Physics of engineered protein hydrogels

Artificially engineered proteins and synthetic polypeptides have attracted widespread interest as building blocks for polymer hydrogels. The biophysical properties of the proteins, such as molecular recognition abilities, folded chain structures, and sequence-dependent thermodynamic behavior, enable advances in functional, responsive, and tunable gels. This review discusses the design of polymer hydrogels that incorporate protein domains, highlighting new challenges in polymer physics that are presented by this emerging class of materials. Five types of engineered protein hydrogels are discussed: (a) physically associating protein polymer gels, (b) amorphous artificially engineered protein networks, (c) engineered proteins with crystalline domains, (d) stretchable protein tertiary structures in gels, and (e) protein gels with biological recognition properties. The physics of the protein component and the physical properties of the resulting hydrogels are summarized, illustrating how advances in understanding these systems are leading to exciting novel biofunctional hydrogels. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

A 4D Composite Reinforced along Cube Diagonals with a Small Content of Yarns under Large Shear Deformations

The deformation behavior of a 4D composite reinforced along cube diagonals under large shear deformations is examined. The investigation is based on an applied theory which allows one to perform a macromechanical analysis of composite materials with small volume contents of reinforcing yarns to an accuracy sufficient in practice. Qualitative differences between the properties of such composites under large and small shear deformations are revealed. The evolution of the structural geometry of the deformed composite material is traced.     

Rheological properties of ground tyre rubber based thermoplastic elastomeric blends

This work analyses the rheological behaviour of thermoplastic elastomeric blends (TPE) based on ground tyre rubber (GTR), more specifically the rheological behaviour of binary and ternary polypropylene (PP) based blends with different rubber materials: an ethylene propylene diene monomer (EPDM), an ethylene propylene rubber (EPR) and GTR. The study was developed under steady-shear rate conditions by capillary rheometry at three different temperatures. Time–Temperature Superposition Principle (TTSP) was applied to the viscosity curves using a temperature dependent shift factor, allowing the construction of master curves for the analysed blends. The Cross-WLF model was used to predict the rheological parameters, giving numerical results for viscosity similar to the experimental data. GTR increased the blends viscosity. EPR showed rheological behaviour similar to PP, and EPDM presented higher power law behaviour. Pseudoplastic behaviour was observed for all the analysed blends. Incorporation of GTR in TPE blends for injection moulding purposes was found to be a feasible strategy to upcycle this type of potentially wasted material.     

Dielectric properties of polymers based on hexafluoropropylene

Dielectric measurements have been made at frequencies from 10 Hz to 100 kHz and temperatures from 4 K to at least 300 K on a number of polymers containing units of hexafluoropropylene (HFP). These included copolymers of tetrafluoroethylene (TFE) and HFP, the homopolymer of HFP, elastomeric copolymers of HFP and vinylidene fluoride, and alternating copolymers of methyl vinyl ether with TFE and HFP. The effect of an ether linkage between the CF₃ group and the chain was also considered. Most of these polymers exhibited a main chain local mode relaxation near 228 K and a side group relaxation near 93 K.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayWe appreciate the helpful discussions with W. W. Schmiegel.     

Advanced chiral molecular media for enantioselective electrochemistry and electroanalysis

An increasing number of strategies and tools have been proposed to endow the electrochemical interphase with chirality, to achieve enantiodiscrimination in analytical and/or preparative applications. So far, chirality has mostly been implemented not only at the electrode surface side but also on the medium one. Recently, the attractiveness of the latter approach has remarkably increased on account of the increasing availability of advanced chiral molecular media with intrinsic attractive features for electrochemistry applications, such as chiral ionic liquids, chiral ionic liquid crystals, and chiral deep eutectic solvents. With respect to solid layer/fixed chiral networks, advanced chiral media can still offer a reasonably high degree of local structuring, while being less demanding concerning preparation and management protocols, as well as less sensitive to fouling/regeneration issues. Different ways to implement chirality in advanced molecular media, including cases of powerful ‘inherent chirality,’ will be presented and discussed, particularly focusing on recent applications in the electrochemical field.     

Boron-bearing species in ceramic matrix composites for long-term aerospace applications

Boron-bearing refractory species are introduced in non-oxide ceramic matrix fibrous composites (such as SiC/SiC composites) to improve their oxidation resistance under load at high temperatures with a view to applications in the aerospace field. B-doped pyrocarbon and hex-BN have been successfully used as interphase (instead of pure pyrocarbon) either as homogeneous or multilayered fiber coatings, to arrest and deflect matrix cracks formed under load (mechanical fuse function) and to give toughness to the materials. A self-healing multilayered matrix is designed and used in a model composite, which combines B-doped pyrocarbon mechanical fuse layers and B- and Si-bearing compound (namely B₄C and SiC) layers forming B₂O₃-based fluid healing phases when exposed to an oxidizing atmosphere. All the materials are deposited by chemical vapor infiltration. Lifetimes under tensile loading of several hundreds hours at high temperatures are reported.     

Fluoroethylene Carbonate Enabling a Robust LiF‐rich Solid Electrolyte Interphase to Enhance the Stability of the MoS2 Anode for Lithium‐Ion Storage

As a high‐capacity anode for lithium‐ion batteries (LIBs), MoS₂ suffers from short lifespan that is due in part to its unstable solid electrolyte interphase (SEI). The cycle life of MoS₂ can be greatly extended by manipulating the SEI with a fluoroethylene carbonate (FEC) additive. The capacity of MoS₂ in the electrolyte with 10 wt % FEC stabilizes at about 770 mAh g^?1 for 200 cycles at 1 A g^?1, which far surpasses the FEC‐free counterpart (ca. 40 mAh g^?1 after 150 cycles). The presence of FEC enables a robust LiF‐rich SEI that can effectively inhibit the continual electrolyte decomposition. A full cell with a LiNi_0.5Co_0.3Mn_0.2O₂ cathode also gains improved performance in the FEC‐containing electrolyte. These findings reveal the importance of controlling SEI formation on MoS₂ toward promoted lithium storage, opening a new avenue for developing metal sulfides as high‐capacity electrodes for LIBs.     

Linear Stability Analysis of a Viscous Liquid Sheet in a High-Speed Viscous Gas

Air-assisted atomizers in which a thin liquid sheet is deformed under the action of a high-speed air flow are extensively used in industrial applications, e.g., in aircraft turbojet injectors. Primary atomization in these devices is a consequence of the onset and growth of instabilities on the air/liquid interfaces. To better understand this process, a temporal linear instability analysis is applied to a thin planar liquid sheet flowing between two semi-infinite streams of a high-speed viscous gas. This study includes the full viscous effects both in the liquid and gas basic states and perturbations. The relevant dimensionless groups entering the non-dimensional Orr–Sommerfeld equations and boundary conditions are the liquid and gas stream Reynolds numbers, the gas to liquid momentum flux ratio, the gas/liquid velocity ratio, the Weber number and the equivalent gas boundary layer to liquid sheet thickness ratio. Growth rates and temporal frequencies as a function of the wave number, varying the different dimensionless parameters are presented, together with neutral stability curves. From the results of this parametric study it is concluded that when the physical properties of gas and liquid are fixed, the momentum flux ratio is especially relevant to determine the instability conditions. It is also observed that the gas boundary layer thickness strongly influences the wave propagation, and acts by damping sheet oscillation frequency and growth. This is especially important because viscosity in the basic gas velocity profile has always been ignored in instability analysis applied to the geometry under study. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mechanical Properties of Seismic Isolation System with Fiber-Reinforced Bearing of Strip Type

This paper describes an experimental and theoretical study of the feasibility of using fiber reinforcement to produce a lightweight and low-cost elastomeric isolator. The fiber in the fiber-reinforced isolator, in contrast to the steel in the conventional isolator, is assumed to be flexible in tension. Several isolators in the form of long strips were fabricated and tested. The theoretical analysis and test results suggest that it is possible to produce a fiber-reinforced strip isolator that behaves like a steel-reinforced isolator. The fiber-reinforced isolator is significantly lighter and can be made in a much less labor-intensive manufacturing process     

Structural and thermodynamic properties of water–membrane interphases: Significance for peptide/membrane interactions

Water appears as a common intermediary in the mechanisms of interaction of proteins and polypeptides with membranes of different lipid composition. In this review, how water modulates the interaction of peptides and proteins with lipid membranes is discussed by correlating the thermodynamic response and the structural changes of water at the membrane interphases.