Efficient adsorption of bulky reactive dyes from water using sustainably-derived mesoporous carbons.

Hazardous reactive dyes can cause serious environmental problems, as they are difficult to remove from water using conventional adsorbents due to their large molecular sizes and bulky structures. Sustainable mesoporous carbons derived from alginic acid demonstrated promising adsorbent capacity for several representative industrial bulky reactive dye molecules that account for almost 30% of the global textile dye market: Procion Yellow H-XEL (PY), Remazol Black (RB), Procion Crimson H-XEL (PC) and Procion Navy H-XEL (PN). These new adsorbents showed high mesoporosity (>90%) and large pore diameters (>20 nm) facilitating more straightforward and efficient adsorption and desorption processes when compared with predominately microporous activated carbon (AC), Norit, of similar surface chemistry, or with Silica gel (Sgel) that shows good mesoporosity but is hydrophilic. Their adsorption capacity was also significantly higher than that of both AC and Sgel, verifying suitability for bulky dye elimination from wastewater. Adsorption kinetic studies showed a best fit with the Elovich model, indicating a heterogeneous surface adsorption process. The adsorption isotherm data was best represented via the Toth model for almost all adsorbent/dye systems (R2 ≥ 0.98), validating the results of the Elovich model whereby the adsorbent is structurally heterogenous with multilayer dye coverage. From thermodynamic analysis, the derived parameters of ΔG (-11.6 âˆ¼ -6.2 kJ/mol), ΔH and ΔS demonstrate a spontaneous, enthalpy controlled adsorption process that was exothermic for RB (-10.0 kJ/mol) and PC (-23.9 kJ/mol) and endothermic for PY (3.9 kJ/mol) and PN (13.2 kJ/mol). Overall these alginic acid based mesoporous carbons are cost-effective, sustainable and efficient alternatives to current predominantly microporous adsorbent systems.

Designing New Sustainable Polyurethane Adhesives: Influence of the Nature and Content of Diels-Alder Adducts on Their Thermoreversible Behavior.

With a view to the development of new sustainable and functional adhesives, two Diels-Alder (DA) adducts are incorporated as a third component into the curing process of solvent-based and solvent-free polyurethanes in this study. The influence of the nature and content of the DA molecules on the retro-DA (rDA) reaction and its reversibility and cyclability is investigated. It is demonstrated that the bonding/debonding properties of the adhesives are mainly controlled by the concentration of the DA adducts, with a minimum thermoreversible bond (TB) content required that depends on the system and the total ratio between all the diols in the formulation. For the solvent-based system, rDA/DA reversibility can be repeated up to ~20 times without deterioration, in contrast to the solvent-free system where a gradual loss in the DA network reconstruction efficiency is observed. Despite this limitation, the solvent-free system presents clear advantages from an environmental point of view. The changes observed in the physical properties of these new thermoreversible adhesives are of great relevance for recycling strategies and, in particular, their potential for separating multilayered film packaging materials in order to recycle the individual polymer films involved.

Investigation of the Crystallization Kinetics and Melting Behaviour of Polymer Blend Nanocomposites Based on Poly(L-Lactic Acid), Nylon 11 and TMDCs WS2.

The aim of this work was to study the crystallization kinetics and melting behaviour of polymer blend nanocomposites based on poly (L-lactic acid) (PLLA), nylon 11 and tungsten disulfide nanotubes (INT-WS2), which are layered transition metal dichalcogenides (TMDCs), using non-isothermal differential scanning calorimetry (DSC). Blends containing different nylon 11 contents ranging from 20 to 80 wt.% with or without INT-WS2 were prepared by melt mixing. Evaluation of their morphology with high-resolution SEM imaging proved that the incorporation of inorganic nanotubes into the immiscible PLLA/nylon 11 mixtures led to an improvement in the dispersibility of the nylon 11 phase, a reduction in its average domain size and, consequently, an increase in its interfacial area. The crystallization temperatures of these PLLA/nylon 11-INT blends were influenced by the cooling rate and composition. In particular, the DSC results appear to demonstrate that the 1D-TMDCs WS2 within the PLLA/nylon 11-INT blend nanocomposites initiated nucleation in both polymeric components, with the effect being more pronounced for PLLA. Moreover, the nucleation activity and activation energy were calculated to support these findings. The nucleation effect of INT-WS2, which influences the melting behaviour of PLLA, is highly important, particularly when evaluating polymer crystallinity. This study opens up new perspectives for the development of advanced PLA-based nanomaterials that show great potential for ecological and biomedical applications.

DPD simulations and experimental study on reduction-sensitive polymeric micelles self-assembled from PCL-SS-PPEGMA for doxorubicin controlled release.

Delivery of anticancer drugs by amphiphilic polymeric micelles with disulfide bonds as the reduction-responsive groups has potential application in the field of drug-controlled release. In this study, three disulfide-linked polycaprolactone-b-polyethylene glycol methyl ether methacrylate (PCL-SS-PPEGMA) were synthesized and confirmed by 1H NMR and GPC, and then used for doxorubicin (DOX) delivery. The CMC values of the three PCL-SS-PPEGMA micelles were low (0.71-4.56 mg/L), indicative of the good stability of micelles in aqueous solution. The drug loading content (LC) and encapsulation efficiency (EE), together with the DOX accelerated release profiles were determined, with good drug loading capacity and well drug-controlled release performance. And to explore the mesoscopic behavior of reduction-responsive drug-loaded polymeric micelles, by using a dedicated disulfide bond-breaking model and script, dissipative particle dynamics (DPD) simulations were carried out on the three PCL-SS-PPEGMA polymers. Their self-assembled behavior, formation of DOX-loaded micelles, the disulfide bond-breaking process, as well as the DOX reduction-responsive release process were simulated and assessed. Comparing the DPD simulation results with the experimental data, we found that they were in good agreement, effectively demonstrating that the DPD simulation method developed can provide a practical mesoscopic approach for the reduction-responsive drug-loaded polymeric micelles that involved the cleavage of dynamic covalent bonds.

Nanocomposite Materials with Poly(l-lactic Acid) and Transition-Metal Dichalcogenide Nanosheets 2D-TMDCs WS2.

Layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) were introduced via melt processing into poly(l-lactic acid) (PLLA) to generate PLLA/2D-WS2 nanocomposite materials. The effects of the 2D-WS2 on the morphology, crystallization, and biodegradation behavior of PLLA were investigated. In particular, the non-isothermal melt-crystallization of neat PLLA and PLLA/2D-WS2 nanocomposites were analyzed in detail by varying both the cooling rate and 2D-WS2 loading. The kinetic parameters of PLLA chain crystallization are successfully described using the Liu model. It was found that the PLLA crystallization rate was reduced with 2D-WS2 incorporation, while the crystallization mechanism and crystal structure of PLLA remained unchanged in spite of nanoparticle loading. This was due to the PLLA chains not being able to easily adsorb on the WS2 nanosheets, hindering crystal growth. In addition, from surface morphology analysis, it was observed that the addition of 2D-WS2 facilitated the enzymatic degradation of poorly biodegradable PLLA using a promising strain of actinobacteria, Lentzea waywayandensis. The identification of more suitable enzymes to break down PLLA nanocomposites will open up new avenues of investigation and development, and it will also lead to more environmentally friendly, safer, and economic routes for bioplastic waste management.

Exceptionally Stable Microporous Organic Frameworks with Rigid Building Units for Efficient Small Gas Adsorption and Separation.

Three microporous organic frameworks (hereafter denoted as MPOF-Ads) based on a rigid adamantane core have been successfully synthesized via Sonogashira-Hagihara polycondensation coupling in high yields, 83.7-94.6%. The obtained amorphous MPOF-Ads networks have high Brunauer-Emmett-Teller surface areas (up to 737.3 m2 g-1), narrow pore size distribution (0.95-1.06 nm), and superior thermal (the initial decomposition temperature T5% under an N2 atmosphere can reach 410 °C) and chemical stability (no apparent degradation in common organic solvents or strong acid/base solutions after 7 days). At 273 K and 1.0 bar, these MPOF-Ads networks present good uptake capacities for small gas molecules (13.9 wt % CO2 and 1.66 wt % CH4) for which the presence of high surface area, predominant microporosity, and narrow pore size distribution are beneficial. In addition, the as-prepared MPOF-Ads networks possess moderate isosteric heats for CO2 (Qst = 19.5-30.3 kJ mol-1) and show desired CO2/N2 and CO2/CH4 selectivity (36.3-38.4 and 4.1-4.3 based on Henry's law and 17.88-24.92 and 4.24-5.70 based on ideal adsorbed solution theory, respectively). With the demonstrated properties, the synthesized MPOF-Ads networks display potential for small gas storage and separation that can be used in harsh environments because of their superior physical and chemical stability.

Adamantane-Based Micro- and Ultra-Microporous Frameworks for Efficient Small Gas and Toxic Organic Vapor Adsorption.

Microporous organic polymers and related porous materials have been applied in a wide range of practical applications such as adsorption, catalysis, adsorption, and sensing fields. However, some limitations, like wide pore size distribution, may limit their further applications, especially for adsorption. Here, micro- and ultra-microporous frameworks (HBPBA-D and TBBPA-D) were designed and synthesized via Sonogashira⁻Hagihara coupling of six/eight-arm bromophenyl adamantane-based "knots" and alkynes-type "rod" monomers. The BET surface area and pore size distribution of these frameworks were in the region of 395⁻488 m² g-1, 0.9⁻1.1 and 0.42 nm, respectively. The as-made prepared frameworks also showed good chemical ability and high thermal stability up to 350 °C, and at 800 °C only 30% mass loss was observed. Their adsorption capacities for small gas molecules such as CO2 and CH4 was 8.9⁻9.0 wt % and 1.43⁻1.63 wt % at 273 K/1 bar, and for the toxic organic vapors n-hexane and benzene, 104⁻172 mg g-1 and 144⁻272 mg g-1 at 298 K/0.8 bar, respectively. These are comparable to many porous polymers with higher BET specific surface areas or after functionalization. These properties make the resulting frameworks efficient absorbent alternatives for small gas or toxic vapor capture, especially in harsh environments.

DPD studies on mixed micelles self-assembled from MPEG-PDEAEMA and MPEG-PCL for controlled doxorubicin release.

In order to better understand and improve the drug loading capacity and release behavior of the pH-responsive mixed micelles in well controlled pH environments, dissipative particle dynamics (DPD) simulations are employed. This is performed by studying the co-micellization behavior of these materials produced from the two specific diblock polymers, poly(ethylene glycol) methyl ether-b-poly(N, N diethylamino ethyl methacrylate) (MPEG-PDEAEMA) and poly(ethylene glycol) methyl ether-b-polycaprolactone (MPEG-PCL) for doxorubicin (DOX) delivery. With the use of appropriate interaction parameters, the formation mechanism of (drug-loaded) mixed micelles, particle sizes, morphology, and composition are investigated. Simulation results show that compared with pure MPEG-PDEAEMA or MPEG-PCL, the mixed MPEG-PDEAEMA and MPEG-PCL system can combine to form multifunctional mixed micelles with larger particle sizes that lead to improved stability, higher drug loading capacity and better-controlled drug release performance. Simulations of the drug release process using the mixed micelles show that, when the environment is acidic, the tertiary amine group of PDEAEMA and DOX3 lead to rapid diffusion and release of the DOX in the aqueous solution. It is found that the presence of MPEG-PCL has a great influence in avoiding the fast release of the drug inside the core of micelles. Therefore, this study offers a deeper understanding of the mechanism on the co-micellization behaviors, the pH-responsive and drug controlled release behaviors of mixed micelles.

Biochemical profiling of rat embryonic stem cells grown on electrospun polyester fibers using synchrotron infrared microspectroscopy.

Therapeutic options for spinal cord injuries are severely limited; current treatments only offer symptomatic relief and rehabilitation focused on educating the individual on how to adapt to their new situation to make best possible use of their remaining function. Thus, new approaches are needed, and interest in the development of effective strategies to promote the repair of neural tracts in the central nervous system inspired us to prepare functional and highly anisotropic polymer scaffolds. In this work, an initial assessment of the behavior of rat neural progenitor cells (NPCs) seeded on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) fiber scaffolds using synchrotron-based infrared microspectroscopy (SIRMS) is described. Combined with a modified touch imprint cytology sample preparation method, this application of SIRMS enabled the biochemical profiles of NPCs on the coated polymer fibers to be determined. The results showed that changes in the lipid and amide I-II spectral regions are modulated by the type and coating of the substrate used and the culture time. SIRMS studies can provide valuable insight into the early-stage response of NPCs to the morphology and surface chemistry of a biomaterial, and could therefore be a useful tool in the preparation and optimization of cellular scaffolds. Graphical abstract Synchrotron IR microspectroscopy can provide insight into the response of neural progenitor cells to synthetic scaffolds.

Polysaccharide-derived mesoporous materials (Starbon®) for sustainable separation of complex mixtures.

The recovery and separation of high value and low volume extractives are a considerable challenge for the commercial realisation of zero-waste biorefineries. Using solid-phase extractions (SPE) based on sustainable sorbents is a promising method to enable efficient, green and selective separation of these complex extractive mixtures. Mesoporous carbonaceous solids derived from renewable polysaccharides are ideal stationary phases due to their tuneable functionality and surface structure. In this study, the structure-separation relationships of thirteen polysaccharide-derived mesoporous materials and two modified types as sorbents for ten naturally-occurring bioactive phenolic compounds were investigated. For the first time, a comprehensive statistical analysis of the key molecular and surface properties influencing the recovery of these species was carried out. The obtained results show the possibility of developing tailored materials for purification, separation or extraction, depending on the molecular composition of the analyte. The wide versatility and application span of these polysaccharide-derived mesoporous materials offer new sustainable and inexpensive alternatives to traditional silica-based stationary phases.

Flexible Bionanocomposites from Epoxidized Hemp Seed Oil Thermosetting Resin Reinforced with Halloysite Nanotubes.

Hemp seed (Cannabis sativa L.) oil comprises a variety of beneficial unsaturated triglycerides with well-documented nutritional and health benefits. However, it can become rancid over a relatively short time period, leading to increased industrial costs and waste of a valuable product. The development of sustainable polymers is presented as a strategy, where both the presence of unsaturation and peroxide content could be effectively used to alleviate both the waste and financial burden. After the reaction with peroxyacetic acid, the incorporation of halloysite nanotubes (HNTs), and the subsequent thermal curing, without the need for organic solvents or interfacial modifiers, flexible transparent materials with a low glass-transition temperature were developed. The improvement in the thermal stability and both the static and dynamic mechanical properties of the bionanocomposites were significantly enhanced with the well-dispersed HNT filler. At an optimum concentration of 0.5 wt % HNTs, a simultaneous increase in stiffness, strength, ductility, and toughness was observed in comparison to the unfilled cured resin. These sustainable food-waste-derived bionanocomposites may provide an interesting alternative to petroleum-based materials, particularly for low-load-bearing applications, such as packaging.

Importance of Micropore-Mesopore Interfaces in Carbon Dioxide Capture by Carbon-Based Materials.

Mesoporous carbonaceous materials (Starbons®) derived from low-value/waste bio-resources separate CO2 from CO2 /N2 mixtures. Compared to Norit activated charcoal (AC), Starbons® have much lower microporosities (8-32 % versus 73 %) yet adsorb up to 65 % more CO2 . The presence of interconnected micropores and mesopores is responsible for the enhanced CO2 adsorption. The Starbons® also showed three-four times higher selectivity for CO2 adsorption rather than N2 adsorption compared to AC.

An Interesting Class of Porous Polymer--Revisiting the Structure of Mesoporous α-D-Polysaccharide Gels.

The processes involved in the transformation of non-porous, native polysaccharides to their highly porous equivalents introduce significant molecular complexity and are not yet fully understood. In this paper, we propose that distinct changes in polysaccharide local short-range ordering promotes and directs the formation of meso- and micro-pores, which are investigated here using N2 sorption, FTIR, and solid-state (13)C NMR. It is found that an increase in the overall double helical amylose content, and their local association structures, are responsible for formation of the porous polysaccharide gel phase. An exciting consequence of this local ordering change is elegantly revealed using a (19)F NMR experiment, which identifies the stereochemistry-dependent diffusion of a fluorinated chiral probe molecule (1-phenyl-2,2,2-trifluoroethanol) from the meso- to the micro-pore region. This finding opens opportunities in the area of polysaccharide-based chiral stationary phases and asymmetric catalyst preparation.

A sustainable freeze-drying route to porous polysaccharides with tailored hierarchical meso- and macroporosity.

Bio-derived polysaccharide aerogels are of interest for a broad range of applications. To date, these aerogels have been obtained through the time- and solvent-intensive procedure of hydrogel fomation, solvent exchange, and scCO2 drying, which offers little control over meso/macropore distribution. A simpler and more versatile route is developed, using freeze drying to produce highly mesoporous polysaccharide aerogels with various degrees of macroporosity. The hierarchical pore distribution is controlled by addition of different quantities of t-butanol (TBA) to hydrogels before drying. Through a systematic study an interesting relationship between the mesoporosity and t-butanol/water phase diagram is found, linking mesoporosity maxima with eutectic points for all polysaccharides studied (pectin, starch, and alginic acid). Moreover, direct gelation of polysaccharides in aqueous TBA offers additional time savings and the potential for solvent reuse. This finding is a doorway to more accessible polysaccharide aerogels for research and industrial scale production, due to the widespread accessibility of the freeze drying technology and the simplicity of the method.

Synthesis, immobilization and catalytic activity of a copper(II) complex with a chiral bis(oxazoline).

A chiral bis(oxazoline) bearing CH2OH groups was synthesized from a commercial bis(oxazoline) and characterized by 1H- and 13C-NMR, high resolution ESI-mass spectrometry and FTIR. The corresponding copper(II) complex was immobilized onto the surface of a mesoporous carbonaceous material (Starbon® 700) in which the double bonds had been activated via conventional bromination. The materials were characterized by elemental analysis, ICP-OES, XPS, thermogravimetry and nitrogen adsorption at 77 K. The new copper(II) bis(oxazoline) was tested both in the homogeneous phase and once immobilized onto a carbonaceous support for the kinetic resolution of hydrobenzoin. Both were active, enantioselective and selective in the mono-benzoylation of hydrobenzoin, but better enantioselectivities were obtained in the homogeneous phase. The heterogeneous catalyst could be separated from the reaction media at the end of the reaction and reused in another catalytic cycle, but with loss of product yield and enantioselectivity.

Layer-by-Layer Assembly of Biopolyelectrolytes onto Thermo/pH-Responsive Micro/Nano-Gels.

This review deals with the layer-by-layer (LbL) assembly of polyelectrolyte multilayers of biopolymers, polypeptides (i.e., poly-l-lysine/poly-l-glutamic acid) and polysaccharides (i.e., chitosan/dextran sulphate/sodium alginate), onto thermo- and/or pH-responsive micro- and nano-gels such as those based on synthetic poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAA) or biodegradable hyaluronic acid (HA) and dextran-hydroxyethyl methacrylate (DEX-HEMA). The synthesis of the ensembles and their characterization by way of various techniques is described. The morphology, hydrodynamic size, surface charge density, bilayer thickness, stability over time and mechanical properties of the systems are discussed. Further, the mechanisms of interaction between biopolymers and gels are analysed. Results demonstrate that the structure and properties of biocompatible multilayer films can be finely tuned by confinement onto stimuli-responsive gels, which thus provides new perspectives for biomedical applications, particularly in the controlled release of biomolecules, bio-sensors, gene delivery, tissue engineering and storage.

Comparative study of the covalent diazotization of graphene and carbon nanotubes using thermogravimetric and spectroscopic techniques.

The direct diazotization of the sp(2) carbon network of graphene and multi-walled carbon nanotubes (MWNTs) is one of the many methods employed to introduce functional groups into these nanostructures. Herein, a methodical study on solvent-free diazotization with ethynylaniline in the presence of isoamyl nitrite is reported. Thermogravimetric analysis and UV-visible, infrared and Raman spectroscopies are used to precisely determine the degree of modification, confirm the presence of physisorption and describe the mechanism of elimination of the modifying groups. The results suggest that the same synthetic protocol in both cases leads to a certain degree of covalent modification, whilst a proportion of the modifying groups remains adsorbed to the carbon nanostructure. A higher level of global modification was observed for MWNTs. It was found that the elimination mechanism of the covalently-linked modifiers is identical for both nanostructures and involves two steps; acetylenic-aromatic bond rupture in the modifier followed by modifier-carbon nanostructure cleavage.

Direct microwave-assisted hydrothermal depolymerization of cellulose.

A systematic investigation of the interaction of microwave irradiation with microcrystalline cellulose has been carried out, covering a broad temperature range (150 → 270 °C). A variety of analytical techniques (e.g., HPLC, (13)C NMR, FTIR, CHN analysis, hydrogen-deuterium exchange) allowed for the analysis of the obtained liquid and solid products. Based on these results a mechanism of cellulose interaction with microwaves is proposed. Thereby the degree of freedom of the cellulose enclosed CH2OH groups was found to be crucial. This mechanism allows for the explanation of the different experimental observations such as high efficiency of microwave treatment; the dependence of the selectivity/yield of glucose on the applied microwave density; the observed high glucose to HMF ratio; and the influence of the degree of cellulose crystallinity on the results of the hydrolysis process. The highest selectivity toward glucose was found to be ~75% while the highest glucose yield obtained was 21%.

Molecular-level understanding of the carbonisation of polysaccharides.

Understanding of both the textural and functionality changes occurring during (mesoporous) polysaccharide carbonisation at the molecular level provides a deeper insight into the whole spectrum of material properties, from chemical activity to pore shape and surface energy, which is crucial for the successful application of carbonaceous materials in adsorption, catalysis and chromatography. Obtained information will help to identify the most appropriate applications of the carbonaceous material generated during torrefaction and different types of pyrolysis processes and therefore will be important for the development of cost- and energy-efficient zero-waste biorefineries. The presented approach is informative and semi-quantitative with the potential to be extended to the formation of other biomass-derived carbonaceous materials.

Simple Preparation of Novel Metal-Containing Mesoporous Starches.

Metal-containing mesoporous starches have been synthesized using a simple and efficient microwave-assisted methodology followed by metal impregnation in the porous gel network. Final materials exhibited surface areas >60 m² g-1, being essentially mesoporous with pore sizes in the 10-15 nm range with some developed inter-particular mesoporosity. These materials characterized by several techniques including XRD, SEM, TG/DTA and DRIFTs may find promising catalytic applications due to the presence of (hydr)oxides in their composition.