ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheory of microphase separation in graft and star copolymersMonica Olvera de la Cruz and Isaac C. SanchezCite this: Macromolecules 1986, 19, 10, 2501–2508Publication Date (Print):October 1, 1986Publication History Published online1 May 2002Published inissue 1 October 1986https://pubs.acs.org/doi/10.1021/ma00164a008https://doi.org/10.1021/ma00164a008research-articleACS PublicationsRequest reuse permissionsArticle Views1212Altmetric-Citations259LEARN 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 InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Dielectric interfaces are crucial to the behavior of charged membranes, from graphene to synthetic and biological lipid bilayers. Understanding electrolyte behavior near these interfaces remains a challenge, especially in the case of rough dielectric surfaces. A lack of analytical solutions consigns this problem to numerical treatments. We report an analytic method for determining electrostatic potentials near curved dielectric membranes in a two-dimensional periodic 'slab' geometry using a periodic summation of Green's functions. This method is amenable to simulating arbitrary groups of charges near surfaces with two-dimensional deformations. We concentrate on one-dimensional undulations. We show that increasing membrane undulation increases the asymmetry of interfacial charge distributions due to preferential ionic repulsion from troughs. In the limit of thick membranes we recover results mimicking those for electrolytes near a single interface. Our work demonstrates that rough surfaces generate charge patterns in electrolytes of charged molecules or mixed-valence ions.
Effective control over the thermal behavior and mechanical strength of polymeric materials has been highly sought for decades and continues to this day, particularly with the urgent demand for highly durable energy storage devices and soft electronics, to name a few. Here, we report a simple yet versatile approach to fine-tune the glass transition range of a family of ionomers via their side-chain structure and charge fraction. We analyze ionomers of poly(3-sulfopropyl methacrylate-ran-methyl methacrylate) that are synthesized by conventional free-radical polymerization. Using derivative heat flow curves from differential scanning calorimetry, we find that above a critical low charge-carrying side-chain fraction (fq), the glass transition temperature shifts to higher values and the glass transition breadth increases significantly in response to thermal treatment. After several thermal cycles, values of glass transition breadth as high as 90–104 °C were obtained, and the evolution from one glass transition regime to two distinct, contiguous glass transition regimes was evident. Quenched molecular dynamics simulations elucidate the roles of several key design parameters of the ionomers near the glass transition, specifically the importance of the charge-carrying polymer side chains. Analysis of energetics and structural relaxation dynamics reveals the effects of strong ionic correlations in a low dielectric constant medium and the side-chain mobility on the transition from liquid to supercooled liquid. As fq increases beyond a critical value and is accompanied by thermal treatment, the local ionic concentrations are more heterogeneous, and the distribution of the ionic cluster sizes becomes broader at the transition point. The resulting enhanced degree of compositional and dynamic heterogeneity leads to a shift in the supercooled liquid transition toward higher temperatures.
We use molecular dynamics simulations to study the crystallization of spherical nucleic-acid (SNA) gold nanoparticle conjugates, guided by sequence-specific DNA hybridization events. Binary mixtures of SNA gold nanoparticle conjugates (inorganic core diameter in the 8-15 nm range) are shown to assemble into BCC, CsCl, AlB(2), and Cr(3)Si crystalline structures, depending upon particle stoichiometry, number of immobilized strands of DNA per particle, DNA sequence length, and hydrodynamic size ratio of the conjugates involved in crystallization. These data have been used to construct phase diagrams that are in excellent agreement with experimental data from wet-laboratory studies.
Anisotropic colloidal crystals are materials with novel optical and electronic properties. However, experimental observations of colloidal single crystals have been limited to relatively isotropic 1018habits. Here, we show DNA-mediated crystallization of two types of nanoparticles with different hydrodynamic radii that form highly anisotropic, hexagonal prism microcrystals with AB2 crystallographic symmetry. The DNA directs the nanoparticles to assemble into a nonequilibrium crystal shape that is enclosed by the highest surface energy facets (AB2(1010) and AB2(0001)). Simulations and theoretical arguments show that this observation is a consequence of large energy barriers between different terminations of the AB2(1010) facet, which results in a significant deceleration of the (1010) facet growth rate. In addition to reporting a hexagonal colloidal crystal habit, this work introduces a potentially general plane multiplicity mechanism for growing nonequilibrium crystal shapes, an advance that will be useful for designing colloidal crystal habits with important applications in both optics and photocatalysis.
As a core component of biological and synthetic membranes, lipid bilayers are key to compartmentalizing chemical processes. Bilayer morphology and mechanical properties are heavily influenced by electric fields, such as those caused by biological ion concentration gradients. We present atomistic simulations exploring the effects of electric fields applied normally and laterally to lipid bilayers. We find that normal fields decrease membrane tension, while lateral fields increase it. Free energy perturbation calculations indicate the importance of dipole-dipole interactions to these tension changes, especially for lateral fields. We additionally show that membrane area compressibilities can be related to their cohesive energies, allowing us to estimate changes in membrane bending rigidity under applied fields. We find that normal and lateral fields decrease and increase bending rigidity, respectively. These results point to the use of directed electric fields to locally control membrane stiffness, thereby modulating associated cellular processes.
Malina Seyffertitz opened a general discussion of the paper by Adam P. Willard: Your simulations are based on a flat electrode geometry. How difficult would it be to introduce curved surfaces, i.e. porous electrodes? Adam P. Willard responded: It is certainly not impossible to si
The hybridization of free oligonucleotides to densely packed, oriented arrays of DNA modifying the surfaces of spherical nucleic acid (SNA)–gold nanoparticle conjugates occurs with negative cooperativity; i.e., each binding event destabilizes subsequent binding events. DNA hybridization is thus an ever-changing function of the number of strands already hybridized to the particle. Thermodynamic quantification of this behavior reveals a 3 orders of magnitude decrease in the binding constant for the capture of a free oligonucleotide by an SNA conjugate as the fraction of pre-hybridized strands increases from 0 to ∼30%. Increasing the number of pre-hybridized strands imparts an increasing enthalpic penalty to hybridization that makes binding more difficult, while simultaneously decreasing the entropic penalty to hybridization, which makes binding more favorable. Hybridization of free DNA to an SNA is thus governed by both an electrostatic barrier as the SNA accumulates charge with additional binding events and an effect consistent with allostery, where hybridization at certain sites on an SNA modify the binding affinity at a distal site through conformational changes to the remaining single strands. Leveraging these insights allows for the design of conjugates that hybridize free strands with significantly higher efficiencies, some of which approach 100%.
