A5069824583- Block Copolymer Self-Assembly
- Advanced Polymer Synthesis and Characterization
- Polymer crystallization and properties
- Polymer Nanocomposites and Properties
- Rheology and Fluid Dynamics Studies
- Surfactants and Colloidal Systems
- Theoretical and Computational Physics
- Material Dynamics and Properties
- biodegradable polymer synthesis and properties
- Polymer Surface Interaction Studies
- Epoxy Resin Curing Processes
- Polymer composites and self-healing
- Synthesis and properties of polymers
- Machine Learning in Materials Science
- Advanced Physical and Chemical Molecular Interactions
- Advanced Sensor and Energy Harvesting Materials
- Conducting polymers and applications
- Electrospun Nanofibers in Biomedical Applications
- Hydrogels: synthesis, properties, applications
- RNA Interference and Gene Delivery
- Surface Chemistry and Catalysis
- Advanced Cellulose Research Studies
- Polymer Foaming and Composites
- Phase Equilibria and Thermodynamics
- Advanced Battery Materials and Technologies
University of Minnesota
2016-2025
University of Minnesota System
1999-2025
Minneapolis Institute of Arts
2015-2021
University of Minnesota Medical Center
2021
Total (Belgium)
2019
University of Cambridge
2017-2018
Material Sciences (United States)
2014-2015
Bates College
2013-2015
Twin Cities Orthopedics
2015
Charité - Universitätsmedizin Berlin
2013
In patients with coronary heart disease and a broad range of cholesterol levels, cholesterol-lowering therapy reduces the risk events, but effects on mortality from overall have remained uncertain.In double-blind, randomized trial, we compared pravastatin (40 mg daily) those placebo over mean follow-up period 6.1 years in 9014 who were 31 to 75 age. The had history myocardial infarction or hospitalization for unstable angina initial plasma total levels 155 271 per deciliter. Both groups...
Block copolymers are macromolecules composed of sequences, or blocks, chemically distinct repeat units. The development this field originated with the discovery termination-free anionic polymerization, which made possible sequential addition monomers to various carbanion-ter minated (living) linear polymer chains. Polymerization just two dis tinct monomer types (e.g. styrene and isoprene) leads a class materials referred as AB block copolymers. Within class, variety molec ular...
Block copolymers are all around us, found in such products as upholstery foam, adhesive tape and asphalt additives. This class of macromolecules is produced by joining two or more chemically distinct polymer blocks, each a linear series identical monomers, that may be thermodynamically incompatible (like oil vinegar). Segregation these blocks on the molecular scale (5–100 nm) can produce astonishingly complex nanostructures, “knitting pattern” shown cover this issue PHYSICS TODAY. striking...
Vesicles were made from amphiphilic diblock copolymers and characterized by micromanipulation. The average molecular weight of the specific polymer studied, polyethyleneoxide-polyethylethylene (EO 40 -EE 37 ), is several times greater than that typical phospholipids in natural membranes. Both membrane bending area expansion moduli electroformed polymersomes (polymer-based liposomes) fell within range lipid measurements, but giant proved to be almost an order magnitude tougher sustained far...
A mean-field phase diagram for conformationally symmetric diblock melts using the standard Gaussian polymer model is presented. Our calculation, which traverses weak- to strong-segregation regimes, free of traditional approximations. Regions stability are determined disordered (DIS) and ordered structures including lamellae (L), hexagonally packed cylinders (H), body-centered cubic spheres (QIm3̄m), close-packed (CPS), bicontinuous network with Ia3̄d symmetry (QIa3̄d). The CPS exists in...
Different polymers can be combined into a single material in many ways, which lead to wide range of phase behaviors that directly influence the associated physical properties and ultimate applications. Four factors control polymer-polymer behavior: choice monomers, molecular architecture, composition, size. Current theories experiments deal with equilibrium thermodynamics non-equilibrium dynamics polymer mixtures are described terms these experimentally accessible parameters. Two...
Amphiphilic compounds such as lipids and surfactants are fundamental building blocks of soft matter. We describe experiments with poly(1,2-butadiene-b-ethylene oxide) (PB-PEO) diblock copolymers, which form Y-junctions three-dimensional networks in water at weight fractions PEOintermediate to those associated vesicle wormlike micelle morphologies. Fragmentation the network produces a nonergodic array complex reticulated particles that have been imaged by cryogenic transmission electron...
Advances in synthetic polymer chemistry have unleashed seemingly unlimited strategies for producing block polymers with arbitrary numbers (n) and types (k) of unique sequences repeating units. Increasing (k,n) leads to a geometric expansion possible molecular architectures, beyond conventional ABA-type triblock copolymers (k = 2, n 3), offering alluring opportunities generate exquisitely tailored materials unparalleled control over nanoscale-domain geometry, packing symmetry, chemical...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolyisoprene-Polystyrene Diblock Copolymer Phase Diagram near the Order-Disorder TransitionAshish K. Khandpur, Stephan Foerster, Frank S. Bates, Ian W. Hamley, Anthony J. Ryan, Wim Bras, Kristoffer Almdal, and Kell MortensenCite this: Macromolecules 1995, 28, 26, 8796–8806Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995https://doi.org/10.1021/ma00130a012RIGHTS &...
Absolute calibration forms a valuable diagnostic tool in small-angle neutron scattering (SANS) experiments, and allows the parameters of given model to be restricted set which reproduces observed intensity. Discrepancies between calculated intensities may arise from potential artifacts or even new physical processes absolute methods are useful delineating these circumstances. General available for scaling discussed along with estimates degree internal consistency achieved various standards....
Janus Drug Delivery Vehicle Efficient drug delivery vehicles need to be produced in a limited size range and with uniform distribution. The self-assembly of traditional small-molecule polymeric amphiphiles has led the production micelles, liposomes, polymersomes for use applications. Now, Percec et al. (p. 1009 ) describe Janus-type (i.e., two-headed) dendrimers produce monodisperse supramolecular constructs, termed “dendrimersomes,” other complex architectures. structures, which showed...
Block polymers have undergone extraordinary evolution since their inception more than 60 years ago, maturing from simple surfactants to an expansive class of macromolecules encoded with exquisite attributes. Contemporary synthetic accessibility coupled facile characterization and rigorous theoretical advances conspired continuously generate fundamental insights enabling concepts that target applications spanning chemistry, biology, physics, engineering. Here, we parse the vast literature...
A low molecular weight poly(ethyleneoxide)-poly(butadiene) (PEO-PB) diblock copolymer containing 50 percent PEO forms gigantic wormlike micelles at concentrations (<5 by weight) in water. Subsequent generation of free radicals with a conventional water-based redox reaction leads to chemical cross-linking the PB cores without disruption cylindrical morphology, as evidenced cryotransmission electron microscopy and small-angle neutron scattering experiments. These rubber exhibit unusual...
Vesicles prepared in water from a series of diblock copolymers"polymersomes"are physically characterized. With increasing molecular weight M̄n, the hydrophobic core thickness for self-assembled bilayers poly(ethylene oxide)−polybutadiene increases up to ∼20 nm, which is considerably greater than any previously studied lipid or polymersome system. Micromanipulation vesicles demonstrates an interface-dominated elasticity that independent M̄n. Furthermore, membrane stability as defined by...
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication the EditorOrigins of Complex Self-Assembly in Block CopolymersM. W. Matsen and F. S. BatesView Author Information Department Chemical Engineering Materials Science, University Minnesota, Minneapolis, Minnesota 55455Cite this: Macromolecules 1996, 29, 23, 7641–7644Publication Date (Web):November 4, 1996Publication History Received21 May 1996Revised19 August 1996Published online4 November inissue 1 January...
Polyethylene (PE) and isotactic polypropylene (iPP) constitute nearly two-thirds of the world's plastic. Despite their similar hydrocarbon makeup, polymers are immiscible with one another. Thus, common grades PE iPP do not adhere or blend, creating challenges for recycling these materials. We synthesized PE/iPP multiblock copolymers using an isoselective alkene polymerization initiator. These can weld commercial together, depending on molecular weights architecture block copolymers....
A detailed examination of the intermediate-segregation regime diblock copolymer melts is presented using incompressible Gaussian chain model and self-consistent field theory (SCFT). We find that competition between interfacial tension stretching used to describe behavior in strong-segregation also explains this regime. Phase transitions from lamellae (L) cylinders (C) spheres (S) occur due spontaneous curvature produced as asymmetry composition increases. Complex phases, gyroid (G),...
Thermoset materials containing ordered structures with ∼10-nm dimensions were prepared from a mixture of low-molecular-weight poly(ethylene oxide)−poly(ethylene-alt-propylene) (PEO−PEP) diblock copolymer and poly(Bisphenol-A-co-epichlorohydrin) epoxy resin that selectively mixes the PEO block. The phase behavior PEO−PEP/epoxy blends, compositions spanning 10−93 wt % block copolymer, was investigated in uncured state (without hardener) using small-angle X-ray scattering (SAXS) dynamic...
The spinodal decomposition of mixtures poly(ethylenepropylene) (PEP) and perdeuterated poly-(ethylenepropylene) has been studied near the surface using forward-recoil spectrometry. Instead composition waves with randomly oriented wave vectors (and random phases) found in bulk, we observe normal to, which propagate inwards from, surface, maintaining coherence for several wavelengths. We argue that these surface-directed are caused by preferential attraction d-PEP to surface.
The thermodynamic and dynamic properties of a partially deuterated poly(ethylene-propylene)–poly(ethylethylene)(PEP–PEE) diblock copolymer containing 55% by volume PEP were characterized above below the order–disorder transition (ODT) small-angle neutron scattering (SANS) rheological measurements, respectively. Both experimental techniques produced unambiguous evidence composition fluctuations well TODT(T−TODT≲50 °C) in disordered state, which increase magnitude as weak first-order is...
Sphere-forming block copolymers are known to self-assemble into body-centered cubic crystals near the order-disorder transition temperature. Small-angle x-ray scattering and transmission electron microscopy experiments on diblock tetrablock copolymer melts have revealed an equilibrium phase characterized by a large tetragonal unit cell containing 30 microphase-separated spheres. This structure, referred as sigma (σ) Frank Kasper more than 50 years ago, nucleates grows from similar its...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComplex Phase Behavior of Polyisoprene-Polystyrene Diblock Copolymers Near the Order-Disorder TransitionStephan Foerster, Ashish K. Khandpur, Jin Zhao, Frank S. Bates, Ian W. Hamley, Anthony J. Ryan, and Wim BrasCite this: Macromolecules 1994, 27, 23, 6922–6935Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November...