pH responsive polymers with amino acids in the side chains and their potential applications

Design and synthesis of pH responsive polymeric materials has become an important subject in academia as well as in industrial field in recent years due to their applications in diverse field including controlled drug delivery, biomedical applications, membrane science, sensors and actuators, oil recovery, colloid stabilization, etc. Efforts have been made to incorporate stimuli‐responsive biomolecules in synthetic polymers to develop pH responsive “smart” non‐biological hybrid macromolecules with high water solubility, enhanced biocompatibility, bio‐mimetic structure and properties. This review is focused on the recent advances in side‐chain amino acid‐based pH responsive polymers synthesis and potential application aspects of these macromolecular architectures in drug and gene delivery, and other fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41084.     

Bio‐Based Nanofibers Involved in Wastewater Treatment

Studies involving bio‐based nanofibers are well utilized in the field of energy, catalysis, electronics, and environmental science. In this review, the importance of utilizing bio‐based materials for the development and optimization of multiplexed nanofibers and the modifications adopted to overcome the drawbacks of conventional electro‐spinning to facilitate better production rates, enhanced adsorption, and its potential in removing heavy metal ions, dyes, and other contaminants polluting the environment are highlighted. This work provides the readers the ability to understand the complexity in fabrication of bio‐based nanofibers focusing primarily on chitosan, cellulose, and protein‐based nanofibers and their mechanism toward quenching/degradation of water contaminants. In addition, it also provides the advantages of using bio‐based materials over synthetic materials for the development of nanofibers.     

Recent advances in solid‐state organic lasers

Organic solid‐state lasers are reviewed, with a special emphasis on works published during the last decade. Referring originally to dyes in solid‐state polymeric matrices, organic lasers also include the rich family of organic semiconductors, paced by the rapid development of organic light‐emitting diodes. Organic lasers are broadly tunable coherent sources, potentially compact, convenient and manufactured at low cost. In this review, we describe the basic photophysics of the materials used as gain media in organic lasers with a specific look at the distinctive features of dyes and semiconductors. We also outline the laser architectures used in state‐of‐the‐art organic lasers and the performances of these devices with regard to output power, lifetime and beam quality. A survey of the recent trends in the field is given, highlighting the latest developments in terms of wavelength coverage, wavelength agility, efficiency and compactness, and towards integrated low‐cost sources, with a special focus on the great challenges remaining for achieving direct electrical pumping. Finally, we discuss the very recent demonstration of new kinds of organic lasers based on polaritons or surface plasmons, which open new and very promising routes in the field of organic nanophotonics. Copyright © 2011 Society of Chemical Industry     

Preparation of pH‐responsive crosslinked materials from natural rubber and poly(4‐vinylpyridine)

Stimuli‐responsive elastomers are smart materials for sensing applications. Natural rubber (NR) is a renewable elastomer with excellent elasticity and fatigue resistance. In this work, a straightforward method for the preparation of pH‐responsive crosslinked materials from NR and poly(4‐vinylpyridine) (P4VP) via free radical crosslinking reaction using benzoyl peroxide (BPO) as an initiator is described. The effects of P4VP and BPO concentrations, reaction time and reaction temperature on immobilization percentage were investigated. It was found that the immobilization percentage reached 90% when using a P4VP concentration of 150 phr and a BPO concentration of 10 phr for 24 h at 90 °C. The pH responsiveness of the crosslinked materials was studied via water swelling, water contact angle and dye release measurements. Unlike unmodified rubber, the P4VP‐crosslinked NR was found to be pH‐responsive in acidic solution. Indigo carmine adsorption studies showed the Langmuir isotherm suggesting monolayer coverage of dye on the rubber surface. The dye could also be released upon increasing the pH of solution above 4. Based on these results, the introduction of pH responsiveness to NR will lead to novel responsive rubber‐based materials that can be used in biomedical and sensing applications. © 2016 Society of Chemical Industry     

Drawing of self‐reinforced cellulose films

Self‐reinforced cellulose films were prepared by incomplete dissolution of commercial microcrystalline cellulose in LiCl/DMAc solvent and subsequent coagulation of regenerated cellulose in the presence of undissolved microcrystalline cellulose. By drawing in wet conditions and subsequent drying, preferred orientation was introduced into the self‐reinforced cellulose films, resulting in significantly improved tensile strength of up to 430 MPa and modulus of elasticity of up to 33 GPa. A linear relationship was observed between applied draw, and the orientation of cellulose in the films, and the measured elastic modulus and tensile strength, respectively. The optically transparent drawn films significantly surpass the strength and modulus of elasticity of current all‐bio‐based planar materials and may therefore present a bio‐degradable alternative to nonbio‐based materials with similar performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2703–2708, 2007     

Temperature‐responsive polymers with LCST in the physiological range and their applications in textiles

Current academic and industrial research sustains large efforts to synthesize and develop environmentally responsive smart materials. The temperature‐responsive materials with a trigger temperature in the physiological range attract much attention due to their potential biomedical applications. We describe their chemistry and the way to synthesize them, focusing on applications for smart clothing fabrication. Copyright © 2007 Society of Chemical Industry     

EPR Relaxation‐Enhancement‐Based Distance Measurements on Orthogonally Spin‐Labeled T4‐Lysozyme

Lanthanide‐induced enhancement of the longitudinal relaxation of nitroxide radicals in combination with orthogonal site‐directed spin labeling is presented as a systematic distance measurement method intended for studies of bio‐macromolecules and bio‐macromolecular complexes. The approach is tested on a water‐soluble protein (T4‐lysozyme) for two different commercially available lanthanide labels, and complemented by previously reported data on a membrane‐inserted polypeptide. Single temperature measurements are shown to be sufficient for reliable distance determination, with an upper measurable distance limit of about 5–6 nm. The extracted averaged distances represent the closest approach in Ln^III–nitroxide distance distributions. Studies of conformational changes and of bio‐macromolecule association‐dissociation are proposed as possible application area of the relaxation‐enhancement‐based distance measurements.     

Bioinspired mineralisation: macromolecule mediated synthesis of amorphous germania structures

The unique optical properties of germanium dioxide or germania (GeO₂), and in particular when compared with other glasses such as silicate glasses, have attracted the attention of scientists and made germania based materials highly suitable for optoelectronic applications. Germanium is known to resemble silicon in some of its chemical properties (in vitro) and biochemical properties (in vivo). The recent findings on the importance of the role of the (bio)macromolecules in (bio)mineralisation has led us to investigate the role of synthetic macromolecules in facilitating the formation of germania particles for the first time. One novelty is that the process described herein was carried out under ambient conditions and at neutral pH. The macromolecules used were poly (allylamine hydrochloride) (PAH) and poly-l-lysine (PLL), and it should be noted that both are cationically charged at neutral pH. Either germanium (IV) ethoxide or germanium (IV) isopropoxide were used as the germania precursors. The products were characterised by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD). Well-defined spherical germania particles were seen by electron microscopy and they were shown to be amorphous by XRD. In addition, based on Energy Dispersive Spectroscopy (EDS) observations, it was proposed that the facilitating macromolecules may be incorporated into the germania. Furthermore, when the reaction mixture was subjected to external shear, the formation of elongated rod-like germania structures was successfully achieved. It is proposed that the macromolecules act as catalyst/scaffold/template in a similar fashion to that described in the literature for the formation of (bio)silica as facilitated by (bio)macromolecules. This novel process is of importance for both the design of new materials based on germania and also silica-germania hybrids. These materials have a variety of potential commercial applications, an example being their use in optical fibre technologies.     

Metallo‐supramolecular materials based on terpyridine‐functionalized polyhedral silsesquioxane

In this study, novel metallo‐supramolecular materials based on terpyridine‐functionalized polyhedral silsesquioxane were synthesized from 4′‐chloro‐2,2′:6′,2″‐terpyridine and amino‐group‐functionalized polyhedral oligomeric silsesquioxane. The obtained terpyridine‐functionalized polyhedral silsesquioxanes were converted to metallo‐supramolecular hybrid materials by coordination polycondensation reaction with Co(II) or Cu(II) ions. The supramolecular polymers created were characterized by means of structure, morphology and stimuli‐responsive performance employing scanning electron microscopy, amperometric techniques and UV–visible and Fourier transform IR spectroscopy. UV?visible and cyclic voltammetry studies showed that both the optical and electrochemical properties of metallo‐supramolecular materials are affected by the substituent at the pyridine periphery. The supramolecular polymers obtained exhibited electrochromism during the oxidation processes of cyclic voltammogram studies. As a result, these terpyridine‐functionalized polyhedral silsesquioxanes are good candidates for electronic, opto‐electronic and photovoltaic applications as smart stimuli‐responsive materials. © 2013 Society of Chemical Industry     

Biolubricants: Raw materials,chemical modifications and environmental benefits

The depletion of the world's crude oil reserve, increasing crude oil prices, and issues related to conservation have brought about renewed interest in the use of bio‐based materials. Emphasis on the development of renewable, biodegradable, and environmentally friendly industrial fluids, such as lubricants, has resulted in the widespread use of natural oils and fats for non‐edible purposes. In this study, we have reviewed the available literature and recently published data related to bio‐based raw materials and the chemical modifications of raw materials. Additionally, we have analyzed the impacts and benefits of the use of bio‐based raw materials as functional fluids or biolubricants. The term biolubricants applies to all lubricants, which are both rapidly biodegradable and non‐toxic to humans and other living organisms, especially in aquatic environments. Biodegradability provides an indication of the persistence of the substance in the environment and is the yardstick for assessing the eco‐friendliness of substances. Scientists are discovering economical and safe ways to improve the properties of biolubricants, such as increasing their poor oxidative stability and decreasing high pour points. “Green” biolubricants must be used for all applications where there is an environmental risk.     

Adaptive Polymeric Coatings with Self‐Reporting and Self‐Healing Dual Functions from Porous Core–Shell Nanostructures

In biological system, early detection and treatment at the same moment is highly required. For synthetic materials, it is demanding to develop materials that possess self‐reporting of early damage and self‐healing simultaneously. This dual function is achieved in this work by introducing an intelligent pH‐responsive coatings based on poly(divinylbenzene)‐graft‐poly(divinylbenzene‐co‐methacrylic acid) (PDVB‐graft‐P(DVB‐co‐AA)) core–shell microspheres as smart components of the polymer coatings for corrosion protection. The key component, synthesized PDVB‐graft‐P(DVB‐co‐AA) core–shell microspheres are porous and pH responsive. The porosity allows for encapsulation of the corrosion inhibitor of benzotriazole and the fluorescent probe, coumarin. Both loading capacities can be up to about 15 wt%. The polymeric coatings doped with the synthesized microspheres can adapt immediately to the varied variation in pH value from the electrochemical corrosion reaction and release active molecules on demand onto the damaged cracks of the coatings on metal surfaces. It leads simultaneously to the dual functions of self‐healing and self‐reporting. The corrosion area can be self‐reported in 6 h, while the substrate can be protected at least for 1 month in 3.5 wt% NaCl solution. These pH‐responsive materials with self‐reporting and self‐healing dual functions are highly expected to have a bright future due to their smart, long‐lasting, recyclable, and multifunctional properties.     

Recent progress in smart polymer composite particles in electric and magnetic fields

Electrorheological (ER) and magnetorheological (MR) fluids based on electro‐ and magneto‐responsive particles, respectively, are smart suspensions with the ability to undergo phase transitions from a liquid‐like to a solid‐like state as a result of stimuli of an electric or magnetic field. The application of polymer composite materials rather than pure polymeric or inorganic materials is aiming to solve the problems in the use of both ER and MR materials, such as low activity, physical and chemical stability, and production cost. Various fabrication methods of polymer composite materials with electro‐activity or magneto‐activity developed and effectively applied in this field to boost the wide commercialization of both ER and MR fluids are briefly reviewed in this perspective. © 2012 Society of Chemical Industry     

Comparative Assay of Antioxidant Packages for Dimer of Estolide Esters

A series of 26 different antioxidants and commercial antioxidant packages designed for petroleum‐based materials, containing both natural and synthetic‐based materials, were evaluated with dimeric coconut‐oleic estolide 2‐ethylhexyl ester (2‐EH), a bio‐based material. The different antioxidants were categorized into different classes of phenolic, aminic, and blended/others materials. The oxidation onset temperatures (OT) using non‐isothermal pressurized differential scanning calorimetry (PDSC) were measured and recorded under previously reported standard conditions. The aminic series gave the best resistance to oxidation as defined by the PDSC method with OT of 246.6 and 244.7 °C for the best two performers, which was a 38 °C improvement over the uninhibited or unformulated dimer estolide material. The phenolic series, containing most of the naturally occurring antioxidants, was the least successful formulation package for the dimer estolide. The blended/other materials, which were specifically designed for petroleum‐based lubricants, did not have the best OT, since the estolides and other bio‐based materials interact differently than their petroleum counterparts. A number of potential antioxidants have been identified as useful additives for the estolides esters. The OT of the estolide and formulated materials correlated well with other bio‐based materials such as biodiesel.     

Bioinspired Poly(vinyl alcohol) Film Actuator Powered by Water Evaporation under Ambient Conditions

Soft humidity‐responsive materials are highly desirable for applications such as actuators, sensors, generators, and soft robots. However, it remains a huge challenge to develop a durable, cost‐effective, fast responsive version of such a smart material powered by water evaporation at ambient conditions. Herein, this challenge is addressed to demonstrate sustained response to humidity gradient from ambient water evaporation by using common poly(vinyl alcohol) (PVA) film as an actuator. The resultant PVA film displays strong mechanical properties in both dry and wet conditions, which cause rapid adsorption and desorption of water vapor to drive the film undergoing swift locomotion with flipping frequency of up to 65 r min^‐1. Based on these features, a mimosa inspired humidity‐responsive actuator is developed which is far superior in response speed and durability than real mimosa. Furthermore, it is demonstrated that the film actuator can convert water evaporation energy into electricity when attached to a piezoelectric element.     

Capturing and Stabilizing Folded Proteins in Lattices Formed with Branched Oligonucleotide Hybrids

The encapsulation of folded proteins in stabilizing matrices is one of the challenges of soft‐matter materials science. Capturing such fragile bio‐macromolecules from aqueous solution, and embedding them in a lattice that stabilizes them against denaturation and decomposition is difficult. Here, we report that tetrahedral oligonucleotide hybrids as branching elements, and connecting DNA duplexes with sticky ends can assemble into materials. The material‐forming property was used to capture DNA‐binding proteins selectively from aqueous protein mixtures. The three‐dimensional networks also encapsulate guest molecules in a size‐selective manner, accommodating proteins up to a molecular weight of approximately 159 kDa for the connecting duplex lengths tested. Exploratory experiments with green fluorescent protein showed that, when embedded in the DNA‐based matrix, the protein is more stable toward denaturation than in the free form, and retains its luminescent properties for at least 90 days in dry form. The noncrystalline biohybrid matrices presented herein may be used for capturing other proteins or for producing functional materials.     

Waterborne polyurethane nanocomposites based on vegetable oil and microfibrillated cellulose

This work analyzes the differences in the final properties of two waterborne polyurethanes (WBPU) prepared with two macrodiols of different chemical structure, but similar molecular weight, as well as the variations caused by incorporating low percentages of microfibrillated cellulose nanocrystals. One of the polyurethanes was based on a synthetic but biodegradable precursor (polycaprolactone diol, PCL) and a second one based on a bio‐based macrodiol derived from castor oil (CO1). The bio‐based material presented higher mechanical properties at room temperature than the synthetic one, with the Young's modulus (MPa) ranging from 2.23 ± 0.09 to 84.88 ± 0.96 for the PCL and bio‐based WBPUs, respectively. Additionally, the PCL‐based WBPU showed to be more sensitive to the incorporation of cellulose than the bio‐based WBPU, and it also suffered changes during time due to delayed crystallization. The behavior of the two systems were compared and related to the different structure of the macrodiols that led to different interfacial interactions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44207.     

Sustainable synthesis of bio‐based hyperbranched ester and its application for preparing soft polyvinyl chloride materials

In this study, bio‐based hyperbranched ester was synthesized from castor oil. The chemical structure of the bio‐based hyperbranched ester obtained was characterized with Fourier transform infrared and ¹H NMR spectra. Soft polyvinyl chloride (PVC) materials were prepared via thermoplastic blending at 160 °C using bio‐based hyperbranched ester as plasticizer. The performances including the thermal stability, glass transition temperature (T_g), crystallinity, tensile properties, solvent extraction resistance and volatility resistance of soft PVC materials incorporating bio‐based hyperbranched ester were investigated and compared with the traditional plasticizer dioctyl phthalate (DOP). The results showed that bio‐based hyperbranched ester enhanced the thermal stability of the PVC materials. The T_g of PVC incorporating bio‐based hyperbranched ester was 23 °C, lower than that of PVC/DOP materials at 28 °C. Bio‐based hyperbranched ester showed a better plasticizing effect, solvent extraction resistance and volatility resistance than DOP. The plasticizing mechanism is also discussed. © 2018 Society of Chemical Industry     

Recent developments in plant oil based functional materials

The increasing interest of academic and industrial sectors in the use of bio‐based materials mirrors the overwhelming need for replacing, as much as possible, petroleum derived chemicals, reducing the negative environmental impact derived from their usage. Vegetable oils fulfill this goal extremely well, because of their worldwide availability, large volume production at comparatively low prices and versatility of the modifications and reactions in which they can participate to produce a large variety of different monomers and polymer precursors. Further reactions of these chemicals can lead to very different types of final materials with varied applications. It is because of this remarkable versatility that many review articles have appeared during the last few years; many of them have dealt with the various routes for vegetable oil modification and options for polymer synthesis, whilst others were dedicated to the analysis of the properties of the derived materials, generally focusing on structural properties. In this review, we focus on the capabilities of vegetable oils to be modified and/or reacted to obtain materials with functional properties suitable for use in coatings, conductive or insulating materials, biomedical, shape memory, self‐healing and thermoreversible materials as well as other special functional applications. © 2015 Society of Chemical Industry     

Effect of halloysite nanotubes on mechanical properties and flammability of soy protein based green composites

To address the growing emphasis on the use and development of sustainable materials, bio‐based polymers and fibers are processed to prepare entirely bio‐based fiber‐reinforced ‘green’ composites. To enable these new materials to perform in lightweight vehicle and infrastructural applications, they must be characterized both structurally and in terms of their various performance characteristics. The results of preparation and characterization of bio‐based composites comprising jute fabric and soy protein concentrate (SPC) modified with glycerol and/or halloysite nanotubes (HNT) are reported herein as a first look at the flammability of these bio‐based nanocomposites. The results reveal that SPC has lower flammability (heat release capacity) than petrochemical‐based resins, such as epoxies and vinyl esters. In addition, incorporating 5% mass fraction of HNT is found to reduce the composite flammability, while having no negative impact on the mechanical properties. Copyright © 2012 John Wiley & Sons, Ltd.     

Ethanol‐responsive characteristics of polyethersulfone composite membranes blended with poly(N‐isopropylacrylamide) nanogels

Ethanol‐responsive smart membranes with different microstructures are prepared from blends of polyethersulfone (PES) and poly(N‐isopropylacrylamide) (PNIPAM) nanogels by immersion precipitation phase inversion method in a convenient and controllable manner. The introduction of PNIPAM nanogels forms the microporous structures on the surface of the top skin layer and on the pore walls of the finger‐like porous sublayer of membranes. The ethanol‐responsive characteristics of the proposed PES composite membranes are systematically investigated. With increasing ethanol concentration in the range from 0 to 15 wt %, the trans‐membrane flux of ethanol solution increases. The microstructures and the resultant ethanol‐responsive characteristics of the composite membranes can be regulated by the content of PNIPAM nanogels blended in the membranes. The more the content of PNIPAM nanogels blended in the membranes, the more the number of the submicron pores is, and thus the better the ethanol‐responsive characteristics of the composite membranes. The proposed ethanol‐responsive smart membranes are expected to be combined with the traditional pervaporation membranes as a smart vavle to achieve continuous and highly efficient ethanol production during the biological fermentation. The preparation technique and results in this study provide valuable guidance for further design and the industrial‐scale fabrication of novel composite membranes for application in ethanol separation systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41032.