Polymeric Bicontinuous Microemulsion Research Articles

Photocrosslinkable Polymeric Bicontinuous Microemulsions.

We present an approach to photocrosslink bicontinuous microemulsions derived from ternary blends of poly(methoxyethyl acrylate) (PM, Mn = 4200 g/mol), poly(hexyl methacrylate-co-coumarin methacrylate) (PHC, Mn = 6800 g/mol), and PM-b-PHC diblock polymer (Mn = 19,400 g/mol) in a phase-selective manner, enabling structural characterization at an unprecedented level of detail. This strategy utilizes the [2 + 2] photodimerization reaction of coumarin derivatives to covalently crosslink blends without the use of harsh reagents or disruptive thermal treatment, thus preserving the intricate network structure throughout curing. The resulting crosslinked bicontinuous microemulsions exhibited rubbery behavior at elevated temperatures, achieving an elastic shear modulus of nearly 1 MPa at 70 °C, owing to the presence of the three-dimensional co-continuous network morphology. The dimensional stabilization afforded by crosslinking further allowed the microstructure to be directly imaged by scanning electron microscopy and atomic force microscopy. Contrary to recent theoretical findings, the BμE appears in a wide temperature and compositional window, suggesting that it is a robust feature of these blends. As a proof of concept demonstrating both the utility of bicontinuous microemulsion-derived materials and versatility of this strategy toward broader applications in energy storage and transport, the uncrosslinked portion of a cured blend was extracted by washing and replaced with an ionic liquid; the resultant heterogeneous solid electrolyte exhibited a room-temperature conductivity of 2 mS/cm, approximately one-quarter that of the pure ionic liquid.

Structure, viscoelasticity, and interfacial dynamics of a model polymeric bicontinuous microemulsion.

We have systematically studied the equilibrium structure and dynamics of a polymeric bicontinuous microemulsion (BμE) composed of poly(cyclohexylethylene) (PCHE), poly(ethylene) (PE), and a volumetrically symmetric PCHE-PE diblock copolymer, using dynamic mechanical spectroscopy, small angle X-ray and neutron scattering, and transmission electron microscopy. The BμE was investigated over an 80 °C temperature range, revealing a structural evolution and a rheological response not previously recognized in such systems. As the temperature is reduced below the point associated with the lamellar-disorder transition at compositions adjacent to the microemulsion channel, the interfacial area per chain of the BμE approaches that of the neat (undiluted) lamellar diblock copolymer. With increasing temperature, the diblock-rich interface swells through homopolymer infiltration. Time-temperature-superposed linear dynamic data obtained as a function of frequency show that the viscoelastic response of the BμE is strikingly similar to that of the fluctuating pure diblock copolymer in the disordered state, which we associate with membrane undulations and the breaking and reforming of interfaces. This work provides new insights into the structure and dynamics that characterize thermodynamically stable BμEs in the limits of relatively weak and strong segregation.

Adhesion forces between humic acid functionalized colloidal probes and polymer membranes to assess fouling potential

Fouling of membrane surfaces by organic, inorganic and biological materials is a significant cause of increased operational costs and power consumption for membrane separation processes including reverse osmosis, nanofiltration, membrane bioreactors and membrane distillation. Novel polymeric membrane surfaces are being developed by numerous research groups to counter foulant attachment and build up. One such type of membranes under development are ones which contain an active surface created using polymeric bicontinuous microemulsions (PBM) [1]. In this work we use humic acid functionalised colloidal probes to simulate organic foulants to investigate the adhesion forces between polymer membranes modified with a PBM coating, both in high purity water and model textile dye wastewater (MTDW). Membrane performance varied considerably when comparing different preparations and with the commercial PES membrane which was used as the base-layer. When making measurements in the two liquid media it was found that the behaviour was very different, with some membranes showing low adhesion in water showing high adhesion in the textile dye wastewater and vice versa. Water contact angle measurements of clean membranes showed good correlation with measured adhesion forces. Conversely, contact angle measurements made with membranes after prolonged exposure to MTDW showed a strong inverse correlation with the measured adhesion forces in MTDW, with more hydrophilic surfaces showing greater adhesion with the functionalised probe. Measurements of contact angle of humic acid before and after exposure to MTDW showed a change from a hydrophobic substance (129°) to a moderately hydrophilic substance (29°). These measurements suggest that the modification of both membranes and probe by components in the MTDW changed the adhesion forces experienced by the HA probe from favouring hydrophobic interactions to hydrophilic ones.

Nanocasting nanoporous inorganic and organic materials from polymeric bicontinuous microemulsion templates

Nanocasting nanoporous inorganic and organic materials from polymeric bicontinuous microemulsion templates

Nanocasting nanoporous inorganic and organic materials from polymeric bicontinuous microemulsion templates

Ternary blends of two homopolymers and a diblock copolymer can self-assemble into interpenetrating, three-dimensionally continuous networks with a characteristic length scale of ∼100 nm. In this review, we summarize our recent work demonstrating that these equilibrium fluid phases, known as polymeric bicontinuous microemulsions (BμE), can be designed as versatile precursors to nanoporous materials having pores with uniform sizes of ∼100 nm. As a model system, nanoporous polyethylene (PE) is derived from BμEs composed entirely of polyolefins. This monolithic material is then used as a template in the synthesis of other nanoporous materials for which structural control at the nm scale has traditionally been difficult to achieve. These materials, which include a high-temperature ceramic, polymeric thermosets and a conducting polymer, are produced by a simple nanocasting process, providing an inverse replica of the PE template. The PE is further used as a template for the production of hierarchically structured inorganic and polymeric materials by infiltration of mesostructured compounds into its pore network. The work described herein represents an unprecedented suite of nanoporous materials with well-defined pore structures prepared from a single PE template. They are anticipated to have potential application in diverse technological areas, including catalysis, separations and electronic devices.

Nanoporous Poly(3,4-ethylenedioxythiophene) Derived from Polymeric Bicontinuous Microemulsion Templates

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTNanoporous Poly(3,4-ethylenedioxythiophene) Derived from Polymeric Bicontinuous Microemulsion TemplatesBrad H. Jones†, Kai-Yuan Cheng†, Russell J. Holmes†, and Timothy P. Lodge*†‡View Author Information† ‡ †Department of Chemical Engineering and Materials Science and ‡Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States*E-mail: [email protected]Cite this: Macromolecules 2012, 45, 1, 599–601Publication Date (Web):December 6, 2011Publication History Received5 October 2011Revised19 November 2011Published online6 December 2011Published inissue 10 January 2012https://doi.org/10.1021/ma202239bCopyright © 2011 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1528Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (3 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Catalyst supports,Genetics,Nanoporous materials,Plastics,Polymers Get e-Alerts

Hierarchically Structured Materials from Block Polymer Confinement within Bicontinuous Microemulsion-Derived Nanoporous Polyethylene

The self-assembly behavior of block polymers under strong two-dimensional and three-dimensional confinement has been well-studied in the past decade. Confinement effects enable access to a large suite of morphologies not typically observed in the bulk. We have used nanoporous polyethylene, derived from a polymeric bicontinuous microemulsion, as a novel template for the confinement of several different cylinder-forming block polymer systems: poly(isoprene-b-2-vinylpyridine), poly(styrene-b-isoprene), and poly(isoprene-b-dimethylsiloxane). The resultant materials exhibit unique hierarchical arrangements of structure with two distinct length scales. First, the polyethylene template imparts a disordered, microemulsion-like periodicity between bicontinuous polyethylene and block polymer networks with sizes on the order of 100 nm. Second, the block polymer networks display internal periodic arrangements produced by the spontaneous segregation of their incompatible constituents. The microphase-separated morphologies observed are similar to those previously reported for confinement of block polymers in cylindrical pores. However, at present, the morphologies are spatially variant in a complex manner, due to the three-dimensionally interconnected nature of the confining geometry and its distribution in pore sizes. We have further exploited the unique structure of the polyethylene template to generate new hierarchically structured porous monoliths. Poly(isoprene-b-2-vinylpyridine) is used as a model system in which the pyridine block is cross-linked, post-infiltration, and the polyethylene template is subsequently extracted. The resultant materials possess a three-dimensionally continuous pore network, of which the pore walls retain the unique, microphase-separated morphology of the confined block polymer.

Hierarchically Porous Silica Prepared from Ionic Liquid and Polymeric Bicontinuous Microemulsion Templates

Polymeric bicontinuous microemulsions (BμE) are unique disordered morphologies found in well-designed ternary blends of two immiscible homopolymers and a diblock copolymer surfactant. By crystallization or vitrification of one component and selective extraction of another, polymeric BμEs are efficient precursors to nanoporous materials having three-dimensionally continuous, ∼100 nm pores. Here, nanoporous polyethylene (PE) derived from a polymeric BμE is used as a rigid template, inside which a so-called silica ionogel is synthesized. The solvent used is a room temperature ionic liquid (RTIL), and is incorporated into the silica product, yielding a disordered, bicontinuous arrangement of discrete silica and RTIL networks with ∼10 nm periodicity. Because of the confinement provided by the PE template, the ionogel and PE are also arranged in a disordered, bicontinuous manner with ∼100 nm periodicity. Subsequent selective extraction of the PE template by a suitable solvent generates a three-dimensionally con...

Nanoporous Polyethylene Thin Films Templated by Polymeric Bicontinuous Microemulsions: Evolution of Morphology on Non-neutral Substrates

Polymeric bicontinuous microemulsions (BμE), found in well-designed ternary blends of two homopolymers and a diblock copolymer, have been extensively studied in the bulk, for example, as versatile templates for the synthesis of nanoporous materials. However, there have been few reports regarding BμE-forming blends as films and the potential impact of confinement on the morphology of such blends. We have investigated the morphology of ternary blends of polyethylene (PE), poly(ethylene-alt-propylene) (PEP), and poly(ethylene-b-ethylene-alt-propylene) (PE-PEP) on a variety of substrates. The films were rendered nanoporous by selective extraction of the PEP component, which also created contrast for scanning electron microscopy (SEM). Blends that form BμEs in the bulk were found to undergo an evolution of morphology from a BμE to a macro-phase separated state, induced by the segregation of blend components to the film interfaces. The dynamics of the transformation are accelerated by decreasing film thickness. The results presented indicate that BμEs can be kinetically trapped on arbitrary substrates, which has important implications for the production of bicontinuous, nanoporous films.

Nanoporous Materials Derived from Polymeric Bicontinuous Microemulsions

We demonstrate a universal approach to the synthesis of nanoporous materials with pore structures that are highly precise replications of bicontinuous microemulsions. The materials can be formed at...

High-Temperature Nanoporous Ceramic Monolith Prepared from a Polymeric Bicontinuous Microemulsion Template

Nanoporous ceramic with a unique pore structure was derived from an all-hydrocarbon polymeric bicontinuous microemulsion (BmuE). The BmuE was designed to allow facile removal of one phase, resulting in a nanoporous polymer monolith with BmuE-like structure. The pores were filled with a commercially available, polymeric precursor to nonoxide, Si-based ceramics. Pyrolysis resulted in a monolith of nanoporous ceramic, stable to at least 1000 degrees C, with a BmuE-like pore structure. The pore structure is disordered and 3-D continuous. Microscopy and gas sorption measurements suggest a well-defined pore size distribution spanning roughly 60-100 nm, sizes previously unattainable through related techniques.

Bicontinuous Polymeric Microemulsions from Polydisperse Diblock Copolymers

Polymeric bicontinuous microemulsions are thermodynamically stable structures typically formed by ternary blends of immiscible A and B homopolymers and a macromolecular surfactant such as an AB diblock copolymer. Investigations of these bicontinuous morphologies have largely focused on model systems in which all components have narrow molecular weight distributions. Here we probe the effects of AB diblock polydispersity in ternary blends of polystyrene (PS), polyisoprene (PI), and poly(styrene-b-isoprene) (PS-PI). Three series of blends were prepared using the same PS and PI homopolymers; two of them contain nearly monodisperse components while the third includes a polydisperse PS-PI diblock. The PS and PI homopolymers and two of the PS-PI diblocks were prepared by anionic polymerization using sec-butyllithium and have narrow molecular weight distributions. The polydisperse PS-PI diblock was prepared by anionic polymerization using the functional organolithium 3-tert-butyldimethylsilyloxy-1-propyllithium; this diblock has a polydisperse PS block (Mw/Mn = 1.57) and a nearly monodisperse PI block (Mw/Mn < 1.1). The phase behavior of the three series of blends was probed using a combination of dynamic mechanical spectroscopy, small-angle X-ray scattering, and cloud point measurements, and a bicontinuous microemulsion channel was identified in each system. These results prove that monodisperse components are not required to form bicontinuous microemulsions and highlight the utility of polydispersity as a tool to tune polymer blend phase behavior. The random-phase approximation, originally advanced by de Gennes, and self-consistent field theory are used to provide a theoretical supplement to the experimental work. These theories are able to predict the directions of the polydispersity-driven shifts in domain spacing, order-disorder transition temperatures, and the location of the microemulsion channel. Self-consistent field theory is also used in conjunction with the experimental data from a series of nearly monodisperse blends to probe the variations of chi with temperature. A single linear relation of the form chi = alpha/T + beta does not describe chi at all blend compositions. Rather, two separate relations describe chi as a function of temperature; one is obtained from data on the diblock-rich side of the bicontinuous microemulsion channel while the other is obtained from data on the homopolymer-rich side of the channel. The blend morphology, rather than the composition (homopolymer fraction), apparently dictates whether the system is in the "diblock chi" or "homopolymer chi" regime. These results reinforce the notion that a true understanding of chi still eludes the polymer science community.

Shear flow behavior of a dynamically symmetric polymeric bicontinuous microemulsion

We have investigated the shear flow behavior of a dynamically symmetric polymeric bicontinuous microemulsion using rheology and in situ small angle x-ray scattering. The microemulsion consists of a ternary blend of poly (ethylene-alt-propylene) (PEP), poly (butylene oxide) (PBO), and a PEP-PBO diblock copolymer. Steady shear experiments reveal an unusual shear thickening behavior at the onset of the non-Newtonian regime, which is consistent with the strain hardening and frequency thickening (at large strains) under oscillatory shear. Scattering experiments indicate development of anisotropy in the bicontinuous structure within the thickening regime. Subsequent shear thinning is observed at intermediate shear rates. Shear-induced bulk phase separation is detected at very high rates. This work complements previous studies on a dynamically extremely asymmetric bicontinuous microemulsion, and thereby establishes the universal rheological properties of polymeric microemulsions. Possible underlying molecular me...

Mesoporous Membrane Templated by a Polymeric Bicontinuous Microemulsion

We demonstrate a facile method for preparing a novel nanoporous material with an isotropic, three-dimensionally continuous pore structure from a polymeric bicontinuous microemulsion precursor, which consists of two immiscible homopolymers and the corresponding diblock copolymer. The protocol for the generation of nanopores is selective cross-linking of one domain with the subsequent removal of the other domain by solvent dissolution.

Transient Rheology of a Polymeric Bicontinuous Microemulsion

Transient rheological measurements are reported for a model polymeric bicontinuous microemulsion. The sample consists of a ternary blend of poly(ethyl ethylene) (PEE) and poly(dimethyl siloxane) (PDMS) homopolymers and a symmetric PEE-PDMS diblock copolymer. Steady-flow rheological data, reported previously, show four regimes as a function of increasing shear rate. Newtonian behavior is observed in regime I, followed by shear thinning in regime II. Flow-induced phase separation is the hallmark of regime III. The microemulsion starts ejecting homopolymer-rich phases, and the shear stress is independent of shear rate. In regime IV, complete phase separation occurs and the sample behaves like an immiscible blend. Transient rheological data on flow inception reveal linear viscoelastic response in regime I, and development of a stress overshoot in regime II. In regime III, a strong stress overshoot is observed, followed by a “shoulder” and a slow decay to the steady, rate-independent value. The normal stress s...

Linear Viscoelasticity of a Polymeric Bicontinuous Microemulsion

Ternary polymer blends of immiscible homopolymers and the corresponding diblock copolymer are useful models for studying equilibrium and nonequilibrium behavior of self-assembled fluids. We report linear viscoelastic data for a polymeric bicontinuous microemulsion, experiments that are possible due to the comparatively high viscosities of the principal components. After subtracting a viscous background contribution from the pure constituents, the microemulsion exhibits “excess” viscoelastic behavior similar in character to that resulting from the Rouse model of polymer dynamics. The data are compared to the predictions of a time-dependent Landau−Ginzburg model developed by Pätzold and Dawson, using structural parameters derived from neutron scattering as input. This model captures the essential characteristics of the viscoelastic behavior very well. However, using independent dynamic light scattering measurements of the Onsager coefficient for these blends, it appears that the model fails to predict either the magnitude or the temperature dependence of the zero shear viscosity and relaxation time of the microemulsion accurately. Possible origins for these discrepancies are discussed.

Effects of shear flow on a polymeric bicontinuous microemulsion: Equilibrium and steady state behavior

We have investigated the effects of shear flow on a polymeric bicontinuous microemulsion using neutron scattering, light scattering, optical microscopy, and rheology. The microemulsion consists of a ternary blend of poly(ethyl ethylene) (PEE), poly(dimethyl siloxane) (PDMS), and a PEE–PDMS diblock copolymer. At equilibrium, the microemulsion contains two percolating microphases, one PEE rich and the other PDMS rich, separated by a copolymer-laden interface; the characteristic length scale of this structure is 80 nm. Low strain amplitude oscillatory shear measurements reveal behavior similar to that of block copolymer lamellar phases just above the order–disorder transition. Steady shear experiments expose four distinct regimes of response as a function of the shear rate. At low shear rates (regime I) Newtonian behavior is observed, whereas at intermediate shear rates (regime II) development of anisotropy in the morphology leads to shear thinning. When the shear rate is further increased, there is an abrup...

Shear-induced nano-macro structural transition in a polymeric bicontinuous microemulsion.

Bicontinuous microemulsions arise in a narrow concentration range for ternary blends containing two immiscible homopolymers and the corresponding diblock copolymer. Steady shear reveals four distinct regimes of response as a function of shear rate, corresponding to flow-induced transitions in fluid structure. In situ neutron scattering shows flow-induced anisotropy in the nanometer-scale microemulsion structure at moderate shear rates, while higher rates induce bulk phase separation, with micron-size morphology, which is characterized with in situ light scattering and optical microscopy.

Polymeric Bicontinuous Microemulsions

High molecular weight block copolymers can be viewed as macromolecular surfactants when blended with thermodynamically incompatible homopolymers. This Letter describes the formation of polymeric bicontinuous microemulsions in mixtures containing a model diblock copolymer and two homopolymers. Although we attribute development of this equilibrium morphology to the effects of fluctuations, mean-field theory provides a quantitative strategy for preparing the bicontinuous state at blend compositions near an isotropic Lifshitz point.