A5073544096- Block Copolymer Self-Assembly
- Material Dynamics and Properties
- Advanced Polymer Synthesis and Characterization
- Liquid Crystal Research Advancements
- Quasicrystal Structures and Properties
- Theoretical and Computational Physics
- Machine Learning in Materials Science
- Polymer crystallization and properties
- Radiation Dose and Imaging
- biodegradable polymer synthesis and properties
- Ultrasound in Clinical Applications
- Enzyme Structure and Function
- X-ray Diffraction in Crystallography
- Research Data Management Practices
- Membrane Separation and Gas Transport
- Polymer Nanocomposites and Properties
- Gastrointestinal disorders and treatments
- Congenital gastrointestinal and neural anomalies
- Crystallography and Radiation Phenomena
- Surfactants and Colloidal Systems
- Surface Chemistry and Catalysis
- Chemistry and Chemical Engineering
- Membrane Separation Technologies
- Scientific Computing and Data Management
- Adsorption, diffusion, and thermodynamic properties of materials
University of Minnesota
2018-2024
AdventHealth East Orlando
2022
New Mexico State University
2019
University of Colorado Anschutz Medical Campus
2014
A renewed focus on the phase behavior of nominally single-component, compositionally asymmetric diblock copolymers has revealed a host previously unanticipated Frank-Kasper (FK) and quasicrystalline phases. However, these periodic aperiodic particle packings have thus far only been reported in low molecular weight, highly conformationally copolymers, leaving researchers with relatively small library polymers which phases can be studied. In this work, we report simple approach to access...
The observation of complex, Frank-Kasper (FK) particle packings in diblock polymer melts has until recently been limited to low molecular weight, conformationally asymmetric polymers. We report temperature-dependent small-angle X-ray scattering (SAXS) studies blends a sphere-forming poly(styrene-block-1,4-butadiene) (SB) (Mn = 33.3 kg/mol, Đ Mw/Mn 1.08, fB 0.18) with two different poly(1,4-butadiene) (B) homopolymer additives. When the B additive Mn is same as that core-forming segment,...
The phase behavior of poly(styrene)-b-poly(1,4-butadiene) diblock copolymers with a polymer block invariant degree polymerization N[over ¯]_{b}≈800 shows no evidence Frank-Kasper phases, in contrast to low molar mass (N[over ¯]_{b}<100) the same conformational asymmetry. A universal self-concentration crossover parameter ¯]_{x}≈400 is identified, directly related entanglement dynamics melts. Mean-field recovered when ¯]_{b}>N[over ¯]_{x}, while complex symmetry formation attributed...
Over the past decade, a wealth of complexity has been reported in packing compositionally asymmetric, particle-forming diblock copolymer melts, beginning with discovery Frank–Kasper σ phase and continuing subsequent discoveries dodecagonal quasicrystal C14, C15, A15 phases. First identified by self-consistent mean-field theory (SCFT), blending copolymers proven to be useful strategy extending these packings new chemistries length scales. However, much immense space created on two remains...
Discoveries of Frank–Kasper phases and closely related dodecagonal quasicrystals (DDQCs) in soft, mesoscopic systems have galvanized efforts to unveil the fundamental mechanisms that drive formation these remarkably complex micellar packings. Toward this end, we report temperature-dependent small-angle X-ray scattering analyses a crystalline–amorphous poly(ethylene oxide)-block-poly(2-ethyl hexylacrylate) (OA) diblock copolymer with Mn = 8300 g/mol, Đ Mw/Mn 1.10, volume composition fO 0.21....
Reanalysis of an asymmetric poly(ethylene-alt-propylene)-block-polydimethylsiloxane (PEP-PDMS) diblock copolymer first investigated in 1999 has revealed a rich phase behavior including dodecagonal quasicrystal (DDQC), Frank–Kasper σ phase, and body-centered cubic (BCC) packing at high temperature adjacent to the disordered state. On subjecting sample large amplitude oscillatory shear well below σ-BCC order–order transition (TOOT), small-angle X-ray scattering evidenced emergence twinned BCC...
We report the sensitivity of diblock copolymer particle packing symmetry to ratio α = Nhomo/Ncore, where Nhomo and Ncore are respective homopolymer core-block degrees polymerization. Three poly(ethylene oxide)-b-poly(2-ethylhexyl acrylate) (OA) copolymers with O volume fractions fO 0.15, 0.16, 0.20 were blended homopolymers characterized by 0.23, 0.42, 0.80, 1.00. Small-angle X-ray scattering revealed rich phase behavior as a function α, overall core fraction (fcore), temperature. BCC, HCP,...
Temperature-dependent x-ray photon correlation spectroscopy (XPCS) measurements are reported for a binary diblock-copolymer blend that self-assembles into an aperiodic dodecagonal quasicrystal and periodic Frank-Kasper $\ensuremath{\sigma}$ phase approximant. The measured structural relaxation times Bragg scattering wavevector independent 5 faster in the than phase, with minimal temperature dependence. underlying dynamical relaxations ascribed to differences particle motion at grain...
Salt-doped A/B/AB ternary polymer blends, wherein an AB copolymer acts as a surfactant to stabilize otherwise incompatible A and B homopolymers, display wide range of nanostructured morphologies with significant tunability. Among these structures, bicontinuous microemulsion (BμE) has been notable target. Here, we report the surprising appearance robust C15 Laves phase, at compositions near where BμE recently reported, in lithium bis(trifluoromethane) sulfonimide (LiTFSI)-doped low-molar-mass...