A5056508088- Polymer Surface Interaction Studies
- Block Copolymer Self-Assembly
- Advanced Polymer Synthesis and Characterization
- Surfactants and Colloidal Systems
- Gold and Silver Nanoparticles Synthesis and Applications
- Material Dynamics and Properties
- Electrostatics and Colloid Interactions
- Pickering emulsions and particle stabilization
- Hydrogels: synthesis, properties, applications
- Dendrimers and Hyperbranched Polymers
- Polymer Nanocomposites and Properties
- Advanced Theoretical and Applied Studies in Material Sciences and Geometry
- Material Properties and Applications
- Plasmonic and Surface Plasmon Research
- Polymer composites and self-healing
- Nanoparticle-Based Drug Delivery
- Conducting polymers and applications
- Nanopore and Nanochannel Transport Studies
- Polymer Nanocomposite Synthesis and Irradiation
- Protein Structure and Dynamics
- Analytical Chemistry and Sensors
- Supramolecular Self-Assembly in Materials
- Supramolecular Chemistry and Complexes
- Polymer crystallization and properties
- Enzyme Structure and Function
Case Western Reserve University
2015-2025
Columbia University
2020
University of Delaware
2020
National Institute of Standards and Technology
2013-2015
University of Pennsylvania
2010-2014
NIST Center for Neutron Research
2013-2014
University of Memphis
2004-2010
University of Southern Denmark
2010
As the macromolecular version of mechanically interlocked molecules, polymers are promising candidates for creation sophisticated molecular machines and smart soft materials. Poly[n]catenanes, where chains consist solely macrocycles, contain one highest concentrations topological bonds. We report, herein, a synthetic approach toward this distinctive polymer architecture in high yield (~75%) via efficient ring closing rationally designed metallosupramolecular polymers. Light-scattering, mass...
Because of their shape anisotropy, nanorods are attractive components for creating functional polymer nanocomposites. In many cases, this anisotropy is the basis physical properties that distinct from those obtained isotropic particles, such as nanospheres. For instance, gold makes them ideal candidates applications involving manipulation incident light and sensitive molecular spectroscopy due to enhanced polarizability particle. On other hand, semiconducting nanorods, composed CdSe, have...
Metallic nanoparticles that absorb and concentrate light are leading to greater efficiencies in nanophotonic devices. By confining gold nanorods (Au NRs) a polymer film, we can control their spacing orientation and, turn, the absorption polarization characteristics of nanocomposite. In this study, systematically increase volume fraction Au NRs (ϕrod) (aspect ratio ν = 3.3) while maintaining uniform dispersion. As ϕrod increases from 1 16 vol %, between rods decreases 120 20 nm scales as...
Small-angle neutron scattering (SANS) is a powerful technique that has been widely used to study polymer materials. In particular, it can provide information on the size, shape, and structure of polymers as well associated thermodynamic quantities. However, properly design SANS experiments correctly interpret results, necessary understand unique advantages inherent measurements soft materials underlying principles technique. addition, may be construct new models. this Tutorial, we an...
Small-angle neutron scattering was used to investigate poly(N-isopropylacrylamide) (PNIPAM) polymer solutions in d-water/d-ethanol mixtures. A wide poor-solvent region observed for mixtures near 60% d-water/40% d-ethanol mixture. Spinodal lines were determined, permitting a mapping of the mixing/demixing regions phase diagram which comprises two main branches: left branch (with mostly d-ethanol) where separation occurs upon cooling (UCST) and right d-water) heating (LCST). The ternary random...
Optical absorption due to surface plasmon resonances in ensembles of gold nanorods (Au NRs) depends strongly on the nanorod separation and orientation. Here, we study dispersion polystyrene-functionalized Au NRs polystyrene (PS) thin films using UV-visible (UV-vis) spectroscopy transmission electron microscopy (TEM) find that are dispersed for brush chain lengths exceed PS matrix length aggregated otherwise. Monte Carlo simulations parameters from classical density functional theory (DFT)...
An understanding of the dispersion nanoparticles into polymer melts is needed in order to control material properties nanocomposites. Here we study polymer-grafted nanorods homopolymer same chemistry, using both experiment and theory. The theoretical calculations are performed over range experimental system parameters. Polymer-grafted gold (Au NRs) were found be dispersed when matrix chain lengths small relative brush lengths, aggregated at higher lengths. Both classical density functional...
Significance We demonstrate that slow monomer addition during step-growth polymer network formation changes the fraction of loop defects within network, thus providing materials with tunable and significantly improved mechanical properties. This phenomenon is general to a range network-forming reactions offers powerful method for tuning mechanics without changing their composition.
Small-angle neutron scattering (SANS) is a sensitive technique that able to probe the structure of polymer-grafted nanoparticles and free polymer chains. Here, we combine SANS measurements with self-consistent field theory (SCFT) calculations study deuterated poly(methyl methacrylate) (dPMMA) nanocomposites containing PMMA-grafted Fe3O4 nanospheres, specific emphasis on conformation PMMA brush We present new, detailed model which account for excluded volume grafted chains, compare...
Nanoparticles are new and valuable additives that can favorably tune thermomechanical, electric, optical, magnetic properties of polymeric materials. The addition nanoparticles also enhance or slow down polymer dynamics depending on the mixture thermodynamics key length scales, namely, nanoparticle size, interparticle spacing (ID), radius gyration (Rg). Presently, a framework for understanding how affect is not available, in part, because lack wide-ranging experimental studies. Here, tracer...
Covalent conjugation of water-soluble polymers to proteins is critical for evading immune surveillance in the field biopharmaceuticals. The most common and long-standing polymer modification attachment methoxypoly(ethylene glycol) (mPEG), termed PEGylation, which has led several clinically approved pharmaceuticals. Recent data indicate that brush-type significantly enhance vitro vivo properties. Herein, conformation poly(ethylene detailed compared with those polyacrylate polynorbornene (PNB)...
Inspired by the ability of sea cucumber to (reversibly) increase stiffness its dermis upon exposure a stimulus, we herein report stimuli-responsive nanocomposite that can reversibly warm water. Nanocomposites composed cellulose nanocrystals (CNCs) are grafted with lower critical solution temperature (LCST) polymer embedded within poly(vinyl acetate) (PVAc) matrix show dramatic in modulus, for example, from 1 350 MPa water, hypothesis being grafting polymers CNCs disrupts interactions between...
In this paper, polymer nanocomposite films containing gold nanorods (AuNRs) and poly(2-vinyl pyridine) (P2VP) have been investigated for their structure–optical property relationship. Using transmission electron microscopy (TEM), the assembly of AuNRs (7.9 nm × 28.4 nm) grafted with a P2VP brush in is examined as function AuNR volume fraction ØAuNRs film thickness h. For h ∼ 40 nm, are confined to align parallel uniformly dispersed at low ØAuNRs. Upon increasing ØAuNRs, form discrete...
Polymer gels are often very soft due to their low branch functionality (f) and the inevitable presence of defects (e.g., primary loops or dangling chains). metal–organic cage (polyMOC) a relatively new class supramolecular with precisely defined junction structures made possible by subcomponent assembly nanoscale MOCs connected polymer chains. Herein, we report that variation molecular weight architecture component polyMOCs provides an entry into ultra-high f. For example, materials f ∼...
When grafted to spherical nanoparticles at high grafting densities, polymers adopt a variety of conformations. Because strong confinement by neighboring chains, portions the polymer near nanoparticle core are highly stretched in concentrated brush region (CPB) layer. Farther away from core, where is less confined, conformation becomes more ideal semidilute (SDPB) region. Using combination small-angle neutron scattering (SANS) and spin echo (NSE) spectroscopy, we directly characterized both...
A novel, solution-based method is presented to prepare bifunctional gold nanorods (B-NRs), assemble B-NRs end-to-end in various solvents, and disperse linked a polymer matrix. The have poly(ethylene glycol) grafted along its long axis cysteine adsorbed ends. By controlling coverage, ligands or can be end-grafted the AuNRs. Here, two dithiol (C6DT C9DT) are used link organic solvents. With increasing incubation time, nanorod chain length increases linearly as longitudinal surface plasmon...
The structure and size of ligands attached to the surfaces gold nanorods, such as adsorbed surfactants or grafted polymers, are important considerations that facilitate use nanoparticles in human body, advanced materials for energy harvesting, devices single molecule detection. Here, we report small-angle neutron scattering (SANS) measurements from surfactant poly(ethylene glycol) (PEG) coated nanorods solution, which quantitatively determine location, structure, composition these surface...
All animals except sponges produce mucus. Across the animal kingdom, this hydrogel mediates surface wetting, viscosity, and protection against microbes. The primary components of mucus hydrogels are mucins-high molecular weight
The addition of nanoparticles (NPs) to polymer blends is an attractive route for controlling their morphology. Here, we investigate the phase separation poly(methyl methacrylate) (PMMA) : poly(styrene-ran-acrylonitrile) (SAN) films with thicknesses from 140 nm 2500 and silica NP concentrations 1 10 wt%. Atomic force microscopy (AFM) focused ion beam (FIB) etching combined scanning electron (SEM) are used identify morphology as discrete or bicontinuous. FIB/SEM introduced a facile method...
We show that polymer diffusion in nanocomposites (PNCs) is controlled by the architecture of brushes grafted to hard spherical nanoparticles (NPs). At high grafting density, diffusing chains are excluded from brush leading greater confinement. However, at lower these penetrate and similar NP case, compared same loading. calculate effective interparticle spacing (IDeff) modeling penetration into using self-consistent field theory. When plotted against a confinement parameter (IDeff/2Rg, where...