Chain (branch) length distributions (CLD) from size-exclusion chromatography of a series of waxy starches were parametrized using both an empirical and a biosynthesis-based method and correlated with ...their crystalline–amorphous lamellar properties obtained from X-ray scattering. Correlations were best seen with the biosynthesis-based parametrization. This showed for the first time that the following links between the CLD and lamellar parameters, the average interlamellar repeat distance and the distribution of these distances, were decreased by an increase in the proportion of very short branches and were increased by an increase in the proportion of intermediate and longer chains; further, the shoulder and linear sections of the CLD were found to affect the lamellar repeat distance and distribution. These effects are rationalized in terms of branch-length effects on the production of crystallites and the presence of portions of longer branches in the amorphous regions.
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Aqueous suspensions of cellulose nanocrystals (CNC) form a re-entrant liquid crystal (LC) phase with increasing salinity. Phase separation occurs in this LC state leading to a ...biphasic gel with a flow programmable structure that can be used to form anisotropic soft materials. We term this state a Liquid Crystal Hydroglass (LCH). Defining the mechanisms by which the LCH forms requires detailed structural analysis at the mesoscopic length scale.
By utilising Small Angle Neutron Scattering (SANS), we investigated the microstructure transitions in CNC suspensions, with a particular focus on the unique LC re-entrancy and gelation into the biphasic LCH.
Scattering from LCH gels comprises contributions from a dispersed liquid state and static heterogeneity, characterised using a Lorentzian-Gaussian model of inhomogeneity. This conceptually supports a gelation mechanism (spinodal decomposition) in CNC suspensions towards a biphasic structure of the LCH. It also demonstrates that, with increasing salinity, the non-monotonic variation in effective volume fraction of CNC rods fundamentally causes the LC re-entrancy. This work provides the first experimental characterisation of the LC-re-entrancy and formation of an anisotropic LCH gel. The proposed mechanism can be extended to understanding the general behaviour of anisotropic colloids.
•Binding capacity of polyphenols on apple cell walls can be predicted by Langmuir isotherms.•Binding of charged polyphenols involves hydrogen bonding and ionic interactions with pectin.•Polyphenols ...selectively bind to different cell walls as a result of diverse wall composition.•Boiling of cell walls exerts no significant effects on polyphenol binding.•Drying reduces polyphenol-cell wall interactions by hindering access to binding sites.
The adsorption capacity of principal phenolic compounds onto cell walls from three apple varieties was investigated. Isothermal adsorption modelled with Langmuir, Freundlich and Redlich-Peterson equations were carried out over a range of concentrations from 0.5 to 30 mM before and after cell walls were subjected to boiling, oven-drying or freeze-drying. The isotherm data were best fitted by the Langmuir model in all cases. Polyphenols selectively adsorbed onto cell walls with maximum binding capacities ranging from 140 to 580 µg/mg cell walls depending on surface charge. Increased pectin in apple cell walls caused a 129%–311% decrease in the adsorption of negatively charged polyphenols, presumably due to electrostatic repulsive forces. Boiling had limited effect on cell wall polysaccharides and polyphenol-cell wall interactions. However, more than twofold reduction in binding capacities of polyphenols was induced after drying by altering the structural (i.e. binding sites) and compositional (i.e. pectin degradation) characteristics of cell walls.
•Porous and pitted corn starch granules made through amyloglucosidase digestion.•The change of morphology and lamellae structures were investigated.•Multi-scale structure changes with different ...digestion times.•Ultra-small angle neutron scattering is used to determine the pore size distribution.
The effects of amyloglucosidase digestion on the multi-scale supramolecular structural changes of native corn starch were examined by ultra-small angle neutron scattering (USANS), small angle X-ray scattering (SAXS), particle sizing, and scanning electron microscopy (SEM). Well-defined and spherical pores were formed upon amyloglucosidase digestion as revealed by SEM. The pore polydispersity was determined using USANS by assuming spherical pore morphology with log-normal distribution. Both USANS and SEM measurements demonstrated that the pores become larger and more polydisperse as the digestion time increased. Moreover, SAXS revealed that the lamellar peak area decreased gradually for both thermally and enzymatically treated starches, indicating partial loss of lamellar organisation. Overall, the results demonstrate structural changes occur on multiple length scales upon enzymatic digestion from granular to lamellar with small-angle scattering demonstrated to provide detailed characterization of the resultant microporous structures.
The nanostructures of temperature-responsive and biocompatible gels were investigated by small-angle neutron scattering (SANS). The gels were copolymerized using two types of monomers with different ...ethylene glycol side chain lengths: diethylene glycol methacrylate (MeO2MA) (short side chain) and oligo-ethylene glycol methyl ether methacrylate (OEGMA) (long side chain). The temperature-responsive behavior was ascribed to the nanoscale structures and depended on the copolymerization ratio. The SANS profiles of swollen OEGMA-rich gels exhibited a characteristic peak, indicating a strong correlation with the hydrophobic main chain domains in the hydrophilic matrix. The long hydrophilic side chains of OEGMA acted as a cushioning material between the domains. On the other hand, the domains were randomly distributed in the MeO2MA-rich gels. As the temperature increased, the domains grew in the gels due to hydrophobic interactions between the dehydrated polymers. As a result, the peaks, that is, the domain periodicity, disappeared in the SANS profiles. The results of this study should lead to a synthesis strategy to control the physical properties and structures of such hydrogels for advanced applications, for example, biofilms, coatings, and carriers.
We investigate the strain hardening behavior of various gelatin networksnamely physical gelatin gel, chemically cross-linked gelatin gel, and a hybrid gel made of a combination of the former ...twounder large shear deformations using the pre-stress, strain ramp, and large amplitude oscillations shear protocols. Further, the internal structures of physical gelatin gels and chemically cross-linked gelatin gels were characterized by small angle neutron scattering (SANS) to enable their internal structures to be correlated with their nonlinear rheology. The Kratky plots of SANS data demonstrate the presence of small cross-linked aggregates within the chemically cross-linked network whereas, in the physical gelatin gels, a relatively homogeneous structure is observed. Through model fitting to the scattering data, we were able to obtain structural parameters, such as the correlation length (ξ), the cross-sectional polymer chain radius (R c) and the fractal dimension (d f) of the gel networks. The fractal dimension d f obtained from the SANS data of the physical and chemically cross-linked gels is 1.31 and 1.53, respectively. These values are in excellent agreement with the ones obtained from a generalized nonlinear elastic theory that has been used to fit the stress–strain curves. The chemical cross-linking that generates coils and aggregates hinders the free stretching of the triple helix bundles in the physical gels.
Despite being the major cause of safety and performance issues in lithium metal batteries, experimental difficulties in quantifying directly the morphology of lithium deposited at electrode surfaces ...have meant that the mechanism of metallic lithium growth within batteries remains elusive. This study demonstrates that quantitative detail about the morphology of metallic lithium within batteries can be derived non‐destructively and directly using in situ ultra‐small and small‐angle neutron scattering. This information is obtained over a large electrode area in cells where lithium deposition processes are typical of real‐world applications. Complex variations of surface area and interfacial distances 1–10 µm and 100–300 nm are revealed in size that are influenced by current density and cell cycling history, providing valuable insight into the growth of metallic lithium features detrimental to battery performance. Such quantitative insight into the process of lithium growth is required for the development of safer high‐performance lithium metal batteries.
Small and ultra‐small angle neutron scattering is used to quantitatively reveal the microstructure and surface area of deposited metallic lithium in batteries. The in situ study captures changes in morphology and surface area and reveals variations that depend on cell cycling history, necessary to understand the mechanism of metallic lithium growth in real‐world applications.
► SAXS and SANS conducted on variety of starches in dry and hydrated state. ► Use of two radiation sources allowed selected structural regions to be highlighted. ► Structures detected in dry starches ...consistent with small blocklets or superhelices. ► Structures detected when hydrated consistent with growth rings, large blocklets.
Small angle scattering (SAS) techniques have a distinguished track record in illuminating the semi-crystalline lamellar structure of the starch granule. To date, there have been few attempts to use SAS techniques to characterise larger-scale structures reported from imaging techniques such as growth rings, blocklets or pores, nor how these structures would modulate the well-known scattering arising from the semi-crystalline lamellar structure. In this study, SAS data collected over an extended q range were gathered from dry and hydrated starch powders from varied botanical sources. The use of neutrons and X-rays, as well as comparing dry and hydrated granules, allowed different levels of contrast in scattering length density to be probed and therefore selected structural regions to be highlighted. The lowest q range, 0.002–0.04Å−1, was found to be dominated by scattering from the starch granules themselves, especially in the dry powders; however an inflection point from a low contrast structure was observed at 0.035Å−1. The associated scattering was interpreted within a unified scattering framework with the inflexion point correlating with a structure with radius of gyration ∼90Å – a size comparable to small blocklets or superhelices. In hydrated starches, it is observed that there is an inflection point between lamellar and q−4 power-law scattering regions at approximately 0.004Å−1 which may correlate with growth rings and large blocklets. The implications of these findings on existing models of starch lamellar scattering are discussed.
•Mature cotton contains 4–5nm core-shell structured cellulose microfibrils.•Each microfibril is formed by the coalescence and annealing of 2–3 elementary fibrils.•These microfibrils present a ...relatively high crystallinity and limited surface disorder.•Low loadings of cell wall matrix components affect strongly the microfibril structure.•G. barbadense presents less densely packed microfibrils with higher solvent accessibility.
The structure of cellulose microfibrils in mature cotton fibres from three varieties – Gossypium hirsutum, G. barbadense and G. arboreum – has been investigated by a multi-technique approach combining small angle scattering techniques with spectroscopy and diffraction. Cellulose microfibrils present a Iβ-rich crystalline structure with limited surface disorder. Small angle scattering (SAXS and SANS) data have been successfully fitted using a core-shell model and the results obtained indicate that the cellulose microfibrils, formed by the association of 2–3 elementary fibrils, are composed of a ca. 2nm impermeable crystalline core, surrounded by a partially hydrated paracrystalline shell, with overall cross-sections of ca. 3.6–4.7nm. Different low levels of cell wall matrix components have a strong impact on the microfibril architecture and enable moisture penetration upon hydration. Furthermore, the higher amounts of non-cellulosic components in G. barbadense result in a less dense packing of cellulose microfibrils and increased solvent accessibility.
•Characterisation of plant cell walls by small angle scattering techniques is reviewed.•SAS techniques minimise structural alterations and cover the size range of interest.•The structure of cellulose ...microfibrils in model plant cell walls is summarised.•Strategies to study the interactions between plant cell wall components are discussed.•Future perspectives in this research field are presented.
Plant cell walls present an extremely complex structure of hierarchically assembled cellulose microfibrils embedded in a multi-component matrix. The biosynthesis process determines the mechanism of cellulose crystallisation and assembly, as well as the interaction of cellulose with other cell wall components. Thus, a knowledge of cellulose microfibril and bundle architecture, and the structural role of matrix components, is crucial for understanding cell wall functional and technological roles. Small angle scattering techniques, combined with complementary methods, provide an efficient approach to characterise plant cell walls, covering a broad and relevant size range while minimising experimental artefacts derived from sample treatment. Given the system complexity, approaches such as component extraction and the use of plant cell wall analogues are typically employed to enable the interpretation of experimental results. This review summarises the current research status on the characterisation of the hierarchical structure of plant cell walls using small angle scattering techniques.
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