Water-polysaccharide interactions and their properties in freezing conditions.

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

In previous studies, we reported that poly(2-methoxyethyl acrylate) (PMEA) exhibited excellent blood compatibility, although it has a simple chemical structure. Since then, we have been investigating the reasons for its blood compatibility. In this short review, we consider the reasons for this compatibility by comparing the structure of water in hydrated PMEA to the water structure of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(meth)acrylate analogs as reference polymers. The hydrated water in PMEA could be classified into three types; free water (or freezing water), freezing-bound water (or intermediate water), and non-freezing water (or non-freezing-bound water). We found that hydrated PMEA possessed a unique water structure, observed as cold crystallization of water in differential scanning calorimetry (DSC). Cold crystallization is interpreted as ice formation at low temperature, an attribute of freezing-bound water in PMEA. The cold crystallization peak was observed for hydrated poly(ethylene glycol) (PEG), poly(vinyl methyl ether) (PVME), polyvinylpyrrolidone (PVP), poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(tetrahydrofurfuryl acrylate) (PTHFA), and newly synthesized poly(2-(2-ethoxyethoxy)ethyl acrylate), as well as various proteins and polysaccharides, which are well-known biocompatible polymers. On the other hand, cold crystallization of water was not observed in hydrated PHEMA and PMEA analogous polymers, which do not show excellent blood compatibility. Based on these findings, we hypothesized that freezing-bound water, which prevents the biocomponents from directly contacting the polymer surface or non-freezing water on the polymer surface, plays an important role in the excellent blood compatibility of PMEA.

Frozen water has a quasi-liquid layer at its surface that exists even well below the bulk melting temperature; the formation of this layer is termed premelting. The nature of the premelted surface layer, its structure, thickness and how the layer changes with temperature have been debated for over 160 years, since Faraday first postulated the idea of a quasi-liquid layer on ice. Here, we briefly review current opinions and evidence on premelting at ice surfaces, gathering data from experiments and computer simulations. In particular, spectroscopy, microscopy and simulation have recently made important contributions to our understanding of this field. The identification of premelting inhomogeneities, in which portions of the surface are quasi-liquid-like and other parts of the surface are decorated with liquid droplets, is an intriguing recent development. Untangling the interplay of surface structure, supersaturation and surface defects is currently a major challenge. Similarly, understanding the coupling of surface structure with reactivity at the surface and crystal growth is a pressing problem in understanding the behaviour and formation of ice on Earth. A quasi-liquid layer on the surface of ice makes it slippery even below the bulk melting temperature. The nature of this premelted layer has long been debated, and this Review gathers experimental and theoretical data and discusses opinions and evidence on premelting at ice surfaces.

Microbial ice-binding structures: A review of their applications

Since the pioneering prediction of surface melting by Michael Faraday, it has been widely accepted that thin water layers, called quasi-liquid layers (QLLs), homogeneously and completely wet ice surfaces. Contrary to this conventional wisdom, here we both theoretically and experimentally demonstrate that QLLs have more than two wetting states and that there is a first-order wetting transition between them. Furthermore, we find that QLLs are born not only under supersaturated conditions, as recently reported, but also at undersaturation, but QLLs are absent at equilibrium. This means that QLLs are a metastable transient state formed through vapor growth and sublimation of ice, casting a serious doubt on the conventional understanding presupposing the spontaneous formation of QLLs in ice-vapor equilibrium. We propose a simple but general physical model that consistently explains these aspects of surface melting and QLLs. Our model shows that a unique interfacial potential solely controls both the wetting and thermodynamic behavior of QLLs.

MOL2NET-07, Conference on Molecular, Biomedical, and Computational Sciences and Engineering, ISSN: 2624-5078, MDPI SciForum, Basel, Switzerland, 2021, 7th ed.

Ice interfaces are pivotal in mediating key chemical and physical processes such as heterogeneous chemical reactions in the environment, ice nucleation, and cloud microphysics. At the ice surface, water molecules form a quasi-liquid layer (QLL) with properties distinct from those of the bulk. Despite numerous experimental and theoretical studies, a molecular-level understanding of the QLL has remained elusive. In this work, we use state-of-the-art quantum dynamics simulations with a realistic data-driven many-body potential to dissect the vibrational sum-frequency generation (vSFG) spectrum of the air/ice interface in terms of contributions arising from individual molecular layers, orientations, and hydrogen-bonding topologies that determine the QLL properties. The agreement between experimental and simulated spectra provides a realistic molecular picture of the evolution of the QLL as a function of the temperature without the need for empirical adjustments. The emergence of specific features in the experimental vSFG spectrum suggests that surface restructuring may occur at lower temperatures. This work not only underscores the critical role of many-body interactions and nuclear quantum effects in understanding ice surfaces but also provides a definitive molecular-level picture of the QLL, which plays a central role in multiphase and heterogeneous processes of relevance to a range of fields, including atmospheric chemistry, cryopreservation, and materials science.

Interfacial mechanical properties of tetrahydrofuran hydrate-solid surfaces: Implications for hydrate management

Surface melting of ice crystals proceeds below the melting point (0 °C) and forms thin liquid water layers, called quasi-liquid layers (QLLs), which govern a wide variety of phenomena in nature. Hence, many studies have been performed so far; however, the lowest temperature above which QLLs exist on ice crystal surfaces varied from −90 to −1 °C. To reveal the cause of such significant variations, here we show, by laser confocal microscopy combined with Michelson interferometry, the behavior of QLLs on polycrystalline ice thin films that include a large amount of grain boundaries and defects. We found that the QLLs can exist stably on the polycrystalline ice thin films even at −16.2 °C (the lowest temperature adopted in this study), although the QLLs on ice single crystals disappear at temperature lower than −2.4 ± 0.5 °C. These results emphasize the importance of grain boundaries and defects for the presence of QLLs. In addition, we also found that critical water vapor pressure above which the QLLs can gr...

Beyond the snow line of protoplanetary discs and inside the dense core of molecular clouds, the temperature of gas is low enough for water vapour to condense into amorphous ices on the surface of pre-existing refractory dust particles. Recent numerical simulations and laboratory experiments suggest that condensation of the vapour promotes dust coagulation in such a cold region. However, in the numerical simulations, cohesion of refractory materials is often underestimated, while in the laboratory experiments, water vapour collides with surfaces at more frequent intervals compared to the real conditions. Therefore, to re-examine the role of water ice in dust coagulation, we carry out systematic investigation of available data on coagulation of water-ice particles by making full use of appropriate theories in contact mechanics and tribology. We find that the majority of experimental data are reasonably well explained by lubrication theories, owing to the presence of a quasi-liquid layer (QLL). Only exceptions are the results of dynamic collisions between particles at low temperatures, which are, instead, consistent with the JKR theory, because QLLs are too thin to dissipate their kinetic energies. By considering the vacuum conditions in protoplanetary discs and molecular clouds, the formation of amorphous water ice on the surface of refractory particles does not necessarily aid their collisional growth as currently expected. While crystallization of water ice around but outside the snow line eases coagulation of ice-coated particles, sublimation of water ice inside the snow line is deemed to facilitate coagulation of bare refractory particles.

PrefaceIt is our great pleasure to introduce you the proceedings of 2017 5th Asia Conference on Mechanical and Materials Engineering (ACMME 2017) held in Tokyo, Japan from June 9-11, 2017. ACMME 2017 is dedicated to issues related to mechanical and materials engineering. One of the objectives of the conference is to establish platforms for collaborative research projects in this field, and to find potential opportunities for international cooperation. The conference program included keynote, oral, and poster presentations from scholars working in the areas of materials science and engineering. It covered recent trends and progress made in the field of mechanical and materials engineering. Professors from USA, Malaysia and Taiwan were invited to deliver keynote speeches regarding the latest information in their respective areas of expertise.These proceedings present a selection from papers submitted to the conference by universities, research institutes, and industries. All the papers were subject to peer-review by conference committee members and international reviewers. The papers were selected based on their quality and their relevance to the conference. The volume presents recent advances in the field of mechanical and materials engineering as well as various related areas, including Materials Science, Biomaterials, Manufacturing Processes, and Mechanical Engineering, among others.We would like to express our gratitude to all the members of the conference committee. We would also like to thank the reviewers, who spared their valuable time, for their advice. It has certainly helped improve the quality, accuracy, and relevance of each paper selected for the conference program and for publication. We also wish to thank all the authors who have contributed to this conference, as well as the organizing committee, reviewers, speakers, chairpersons, sponsors, and all the conference participants for their support for ACMME 2017.Prof. Omar S. Es-Said, Loyola Marymount University, USASeptember 5, 2017

Ice formation and non-freezable water (WNFW) of rice flour and tapioca starch gels were studied at two different freezing rates (–10 and –100°C/min) using differential scanning calorimetry. Ice crystal growth was observed in the slow freezing but not in the fast one. Ice melting enthalpies, however, were similar since more ice formed in holding and reheating steps. Melting enthalpy of fully gelatinized systems with water contents ~ 0.50–0.66 was associated to starch composition and granule morphology. Highly swollen tapioca starch gave the lowest enthalpy and the highest WNFW (0.40 g/g dry starch versus 0.32 and 0.38 g/g dry starch of normal and waxy rice flours, respectively). The further studies revealed that the WNFW values were associated to swelling power, solubility, and granule morphology.

Advanced materials are often based on smart molecular self-assemblies that either respond to external stimuli or have hierarchical structures. Approaches to this goal usually stem from complicated molecular design and difficult organic synthesis. In this invited feature article, we demonstrate that desired molecular self-assemblies can be made conveniently by introducing simple functional molecules into amphiphilic systems. We show that upon introducing specific small molecules which serve as responders, modulators, or even building blocks, smart supramolecular architectures can be achieved which avoid complicated organic synthesis. We expect that this could be a general and economical way to produce advanced materials in the near future.

The emergence of gastronomic engineering

Evaluation of water in silica pores using differential scanning calorimetry