical, food, and cosmetic fields. Due to their labile characteristics, the covalent conjugation of polyphenols while retaining antioxidant properties has been a challenging task. Herein, four structurally different polyphenols, three with and one without a catechol group, were conjugated onto pectin macromolecules via a simple and efficient preparation method involving epichlorohydrin chemistry. The conjugation reactions were confirmed by FT-IR and UV–vis characterization, and the free radical scavenging assay confirmed that the polyphenols maintained their antioxidant activity after the reaction. The conventional structure-antioxidant property relationship can be applied to the assay results, and hesperidin without a catechol group showed the lowest antioxidant capability. The coordination of multivalent metal ions with polyphenols enabled ionic crosslinking and the moduli of hydrogels depend on the type of polyphenols and their molecular interactions with metal ions. The simplicity of preparation and the resulting unique properties could make the pectin conjugates useful in a wide range of application areas.

In the history of man-made macromolecules, water-soluble polymers have primarily maintained passive roles; examples include the uses of water-soluble polymers for viscosity control and as binders. The importance of water on earth has increased research into the development of active roles for water-soluble polymers. These expanding roles span from medical applications, such as drug delivery to environmental applications, such as the removal of heavy metals. The development of water-soluble polymers brings significant benefits to the structural engineering and production of nanomaterials and electronic materials. The current limits of the structure–property relationship have been challenged to meet these rapidly-developing application areas.

In the area of artificial hydrogels, simultaneous engineering of the volume transition characteristics and mechanical properties of stimuli-responsive hydrogels is an important subject. By unrestricted architecting of hierarchical structures, natural hydrogels are able to provide a wide range of swelling and mechanical properties, beyond the limits of artificial hydrogels. Herein, a combination of nanostructures and microstructures was developed to construct superporous hydrogels. Fibers of microfibrillated cellulose (MFC), an eco-friendly reinforcing material, were used as nanostructures, aligned micropores were used as microstructures, and in situ photopolymerization was used to immobilize the two structures together within the gel networks of poly(N-isopropyl acrylamide) (PNIPAm). The introduction of MFC distinctly enhanced volume transition, mainly by decreasing the swelling ratios above the transition. The introduction of directional micropores increased the swelling ratio below the transition and decreased the swelling ratio above the transition, thereby also enhancing the volume transition. Additionally, the formation of aligned micropores achieved fast water infiltration, which is beneficial for superabsorbent applications. The introduction of aligned micropores reduced the elastic modulus, but this could partially be compensated for by reinforcement with MFC. This combination of crystalline nanofibers and aligned micropores has great potential for the development of stimuli-responsive superporous hydrogels outperforming current artificial hydrogels.

Cellulose is a well-known versatile polymer that presents a wide range of material properties via the substitution and grafting reactions of its hydroxyl groups. Because of their commercial potential, combinations of cellulose and vinyl polymers have been examined with various grafting methods. In this study, the condensation reactions of regioselective and nonregioselective substitution with 2-isocyanatoethylmethacrylate were performed in a homogeneous solvent system of dimethyl acetamide/lithium chloride. The successful substitution was confirmed by Fourier transform infrared spectroscopy, 1H-NMR, cross-polarization/magic angle spinning 13C-NMR, thermogravimetric analysis, and X-ray diffraction. The substituted celluloses showed excellent thermal stability and a different polymorph with a depressed cellulose–intrinsic polymorphic phase. The 2-isocyanatoethylmethacrylate side chain seemed to expand the intermolecular distance with enhanced chain mobility and trigger the formation of a novel crystalline polymorph with a dramatically improved thermal stability. This investigation provided us with a useful understanding of the modification of cellulose with spatial distribution control for advanced future applications requiring a combination of cellulose with vinyl polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013