Modulating the chiral nematic structure of cellulose nanocrystal suspensions with electrolytes.

Hypothesis: The iridescent optical properties of films made of cellulose nanocrystals (CNC) are controlled by the pitch and range of the chiral nematic structures. These are further tuned with the addition of electrolyte.

Experiments: Electrolyte type, valency and concentration were varied.

Self-assembly of cellulose nanocrystals of different lengths.

Hypothesis The self-assembly (SA) of cellulose nanocrystals (CNC) in suspensions is important both from the fundamental and advanced technology development perspective. CNC of different lengths self-assemble differently in suspensions by balancing attractive and repulsive interactions which depends strongly on morphology, surface chemistry and concentrations. Experiments Two different commercial CNC samples (CNC-M and CNC-C) of different lengths were dispersed in Milli-Q water at different concentrations (0.

Tailoring the humidity response of cellulose nanocrystal-based films by specific ion effects.

Hypothesis: The optical properties and humidity response of iridescent films made of cellulose nanocrystal (CNC) and polyethylene glycol (PEG) can be tailored by the incorporation of electrolytes chosen based on specific ion effects (SIE).

Experiments: A series of inorganic salts comprising five different cations and five anions based on the Hofmeister series were mixed with CNC/PEG suspensions, followed by an air-dried process into iridescent solid films. These films were tested in changing relative humidity (RH) environments from 30% to 90% and their photonic properties and mass change monitored.

Thermoresponsive Poly(-isopropylacrylamide) Grafted from Cellulose Nanofibers Silver-Promoted Decarboxylative Radical Polymerization.

A family of thermoresponsive poly(-isopropylacrylamide) [PNIPAM]-grafted cellulose nanofibers (CNFs) was synthesized a novel silver-promoted decarboxylative polymerization approach. This method relies on the oxidative decarboxylation of carboxylic acid groups to initiate free radicals on the surface of CNFs. The polymerization reaction employs relatively mild reaction conditions and can be performed in a one-step, one-pot fashion.

Modulating the chiral nanoarchitecture of cellulose nanocrystals through interaction with salts and polymer.

Hypothesis: The conditions to allow self-assembly of cellulose nanocrystal (CNC) suspensions into chiral nematic structures are based on aspect ratio, surface charge density and a balance between repulsive and attractive forces between CNC particles.

Experiments: Three types of systems were characterized in suspensions and subsequently in their solid dried films: 1) neat water dialyzed CNC, 2) CNC combined with polyethylene glycol(PEG) (CNC/PEG), and 3) CNC with added salt (CNC/Salt). All suspensions were characterized by polarized optical microscope (POM) and small angle X-ray scattering (SAXS), while the resultant dried films were analyzed by reflectance spectrometer, scanning electron microscope (SEM) and SAXS.

Moulding of micropatterned nanocellulose films and their application in fluid handling.

Hypothesis: Well-controlled micropatterned nanocellulose films are able to be fabricated via spray coating onto a micropatterned impermeable moulded surface. The micropattern size is able control the directionality of wicking fluid flow.

Experiments: Using photolithography and etching techniques, silicon moulds with channel widths of 5-500 µm and depths of 6, 12 and 18 µm were fabricated.

Grafting Nature-Inspired and Bio-Based Phenolic Esters onto Cellulose Nanocrystals Gives Biomaterials with Photostable Anti-UV Properties.

Invited for this month's cover is the international collaborative work from the Bioresource Processing Research Institute of Australia (BioPRIA)-Monash University and URD Agro-Biotechnologies Industrielles (ABI)-AgroParisTech. The cover image shows how the grafting of Nature-inspired and bio-based phenolic esters on cellulose nanocrystals through click-chemistry provides materials with highly photostable UV-blocking properties. Cover art by David Mendoza.

Modulating transparency and colour of cellulose nanocrystal composite films by varying polymer molecular weight.

Hypothesis: Cellulose nanocrystals (CNC) can produce photonic composite films that selectively reflect light based on their periodic cholesteric structure. The hypothesis of this research is that by incorporating water-soluble polymer, photonic properties of CNC composite film can be designed by manipulating the polymer molecular weight.

Experimental: Flexible free-standing composite films of five different poly (ethylene glycol) (PEG) molecular weights were prepared via air drying under a controlled environment, and characterised by reflectance UV-vis spectrometer, atomic force microscopy (AFM) and scanning electron microscopy (SEM).

An energy efficient production of high moisture barrier nanocellulose/carboxymethyl cellulose films via spray-deposition technique.

Nanocellulose (NC) films are considered as a prospective alternative to non-sustainable packaging materials, however, their higher embodied energy and limited moisture barrier properties are regarded as a huge constraint regarding their commercialization. This study aims to produce films with relatively low environmental impact and improved barrier performance. For this purpose, carboxymethyl cellulose (CMC) and NC were combined, and this resulted in multidimensional advantages.

Grafting Nature-Inspired and Bio-Based Phenolic Esters onto Cellulose Nanocrystals Gives Biomaterials with Photostable Anti-UV Properties.

New nature-inspired and plant-derived p-hydroxycinnamate esters and p-hydroxycinnamate diesters provide excellent protection against UV radiation when incorporated into a matrix. Herein, an efficient and sustainable pathway is reported to graft these phenolic compounds onto cellulose nanocrystals (CNCs) via click-type copper-catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The successful grafting of the phenolic esters on CNC surface was evidenced by a range of chemical analyses, and the degrees of substitution (DS) of the CNC were found to depend on the structure of the phenolic ester grafted.

Controlling the transparency and rheology of nanocellulose gels with the extent of carboxylation.

TEMPO and periodate are combined in a one-shot reaction to oxidise cellulose and produce nanocellulose gels with a wide range of degree of substitution (DS). Highly-oxidised cellulose nanofibres with a high charge of -80 mV were produced. The strong electrical repulsion between TEMPO-periodate oxidised nanofibres (TPOF) results in the formation of well-separated nanofibres with a diameter of 2-4 nm, albeit depolymerised due to high oxidation.

Reversible pH Responsive Bovine Serum Albumin Hydrogel Sponge Nanolayer.

A pH dependent reversible sponge like behavior of a bovine serum albumin (BSA) nanolayer adsorbed at the gold-saline interface is revealed by quartz crystal microbalance with dissipation (QCM-D), atomic force microscope (AFM) and contact angle measurements. During the saline rinsing cycles, the BSA layer adsorbs water molecules at pH 7.0 and releases them at pH 4.

One-shot TEMPO-periodate oxidation of native cellulose.

TEMPO/NaClO/NaBr and sodium periodate were combined in a one-shot reaction to oxidise cellulose from bleached pulp. Oxidation of cellulose forms two fractions: a highly-carboxylated water-insoluble (up to 1.9 mmol COO/g, DS = 0.

Direct AFM force measurements between air bubbles in aqueous monodisperse sodium poly(styrene sulfonate) solutions.

Structural forces play an important role in the rheology, processing and stability of colloidal systems and complex fluids, with polyelectrolytes representing a key class of structuring colloids. Here, we explore the interactions between soft colloids, in the form of air bubbles, in solutions of monodisperse sodium poly(styrene sulfonate) as a model polyelectrolyte. It is found that by self-consistently modelling the force oscillations due to structuring of the polymer chains along with deformation of the bubbles, it is possible to precisely predict the interaction potential between approaching bubbles.

Direct AFM force measurements between air bubbles in aqueous polydisperse sodium poly(styrene sulfonate) solutions: effect of collision speed, polyelectrolyte concentration and molar mass.

Interactions between colliding air bubbles in aqueous solutions of polydisperse sodium poly(styrene sulfonate) (NaPSS) using direct force measurements were studied. The forces measured with deformable interfaces were shown to be more sensitive to the presence of the polyelectrolytes when compared to similar measurements using rigid interfaces. The experimental factors that were examined were NaPSS concentration, bubble collision velocity and polyelectrolyte molar mass.

Bubble coalescence during acoustic cavitation in aqueous electrolyte solutions.

Bubble coalescence behavior in aqueous electrolyte (MgSO(4), NaCl, KCl, HCl, H(2)SO(4)) solutions exposed to an ultrasound field (213 kHz) has been examined. The extent of coalescence was found to be dependent on electrolyte type and concentration, and could be directly linked to the amount of solubilized gas (He, Ar, air) in solution for the conditions used. No evidence of specific ion effects in acoustic bubble coalescence was found.

Synthesis and fluorescence characterization of MEHPPV oligomers.

Trimer, tetramer, and pentamer oligomers based on the polymer backbone structure of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV) have been synthesized by Horner-Wadsworth-Emmons reactions. The fluorescence spectra, emission quantum yields, and lifetimes of the oligomers have been characterized in dilute chloroform solutions. The oligomers exhibit a sequential increase in absorption and emission wavelength maxima and a decrease in fluorescence lifetime as the π conjugation length is increased.