Annie Dorris

Bio: Annie Dorris is an academic researcher from McGill University. The author has contributed to research in topics: Polyelectrolyte & Cellulose. The author has an hindex of 7, co-authored 7 publications receiving 3630 citations.

Nanocelluloses: A New Family of Nature-Based Materials

Abstract: Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.

Nanocellulosen: eine neue Familie naturbasierter Materialien

Abstract: Cellulosefibrillen und -kristalle mit einem Durchmesser im Nanometerbereich sind naturbasierte Materialien mit einzigartigen und potenziell wertvollen Eigenschaften. Vor allem eroffnen diese neuartigen Nanocellulosen dem naturlichen Polymer Cellulose die stark expandierenden Einsatzgebiete nachhaltige Materialien, Nanokomposite sowie Produkte fur die Medizin und die Lebenswissenschaften. Die Nanodimensionen der Strukturelemente fuhren zu grosen Oberflachen und damit zu starken Wechselwirkungen dieser Cellulosen mit umgebenden Stoffen wie Wasser, anorganischen, organischen und polymeren Verbindungen, Nanopartikeln und lebenden Zellen. Diese Ubersicht bietet das aktuelle Wissen uber die Isolierung mikrofibrillierter Cellulose aus Holz und ihre Anwendung in Nanokompositen, die Herstellung nanokristalliner Cellulose und ihren Einsatz als Verstarkungsmaterial sowie die biotechnologische Erzeugung bakterieller Nanocellulose einschlieslich ihrer Eignung als Biomaterial fur medizinische Implantate.

Preparation and characterization of polyelectrolyte-coated gold nanoparticles.

Abstract: Gold nanoparticles of 5 nm diameter, stabilized by 4-(dimethylamino)pyridine (DMAP), were coated with poly(sodium 4-styrene sulfonate) (PSS) via electrostatic self-assembly. The suspension stability, monitored by the gold surface plasmon band (SPB), was studied by varying the pH, the PSS chain length, and PSS concentration. Enhanced stability is obtained at pH 10 (above the pKa of DMAP) when the polymer chain length matches or exceeds the particle circumference. Solid state 13C NMR was used to determine the presence of DMAP and polymers after subsequent deposition of weak and strong polycations: poly(allylamine hydrochloride) (PAH) and poly(diallyldimethylammonium chloride) (PDADMAC). At pH 10, DMAP remains associated with the nanoparticle after the first PSS layer has been formed. When PAH or PDADMAC are subsequently added at pH 4.5, DMAP is expelled, the suspensions remain stable, and zeta potential values indicate complete charge reversal. In the case of PDADMAC, however, the first layer of PSS is not fully retained. When PDADMAC is added at pH 10, DMAP and the first PSS layer are retained but lower zeta potentials and a higher SPB shift indicate a degraded stability. For PAH addition at pH 9.5, both DMAP and PSS are expelled and the suspension becomes unstable. These differences in stability of the multilayer components and the nanoparticle suspension are rationalized in terms of chain flexibility, polymer charge density, and the ability of the polymer functional groups to directly interact with the gold surface.

Gelation of cellulose nanocrystal suspensions in glycerol

Abstract: Aqueous suspensions of cellulose nanocrystals (NCC) produced by sulfuric acid hydrolysis of natural cellulose fibres display a number of unique properties. In addition to forming equilibrium chiral nematic phases above some critical concentration, cellulose nanocrystal suspensions tend to gel or aggregate if the stability of the suspension decreases, for example because of a decrease in the surface charge density of sulfate ester groups, or a change in the properties of the suspending medium. Direct incorporation of unmodified nanocrystals into organic media usually leads to aggregation. We have found that it is possible to circumvent this difficulty and form clear thixotropic gels of unmodified NCC in glycerol, by careful evaporation of water from aqueous glycerol suspensions of NCC. The physical gels form at a fairly low (<3 wt%) concentrations of cellulose. The initial composition of the suspension, the temperature and rate of evaporation, and the time resting at room temperature all influence the formation of thixotropic gels. Desulfation of the acid-form nanocrystals, enhanced in the glycerol-rich suspensions, is shown to be a key step in this gelation process.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Key advances in the chemical modification of nanocelluloses

Abstract: Nanocelluloses, including nanocrystalline cellulose, nanofibrillated cellulose and bacterial cellulose nanofibers, have become fascinating building blocks for the design of new biomaterials. Derived from the must abundant and renewable biopolymer, they are drawing a tremendous level of attention, which certainly will continue to grow in the future driven by the sustainability trend. This growing interest is related to their unsurpassed quintessential physical and chemical properties. Yet, owing to their hydrophilic nature, their utilization is restricted to applications involving hydrophilic or polar media, which limits their exploitation. With the presence of a large number of chemical functionalities within their structure, these building blocks provide a unique platform for significant surface modification through various chemistries. These chemical modifications are prerequisite, sometimes unavoidable, to adapt the interfacial properties of nanocellulose substrates or adjust their hydrophilic–hydrophobic balance. Therefore, various chemistries have been developed aiming to surface-modify these nano-sized substrates in order to confer to them specific properties, extending therefore their use to highly sophisticated applications. This review collocates current knowledge in the research and development of nanocelluloses and emphasizes more particularly on the chemical modification routes developed so far for their functionalization.