Polymer Blend Phase Research Articles

Large-Scale Fabrication of Freestanding Polymer Ultrathin Porous Membranes for Transparent Transwell Coculture Systems.

Advancements in cell coculture systems with porous membranes have facilitated the simulation of human-like in vitro microenvironments for diverse biomedical applications. However, conventional Transwell membranes face limitations in low porosity (ca. 6%) and optical opacity due to their large thickness (ca. 10 μm). In this study, we demonstrated a one-step, large-scale fabrication of freestanding polymer ultrathin porous (PUP) membranes with thicknesses of hundreds of nanometers. PUP membranes were produced by using a gap-controlled bar-coating process combined with polymer blend phase separation. They are 20 times thinner than Transwell membranes, possessing 3-fold higher porosity and exhibiting high transparency. These membranes demonstrate outstanding molecular permeability and significantly reduce the cell-cell distance, thereby facilitating efficient signal exchange pathways between cells. This research enables the establishment of a cutting-edge in vitro cell coculture system, enhancing optical transparency, and streamlining the large-scale manufacturing of porous membranes.

Hierarchically Superstructured Anisotropic Carbon Particles by Multiscale Assembly Driven by Spinodal Decomposition.

Hierarchical superstructures have novel shape-dependent properties, but well-defined anisotropic carbon superstructures with controllable size, shape, and building block dimensionality have rarely been accomplished thus far. Here, a hierarchical assembly technique is presented that uses spinodal decomposition (SD) to synthesize anisotropic oblate particles of mesoporous carbon superstructure (o-MCS) with nanorod arrays by integrating block-copolymer (BCP) self-assembly and polymer-polymer interface behaviors in binary blends. The interaction of major and minor phases in binary polymer blends leads to the formation of an anisotropic oblate particle, and the BCP-rich phase enables ordered packing and unidirectional alignment of carbon nanorods. Consequently, this approach enables precise control over particles' size, shape, and over the dimensionality of their components. Exploiting this functional superstructure, o-MCS are used as an anode material in potassium-ion batteries, and achieve a notable specific capacity of 156mAhg-1 at a current density of 2Ag-1, and long-term stability for 3000 cycles. This work presents a significant advancement in the field of hierarchical superstructures, providing a promising strategy for the design and synthesis of anisotropic carbon materials with controlled properties, offering promising applications in energy storage and beyond.

The potential of near-infrared diffuse reflectance spectroscopy as a tool for characterizing the particle size of dispersion phase in polymer blends

In this study, we investigated the impact of the particle size of dispersion phase in polymer blends on the near-infrared (NIR) diffuse reflectance spectrum. Polypropylene/Polystyrene (PP/PS) blends with different particle sizes of dispersion phase were prepared at the weight ratio of 80/20. When compared to the spectra of the virgin PP, PS, and two-layer sheet of PP-PS, a clear baseline tilt is revealed by the spectrum of the PP/PS blends. By combining the diameter data of the particle size of the PS phase counted by SEM image, the reflectance of the spectrum decreases as the diameter of the particle size of the PS phase increases. In the Monte Carlo simulation results, the number of received scattering photons decreases with an increase in particle size and wavelength respectively, which can well explain the actual spectra variation. The volume mean diameter (Dv) predicted model was built through principal component regression, and the model showed good performance which correlation coefficient (R2) was 0.9532 and root mean square errors of calibration (RMSEC) was 0.2792 μm.

Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

Visualization of Macrophase Separation and Transformation in Immiscible Polymer Blends

A New Approach to Recycling PET Bottles by Blending Polyethylene- Terephthalate and HDPE Using Chemical Reactions in One Step Process

The overall goal of this study is to propose a new approach to simplify the recycling process for producing high quality material from the waste of beverage bottles and other sources at a lower cost by using mechanical recycling and chemical reactions inside injection molding machines in a one-step process. The water and soft drink bottles are made of PET material, while the caps are made mainly of HDPE. The blends of PET and HDPE are incompatible. The resulted material has poor mechanical properties due to the immiscibility of polymer blend components, phase separation, and lack of interfacial adhesion. (HDPE-g-MA) was found to be an excellent reactive compatibilizer for the PET/HDPE blend. For the purpose of investigating the mechanical and morphological properties in this study, blends of rPET and virgin HDPE in weight compositions of 80/20, and 60/40 were modified with concentrations of 2 and 5 wt percent of (HDPE-g-MA). The addition of 4,4-Methylenebis (phenyl isocyanate) and compatiblizer increased the viscosity and molecular weight of the blends while also improving miscibility and interaction bonds between molecules, resulting in a significant reduction in interfacial tension and improved phase dispersion and adhesion via interpenetration and entanglements at the interface. The rPET segments have been grafted onto HDPE backbone chains. Since the crystallinity of HDPE is low, the crystallinity and crystallization temperature of rPET in the blends were reduced. The mechanical characteristics were improved by achieving uniform phase morphology. The main finding of this study is that the immiscible rPET/HDPE materials can be treated and processed in a single step inside the injection molding process. The one-step process is sufficient because it shows high improvement in the mechanical characteristics, while the two-step process, namely the extrusion followed by injection molding, improves fewer mechanical characteristics and is more expensive.

Polymer blends with ordered distribution of conductive filler

This review highlight approaches to the formation of an ordered distribution of conductive filler in polymer blends. This distribution leads to a significant decrease of the percolation threshold in the polymer mixture, i.e. to a decrease in the critical concentration of the filler, at which the transition of the system from a non-conductive to a conductive state occurs. This improves the mechanical properties of the composition and its processability. It is shown that the ordered structure of the filler is formed in the polymer blend upon mixing the components in the melt under the action of three factors - thermodynamic (the ratio between the values of the interfacial tension of the filler-polymer A and filler-polymer B, as well as between polymers A and B), kinetic (the ratio between viscosities of polymer components A and B) and technological (the intensity and temperature of processing, as well as the order of introduction of a filler into a heterogeneous polymer matrix, which can enhance or suppress the effect of thermodynamic or kinetic factors). On the example of the works performed by the author on mixtures of thermoplastics filled with electrically conductive carbon fillers such as carbon black and carbon nanotubes, as well as a metal filler - dispersed iron, with the involvement of literature data on filled polymer blends, the influence of each of the factors on the formation of an ordered structure of the conducting phase in polymer blends is shown.

Novel Structure to Improve Mechanical Properties of Polymer Blends: Multilayered Ribbons

Ribbon-like dispersed phase in polymer blends can provide excellent mechanical properties for the matrix, compared with the fibrillar or spherical dispersed phase. However, it is difficult to contr...

One-pot fabrication of polymer micro/nano-discs via phase separation and a roll-to-roll coating process

Disc-shaped particles are one of the unique and promising shapes that can improve adhesion to interfaces and can function as the key feature in various applications; e.g. injectable drug carriers. However, most of these methods include the shape deformation process from spheres to discs using various external stimuli or require multiple processing steps, which is complicated and has limitations in terms of continuous fabrication. We herein propose a novel method combining polymer blend phase separation and a roll-to-roll coating process to continuously fabricate polymer micro/nano-discs in a one-pot manner on a large-scale. The evaporation of solvent during a roll-to-roll coating process encourages the formation of homogenous island-like domains composed of the minor component dispersed in a matrix of the major component on a water-soluble polyvinyl alcohol (PVA) film. In fact, polyvinylpyrrolidone (PVP) was chosen as the major component since it dissolves in both water and chloroform. Another polymer, polystyrene (PS), as a minor component was dissolved in chloroform with PVP. A PVP and PVA matrix film can be easily washed out by water, and micro/nano-discs of the PS minor component can be obtained in a one-pot manner. This method is shown to be capable of continuously fabricating PS micro/nano-discs at a very high rate of ∼108 particles/min. The effects of fabrication conditions, such as the blend ratio and total polymer concentration on the dimensions of the PS discs were investigated, and a maximum aspect ratio (ratio between diameter and thickness) of 6.3 (diameter ∼830 nm, thickness ∼130 nm) was demonstrated. The method proposed in this study could provide a straightforward and time-saving way to continuously fabricate micro/nano-discs via polymer phase separation and a roll-to-roll coating process.

Direct visualization of the nanoscopic three‐phase structure and stiffness of NBR/PVC blends by AFM nanomechanical mapping

ABSTRACTThe PeakForce Quantitative Nanomechanical Mapping based on atomic force microscope (AFM) is employed to first visualize and then quantify the elastic properties of a model nitrile rubber/poly(vinyl chloride) (NBR/PVC) blend at the nanoscale. This method allows us to consistently observe the changes in mechanical properties of each phase in polymer blends. Beyond measuring and discriminating elastic modulus and adhesion forces of each phase, we tune the AFM tips and the peak force parameters in order to reliably image samples. In view of viscoelastic difference in each phase, a three‐phase coexistence of an unmixed NBR phase, the mixed phase, and PVC microcrystallites is directly visualized in NBR/PVC blends. The nanomechanical investigation is also capable of recognizing the crosslinked rubber phase in cured rubber. The contribution of the mixed phase was quantified and it was found that the mechanical properties of blends are mainly determined by the homogeneity and stiffness of the mixed phase. This study furthers our understanding the structure–mechanical property relationship of thermoplastic elastomers, which is important for their potential design and applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 662–669

Catalyst driven preferential growth of in-situ generated nanosilica particles in the phases of incompatible polymer blend and its effect on physico-mechanical properties

Selectively localizing nanofillers in a particular phase of polymer blend to achieve required properties are hardly possible. Herein, an approach to solve the above mentioned problem is reported by exploring the effect of catalyst in preferentially growing in-situ generated nanosilica particles in the phases of incompatible natural rubber (NR): carboxylated nitrile rubber (XNBR) (50:50) blend. In-situ generated nanosilica particles prepared using tetraethylorthosilane (TEOS) as silica precursor and n-butylamine (nBA) as catalyst preferentially grow in the dispersed non polar NR phase (due to the hydrophobic nature of the silica particles) and ultimately leads to significant enhancement in the blend properties. On the other hand, in-situ generated nanosilica particles prepared using TEOS as silica precursor and hydrochloric acid (HCl) as catalyst preferentially grow in the continuous polar XNBR phase (due to the hydrophilic nature of the silica particles) and ultimately does not increase the blend properties to a greater extent.

A comparison study of high shear force and compatibilizer on the phase morphologies and properties of polypropylene/polylactide (PP/PLA) blends

Exerting high shear force and adding compatilizer are two different methods used for regulating the size of dispersed phase of polymer blends. Nevertheless, the comparison of the effect of the high shear force and adding compatilizer on the phase morphologyies and properties is less studied, not to mention the synergistic effect. In this work, the incompatible PP/PLA binary blends with large polarity differences were prepared using high-shear processing, compared with the effect of adding ethylene-(methyl acrylate)-(glycidyl methacrylate) (EMA-GMA) as reactive compatibilizer for PP/PLA blends. It was found that adding compatilizer under relative low shear force was more efficient on improving the interface, showing blurred boundaries, compared with the reduction of the dispersed phase size under high shear force without compatilizer. As a result, the blends with the compatilizer presented a higher elongation at break; yet the yield strength of the binary blends prepared under high shear force was higher than that of the ternary blends. Furthermore, the synergistic effect of adding compatibilizer and high shear force was limited, which could be attributed to the fact that the degree of reactive compatibilization had already reached saturation under the rotation speed of 100 rpm due to the high efficiency of EMA-GMA.

Understanding the Molecular Weight Dependence of χ and the Effect of Dispersity on Polymer Blend Phase Diagrams

Gibbs ensemble Monte Carlo simulations and cloud point measurements were performed to understand the molecular weight dependence of χ and the effect of dispersity on the phase behavior of polymer mixtures. Oligomeric blends consisting of poly(ethylene-alt-propylene) (PEP) and poly(ethylene oxide) dimethyl ether (PEO) were used as the model systems. First, the molecular weight dependence of χ for PEP/PEO mixtures was studied using simulations and experiments for PEP/PEO mixtures with various molecular weights. An empirical model with a single adjustable parameter kij is used to quantify this molecular weight dependence, and it allows for the accurate prediction of χ of PEP/PEO mixtures with arbitrary molecular weights. Second, the effects of molecular weight distribution (MWD) and dispersity (Đ) of PEO on the PEP/PEO phase diagram were investigated via both simulations and experiments. When PEO is relatively monodisperse (Đ < 1.2), the phase diagram is found to be insensitive to either MWD or Đ, despite di...

About the Art and Science of Visualizing Polymer Morphology using Transmission Electron Microscopy

AbstractTransmission electron microscopy (TEM) is a unique tool to visualize polymer morphology: an intimate organization of the matter, encompassing crystalline features in semicrystalline polymers and a kaleidoscopic collection of patterns produced by microseparated phases in polymer blends. This manuscript aims at demonstrating the various opportunities this technique enables, through a miscellany of studies performed in our laboratory. Materials as different as bulk and composite compounds, thin films, hollow fiber membranes, and rubbers are presented, from the viewpoint of the interrelation of TEM with other techniques like scattering, mechanical, and thermomechanical experiments.

Elongated phase separation domains in spin-cast polymer blend thin films characterized using a panoramic image.

Polymer thin films with micro/nano-structures can be prepared by a solvent evaporation induced phase separation process via spin-casting a polymer blend, where the elongated phase separation domains are always inevitable. The striation defect, as a thickness nonunifomity in spin-cast films, is generally coexistent with the elongated domains. Herein, the morphologies of polymer blend thin films are recorded from the spin-cast center to the edge in a panoramic view. The elongated domains are inclined to appear at the ridge regions of striations with increasing radial distance and align radially, exhibiting a coupling between the phase separation morphology and the striation defect that may exist. We demonstrate that the formation of elongated domains is not attributed to shape deformation, but is accomplished in situ. A possible model to describe the initiation and evolution of the polymer blend phase separation morphology during spin-casting is proposed.

Charge carrier trapping controlled by polymer blend phase dynamics

Blend phase composition governs electron trapping in insulator:semiconducting polymer mixtures used in organic light-emitting diodes.

Assembling copper nanowires at the interface and in discrete phases in PLA-based polymer blends

This work examines the effects of kinetic parameters on the assembly of copper nanowires (CuNWs) in discrete phases and at the interface in two distinct blend systems: a high interfacial tension blend of poly(lactic acid), PLA, /low density polyethylene (LDPE) and a low interfacial tension blend of PLA/poly(butylene adipate-co-terephthalate), PBAT. CuNWs were synthesized through electrodeposition in a porous alumina oxide template. Considering the surface polarity of polymer melts and the hydrophilicity of the surface of CuNWs, the particles should be located in the more polar phase (PLA in PLA/LDPE or PBAT in PLA/PBAT). TEM images confirm that when CuNWs are initially premixed with the more polar phase, they remain in that phase in a stable fashion irrespective of the interfacial tension of the system. However, when the particles are premixed with the less polar phase, to investigate kinetic effects, different behaviors are observed; in PLA/LDPE blends, CuNWs partition between both phases, while in PLA/PBAT blends, CuNWs assemble at the interface and in the less polar PLA phase. The effects of mixing time and shear rate on these phenomena are examined, and importantly, for the low interfacial tension PLA/PBAT blend, it is shown that CuNWs can be assembled in a stable fashion at the interface. The mechanism of interfacial assembly of these cylindrically shaped CuNWs in PLA/PBAT is the result of enhanced bulk migration in the less polar PLA phase and slow migration rate across the interface.

Confined Pattern-Directed Assembly of Polymer-Grafted Nanoparticles in a Phase Separating Blend with a Homopolymer Matrix.

The controlled organization of nanoparticle (NP) constituents into superstructures of well-defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. We show that the phase separation of polymer-tethered nanoparticles immersed in a chemically different polymer matrix provides an effective and scalable method for fabricating defined submicron-sized amorphous NP domains in melt polymer thin films. We investigate this phenomenon with a view towards understanding and controlling the phase separation process through directed nanoparticle assembly. In particular, we consider isothermally annealed thin films of polystyrene-grafted gold nanoparticles (AuPS) dispersed in a poly(methyl methacrylate) (PMMA) matrix. Classic binary polymer blend phase separation related morphology transitions, from discrete AuPS domains to bicontinuous to inverse domain structure with increasing nanoparticle composition is observed, yet the kinetics of the AuPS/PMMA polymer blends system exhibit unique features compared to the parent PS/PMMA homopolymer blend. We further illustrate how to pattern-align the phase-separated AuPS nanoparticle domain shape, size and location through the imposition of a simple and novel external symmetry-breaking perturbation via soft-lithography. Specifically, submicron-sized topographically patterned elastomer confinement is introduced to direct the nanoparticles into kinetically controlled long-range ordered domains, having a dense yet well-dispersed distribution of non-crystallizing nanoparticles. The simplicity, versatility and roll-to-roll adaptability of this novel method for controlled nanoparticle assembly should make it useful in creating desirable patterned nanoparticle domains for a variety of functional materials and applications.

Influences of the Viscosity Ratio and Processing Conditions on the Formation of Highly Oriented Ribbons in Polymer Blends by Tape Extrusion

The deformation of the dispersed phase in polymer blends by tape extrusion was studied systematically under different processing conditions and viscosity ratios of the dispersed phase to the matrix. During tape extrusion, the spherical dispersed phases were first elongated into rotational ellipsoidal or rodlike shapes and then merged to form longer and even endless microfibrils by coalescence, which were eventually squeezed into highly oriented ribbons. The speed of two running rollers has a large effect on the morphology development of the dispersed phase. With an increase of the roller surface speed, the stretching and squeezing forces increased dramatically. As a result, the dispersed phase gradually deformed from spherical to ellipsoidal, fibrous, and ribbonlike shapes. More interestingly, the tensile strength of the obtained blend film with highly oriented ribbons increased significantly as well. The viscosity ratio of the dispersed phase to the matrix is another important factor influencing the form...

Matrix-fibril morphology development of polypropylene/poly(butylenes terephthalate) blend fibers at different zones of melt spinning process and its relation to mechanical properties

Different shapes of dispersed phase such as sphere, laminar and fibrillar can form in the matrix phase of polymer blends. Production of blend fibers in melt spinning process can result more effective in fibrillar phase morphology formation than in other processes. In this research, the matrix-fibril morphology development during the melt spinning of polypropylene/poly(butylenes terephthalate) was studied. The shapes of blend dispersed phase collected from different zones of the melt spinning line were evaluated by scanning electron micrographs (SEM) and rheological mechanical spectra (RMS). The results showed that fibrillar shape could not be created in the PP/PBT blend fiber samples exited from the spinneret orifice (gravity spun fibers) at low contents (5 percent) of the PBT dispersed phase. However, a complete fibrillar structure was formed in all the as-spun PP/PBT blend fiber samples (melt drawn). The rheological evaluations confirmed a network structure resulting from fibril formation for the samples with high contents (20–40 %) of the PBT dispersed phase and the formation of spherical shape with low contents (5–10 %) of the PBT dispersed phase in matrix of the blend fibers. It was observed that the flow fields of processing zones and blend ratio, in producing the blend fibers, have intensive effects on morphological variations; besides there was a strong relation between the mechanical and morphological properties.

마이크로 채널을 흐르는 PS/PP 블렌드의 유변학적 특성에 관한 연구

이 논문에서는 미세한 통로를 흐르는 고분자 블렌드의 유변학적 특성에 관하여 연구하였다. 우선 두께가 각각 0.1, 0.2 0.5 mm 인 세 종류의 슬릿 다이를 제작하였고 특수 제작한 피스톤을 부착한 모세관 점도계로 고분자 블렌드의 점도 거동을 관찰하였다. 관찰 결과 상구조가 해도 구조를 가지는 경우 고분자 블렌드의 점도는 다이의 크기에 의존하지 않음을 알 수 있었다. 그러나 상구조가 co-continuous 구조를 가지는 경우에는 점도가 다이의 크기에 의존함을 관찰하였는데, 몇몇 부가 실험 결과 이는 각 상 간의 미끄러짐이 원인임을 알 수 있었다. In this paper, rheological property of polymer blends in a confined geometry was investigated. The shear viscosity was measured in a capillary rheometer incorporated with a specially designed piston and three slit dies having 0.1, 0.2 and 0.5 mm in thickness. It was observed that the viscosity of polymer blends does not depend on the die size when the phase of polymer blends is a sea-island structure. However, when the phase of polymer blends is a co-continuous structure, the viscosity of the blends was dependent on the die size. By additional investigations, this result is attributed to the slip phenomenon between polymer phases in the blends.