Identification of an enantiotropic system with hindered multiphase transitions

Some preliminary considerations suggest that the so-called ‘compensation law’ is a result of the misinterpretation of evaluation procedure. The both parameters: pre-exponential factor and activation energy are calculated from the same set of experimental data. A confidence ellipse could describe the precision of these parameters. In the case of using the least square method for straight-line parameters evaluation, we could calculate a axes of the ellipse, using experimental data. If the observed relationship between pre-exponential factor and activation energy agree with the ‘pre-calculated’ direction of main axis of confidence ellipse, we have a strong support to believe that the observed ‘compensation’ effect is only an artificial effect of misinterpretation. Some calculations performed for a published experimental data have confirmed these suspicions. This also, indirectly indicates that precision of such experiments is probably lower than expected.     

Nucleation-controlled growth. Observations on (110) twinned polyethylene crystals

The growth of (110) twinned crystals of a sharp fraction of linear polyethylene (M_w/M_n = 1.10) of moderate molecular weight (M_w = 17,000) is followed during crystallization by the isochronous decoration method. New morphological features are observed. The fast-growing tip of our laths presents, in addition to the two (100) facets usually observed, a possibly stable small reentrant (110) corner. This is a situation intermediate between the facies described by Dawson and Keller. Moreover, the slow tip of our laths presents various degrees of asymmetry with respect to the junction plane. A new characteristic length L_n = j/i is introduced to explain our morphological observations on (110) twinned crystals: j is the nucleation rate at a reentrant corner and i the nucleation rate on a smooth facet. Three linear growth rates G_hkl are calculated as a function of the length L of the face (hkl): G_hkl and G_?kl or G′_hkl are respectively the growth rates of a face bordered by two salient corners and by a reentrant corner. A distinction between G_?kl and G′_hkl is introduced to take into account the relative sizes of the two faces of the reentrant dihedral angle. The major points of the discussion concern (i) the stability of the (110) reentrant corner of the fast tip of the lath, (ii) the nearly constant shape of the twinned crystals, (iii) the effects of dislocations incorporated in the fast edge of the laths, and (iv) the various asymmetries observed in the slow tip of our laths. Theories of surface nucleation-controlled growth explain our various morphological observations on (110) twinned PE crystals, and growth usually proceeds in regime II.     

Nucleation-controlled growth in polyethylene single crystals: Growth and shape of {100} sectors

The nucleation rate and propagation rate of steps on the {100} faces of polyethylene crystals have been determined. For single crystals, under conditions where the width of the {100} sectors remains constant during growth, it is confirmed that the growth is in regime I or the crossover region between regime I and II. In {110} twinned crystals, the {100} sectors are well developed and the width increases linearly with time; therefore, the growth in the twins must be in regime II. It is shown that the differing growth regimes of {100} faces in single crystals and twins allow the independent determination of the nucleation rate and the propagation rate of steps. The nucleation rate and propagation rate of steps on the {100} faces were determined from measurements of the constant width of the {100} faces in single crystals and the growth rate of the {100} faces in single crystals and twins. The observed rates show abnormal dependence on supercooling and concentration. The results are attributed to a weaker dependence of the constant width of {100} sectors on supercooling and concentration than predicted.     

In vivo comprehensive multiphase NMR

Traditionally, due to different hardware requirements, nuclear magnetic resonance (NMR) has developed as two separate fields: one dealing with solids, and one with solutions. Comprehensive multiphase (CMP) NMR combines all electronics and hardware (magic angle spinning [MAS], gradients, high power Radio Frequency (RF) handling, lock, susceptibility matching) into a universal probe that permits a comprehensive study of all phases (i.e., liquid, gel-like, semisolid, and solid), in intact samples. When applied in vivo, it provides unique insight into the wide array of bonds in a living system from the most mobile liquids (blood, fluids) through gels (muscle, tissues) to the most rigid (exoskeleton, shell). In this tutorial, the practical aspects of in vivo CMP NMR are discussed including: handling the organisms, rotor preparation, sample spinning, water suppression, editing experiments, and finishes with a brief look at the potential of other heteronuclei (²H, ¹⁵N, ¹⁹F, ³¹P) for in vivo research. The tutorial is aimed as a general resource for researchers interested in developing and applying MAS-based approaches to living organisms. Although the focus here is CMP NMR, many of the approaches can be adapted (or directly applied) using conventional high-resolution magic angle spinning, and in some cases, even standard solid-state NMR probes.     

Modeling multiphase latex particle equilibrium morphology

Multiphase waterborne polymer particles provide advantages in more demanding applications and their performance depends on particle morphology. Currently, no general approach to predict the morphology of multiphase latex particles is available. In this work, a model based on Monte Carlo methods was developed for the prediction of equilibrium morphologies of multiphase waterborne systems, such as polymer‐polymer and polymer‐polymer‐inorganic hybrids. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2579–2583, 2010     

Recent advances in water-mediated multiphase catalysis

Water is the most sustainable solvent, making it the obvious choice to replace organic solvents in various synthesis techniques. However, its applications in the chemical and pharmaceutical industries are often restricted by the low solubility of organic compounds in water. Essentially, the reactions of organic compounds in water are multiphase systems. Therefore, this review classifies aqueous-phase organic reactions into liquid–liquid, liquid–solid and gas–liquid–solid phase from the perspective of phase interfaces of multiphase reactions, and summarizes the research progress and breakthroughs in recent years, including the application of micellar catalysis, Pickering emulsion catalysis, micro-nanobubble/foam catalysis and “dry water” catalysis, as well as the unique advantages of using water as a medium. Finally, we point out the current challenges and future perspectives on multiphase catalysis in aqueous-phase reactions.     

Contact angle hysteresis in multiphase systems

Contact angle (CA) hysteresis is the difference between the maximum (advancing) and minimum (receding) water CA. Hysteresis is caused by adhesion hysteresis in the solid–water contact area (2D effect) and by pinning of the solid–water–air triple line due to the surface roughness (1D effect). In this work, we show that CA hysteresis is present also in more complex systems, such as an organic liquid (oil) in contact with a solid immersed in water. In order to decouple the 1D and 2D effects, we study CA hysteresis in solid–water–air (droplet), solid–air–water (bubble), solid–water–oil, and solid–water–air–oil systems involving rough and microstructured surfaces. The comparative analysis of these systems allows decoupling the 1D and 2D effects as well as hydrogen bonding and entropic forces (water–air tension) and dispersion forces (oil–air tension).     

Wetting transitions

When a liquid droplet is put onto a surface, two situations distinguishable by the contact angle may result. If the contact angle is zero, the droplet spreads across the surface, a situation referred to as complete wetting. If the contact angle is between zero and 180°, the droplet does not spread, a situation called partial wetting. A wetting transition is a surface phase transition from partial to complete wetting. The wetting transition is generally first-order (discontinuous), implying a discontinuity in the first derivative of the surface free energy. As a consequence, at the transition a discontinuous jump in film thickness occurs from a molecularly thin to a thick film. We show here that the first-order nature of the transition can lead to the observation of metastable surface states and an accompanying hysteresis. The second part of this review deals with the exceptions to the first-order nature of the wetting transition. Two different types of continuous or critical wetting transitions have been reported, for which a discontinuity in a higher derivative of the surface free energy occurs. This consequently leads to a continuous divergence of the film thickness. The first type is long-range critical wetting, due to the long-range van der Waals forces. We show that this transition is preceded by the usual first-order wetting transition, which, however, is not achieved completely. This leads to the existence of a new intermediate wetting state, in which droplets coexist with a mesoscopic film: frustrated complete wetting. The film thickness diverges continuously from this mesoscopic film to a thick film. The second type of continuous transition is short-range critical wetting, for which the layer thickness diverges continuously all the way from a microscopic to a macroscopically thick film. This transition is interesting, as renormalization-group studies predict non-universal behaviour for the critical exponents characterizing the wetting transition. The experimental results, however, show mean field behaviour, the reason for which remains unclear.     

Thermodynamic speed of sound in multiphase systems

A procedure to evaluate the thermodynamic speed of sound in systems with any number of fluid phases is presented in this paper. Starting from the definition of speed of sound, the derivation of the procedure uses the conservation equations for volume, entropy, and number of moles of each component, the derivatives of several thermodynamic properties, and the solution of a system of linear equations. A computer algebra program was used to automatically derive and implement in computer the required expressions. The calculated thermodynamic speeds of sound reported in this paper are in very good agreement with results published recently, based on numerical derivatives, but show some discrepancies with earlier results available in the literature.     

Tuning multiphase amphiphilic rods to direct self-assembly

New methods to direct the self-assembly of particles are highly sought after for multiple applications, including photonics, electronics, and drug delivery. Most techniques, however, are limited to chemical patterning on spherical particles, limiting the range of possible structures. We developed a lithographic technique for fabrication of chemically anisotropic rod-like particles in which we can specify both the size and shape of particles and implement multiple diverse materials to control interfacial interactions. Multiphase rod-like particles, including amphiphilic diblock, triblock, and multiblock were fabricated in the same template mold having a tunable hydrophilic/hydrophobic ratio. Self-assembly of diblock or triblock rods at a water/oil interface led to the formation of bilayer or ribbon-like structures.     

Multicomponent,multiphase interactions in fuel-cell inks

Fuel-cell catalyst layers (CLs) are porous electrodes that are fabricated from CL inks: colloidal dispersions of catalyst particles and ion-conducting polymer (ionomer), dispersed in solvent(s). The complex interactions between the ink components ultimately dictate CL microstructure and electrochemical performance. To control the CL formation process and optimize fuel-cell performance, knowledge of these ink interactions is vital. In this review, we analyze data from ink-focused papers to elucidate how ink parameters (solvent type, ionomer-to-carbon ratio, etc.) impact ink interactions and CL performance. We then discuss these results in the context of the current understanding of two critical ink interactions: ionomer/solvent and ionomer/catalyst particle interactions.     

Photoinduced phase transitions

Employing actinic light to alter/stabilise a particular thermodynamic phase via the photo-isomerisation of the constituent molecules is an interesting tool to investigate soft matter from a new dimension. This article focuses on our recent results on several aspects of these non-equilibrium phase transitions, which are isothermal in nature. We specifically discuss (i) the influence of different parameters, such as confinement, applied electric field, pressure etc., on the dynamics associated with both the photochemical transition driving the equilibrium nematic to the non-equilibrium isotropic phase and the thermal back relaxation recovering the nematic phase, (ii) unique light-driven disorder–order transition in a reentrant system, (iii) dynamic self-assembly of the smectic A phase, which is stabilised only in the presence of actinic light, (iv) novel temperature-intensity phase diagrams and an example of primary and secondary photo-ferroelectric effects in an antiferroelectric smectic C system. These results highlight the fact that the actinic light can be used as a new tool to study phase transitions and the associated critical phenomena that could also bring about effects that are not seen in equilibrium situations.     

Magnetic-field-induced radiationless transitions

A quantum-mechanical theory of the magnetic field effect on radiationless transitions in an isolated molecule is presented. The mechanism of this phenomenon is a second-order process relying on the simultaneous radiationless relaxation of an excited electronic state and the interaction of the molecule with a constant uniform magnetic field.     

Thermodynamic origins of two-component multiphase condensates of proteins

Intracellular condensates are highly multi-component systems in which complex phase behaviour can ensue, including the formation of architectures comprising multiple immiscible condensed phases. Relying solely on physical intuition to manipulate such condensates is difficult because of the complexity of their composition, and systematically learning the underlying rules experimentally would be extremely costly. We address this challenge by developing a computational approach to design pairs of protein sequences that result in well-separated multilayered condensates and elucidate the molecular origins of these compartments. Our method couples a genetic algorithm to a residue-resolution coarse-grained protein model. We demonstrate that we can design protein partners to form multiphase condensates containing naturally occurring proteins, such as the low-complexity domain of hnRNPA1 and its mutants, and show how homo- and heterotypic interactions must differ between proteins to result in multiphasicity. We also show that in some cases the specific pattern of amino-acid residues plays an important role. Our findings have wide-ranging implications for understanding and controlling the organisation, functions and material properties of biomolecular condensates.

We develop a computational method integrating a genetic algorithm with a residue-level coarse-grained model of intrinsically disordered proteins in order to uncover the molecular origins of multiphase condensates and enable their controlled design.     

Phase transitions of a polymer threading a membrane coupled to coil-globule transitions

We theoretically study phase transitions of a polymer threading through a pore imbedded in a membrane. We focus on the coupling between a partition of the polymer segments through the membrane and a coil-globule transition of the single polymer chain. Based on the Flory model for collapse transitions of a polymer chain, we calculate the fraction of polymer segments and the expansion factor of a polymer coil on each side of the membrane. We predict a first-order phase transition of a polymer threading a membrane; polymer segments in one side are discontinuously translocated into the other side, depending on solvent conditions and molecular weight of the polymer. We also discuss the equilibrium conformation of the polymer chain on each side of the membrane.     

Self-programmed enzyme phase separation and multiphase coacervate droplet organization

Membraneless organelles are phase-separated droplets that are dynamically assembled and dissolved in response to biochemical reactions in cells. Complex coacervate droplets produced by associative liquid–liquid phase separation offer a promising approach to mimic such dynamic compartmentalization. Here, we present a model for membraneless organelles based on enzyme/polyelectrolyte complex coacervates able to induce their own condensation and dissolution. We show that glucose oxidase forms coacervate droplets with a cationic polysaccharide on a narrow pH range, so that enzyme-driven monotonic pH changes regulate the emergence, growth, decay and dissolution of the droplets depending on the substrate concentration. Significantly, we demonstrate that time-programmed coacervate assembly and dissolution can be achieved in a single-enzyme system. We further exploit this self-driven enzyme phase separation to produce multiphase droplets via dynamic polyion self-sorting in the presence of a secondary coacervate phase. Taken together, our results open perspectives for the realization of programmable synthetic membraneless organelles based on self-regulated enzyme/polyelectrolyte complex coacervation.

Self-programmed enzyme phase separation is exploited to assemble dynamic multiphase coacervate droplets via spontaneous polyion self-sorting under non-equilibrium conditions.