Range Of Polymer Concentrations Research Articles

Drag reduction assisted emulsification in a micro-channel

An experimental study of the turbulent dynamics of emulsification in a cross-slot microfluidic device is presented. The continuous phase contains a minute amount of an inelastic polymer (xanthan). The Reynolds numbers are sufficiently large (up to 16000) so the drag reduction phenomenon is observed during the emulsification process. The statistics of droplet sizes in the resulting emulsions are measured ex-situ by means of digital microscopy in a wide range of Reynolds numbers and polymer concentrations in the continuous phase. Integral measurements of the statistics of the pressure drops in the micro-channel allow one to systematically map the drag reduction states. Corresponding to each state, the space–time dynamics of the emulsification process are assessed by means of in-situ high speed imaging of the interface between the two fluids which further allows one to extract the characteristic time and space scales associated to the dynamics of the interface. Various dynamic regimes of the microscopic emulsification process are mapped in terms of the Reynolds number and shear thinning rheology of the continuous phase.

Diblock bottlebrush polymer in a non-polar medium: Self-assembly, surface forces, and superlubricity

Whilst bottlebrush polymers have been studied in aqueous media for their conjectured role in biolubrication, surface forces and friction mediated by bottlebrush polymers in non-polar media have not been previously reported. Here, small-angle neutron scattering (SANS) showed that a diblock bottlebrush copolymer (oligoethyleneglycol acrylate/ethylhexyl acrylate; OEGA/EHA) formed spherical core–shell aggregates in n-dodecane (a model oil) in the polymer concentration range 0.1–2.0 wt%, with a radius of gyration Rg ∼ 7 nm, comprising 40–65 polymer molecules per aggregate. The surface force apparatus (SFA) measurements revealed purely repulsive forces between surfaces bearing inhomogeneous polymer layers of thickness L ∼ 13–23 nm, attributed to adsorption of a mixture of polymer chains and surface-deformed micelles. Despite the surface inhomogeneity, the polymer layers could mediate effective lubrication, demonstrating superlubricity with the friction coefficient as low as µ ∼ 0.003. The analysis of velocity-dependence of friction using the Eyring model shed light on the mechanism of the frictional process. That is, the friction mediation was consistent with the presence of nanoscopic surface aggregates, with possible contributions from a gel-like network formed by the polymer chains on the surface. These unprecedented results, correlating self-assembled polymer micelle structure with the surface forces and friction the polymer layers mediate, highlight the potential of polymers with the diblock bottlebrush architecture widespread in biological living systems, in tailoring desired surface interactions in non-polar media.

Factors That Influence Base-Catalyzed Thiol-Ene Hydrogel Synthesis.

Injectable, localized drug delivery using hydrogels made from ethoxylated trimethylolpropane tri-3-mercaptopropionate (ETTMP) and poly(ethylene glycol) diacrylate (PEGDA) has shown great potential due to these hydrogels' ability to exhibit non-swelling behavior and tunable drug release properties. However, current synthesis methods in the literature suffer from poor ETTMP solubility in water, slow gelation times exceeding 20 min, and a lack of reproducibility. To address these limitations, we have developed a reliable synthesis procedure and conducted a sensitivity analysis of key variables. This has enabled us to synthesize ETTMP-PEGDA hydrogels in a polymer concentration range of 15 to 90 wt% with gelation times of less than 2 min and moduli ranging from 3.5 to 190 kPa. We overcame two synthesis limitations by identifying the impact of residual mercaptopropionic acid and alumina purification column height on gelation time and by premixing ETTMP and PEGDA to overcome low ETTMP solubility in water. Our ETTMP-PEGDA mixture can be stored at -20 °C for up to 2 months without crosslinking, allowing easy storage and shipment. These and previous results demonstrate the potential of ETTMP-PEGDA hydrogels as promising candidates for injectable, localized drug delivery with tunable drug release properties.

Physics-Based and Data-Driven Polymer Rheology Model

Summary Polymer flooding is a common enhanced oil recovery (EOR) method used to increase aqueous phase sweep efficiency by increasing viscosity. Estimating polymer viscosity for given reservoir conditions (i.e., oil viscosity, temperature, and brine composition) requires intensive laboratory work. There are existing empirical models to estimate polymer bulk rheology without prior laboratory work; however, they have many coefficients, simple brine composition, and lack physics-based regression boundaries. This study benchmarks the existing polymer empirical and machine learning (ML) models against a new data-driven model with some physics basis for common synthetic polymers. We cover a broad range of polymer concentrations, temperature, salinity, and hardness with an upper limit of 5,000 ppm, 120℃, 290,000 ppm, and 33,000 ppm, respectively. The data were preprocessed through data analytics techniques, and a model was developed with some physics basis by fitting Martin’s equation for Carreau model coefficients. Our regression boundaries obey flexible polymers’ physical and laboratory behavior. We benchmarked the bulk rheological model with existing models in the literature. We used the published models’ coefficients and then tuned their coefficients for our data set for a fair comparison. We then investigated ML as a predictive tool without compromising overfitting the data using the simplest ML model (linear regression) all the way to artificial neural network (ANN) and hybrid ML models. This is the first study that comprehensively benchmarks polymer rheology models and proposes a simple, least number of coefficients, and tunable polymer-rheology model. We provide a predictive bulk rheology model that enables the user to accurately predict polymer viscosity without laboratory measurements and for a wide range of temperatures and brine compositions. Moreover, our study includes the recently common polymer SAV-10 that was not previously studied. We present a simple water viscosity model for a broad brine salinity and temperature range. Our study shows that ML techniques might provide deceptively high accuracy for small data sets, unless due diligence is done to avoid a high-variance model.

Optimization of surfactant-polymer formulations for improving oil production

This study investigated the optimal concentration of an anionic surfactant (APA-H1) and a sulfonated polyacrylamide (SPAM-A5) formulation for SP flooding at high temperature high salinity conditions. IFT, viscosity and oil production rate in micromodel tests of the formulation were evaluated from 200 to 2000 ppm in high salinity water at 90 °C. Results showed by injecting 1000 ppm APA-H1 and 1,500 ppm SPAM-A5 with ∼10−4 mN/m IFT and 5.4 cP viscosity, the highest incremental oil production was 27%, which were not improved by increasing chemical concentrations. The work reveals there exists an optimal range of surfactant polymer concentrations in SP flooding.

Structure and Intermolecular Interactions in Aqueous Solutions of Polyethylene Glycol.

Aqueous solutions of polyethylene glycol are studied by small-angle neutron scattering over a broad range of polymer molecular masses and concentrations. The scattering data were modeled by a Gaussian chain form factor combined with random phase approximation, which provided good fits over the whole studied concentration range. The results showed that polyethylene glycol in the molecular mass range –20 kDa in water at physiological temperature T = 37 C behaves like a random coil in nearly theta solvent conditions. The obtained results serve as a reference for the description of complex mixtures with PEG used in various applications.

Antibacterial Hydrogels Derived from Poly(γ-glutamic acid) Nanofibers.

Biocompatible hydrogels with antibacterial properties derived from γ-polyglutamic acid (γ-PGA) were prepared from bulk and electrospun nanofibers. The antibacterial drugs loaded in these hydrogels were triclosan (TCS), chlorhexidine (CHX) and polyhexamethylene biguanide (PHMB); furthermore, bacteriophages were loaded as an alternative antibacterial agent. Continuous and regular γ-PGA nanofibers were successfully obtained by the electrospinning of trifluoroacetic acid solutions in a narrow polymer concentration range and restricted parameter values of flow rate, voltage and needle-collector distance. Hydrogels were successfully obtained by using cystamine as a crosslinking agent following previous published procedures. A closed pore structure was characteristic of bulk hydrogels, whereas an open but structurally consistent structure was found in the electrospun hydrogels. In this case, the morphology of the electrospun nanofibers was drastically modified after the crosslinking reaction, increasing their diameter and surface roughness according to the amount of the added crosslinker. The release of TCS, CHX, PHMB and bacteriophages was evaluated for the different samples, being results dependent on the hydrophobicity of the selected medium and the percentage of the added cystamine. A high efficiency of hydrogels to load bacteriophages and preserve their bactericide activity was demonstrated too.

Understanding the self-assembly of the polymeric drug solubilizer Soluplus®

HypothesisSoluplus® is one of the most widely used amphiphilic copolymers in drug delivery and has been reported to strongly enhance the adsorption of model drugs. However, there is still a limited understanding of its micellar behavior as it responds to the different routes of administration, which involve important changes in concentration. ExperimentsThe microstructure of Soluplus aqueous solutions has been investigated at a wide range of polymer concentrations (2 × 10−6 – 0.2 g/mL) by a combination of diffusion NMR (dNMR), small angle X-ray scattering (SAXS), static (SLS) dynamic (DLS) light scattering and viscosity measurements. These techniques have been coupled with surface tension measurements to frame the polymer’s critical micellar concentration (cmc). FindingsWe demonstrate the presence at all tested concentrations of two forms of Soluplus, with hydrodynamic radii of 3 and 26 nm, where the fraction of smaller objects accounts for as much as 60–70%. dNMR, SAXS, DLS and SLS indicate that Soluplus spontaneously self-assembles into large spherical particles with a core-shell structure. However, self-assembly takes place three orders of magnitude above the cmc evaluated via surface tension measurements. Instead of the traditional cooperative micellization process, we propose a thermal-activated isodesmic self-assembly of the small aggregates into core-shell micelles.

Dual Transient Networks of Polymer and Micellar Chains: Structure and Viscoelastic Synergy.

Dual transient networks were prepared by mixing highly charged long wormlike micelles of surfactants with polysaccharide chains of hydroxypropyl guar above the entanglement concentration for each of the components. The wormlike micelles were composed of two oppositely charged surfactants potassium oleate and n-octyltrimethylammonium bromide with a large excess of anionic surfactant. The system is macroscopically homogeneous over a wide range of polymer and surfactant concentrations, which is attributed to a stabilizing effect of surfactants counterions that try to occupy as much volume as possible in order to gain in translational entropy. At the same time, by small-angle neutron scattering (SANS) combined with ultrasmall-angle neutron scattering (USANS), a microphase separation with the formation of polymer-rich and surfactant-rich domains was detected. Rheological studies in the linear viscoelastic regime revealed a synergistic 180-fold enhancement of viscosity and 65-fold increase of the longest relaxation time in comparison with the individual components. This effect was attributed to the local increase in concentration of both components trying to avoid contact with each other, which makes the micelles longer and increases the number of intermicellar and interpolymer entanglements. The enhanced rheological properties of this novel system based on industrially important polymer hold great potential for applications in personal care products, oil recovery and many other fields.

Monodisperse droplets and particles by efficient neutralization of electrosprays

We present a new approach for micro- and nanoparticle production by in-situ charge reduction of electrospray droplets, which prevents their Coulombic instabilities and allow the efficient transport (extraction) of the particles. A unipolar ion source based on corona discharge generates a controllable ion flux of opposite polarity to the electrospray. The ions are introduced axially into the spray, while the Taylor cone is screened from the ions by an extractor ring electrode. Efficient and steady droplet discharge and extraction through an orthogonal aerosol-extraction tube was attained when the inlet of the tube was near the spray emission and the ring electrode, resulting in dramatic changes in droplets’ trajectories. The best extraction conditions (highest filter collections) were associated with the best discharging (lowest residual electrical charge) and the most globular particles. The size distributions on the particles collected on the filters were monomodal and homogeneous, with small relative standard deviations (as small as 10.6%). The use of corona ions significantly expands the range of polymer concentrations over which globular particles with monomodal size distribution can be made by electrospray.

The Effect of Biopolymer Chitosan on the Rheology and Stability of Na-Bentonite Drilling Mud.

The utilization of greens resources is a grand challenge for this century. A lot of efforts are paid to substitute toxic ingredients of the conventional drilling mud system with nontoxic natural materials. In this paper, the effect of the natural polymer chitosan on the rheology and stability of sodium-bentonite drilling mud was investigated in the polymer concentration range of 0.1–3.0 wt.%. Both the shear and time dependent rheological properties of pure chitosan, pure bentonite and bentonite–chitosan dispersions were studied. Moreover, zeta potential measurements were used to evaluate the stability of bentonite-chitosan suspension. Adding chitosan improved the natural properties of drilling mud, namely: yield stress, shear thinning, and thixotropy. The viscosity of bentonite suspension increased significantly upon the addition of chitosan in the concentration range of 0.5 to 3.0 wt.% forming network structure, which can be attributed to the interactions of hydrogen bonding between -OH clusters on the bentonite surface with the NH group in the chitosan structure. On the other hand, dispersed chitosan–bentonite suspension was observed at low chitosan concentration (less than 0.5 wt.%). Increasing both bentonite and chitosan concentrations led to the flocculation of the bentonite suspension, forming a continuous gel structure that was characterized by noteworthy yield stress. The desired drilling mud rheological behavior can be obtained with less bentonite by adding chitosan polymer and the undesirable effects of high solid clay concentration can be avoided.

Poroviscoelasticity and compression-softening of agarose hydrogels

Agarose hydrogels are poroviscoelastic materials that exhibit a waterlogged-crosslinked microstructure. Despite an extensive use in biotechnologies and numerous studies of the elastic properties of agarose gels, little is known about the compressible behavior and the microstructural changes of such fibrillar hydrogels under compression. The present work investigates the mechanical response of centimeter-sized pre-molded agarose cylinders when applying a compressive strain ramp over an extended range of loading speed and polymer concentration. One of the original contributions is the simultaneous monitoring of the changes in the hydrogel volume to determine the Poisson’s ratio through a spatiotemporal method. The linear poroelastic response of agarose hydrogels shows a compressible behavior at strain rates less than 0.7 % s−1. The critical compressive strain of a few percent at the onset of the non-linear regime and the always positive Poisson’s ratio decrease when applying a slow compressive ramp. The mechanical response in the linear regime is typical of a deformation mode either dominated by the bending of semiflexible strands (enthalpic regime) or by the stretching of the network (entropic regime) at higher agarose concentration. Cyclic linear shear deformations superimposed to a compressive strain from 0.5 up to 40% further give evidence of a compression-softening of the network causing the transition to the non-linear regime without dependence upon the network topology and connectivity. Finally, the buckling-induced aging of the network under a weak compression and the poroviscoelasticity of the hydrogel are shown to impact the relaxation of the normal stress and the equilibrium stress.

Experimental Measurements of Thermal Conductivity for Non-Newtonian Polymeric Fluids Using a Concentric Cylindrical Cell Under Static Conditions

In the current article, the experimental measurement of thermal conductivities for non-Newtonian polymeric fluids has been performed over a wide range of polymer concentrations. Measurements of the thermal conductivity for three Newtonian fluids and three different groups of non-Newtonian polymeric aqueous fluids (twenty-four polymeric solutions) under static conditions are conducted using the cell of concentric cylinders with the annular gap of 0.4 mm. Various polymer concentrations ranged from 100 ppm to 5000 ppm by weight are implemented in the experiments with temperature changed from 20 °C to 50 °C. Accordingly, the impact of relevant non-Newtonian fluid parameters, such as polymer concentrations, polymer types and molecular weights as well as the kind of solvents on the thermal conductivity of non-Newtonian fluids were systematically tested. The experimental results of thermal conductivity for the Newtonian fluids (distilled water, 50 % methanol-50 % water and 50 % glycerin-50 % water) are in a reasonable agreement with the previously published data with the differences always being less than 4.5 %. Moreover, thermal conductivities of non-Newtonian polymeric solutions are approximately the same values of Newtonian fluids with the corresponding temperatures under rest condition and any fluctuation in the measured data is within the permissible error uncertainty. Although, the addition of polymeric particles has the ability to turn the state of the fluid from Newtonian to non-Newtonian, there is no noteworthy influence on the thermal conductivity of these non-Newtonian fluids.

Cylindrical confinement of solutions containing semiflexible macromolecules: surface-induced nematic order versus phase separation.

Solutions of semiflexible polymers confined in cylindrical pores with repulsive walls are studied by Molecular Dynamics simulations for a wide range of polymer concentrations. Both the case where both lengths are of the same order and the case when the persistence length by far exceeds the contour length are considered, and the enhancement of nematic order along the cylinder axis is characterized. With increasing density the character of the surface effect changes from depletion to the formation of a layered structure. For binary 50 : 50 mixtures of the two types of polymers an interplay between surface enrichment of the stiffer component and the isotropic-nematic transition is found, and a phase separated structure with cylindrical symmetry occurs, with the isotropic phase located around the cylinder axis. For melt densities the mixed nematic phase forms at the wall a layer with a screw-like structure of a tilted smectic phase. The observed behavior is tentatively interpreted in terms of the competition of the chain orientational entropy with entropy of mixing and excluded volume due to the wall.

Large-Grained Cylindrical Block Copolymer Morphologies by One-Step Room-Temperature Casting.

We report a facile method of ordering block copolymer (BCP) morphologies in which the conventional two-step casting and annealing steps are replaced by a single-step process where microphase separation and grain coarsening are seamlessly integrated within the casting protocol. This is achieved by slowing down solvent evaporation during casting by introducing a nonvolatile solvent into the BCP casting solution that effectively prolongs the duration of the grain-growth phase. We demonstrate the utility of this solvent evaporation annealing (SEA) method by producing well-ordered large-molecular-weight BCP thin films in a total processing time shorter than 3 min without resorting to any extra laboratory equipment other than a basic casting device, i.e., spin- or blade-coater. By analyzing the morphologies of the quenched samples, we identify a relatively narrow range of polymer concentration in the wet film, just above the order–disorder concentration, to be critical for obtaining large-grained morphologies. This finding is corroborated by the analysis of the grain-growth kinetics of horizontally oriented cylindrical domains where relatively large growth exponents (1/2) are observed, indicative of a more rapid defect-annihilation mechanism in the concentrated BCP solution than in thermally annealed BCP melts. Furthermore, the analysis of temperature-resolved kinetics data allows us to calculate the Arrhenius activation energy of the grain coarsening in this one-step BCP ordering process.

Ficoll as testing material for diffusion weighted imaging-quality assurance phantoms

PurposeThe aim of this work is to test the use of aqueous solutions of Ficoll®**, a highly branched polymer displaying crowding properties, to build a phantom suitable for Diffusion Weighted Imaging (DWI) in Magnetic Resonance Imaging (MRI). MethodsWe developed a test object made of a cylindrical plastic container with a precise geometrical arrangement suitable for measuring several samples at the same time. The container was designed to host single vials with variable geometry and number, and to fit inside common commercial head coils for MRI scanners.In our experiments, vials were filled with 8 aqueous solutions of Ficoll 70 and Ficoll 400 spanning a range of polymer concentration from 5 to 30% by weight. Vials containing ultra-pure water were also used as reference. Experiments were performed on both 1.5 and 3 T clinical scanners (GE, Philips and Siemens), under the conditions of a standard clinical examination. ResultsThe geometry of the phantom provided reduced imaging artifacts, especially image distortions at magnetic interfaces. We found that the Apparent Diffusion Coefficient (ADC) varied in the range of 0.00125–0.00223 mm2/s and decreased with Ficoll concentration. ADC vs Ficoll concentration exhibited a linear trend. Results were consistent over time and among different MRI clinical scanners, showing an average variability of 3% at 1.5 T and of 7.5% at 3 T. Moreover, no substantial difference was found between Ficoll 70 and 400. By varying Ficoll concentration, ADC can be modulated to approach tissue-mimicking values. Preliminary results for relaxation measurements proved that both T1 and T2 decreased with Ficoll concentration in the ranges 1.3–2.4 s and 150–800 ms respectively. ConclusionsIn this work, we propose a 3D phantom design based on the widespread crowding agent Ficoll, which is suitable for DWI quality assurance purposes in MRI acquisitions. Aqueous Ficoll solutions provide good performance in terms of stability, ease of preparation, and safety.

Phase Diagram for Ideal Diblock-Copolymer Micelles Compared to Polymerization-Induced Self Assembly.

In this work we constructed a detailed phase diagram for the solutions of ideal diblock-copolymers and compared such diagram with that obtained during polymerization-induced self-assembly (PISA); a wide range of polymer concentrations as well as chain compositions was studied. As the length of the solvophobic block nB increases (the length of the solvophilic block nA was fixed), the transition from spherical micelles to cylinders and further to vesicles (lamellae) occurs. We observed a rather wide transition region between the spherical and cylindrical morphology in which the system contains a mixture of spheres and short cylinders, which appear to be in dynamic equilibrium; the transition between the cylinders and vesicles was found to be rather sharp. Next, upon increasing the polymer concentration in the system, the transition region between the spheres and cylinders shifts towards lower nB/nA values; a similar shift but with less magnitude was observed for the transition between the cylinders and vesicles. Such behavior was attributed to the increased number of contacts between the micelles at higher polymer volume concentrations. We also found that the width of the stability region of the cylindrical micelles for small polymer volume concentrations is in good quantitative agreement with the predictions of analytical theory. The obtained phase diagram for PISA was similar to the case of presynthesized diblock copolymer; however, the positions of the transition lines for PISA are slightly shifted towards higher nB/nA values in comparison to the presynthesized diblock copolymers, which is more pronounced for the case of the cylinders-to-vesicles transition. We believe that the reason for such behavior is the polydispersity of the core-forming blocks: The presence of the short and long blocks being located at the micelle interface and in its center, respectively, helps to reduce the entropy losses due to the insoluble block stretching, which leads to the increased stability of more curved micelles.

Quantification of Visco-Elastic Properties of a Matrigel for Organoid Development as a Function of Polymer Concentration

The biophysical properties of polymer based gels, for instance the commonly used Matrigel, crucially depend on polymer concentration. Only certain polymer concentrations will produce a gel optimal for a specific purpose, for instance for organoid development. Hence, in order to design a polymer scaffold for a specific purpose, it is important to know which properties are optimal and to control the biophysical properties of the scaffold. Using optical tweezers, we perform a biophysical characterization of the biologically relevant Matrigel while systematically varying the polymer concentration. Using the focused laser beam we trace and spectrally analyze the thermal fluctuations of an inert tracer particle. From this, the visco-elastic properties of the Matrigel is quantified in a wide frequency range through scaling analysis of the frequency power spectrum as well as by calculating the complex shear modulus. The viscoelastic properties of the Matrigel are monitored over a timespan of seven hours. At all concentrations, the Matrigel is found to be more fluid-like just after formation and to become more solid-like during time, settling to a constant state after 1-3 hours. Also, the Matrigel is found to display increasingly more solid-like properties with increasing polymer concentration. To demonstrate the biological relevance of these results, we expand pancreatic organoids in Matrigel solutions with the same polymer concentration range and demonstrate how the polymer concentration influences organoid development. In addition to providing quantitative information about how polymer gels change visco-elastic properties as a function of polymer concentration and time, these results also serve to guide the search of novel matrices relevant for organoid development or 3D cell culturing, and to ensure reproducibility of bio-relevant Matrigels.

High-Strain-Rate Behavior of a Viscoelastic Gel Under High-Velocity Microparticle Impact

Impact experiments, routinely performed at the macroscale, have long been used to study mechanical properties of materials. Microscale high-velocity impact, relevant to applications such as ballistic drug delivery has remained largely unexplored at the level of a single impact event. In this work, we study the mechanical behavior of polymer gels subjected to high-velocity microparticle impact, with strain rates up to 107 s−1, through direct visualization of the impact dynamics. In an all-optical laser-induced particle impact test, 10–24 μm diameter steel microparticles are accelerated through a laser ablation process to velocities ranging from 50 to 1000 m/s. Impact events are monitored using a high-speed multi-frame camera with nanosecond time resolution. We measure microparticle trajectories and extract both maximum and final penetration depths for a range of particle sizes, velocities, and gel concentrations. We propose a modified Clift-Gauvin model and demonstrate that it adequately describes both individual trajectories and penetration depths. The model parameters, namely, the apparent viscosity and impact resistance, are extracted for a range of polymer concentrations. Laser-induced microparticle impact test makes it possible to perform reproducible measurements of the single particle impact dynamics on gels and provides a quantitative basis for understanding these dynamics. We show that the modified Clift-Gauvin model, which accounts for the velocity dependence of the drag coefficient, offers a better agreement with the experimental data than the more commonly-used Poncelet model. Microscale ballistic impact imaging performed with high temporal and spatial resolution can serve as direct input for simulations of high-velocity impact responses and high strain rate deformation in gels and other soft materials.

Computer simulations on double hydrophobic PS-b-PMMA porous membrane by non-solvent induced phase separation

The formation of porous membrane of double hydrophobic Polystyrene-b-Poly (methyl methacrylate) (PS-b-PMMA) block copolymer is studied by dissipative particle dynamics (DPD) simulations with the non-solvent induced phase separation (NIPS) method. It is also the first time to investigate the mechanism for double hydrophobic copolymer to form porous membrane. Results show that polymer concentration has the most significant effect on the membrane morphology. Different polymer concentrations lead to diversified morphologies. For the double hydrophobic PS-b-PMMA system, although PS and PMMA are both hydrophobic, due to their relative difference in hydrophobicity, the polymer and non-solvent undergo micro-phase separation. Channel membrane could be observed among the polymer concentration range of 30~40%. The block ratio influences the distribution of PS and PMMA block; meanwhile, block ratio has certain effect on the pore size. Effects of two different good solvents, dimethylacetamide (DMAC) and tetrahydrofuran (THF), on the membrane morphologies are also studied, the results exhibit that the block copolymer PS25-b-PMMA25 dissolved in both DMAC and THF could form channel pore, but the pore size is bigger for the DMAC system.