Catalytic carbonyl-olefin metathesis has emerged as a new strategy for the direct formation of carbon–carbon double bonds. Successful approaches for ring-closing carbonyl-olefin metathesis exist, but limitations remain in accessing systems larger than 5-membered rings. Currently available strategies rely on Lewis acidic superelectrophiles as stronger catalysts, which require precious metal additives for their formation upon chloride abstraction from otherwise environmentally benign metal salts, such as FeCl3. Herein we report the development of a continuous flow reactor that overcomes this challenge and can access 6-membered rings using FeCl3 as the Lewis acid catalyst. The plug-flow reactor design is user friendly, benchtop amenable, and demonstrates up to 200x improved reaction efficiency over batch conditions. Computational investigations reveal that this transformation proceeds through an unprecedented bimolecular stepwise pathway via intermolecular proton transfer. These insights represent a significant advance for catalytic carbonyl–olefin metathesis and are expected to spur future developments in catalyst design and reaction scope.

Highly processable hydrogels loaded with active components for localised drug delivery and/or live cells for regenerative medicine are an attractive target for biotechnology research. We describe a single-pot precipitation polymerisation of poly (N-isopropylacrylamide) (pNIPAM) from the surface of dispersed Laponite® platelets in aqueous media above its lower critical solution temperature (LCST), yielding tightly packed pNIPAM globules that resist aggregation and can be maintained for long periods of time as a low viscosity colloidal suspension. Upon cooling, the pNIPAM chains transform from the 'globule' to the 'coil' conformation, establishing multiple physical interactions and chain entanglement leading to irreversible gel formation. We have shown that the temperature and rate of phase transition and the rheological and mechanical properties of Laponite®-pNIPAM hydrogel can be tailored by addition of N, N′-dimethylacrylamide (DMAc) comonomer and other biologically relevant additives. The tuneable properties of Laponite®-pNIPAM hydrogel confirms its excellent potential for a wide range of therapeutic applications.

Effective food packaging is a major factor in the current global drive to minimise food waste. Starch is an excellent oxygen barrier for packaging but it is brittle and moisture sensitive. The addition of layered minerals and plasticizers can significantly improve the moisture barrier and flexibility of the resulting composite. Some combinations of starch and plasticizer are incompatible but our results show that the addition of bentonite ensures the formation of coherent starch films with much improved moisture barrier regardless of the starch-plasticizer compatibility. It was clearly demonstrated that improvement of the moisture barrier was critically dependent on the layer charge of the bentonite used. Starch was readily accommodated in the interlayer space of bentonites with a layer charge of < 0.4 electrons per formula unit but was not adsorbed if the layer charge was above this value. Starch-bentonite-plasticizer coatings prepared using bentonites with the lower layer charge routinely produced higher barriers to water vapour. The water vapour transmission rate (WVTR) of the base paper was reduced from 780 to 340 +/- 20 gm(2) day(-1) when coated with starch alone. This was further reduced to 48 or 66 gm(2) day(-1) if glycerol or lower charge bentonite, respectively, was added to the starch. Optimised coatings of starch-lower charge bentonite-plasticizer provided WVTR values of <= 10 gm(2) day(-1) whereas WVTR values for comparative coatings prepared using the higher charge bentonites were three to four times higher (35 +/- 7 gm(2) day(-1)). Scanning electron micrographs provided clear evidence for the presence of 60 nm thick supramolecular layers formed from starch-bentonite-plasticizer in the samples coated on either glass or paper. The WVTR values for these low-eco footprint coatings are competitive with proprietary coatings prepared using petroleum derived resins.

The effect of silver nitrate concentration, pre-washed bentonite (to remove extraneous salt) and back-exchange procedures have been explored to assess the type of silver species formed and their behaviour upon exposure to further salts. X-ray fluorescence was used to quantify the amount of silver present and whether in cation exchange sites, whereas X-ray diffraction and transmission electron microscopy identified the silver compounds present. A further objective was to assess the antimicrobial, barrier and dispersion properties of the silver/sodium bentonites when incorporated into a starch-plasticiser-clay coating used for packaging. The silver/sodium bentonites demonstrated very strong antimicrobial activity towards Escherichia con, Kocuria rhizophila and Aspergillus niger. Incorporating just 0.03 wt% of silver/sodium bentonite in the coating (0.2 mu mol/m(2) Ag in dried coating with thickness of 14 mu m) produced a > 4.4 log reduction against an initial loading of 2.1 x 10(5) CFU/object for E. coli. Water vapour barrier properties of coatings prepared on paper and containing the mixed silver/sodium bentonite were unaffected since water vapour transmission rate values of similar to 20-40 g/m(2).day (23 degrees C, 50% relative humidity) were maintained. Also the presence of silver did not adversely affect the clay dispersion. The Ag+ release profile from mixed silver/sodium clay upon addition of HNO3 and NaNO3 is discussed.

The applicability of the n-nonane pre-adsorption method for characterising the porosity in clays is presented. Na-SD, a Na+-exchanged purified bentonite, and materials obtained by Al3+-exchange and acid treatments of Na-SD and SAz-1 were used. Nitrogen adsorption isotherms, at -196 degrees C, were determined before and after n-nonane pre-adsorption on each of the samples. In all materials, n-nonane remained adsorbed in ultramicropores after outgassing at 25 degrees C. Outgassing at higher temperatures (50, 75 and 200 degrees C) removed nonane and ultramicropores became available for nitrogen adsorption. All treatments on Na-SD led to increase in micropore volume. Larger ultramicropore and supermicropore volumes were obtained for Na-SD acid activated with HCl at 95 degrees C than for treatments at 25 degrees C with HCl or following Al3+-exchange (Al-SD), and increased with increasing acid concentration to 3 M. Activation with 4 M HCl led to the largest pore volume with contribution from mesopores. However, the specific external surface area was the same as that obtained for Na-SD, Al-SD and for most of the other acid activated samples. Treatments at 95 degrees C with 1 M and 6 M HCl promoted increase in specific external surface area. The micropore volumes and specific external surface area for SAz-1 treated with 1 M HCl at 95 degrees C were larger than those of Al-SAz-1, but lower than those obtained for corresponding materials derived from Na-SD. The n-nonane pre-adsorption method enabled micropore volumes and specific external surface areas to be obtained for all samples. (C) 2016 Elsevier Inc. All rights reserved.

Shape Memory Polymers (SMPs) exhibit the intriguing ability to change back from an intermediate, deformed shape back to their original, permanent shape. In this contribution a systematic series of t-butylacrylate-co-poly(ethyleneglycol) dimethacrylate (tBA-co-PEGDMA) polymers have been synthesised and characterised prior to incorporation of organoclay. Increasing the poly(ethyleneglycol) dimethacrylate (PEGDMA) content in increments of 10% increased the storage modulus from 2005 to 2250MPa, reduced the glass transition temperature from +41 to −26°C and reduced the intensity of the associated tan δ peak. The tBA-co-PEGDMA crosslinked networks displayed useful shape memory properties up to PEGDMA contents of 40%. Above this PEGDMA percentage the materials were prone to fracture and too brittle for a realistic assessment of their shape memory capability. The system containing 90% t-butylacrylate (tBA) and 10% PEGDMA was selected as the host matrix to investigate how the incorporation of 1 to 5mass% of a benzyl tallow dimethylammonium-exchanged bentonite (BTDB) influenced the shape memory properties. X-ray diffraction data confirmed that BTDB formed a microcomposite in the selected matrix and exerted no influence on the storage modulus, rubbery modulus, glass transition temperature, Tg, or the shape or intensity of the tan δ peak of the host matrix. Therefore, it was anticipated that the presence of BTDB would have no effect, positive or negative, nor on the shape memory properties of the host matrix. However, it was found that the incorporation of clay, especially at the 1mass% level, significantly accelerated the speed, compared with the clay-free SMP, at which the microcomposite returned to the original, permanent shape. This accelerated return to the permanent shape was also observed when the microcomposite was coated onto a 100μm PET film.

The competitive adsorption of poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVOH) onto Na-bentonite has been assessed quantitatively. Particular emphasis was focused on the amount of organic located within the bentonite interlayer and any subsequent effects on the extent of layer expansion. The individual isotherms showed strong adsorption for both PVOH and PEG at amounts lower than the quantities required to produce a fully loaded bilayer (0.33 g of PVOH/g of clay) and single layered structures (0.10 g of PEG/g of clay), respectively. Above these concentrations, the incremental amounts adsorbed were smaller, and the concentration of adsorbates in solution gradually increased. Na-bentonite adsorbed more PVOH than PEG at any given concentration. In the competitive study, the amount of PVOH adsorbed was enhanced in the presence of PEG (0.10 and 0.30 g/g of clay), but less PEG was adsorbed. At low loadings of PVOH (0.02-0.10 g/g of clay), the amount of adsorbed PEG was increased but at higher PVOH levels PEG adsorption was reduced. The XRD data showed stepped changes in the d-spacing as the adsorbed amounts of both PEG and PVOH increased. The PEG-bentonite samples did not expand beyond a bilayer structure (18 Å), but the XRD data for PVOH-treated samples indicated the formation of multilayer structures (d ≥ 44 Å).

In this study, we report the use of clay-based catalysts in the methoxylation of a-pinene, for the selective synthesis of a-terpinyl methyl ether, TME. The main reaction products and intermediates were identified by GC-MS. The reaction conditions (stirring rate and catalyst load) that afford a kinetic regime were established. SAz-1 (Cheto, Arizona, USA) source clay and a montmorillonite (SD) from Porto Santo, Madeira Archipelago, Portugal, were modified by ion-exchange with Al3+ to produce catalysts with markedly different acidities and textural properties. The catalysts based on the high layer-charge SAz-1 montmorillonite proved to be the most active. Ion-exchange with Al3+, followed by thermal activation at 150 degrees C, afforded the highest number of Bronsted acid sites - a significant proportion of which were located in the clay gallery - and this coincided with the maximum catalytic activity. The influence of various reaction conditions, to maximize a-pinene conversion and selectivity, was studied over AISAz-1. When the reaction was performed for 1 h at 60 degrees C, the conversion reached 65% with 65% selectivity towards the mono-ether, TME. Similar conversions and selectivities required up to 50 h over zeolites and other solid acid catalysts. The kinetic dependencies of this reaction on temperature and reagent concentration, over the selected clays were also investigated. It was established that, in the temperature and reagent concentration regime studied, the reaction was first order with respect to a-pinene. The apparent activation energies over the two catalysts, calculated from Arrhenius plots, were almost identical at 72 kJ mol(-1). (C) 2014 Elsevier B.V. All rights reserved.

Paper and paperboard are the most widely used packaging materials for both food and non-food products. Because they are composed of highly porous cellulose networks, they readily absorb moisture in high humidity environments or when in contact with liquid or high moisture foods. Therefore they are often coated with hydrophobic coating materials such as polyethylene (PE) to improve their water-resistant properties. One of the major uses of such hydrophobic material coated paperboard is a disposable single-use paper cup with or without a lid. Today, the paper-based materials are coated with a thin layer of a petroleum derived plastic, mostly polyethylene, which has provided the cups and other packaging solutions with the required barrier property and water resistance. Hence, the ongoing challenge is to coat the paper with a biobased, hydrophobic polymeric material which must be repulpable or otherwise biodegradable in most of the environments considered. Many interesting developments are already known for the manufacturing of cellulose-based products, such as microfibrillated celluloses (MFC's) or modified celluloses, usable in the paper packaging industry. Paper and paperboard in combination with Green-Polyethylene, MFC's and polyhydroxyalkanoates (PHA's) seems to be the most promising solution for the packaging industry in the near future and the development of the thermoplastic modified celluloses for the next future. Regarding environmental considerations, PHA is a promising solution for the paper packaging industry but the problem of material recycling has to be solved and a solution comparable with the recyclability of PE-coated paper packaging products should be obtained. This review consists of a critical analysis of published results of 1-way food packaging and discusses more in detail what will be necessary for the development of 1-way food packaging based solely on wood derived products and biodegradable polymers.

The concept and development of mixed modifier clays have been investigated in order to optimize clay dispersion within polymer matrices in general and polycaprolactone (PCL) in particular. A range of mixed modifier clays have been prepared by the inclusion of a second, more polar, organomodifier of much shorter chain length (Me3(CH2CH2OH)N+) within a benzyl(hydrogenatedtallowalkyl)dimethylammonium organoclay. The focus was to produce a range of organoclays with a systematic progression of selected polarities so that an optimum compatibility with the host polymer, PCL, could be achieved. The key to success was to attain that delicate balance where the long alkyl chains on the first modifier just overcame the layer–layer attraction whilst the second, shorter chain, modifier offered the potential to optimise the polarity of the clay surface and reduce the congestion in the interlayer space to ease polymer ingress. The organo-modification, subsequent polymer dissolution and casting were achieved using nitrobenzene as the solvent. X-ray diffraction (XRD) evidence, supported by, carbon/nitrogen analysis, proton nuclear magnetic resonance spectroscopy and thermogravimetry–mass spectroscopy, indicated that, when fully optimized, a homogeneous distribution of the two modifiers had been achieved within each individual interlayer space and that the amount of each modifier could be controlled. XRD data and transmission electron microscopy images confirmed that the extent of dispersion, of the mixed modifier clay in PCL, could be controlled to produce layered aluminosilicate–polymer systems that were either exfoliated, intercalated or a mixture of both.

In this study, we report the use of clay-based catalysts in the methoxylation of limonene, for the selective synthesis of alpha-terpinyl methyl ether. Na-SAz-1, Ca-SWy-2 and Sap-Ca source clays and a montmorillonite (SD) from Porto Santo, Madeira Archipelago, Portugal were modifledby(i) ion-exchange with Al, Fe, Ni and Na and (ii) acid activation, to produce catalysts with markedly different acidic and textural properties. The lack of activity of Ni2+-SAz-1 (with Lewis acidity maximized), provided evidence that the process occurs preferentially on Bronsted acid sites. The catalysts based on the high layer-charge SAz-1 montmorillonite proved to be the most active. Ion-exchange with Al3+, followed by thermal activation at 150 degrees C, afforded the highest number of Bronsted acid sites located in the clay gallery and this coincided with the maximum catalytic activity. The influence of various reaction conditions, to maximize limonene conversion and selectivity, was studied over Al-SAz-1. When the reaction was performed for 20h at 40 degrees C, the conversion reached 71% with 91% selectivity to the mono-ether. Mild acid activation (1 M HCl, 30 min, reflux) of the raw SAz-1 clay leads to a material with a good catalytic behaviour (slightly inferior to Al-SAz-1), while any increase in the severity of the acid-treatment (6 M HCl, 30 min, reflux), caused a marked decrease in catalytic activity. (C) 2013 Elsevier B.V. All rights reserved.

The simultaneous ingress of acetone and water into dried PVOH-clay nanocomposites containing 2.5 wt% or 5 wt% of well dispersed Na-Cloisite, using FTIR-ATR, has been compared with that into pure PVOH films. The rate at which water and acetone moved through the PVOH films is significantly reduced (i) at high acetone concentrations and (ii) when clay is incorporated in the PVOH film. For example, it takes 9 min and 17 min for water and acetone, respectively, to saturate a 25 +/- 5 mu m PVOH film containing 2.5 wt% of well dispersed clay when the acetone:water ratio is 90:10 v/v compared with ca. 1 min for a pure PVOH film when the acetone:water ratio is 70:30 v/v. The presence of significant quantities of water in the PVOH (nanocomposite) films was necessary before acetone began to permeate the film. The acetone entering the evanescent field was always highly hydrated even if the water content of the reservoir in contact with the film was low. There was no substantial evidence that the presence of clay altered the way in which the PVOH interacted with the acetone:water mixtures. The clay only acted to increase the tortuosity of the path through the film to the ATR prism. (C) 2012 Elsevier Ltd. All rights reserved.

This review describes the state-of-the-art of material derived from the forest sector with respect to its potential for use in the packaging industry. Some innovative approaches are highlighted. The aim is to cover recent developments and key challenges for successful introduction of renewable materials in the packaging market. The covered subjects are renewable fibers and bio-based polymers for use in bioplastics or as coatings for paper-based packaging materials. Current market sizes and forecasts are also presented. Competitive mechanical, thermal, and barrier properties along with material availability and ease of processing are identified as fundamental issues for sustainable utilization of renewable materials.

This study concentrated on the direct immobilization of anatase nano titanium dioxide particles (TiO2, 10nm particle size) into or onto a biodegradable polymer, polycaprolactone, by solvent-cast processes. The self-cleaning, namely photocatalytic properties of the produced materials were tested by photocatalytic removal of methylene blue as model compound and antimicrobial properties were investigated using Candida albicans as model microorganism. Produced TiO2 immobilized polymer successfully removed methylene blue (MB, 1×10−5M) from aqueous solution without additional pH arrangement employing a UV-A light (365nm) source. Almost 83.2% of dye was removed or decomposed by 5wt% TiO2 immobilized into PCL (0.08g) and removal percentage reached to 94.2% with 5wt% TiO2 immobilized onto PCL after a 150min exposure period. Although removal percentage decrease with increased ionic strength and usage of a visible light source, produced materials were still effective. TiO2 immobilized onto PCL (5wt%) was quite effective killing almost 54% of C. albicans (2×106CFU/mL) after only 60min exposure with a near visible light source. Control experiments employing PCL alone in the presence and absence of light were ineffective under the same condition.

In this study, both suspensions and thin films of TiO2 and silver loaded TiO2 (Ag-TiO2) were used in the photocatalytic degradation/disinfection of C. albicans. In the case of thin films coated materials, both microscope slides and steel pieces of similar dimensions were dip coated using sol-gel solutions prepared from titanium isopropoxide. Surface analysis of the materials confirmed that thin film formation had been succesful. After set periods of irradiation in the presence of suspension or thin film coated material, 10 mu L aliquots of the solution were withdrawn and directly cultivated on sabouraud dextrose agar for 24 h at 37 degrees C. The number of living colonies was counted. The results show that both the suspensions and the thin films displayed superior antimicrobial properties towards C. albicans. In particular the Ag-TiO2 catalyst was extremely active even in the dark, for disinfection of C. albicans. The degradation percentage over TiO2 and Ag-TiO2 thin films coated on the steel substrate was higher than those coated on glass achieving 80 and 97.9%, respectively, using the 365 nm, near visible region light source.

Selected instrumental techniques [dilatometry, thermogravimetry – mass spectrometry (TG‐MS), and variable temperature – diffuse reflectance infrared Fourier transform spectroscopy (VT‐DRIFTS)] have been used to investigate the role of moisture in the rehydroxylation reaction which causes expansion and mass gain in fired clay ceramics. The temperature range over which adsorbed water molecules and structural hydroxyl groups are desorbed from fired clay ceramic as it is reheated, and the nature of the structural hydroxyls that are formed as the ceramic is cooled and then held under controlled conditions have been explored. The mass chromatogram for m/z = 18, supported by VT‐DRIFTS, showed that physisorbed water molecules were removed from the ceramic at about 105°C, whereas strongly bound molecules of water and structural hydroxyls were held to ≤500°C. Dilatometry revealed a marked contraction of the ceramic between 200°C and 330°C which corresponded to loss of strongly bound molecules of water. The VT‐DRIFTS also showed that the interaction of water molecules with the ceramic body following reheating occurred in two stages and confirmed the kinetic law previously derived from mass gain and moisture expansion in fired clay ceramics.

In this study, both suspensions and thin films of TiO 2 and silver loaded TiO 2 (Ag-TiO 2 ) were used in the photocatalytic degradation/disinfection of C. albicans . In the case of thin films coated materials, both microscope slides and steel pieces of similar dimensions were dip coated using sol–gel solutions prepared from titanium isopropoxide. Surface analysis of the materials confirmed that thin film formation had been succesful. After set periods of irradiation in the presence of suspension or thin film coated material, 10 μL aliquots of the solution were withdrawn and directly cultivated on sabouraud dextrose agar for 24 h at 37 °C. The number of living colonies was counted. The results show that both the suspensions and the thin films displayed superior antimicrobial properties towards C. albicans . In particular the Ag-TiO 2 catalyst was extremely active even in the dark, for disinfection of C. albicans . The degradation percentage over TiO 2 and Ag-TiO 2 thin films coated on the steel substrate was higher than those coated on glass achieving 80 and 97.9%, respectively, using the 365 nm, near visible region light source.