Latex-based nanocomposites containing carboxylated cellulose nanocrystals (cCNCs) were synthesized via in situ seeded semibatch emulsion polymerization. Inspired by nature's use of CNCs to enhance rigidity and mechanical strength in cellulosic materials, we explored similar principles to improve the properties of acrylate water-based coatings. The cCNCs, loaded at 0.
View Article and Find Full Text PDFMicroplastics are an emerging anthropogenic pollutant risk with a significant body of research dedicated to understanding the implications further. To generate the databases required to characterize the impact of microplastics on our environment, and improve recovery and recycling of current plastic materials, we need rapid, in-line characterization that can distinguish individual polymer types. Here, autofluorescence spectroscopy was investigated as an alternative characterization method to the current leading techniques based on vibrational spectroscopy.
View Article and Find Full Text PDFDifferent cellulose nanocrystal (CNC) forms (dried vs never-dried) can lead to different degrees of CNC reassembly, the formation of nanofibril-like structures, in nanocomposite latex-based pressure-sensitive adhesive (PSA) formulations. CNC reassembly is also affected by CNC sonication and loading as well as the protocol used for CNC addition to the polymerization. In this study, carboxylated CNCs (cCNCs) were incorporated into a seeded, semibatch, 2-ethylhexyl acrylate/methyl methacrylate/styrene emulsion polymerization and cast as pressure-sensitive adhesive (PSA) films.
View Article and Find Full Text PDFThree size-fractionated samples of pine beetle-killed wood particles were used to prepare lightweight insulative foams. The foams were produced by foam-forming an aqueous slurry containing wood particles (125-1000 μm), a polymer binder, and surfactant, followed by oven drying. The effect of wood particle size on the aqueous foam stability, structure, and performance of insulative foams was investigated.
View Article and Find Full Text PDFCellulose nanocrystals (CNCs) are sustainable particles that are effective at stabilizing emulsions by adsorbing at droplet interfaces and providing a steric barrier to coalescence. However, CNCs have surface charges that reduce the coverage of the emulsion droplets due to the electrostatic repulsion between CNCs. In such cases, adding salt is a typical (and straightforward) way to adjust the formulation so that the charges are screened, allowing increased coverage of the droplets.
View Article and Find Full Text PDFThe scale of production of cellulose nanocrystals (CNCs) has increased dramatically to meet the growing demand for sustainably sourced materials. This work defines the colloidal stability window for commercially produced carboxylated CNCs (DextraCel) compared to the more traditional sulfated CNCs. Phase diagrams showing the stable, reversibly agglomerated, irreversibly aggregated/sedimented, and colloidal glass "zones" as a function of suspension pH, ionic strength, CNC surface charge content, counterion, and concentration are presented.
View Article and Find Full Text PDFTo maintain the activity of sensitive biologics during encapsulation by spray drying, a better understanding of deactivation pathways in dried particles is necessary. The effect of solid-air interfaces within dried particles on viral deactivation was examined with three binary excipient blends, mannitol/dextran (MD), xylitol/dextran (XD), and lactose/trehalose (LT). Particles encapsulating human serotype 5 adenovirus viral vector (AdHu5) were produced via both spray drying and acoustic levitation.
View Article and Find Full Text PDFUnderstanding water absorbency in paper is challenging as fibre swelling and out-of-plane deformation occur simultaneously during liquid imbibition. Liquid absorption is commonly accessed by gravimetric tests, which provides limited information on the local spatial and temporal distribution of fluid in the substrate. In this work, we developed iron tracers to map liquid imbibition in paper by in situ precipitation of iron oxide nanoparticles during passage of the wetting front.
View Article and Find Full Text PDFPurpose: Intratracheal delivery and consistent dosing of dry powder vaccines is especially challenging in mice. To address this issue, device design of positive pressure dosators and actuation parameters were assessed for their impacts on powder flowability and in vivo dry powder delivery.
Methods: A chamber-loading dosator assembled with stainless-steel, polypropylene or polytetrafluoroethylene needle-tips was used to determine optimal actuation parameters.
Blended films comprising poly(butyl acrylate) (PBA)-grafted cellulose nanocrystals (CNCs) and poly(3-hexylthiophene) (P3HT), exhibited more intense photoluminescence (PL) and longer PL emission lifetimes compared to pristine P3HT films. Optical absorption and photoluminescence spectra indicated reduced torsional disorder i.e.
View Article and Find Full Text PDFModern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it.
View Article and Find Full Text PDFThe ability to determine the physicochemical properties of nanoparticles, such as cellulose nanocrystals, in suspension is critically important to maximize their potential. Currently, various techniques are required to ascertain different properties, which results in a laborious analysis procedure. Here, autofluorescence arising from the cluster-triggered emission (CTE) photoluminescence mechanism is utilized as an analytical spectroscopic tool to determine multiple properties from one data acquisition sequence.
View Article and Find Full Text PDFPurpose: Thermally stable, spray dried vaccines targeting respiratory diseases are promising candidates for pulmonary delivery, requiring careful excipient formulation to effectively encapsulate and protect labile biologics. This study investigates the impact of dextran mass ratio and molecular weight on activity retention, thermal stability and aerosol behaviour of a labile adenoviral vector (AdHu5) encapsulated within a spray dried mannitol-dextran blend.
Methods: Comparing formulations using 40 kDa or 500 kDa dextran at mass ratios of 1:3 and 3:1 mannitol to dextran, in vitro quantification of activity losses and powder flowability was used to assess suitability for inhalation.
Increasing viral dosage within dry powder vaccines reduces the powder mass required to elicit an immune response through pulmonary delivery. This work analyzes how cryoprotective agents affect viral activity, particle properties and thermal stability of a spray dried, inhalable vaccine vector under high viral loading. Stock suspensions of a human serotype 5 adenovirus (AdHu5) vector in either neat phosphate buffered saline (PBS), 10% glycerol in PBS, or 5% trehalose in PBS were added to a mannitol-dextran formulation prior to spray drying.
View Article and Find Full Text PDFWhile the improvement of water-based adhesives with renewable additives is important as industry shifts toward more sustainable practices, a complete understanding of how the compatibility between additives and polymers affects adhesive performance is currently lacking. To elucidate these links, cellulose nanocrystals (CNCs) were first functionalized via surface-initiated atom-transfer radical polymerization with the hydrophobic polymers poly(butyl acrylate) (PBA) and poly(methyl methacrylate) (PMMA) to facilitate their incorporation into latex-based pressure-sensitive adhesives (PSAs). Next, PBA latexes were synthesized using seeded semibatch emulsion polymerization with unmodified or polymer-grafted CNCs added in situ at a loading of 0.
View Article and Find Full Text PDFEmulsion polymerized latex-based pressure-sensitive adhesives (PSAs) are more environmentally benign because they are synthesized in water but often underperform compared to their solution polymerized counterparts. Studies have shown a simultaneous improvement in the tack, and peel and shear strength of various acrylic PSAs upon the addition of cellulose nanocrystals (CNCs). This work uses atomic force microscopy (AFM) to examine the role of CNCs in (i) the coalescence of hydrophobic 2-ethyl hexyl acrylate/-butyl acrylate/methyl methacrylate (EHA/BA/MMA) latex films and (ii) as adhesion modifiers over multiple length scales.
View Article and Find Full Text PDFThe hydrophilic polymer poly[2-(2-(2-methoxy ethoxy)ethoxy)ethylacrylate] (POEGA) was grafted onto the reducing end-groups (REGs) of cellulose nanocrystal (CNC) allomorphs, and their liquid crystalline properties were investigated. The REGs on CNCs extracted from cellulose I (CNC-I) are exclusively located at one end of the crystallite, whereas CNCs extracted from cellulose II (CNC-II) feature REGs at both ends of the crystallite, so that grafting from the REGs affords asymmetrically and symmetrically decorated CNCs, respectively. To confirm the REG modification, several complementary analytical techniques were applied.
View Article and Find Full Text PDFThe trend to replace petroleum-based products with sustainable alternatives has shifted research efforts toward plant-based materials such as cellulose nanocrystals (CNCs). CNCs show promise in numerous applications (e.g.
View Article and Find Full Text PDFHydrophobic polymer-grafted cellulose nanocrystals (CNCs) were produced surface-initiated atom-transfer radical polymerization (SI-ATRP) in two different solvents to examine the role of reaction media on the extent of surface modification. Poly(butyl acrylate)-grafted CNCs were synthesized in either dimethylformamide (DMF) (D-PBA--CNCs) or toluene (T-PBA--CNCs) alongside a free polymer from a sacrificial initiator. The colloidal stability of unmodified CNCs, initiator-modified CNCs, and PBA--CNCs in water, DMF, and toluene was evaluated by optical transmittance.
View Article and Find Full Text PDFThe demand for industrially produced cellulose nanocrystals (CNCs) has been growing since 2012, when CelluForce Inc. opened its inaugural demonstration plant with a production capacity of 1 tonne per day. Currently, there are 10 industrial CNC producers worldwide, each producing a unique material.
View Article and Find Full Text PDFDevelopment of thermally stable spray dried viral-vectored vaccine powders is dependent on the selection of a proper excipient or excipient blend for encapsulation, which can be a time and resource intensive process. In this work, a diffusion-based droplet drying model was developed to compute droplet drying time, size, and component distribution. The model predictions were validated using an acoustic levitator to dry droplets containing protein-coated or fluorescently labelled silica nanoparticles (as adenoviral vector analogues) and a range of excipient blends.
View Article and Find Full Text PDFTo engineer tunable thin-film materials, the accurate measurement of their mechanical properties is crucial. However, characterizing the elastic modulus with current methods is particularly challenging for sub-micrometer thick films and hygroscopic materials because they are highly sensitive to environmental conditions and most methods require free-standing films which are difficult to prepare. In this work, we directly compared three buckling-based methods to determine the elastic moduli of supported thin films: (1) biaxial thermal shrinking, (2) uniaxial thermal shrinking, and (3) the mechanically compressed, strain-induced elastic buckling instability for mechanical measurements (SIEBIMM) method.
View Article and Find Full Text PDFWhen cellulose nanocrystals (CNCs) are isolated from cellulose microfibrils, the parallel arrangement of the cellulose chains in the crystalline domains is retained so that all reducing end-groups (REGs) point to one crystallite end. This permits the selective chemical modification of one end of the CNCs. In this study, two reaction pathways are compared to selectively attach atom-transfer radical polymerization (ATRP) initiators to the REGs of CNCs, using reductive amination.
View Article and Find Full Text PDFStructured hydrogel sheets offer the potential to mimic the mechanics and morphology of native cell environments in vitro; however, controlling the morphology of such sheets across multiple length scales to give cells consistent multi-dimensional cues remains challenging. Here, we demonstrate a simple two-step process based on sequential electrospinning and thermal wrinkling to create nanocomposite poly(oligoethylene glycol methacrylate)/cellulose nanocrystal hydrogel sheets with a highly tunable multi-scale wrinkled (micro) and fibrous (nano) morphology. By varying the time of electrospinning, rotation speed of the collector, and geometry of the thermal wrinkling process, the hydrogel nanofiber density, fiber alignment, and wrinkle geometry (biaxial or uniaxial) can be independently controlled.
View Article and Find Full Text PDFConsidering the substantive potential benefits of thermally stable dry powder vaccines to public health, causes for inactivation of their sensitive viral vectors during preparation require intensive study. The focus of this work was atomization of suspensions containing encapsulating excipients and a human type 5 adenovirus, involving a detailed investigation of shear stresses in the nozzle of a spray dryer. Samples were sprayed at 25 °C into falcon tubes and immediately evaluated for viral activity by in vitro testing, minimizing the confounding of thermal effects on the deactivation of the virus, although interfacial stresses could not be decoupled from shear stresses.
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