Diffuse Interphase Research Articles

Marine Fouling Release Performance of Amphiphilic Carboxybetaine Perfluoropolyether Methacrylate Polymer Coatings

AbstractAmphiphilic polymer systems have been demonstrated to be an effective and environmentally friendly approach to combat the challenges of biofouling, especially in the real ocean environment. A variety of polymer compositions containing fluorophilic perfluoropolyether (PFPE) urethane dimethacrylate and zwitterionic carboxybetaine methacrylate (CBMA) are in situ copolymerized across a broad concentration range and anchored to chemically functionalized substrates by grafting‐through polymerization. Dynamic accumulation assays with the marine diatom Navicula perminuta and the marine bacterium Cobetia marina revealed an enhanced antifouling performance in most of the amphiphilic polymer mixtures when zwitterionic units are combined with hydrophobic PFPE compounds. It is noticed that the resulting polymer networks still possess enough orientational freedom to quickly rearrange in the presence of water. It is further observed that several of the very hydrophilic formulations and some of the moderately hydrophobic formulations exhibit low fouling against the marine fouling organisms Navicula perminuta and Cobetia marina. This correlated with increased surface roughness and the ability for underwater rearrangement. Furthermore, it is discussed whether the probability that highly hydrated hydrogels, which appear sponge‐like, may create a diffuse interphase which promotes the incorporation of silt. Latter is counteracted by the hydrophobic PFPE building blocks in the amphiphilic coatings.

Biosourced Multiphase Systems Based on Poly(Lactic Acid) and Polyamide 11 from Blends to Multi-Micro/Nanolayer Polymers Fabricated with Forced-Assembly Multilayer Coextrusion

The objective of the present study was to investigate multiphase systems based on polylactic acid (PLA) and polyamide 11 (PA11) from blends to multilayers. Firstly, PLA/PA11 blends compatibilized with a multifunctionalized epoxide, Joncryl, were obtained through reactive extrusion, and the thermal, morphological, rheological, and mechanical behaviors of these materials were investigated. The role of Joncryl as a compatibilizer for the PLA/PA11 system was demonstrated by the significant decrease in particle size and interfacial tension as well as by the tensile properties exhibiting a ductile behavior. Based on these findings, we were able to further clarify the effects of interdiffusion and diffuse interphase formation on the structure, rheology, and mechanics of compatible multilayered systems fabricated with forced-assembly multilayer coextrusion. The results presented herein aim to provide a deeper understanding of the interfacial properties, including the rheological, mechanical, and morphological behaviors, towards the control of the interface and confinement in multilayer polymers resulting from coextrusion, and also to permit their use in advanced applications.

Investigation of interdiffusion between compatible polymers under static and co‐extrusion processing conditions

AbstractWhen two compatible polymer melts are brought into contact, a diffuse interphase is formed that governs the adhesion between them. The degree of interdiffusion is defined mainly by the processing conditions and the physico‐chemical properties of the materials. Despite the great industrial relevance of co‐extrusion in manufacturing multilayer structures, little research has dealt with interdiffusion under these processing conditions, where polymer‐polymer interfaces are subject to shear load. In this work, procedures for investigating interdiffusion both under static and real co‐extrusion flow conditions were developed. Using various grades of poly(methyl methacrylate) and styrene‐co‐acrylonitrile copolymer, we studied both theoretically and experimentally the effects of interfacial contact time, temperature, material compatibility, and interfacial shear stress on interdiffusion. Spectroscopic analysis of the interfaces using confocal Raman microscopy showed that the general relationships between interdiffusion, time (Fick's law) and temperature (Arrhenius relationship) are identical under both static and co‐extrusion conditions. However, the interdiffusion rate is significantly higher under shear influence. Since the prediction of the interdiffusion process supports material selection and process design in multilayer manufacturing, a simple analytical model was developed to quantify the effects of aforementioned material properties and processing conditions on the apparent mutual interdiffusion coefficient.

Hydrogen bond induced solvent ordering in aqueous poly (sodium p-styrenesulfonate)

Molecular dynamics simulations were used to investigate the structure and dynamics of the diffuse interphase in aqueous poly (sodium p-styrenesulfonate) (NaPSS). The effect of temperature and the distance between Sδ+Oδ– and Oδ–Hδ+ dipoles on the ordering of explicit solvent molecules were extensively studied. With an increase in temperature, the atomic radial distribution function indicated a reduced density of water in the immediate vicinity of SO3− groups and a slight increase in density afterward. Using the dipole radial distribution function, water molecules were classified into multiple layers on the basis of the distance between Sδ+Oδ– (PSS) and Oδ–Hδ+ (H2O) dipoles. Orientation of Oδ–Hδ+ around Sδ+Oδ–, influenced by coulombic interactions, resulted in a greater number of hydrogen bonds (H-bonds) and improved H-bond correlation function between adjacent layers. The altered H-bond dynamics were found to severely restrict the solvent mobility in the layer close to SO3− groups. While the number of inter-layer H-bonds was found to be a result of water orientation, the H-bond correlation function was dependent on the mobility of water molecules. Mean square displacement and autocorrelation of dipole radial distances were calculated to distinguish between inter- and intra-layer solvent mobility. Our results provide molecular-level insights into the structure and dynamics of solvent water molecules in the diffuse interphase with a polyelectrolyte.

Misfit Stress in Radial Core-Shell Nanowires with Diffuse Interface Boundaries

The elastic models of radial core-shell nanowires with diffuse interphase boundaries are suggested. The concept of eigenstrain is employed to consider a misfit stress distribution induced by diffusive interfaces with different range of distinctness. The eigenstrain profile described by the misfit parameter is approximated by piecewise-linear, error and arctangent functions. For these approximations the elastic stresses in core-shell nanowires are analytically derived, illustrated with plots and discussed in detail.

Transparent PC/PMMA Blends with Enhanced Mechanical Properties via Reactive Compounding of Functionalized Polymers.

Reactive compounding of terminally phenolic OH-functionalized polycarbonate (PC) with epoxy-functionalized polymethylmethacrylate (PMMA) prepared by copolymerization with glycidyl methacrylate was investigated. It was spectroscopically demonstrated that a PC/PMMA copolymer was formed during the melt reaction of the functional groups. Zirconium acetylacetonate could catalytically accelerate this reaction. Correlations of the phenomenological (optical and mechanical) properties with the molecular level and mesoscopic (morphological) structure were discussed. By the investigated reactive compounding process, transparent PC/PMMA blends with two-phase morphologies were obtained in a continuous twin-screw extruder, which, for the first time, combined the high transmission of visible light with excellent mechanical performance (e.g., synergistically improved tensile and flexural strength and high scratch resistance). The transparency strongly depended on (a) the degree of functionalization in both PC and PMMA, (b) the presence of the catalyst, and (c) the residence time of the compounding process. The in-situ-formed PC/PMMA copolymer influenced the observed macroscopic properties by (a) a decrease in the interphase tension, leading to improved and stabilized phase dispersion, (b) the formation of a continuous gradient of the polymer composition and thus of the optical refractive indices in a diffuse mesoscopic interphase layer separating the PC and PMMA phases, and (c) an increase in the phase adhesion between PC and PMMA due to mechanical polymer chain entanglement in this interphase.

Existence of smooth solutions for the compressible barotropic Navier‐Stokes‐Korteweg system without increasing pressure law

This paper is concerned with a barotropic model of capillary compressible fluids describing the dynamics of a liquid‐vapor mixture with diffuse interphase, in the case of general pressure law including Van der Waals gas. In the Sobolev spaces as close as possible to the physical energy spaces, we first prove local in time existence and uniqueness of the smooth solutions to the Cauchy problem in , based on the estimates of a linearized system and the contraction mapping principle. Next, we show that there exists a global unique solution for the initial boundary value problem with periodic conditions in torus , by using a continuation argument of local solution. Notice that it is one of the main difficulties that pressure p is not increasing function of density ρ.

Global Well-Posedness and Time-Decay Estimates of the Compressible Navier–Stokes–Korteweg System in Critical Besov Spaces

We consider the compressible Navier-Stokes-Korteweg system describing the dynamics of a liquid-vapor mixture with diffuse interphase. The global solutions are established under linear stability conditions in critical Besov spaces. In particular, the sound speed may be greater than or equal to zero. By fully exploiting the parabolic property of the linearized system for all frequencies, we see that there is no loss of derivative usually induced by the pressure for the standard isentropic compressible Navier-Stokes system. This enables us to apply Banach's fixed point theorem to show the existence of global solution. Furthermore, we obtain the optimal decay rates of the global solutions in the $L^2(\mathbb{R}^d)$-framework.

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate).

It is known that the macroscopic properties of multilayer polymer films are largely dominated by the diffuse interphase formed via interfacial diffusion between neighboring layers. However, not much is known about the origin of this effect. In this work, we reveal the role of interfacial diffusion and the diffuse interphase development in multilayer polymer films, based on a compatible poly(vinylidene fluoride)/poly(methyl methacrylate) system fabricated by forced-assembly micro-/nanolayer coextrusion. Interestingly, the layer morphology is found to prevail in all investigated multilayer films, even for the nanolayered system where the interdiffusion is substantial. It is also demonstrated that, in the presence of macromolecular and geometrical confinements, interfacial diffusion significantly alters the crystalline morphology and microstructure of the resulting micro-/nanolayered films, which leads to quantitatively different dielectric and rheological properties. More importantly, the combination of dielectric relaxation spectroscopy and energy-dispersive X-ray analysis further reveals that multiple diffuse interphases with various length scales exist in the multilayer structures. The presence of these multiple interphases is explained in terms of a proposed physical picture for the interdiffusion of fast-mode mechanism occurring in the coextrusion process, and their length scales (i.e., interphase thicknesses) are further mapped quantitatively. These findings provide new insights into the effects of interfacial diffusion and diffuse interphases toward tailoring interfaces/interphases in micro-/nanolayered polymer structures and for their advanced applications.

A nonlinear shear and elongation rheological study of interfacial failure in compatible bilayer systems

This work aims to examine whether or not interfacial failure can occur in a compatible polymer bilayer system under large shear and elongation deformations, as well as to probe the sensitivity of nonlinear transient rheology to the presence of interface/interphase at neighboring layers. For this, stress relaxation after a step strain and fast startup in simple shear and uniaxial extension experiments have been performed on healed and coextruded poly(methyl methacrylate)/poly(vinylidene fluoride) bilayers with the presence of a robust diffuse interphase as evaluated by energy dispersive X ray. For unhealed bilayers, interfacial failure occurred in shear flows at intermediate deformations, while for healed bilayers the interphase greatly delayed the onset of interfacial failure to larger deformation steps and to a higher deformation rate in the startup shear. Extensional rheology demonstrated that the presence of an interphase in the bilayers greatly enhanced the transient extensional viscosity ηE+(t) as well as the tensile relaxation modulus E(t) of the structure, even though the entanglement density was relatively low. Moreover, models are presented to predict the nonlinear relaxation behavior of bilayers and to estimate the relaxation behavior of the interphase. Fitting of the tube model to the shear relaxation indicates a dilated tube diameter in the interphase, confirming its weak entanglement intensity and its readiness to flow-induced disentanglement under large external deformations. Finally, the physics of the interfacial failure was assessed based on some recent molecular dynamic theories.

Chromosome Condensation: Weaving an Untangled Web

The compaction of diffuse interphase chromatin into stable mitotic chromosomes enables the segregation of replicated DNA to daughter cells. Two new studies characterise, both invivo and invitro, the essential contribution of the vertebrate condensin complex to chromosome organisation.

Fundamental understanding and modeling of diffuse interphase properties and its role in interfacial flow stability of multilayer polymers

This work aims to investigate the growth and structural evolution of a diffuse interphase generated in a flow field and to highlight its importance on controlling the final properties of compatible multilayer materials. The model polymers chosen are poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVDF). Interdiffusion kinetics, geometrical, and rheological properties of the interphase decoupled and coupled to flow have been probed and quantified under fundamental conditions of rheological measurement and under real practical conditions of processing, respectively. Polymer chain orientation is shown to decelerate the interdiffusion coefficient. This phenomenon is demonstrated to be balanced by intermixing (i.e. flow effect) at the vicinity of the interface triggered from excess interfacial shear stress, thus favors development of the interphase. The diffuse interphase generated therein during the processing has been well characterized via scanning electron microscopy coupled with energy dispersive X‐ray analysis (SEM‐EDX) and transmission electron microscopy (TEM). Results indicate that the interphase is robust with a geometrical property of tens microns depending on processing conditions and the interfacial structure is shown to be smooth with continuous amorphous‐crystallization transition between neighboring layers without causing any interfacial disturbances. Finally, experimental studies concerning the interfacial flow instability and encapsulation in coextrusion process have been performed, taking into account some key classical decisive parameters such as viscosity ratio, thickness ratio and elasticity ratio, etc. Different from severe flow instability observed in incompatible multilayer systems, presence of the interphase at PMMA/PVDF multilayers plays a vital role in weakening (or even eliminating) the viscous instabilities and elastic instabilities despite of the very high rheological contrast. POLYM. ENG. SCI., 55:771–791, 2015. © 2014 Society of Plastics Engineers

Cement paste–epoxy adhesive interactions

In the field of civil engineering, the durability of concrete assemblies using adhesives is widely conditioned by the properties of the interface between the resin and the mineral support (concrete). In this context we studied first the molecular interactions at the interface between an epoxy resin and cement pastes by several approaches based on XPS and IR spectroscopies, DSC, and inverse gas chromatography (IGC). XPS showed evidence of crosslinking of the polymer at the surface of hardened cement pastes. XPS chemical shifts of the N1s peak from the adsorbed hardener testified for the existence of interfacial donor–acceptor interactions between the cement and hardener. Such a specific interaction is probably responsible for the increase in the of glass transition temperature ( T g) of the adhesive near the cement substrate surface. FTIR study of the interactions of the epoxy adhesive with the main hydrates taken separately (namely C–S–H, ettringite and portlandite) permitted to better understand the complex cement paste–adhesive interfacial system. The IGC-determined dispersive and acid–base components of the surface energy of the cement pastes were found to be depressed after coating, a result that correlates with surface chemical composition data. Small area XPS analysis of cement paste/adhesive interphase revealed, on a prototype of cement paste–adhesive joint, modifications of the Ca2p and N1s regions, which suggests that this zone is the locus of chemical reactions that favour mineral substrate–resin adhesion. Small area XPS firmly showed the existence of a diffuse interphase rather than a sharp cement paste–adhesive interface.

Atomic-level dynamic behavior of a diffuse interphase boundary in an Au–Cu alloy

This investigation uses in situ high-resolution transmission electron microscopy to quantify the atomic-level dynamic behavior of a diffuse interphase boundary between ordered and disordered phases in an Au–Cu alloy at elevated temperature. It is found that both the interphase boundary position and thickness fluctuate with time and that the behavior of the disordered side of the interphase boundary differs from that of the ordered side. Analysis of the interphase boundary shape shows that it fluctuates by a mechanism involving the collective motion of many atoms rather than by single-atom jumps. These features are explained in terms of the physical properties of the different phases at the interphase boundary.

Assessment of morphology in transient and steady state regimes resulting from phase separation in polystyrene/poly(vinyl methyl ether) blend

Morphology development after phase separation in polystyrene (PS)/poly(vinyl methyl ether) (PVME) blend was assessed both in transient and in steady state regimes. Phase segregation was evaluated by various techniques including optical microscopy, light transmission, dynamic scanning calorimetry and rheological analyses. The steady state particle size resulted from phase separation was determined experimentally and then compared to the predictions of both the emulsion models that assume zero-thickness interfacial boundaries and to the asymptotic value of the Cahn–Hilliard theory that assumes rather a diffuse interphase.

A phase field model for the simulation of grain growth in materials containing finely dispersed incoherent second-phase particles

A phase field model is presented for simulating grain growth in materials containing small incoherent second-phase particles that are constant in time. The model of [L.-Q. Chen, W. Yang, Phys. Rev. B 50 (1994) 15752] for grain growth in single phase materials, that represents a polycrystalline microstructure with a set of phase field variables η i ( r, t), has been modified to incorporate the presence of second-phase particles by adding an extra term ϵ Φ ∑ i η i 2 to the free energy expression, with Φ a spatially dependent parameter that equals one inside the particles, and zero elsewhere and ϵ a positive constant. The interaction between a particle and a diffuse interphase is analyzed from an energetic point of view and the effect of pinning particles on the shape and the evolution of an initially spherical grain is studied for two-dimensional and three-dimensional systems.

Interface between a Liquid Crystalline Polymer and a Flexible Polymer

The properties of the interfacial region between melt phases of a liquid crystalline polymer and a flexible polymer were studied using the three-dimensional bond fluctuation model. The far-field orientation has a strong effect on the magnitude of the interfacial tension and the structure of the “interphase”. The interfacial tension is an increasing function of the nematic order parameter S for a parallel far field, while it is a decreasing function for a homeotropic (orthogonal) far field, with the difference in the magnitude of the interfacial tension growing exponentially in S. The interfacial tension for both far-field orientations is insensitive to liquid crystalline polymer chain length. Chain ends penetrate the adjacent phase with a homeotropic orientation, resulting in a more diffuse interphase. There is, nevertheless, a substantial orientation parallel to the interface even with a homeotropic far field, and order parallel to the interface is induced in the flexible polymer phase with both parallel and homeotropic far fields. The computed parameters for the continuum theory of nematic/isotropic interfaces lead to an “easy axis” that is orthogonal to the interface. The interfacial tension for a parallel far field scales linearly with (ε/kBT)1/2S2, where ε is the magnitude of the repulsive interaction between unlike chain segments; similar scaling is not obtained for an orthogonal far field.

Local and segmental dynamics in homopolymer and triblock copolymers with one semicrystalline block.

Thermally stimulated depolarization currents, TSDC, experiments have been performed on a series of poly(styrene)-b-poly(butadiene)-b-poly(epsilon-caprolactone) triblock copolymers SBC with different proportions of the poly(epsilon-caprolactone) crystallizable block, PCL. The morphology of the segregated microphases varies with the PCL content and has been observed by transmission electron microscopy. The crystallinity of the PCL block is estimated by wide angle x-ray scattering, WAXS. The relaxation times distribution is extracted by a numerical decomposition of the TSDC spectra and it is shown that this distribution is not significantly changed on going from the homopolymer to the triblock copolymer with 16 wt % to 77 wt % of PCL in the original samples. Better segregation of the mesophase structure is reached when the samples are annealed at 413 K and important variations in the TSDC and WAXS spectra are observed as a result of the thermal treatment. For the S09B14C77 triblock copolymer the results obtained can be explained by postulating the existence of a rigid amorphous phase in the PCL block. Such rigid amorphous phase is located between the core-shell cylinders formed by the other blocks [with poly(styrene)(PS) as core and poly(butadiene)(PB) as shell] and is constrained by undulated lamellae of crystalline PCL material. In the case of S35B15C50 triblock copolymer, an important amount of diffuse PS-PCL interphase where the homopolymers are mixed must be present before annealing. The results for the material with the less abundant PCL block are explained as a result of the confinement in nanotubes of PCL surrounded by PB embedded in a vitreous PS matrix. Broadband dielectric experiments on these same materials confirm the results obtained by TSDC spectroscopy.

Modulated differential scanning calorimetry: 12. Interphase boundaries and fractal scattering in interpenetrating polymer networks

The morphology of polyurethane (PU)–poly(methyl methacrylate) (PEMA) interpenetrating polymer networks (IPNs) were investigated by means of small-angle X-ray scattering (SAXS) and modulated-temperature differential scanning calorimetry (M-TDSC) techniques. Based on the analysis method employed by Tan et al. [Polymer 1997;38:4571], the interfacial thickness in the IPNs was calculated from SAXS data. The conclusion is that the interfacial thickness is zero and there are sharp domain boundaries in the PU-PEMA IPNs. M-TDSC results show that the PU-PEMA IPNs have a multi-phase morphology with a diffuse interphase region. The M-TDSC results are in agreement with DMTA and TEM findings. The M-TDSC, TEM and DMTA results, therefore, conflict with those obtained from the analysis of the SAXS data. We believe that the analysis method employed by Tan et al. is questionable for IPNs.

Theory of anisotropic growth rates in the ordering of an f.c.c. alloy

A multiple-order-parameter theory of ordering on a binary face-centred-cubic (f.c.c.) crystal lattice is used to model diffuse interphase boundaries and provide expressions for the anisotropy of the kinetic coefficient that characterizes the speed of the order–disorder boundary. The anisotropy is varied parametrically with the ratio of two gradient energy coefficients. In contrast to the results from single-order-parameter theories, the orientation dependence of the kinetic coefficient differs significantly from that of the surface energy. Although the interfacial free energy anisotropy from this model is not strong enough to eliminate any orientations in the (three-dimensional) equilibrium shapes, the kinetic coefficient is sufficiently anisotropic to eliminate some orientations during growth. The long-time kinetic growth shapes show the development of edges and corners in a definite sequence as the anisotropy increases.