Francis Starr

Dynamical Behavior Near a Liquid-Liquid Phase Transition in Simulations of Supercooled Water

Peter H. Poole et al. — Fri, 26 Aug 2011 06:50:20 PDT

Stability of DNA-linked nanoparticle crystals II: Effect of number of strands, core size, and rigidity of strand attachment

Olivia Padovan-Merhar et al. — Fri, 17 Jun 2011 13:09:06 PDT

Modifying Fragility and Collective Motion in Polymer Melts with Nanoparticles

Francis W. Starr et al. — Tue, 15 Mar 2011 19:01:10 PDT

Stability of DNA-linked nanoparticle crystals I: Effect of linker sequence and length

Francis W. Starr et al. — Thu, 23 Dec 2010 19:12:04 PST

Universal two-step crystallization of DNA-functionalized nanoparticles

Wei Dai et al. — Thu, 12 Aug 2010 08:32:28 PDT

Theoretical Description of a DNA-Linked Nanoparticle Self-Assembly

Chia Wei Hsu et al. — Mon, 12 Jul 2010 08:51:27 PDT

Current issues in research on structure-property relationships in polymer nanocomposites

J. Jancar et al. — Thu, 01 Jul 2010 08:04:52 PDT

Science and Engineering of Nanoparticle-Polymer Composites: Insights from Computer Simulation

Francis W. Starr et al. — Wed, 07 Apr 2010 19:13:45 PDT

Rapid Transport of Water via a Carbon Nanotube Syringe

Jose L. Rivera et al. — Sat, 13 Mar 2010 08:41:57 PST

Morphology and Transport Properties of Two-Dimensional Sheet Polymers

Scott T. Knauert et al. — Fri, 12 Mar 2010 20:48:29 PST

Whereas there has been extensive theoretical and experimental investigation of the properties of linear polymer chains in solution, there has been far less work on sheet-like polymers having 2D connectivity and 3D crumpled or collapsed shapes caused by thermal fluctuations, attractive self-interactions, or both. Sheet-like polymers arise in a variety of contexts ranging from self-assembled biological membranes (e.g., the spectrin network of red blood cells, microtubules, etc.) to nanocomposite additives to polymers (carbon nanotubes, graphene, and clay sheets) and polymerized monolayers. We investigate the equilibrium properties of this broad class of polymers using a simple model of a sheet polymer with a locally square symmetry of the connecting beads. We quantify the sheet morphology and the dilute-limit hydrodynamic solution properties as a function of molecular mass and sheet stiffness. First, we reproduce the qualitative findings of previous work indicating that variable sheet stiffness results in a wide variety of morphologies, including flat, crumpled or collapsed spherical, cylindrical or tubular, and folded sheets that serve to characterize our particular 2D polymer model. Transport properties are of significant interest in characterizing polymeric materials, and we provide the first numerical computations of these properties for sheet polymers. Specifically, we calculate the intrinsic viscosity and hydrodynamic radius of these sheet morphologies using a novel path-integration technique and find good agreement of our numerical results with previous theoretical scaling predictions.

Dynamic heterogeneities in supercooled water

Nicolas Giovambattista et al. — Thu, 11 Mar 2010 21:23:18 PST

Spatially Heterogeneous Dynamics and the Adam-Gibbs Relation in the Dzugutov Liquid

Yeshitela Gebremichael et al. — Thu, 11 Mar 2010 21:20:00 PST

Clusters of mobile molecules in supercooled water

Nicolas Giovambattista et al. — Thu, 11 Mar 2010 21:16:18 PST

Cyberinfrastructure and the Sciences at Liberal Arts Colleges

Francis W. Starr — Thu, 11 Mar 2010 20:00:24 PST

Valency Dependence of Polymorphism and Polyamorphism in DNA-Functionalized Nanoparticles

Wei Dai et al. — Thu, 11 Mar 2010 18:32:52 PST

Nanoparticles (NP) functionalized with single-stranded DNA (ssDNA) offer a route to custom-designed, self- assembled nanomaterials with potentially unusual properties. The bonding selectivity of DNA guarantees one-to-one binding to form double-stranded DNA (dsDNA), and an appropriate base sequence results in head-to-tail binding linking NP into networks. We explore the phase behavior and structure of a model for NP functionalized with between 3 and 6 short ssDNA through simulations of a coarse-grained molecular model, allowing us to examine both the role of the number of attached strands (valency) and their relative orientations. The NP assemble into networks where the number of NP links is controlled by the number of attached strands. The large length scale of the DNA links relative to the core NP size opens the possibility for the formation of interpenetrating networks that give rise to multiple thermodynamically distinct states. We find that the 3-functionalized NP have only a single phase transition between a dilute solution of NPs and an assembled network state. 4-Functionalized NP (with tetrahedral symmetry) exhibit four amorphous phases, or polyamorphism, each higher density phase consisting of an additional interpenetrating network. The two investigated geometries of 5-functionalized NP both exhibit two phase transitions and three amorphous phases. Like the 4-functionalized NP, the highest density phase consists of interpenetrating networks, demonstrating that regular symmetry is not a prerequisite for interpenetration to produce thermodynamically distinct phases. The width of the coexistence regions for all phase transitions increases with increasing functionality. Finally, for 6-functionalized NP with octahedral symmetry, the possibility of observing disordered phases with significantly bonded particles is preempted by the formation of ordered crystal phases. Interestingly, the extreme softness of the potential combined with the directional interaction allows for the formation of (at least) six distinct crystalline structures (i.e., polymorphism) consisting of up to six interpenetrating simple cubic lattices.

Fast and Slow Dynamics of Hydrogen Bonds in Liquid

Francis W. Starr et al. — Wed, 29 Apr 2009 18:35:24 PDT

Thermodynamic and structural aspects of the potential energy surface of simulated water

Francis W. Starr et al. — Wed, 29 Apr 2009 18:35:20 PDT

Hydrogen Bond Dynamics in the extended simple point

Francis W. Starr et al. — Wed, 29 Apr 2009 18:35:19 PDT

Dynamics of Supercooled Water in Configuration Space

Emilia La Nave et al. — Wed, 29 Apr 2009 18:35:12 PDT

Transitions between Inherent Structures in Water

Nicolas Giovambattista et al. — Wed, 29 Apr 2009 18:35:07 PDT