Polymer-Grafted Nanoparticle Membranes with Unusual Gas Separation Properties

Polymer membranes are employed in several critical sustainability applications involving the separation of gas mixtures based on size differences. In spite of their widespread use, important performance challenges remain outstanding - the need to dramatically affect the transport of a desired mixture component and improving mechanical resilience relative to the current state-of-the-art. Here, we develop novel membranes based on polymer-grafted nanoparticles (GNPs) which possess controllable, spatially inhomogeneous gas transport behavior. We show that smaller gases are transported more uniformly than larger solutes in the polymer layer of pure GNPs; these larger gases preferentially move through the interstices between the NPs. Free chains added to these GNPs preferentially segregate into these interstices where they selectively hinder large solute motion and thus yield dramatic performance improvements for several industrially relevant gas pairs. The magnitude of these effects are controlled by grafting parameters and the length of the free chains. Our ability to create and tune spatial inhomogeneities in GNPs, apparently through judicious manipulation of chain entropy, is thus a new, apparently general, physics-based paradigm to design membranes with unprecedented performance even using common polymers. Collaborators: Connor Bilchak, Yucheng Huang, Daniele Parisi, Zaid Abbas, Werner Egger, Ferruccio Doghieri, Matteo Minelli, Marcel Dickmann, Brian Benicewicz, Jacques Jestin, Michael Rubinstein, Dimitris Vlassopoulos, Ludwik Leibler, Christopher Durnin

Combinatorial-Entropy-Driven Aggregation in {DNA}-Grafted Nanoparticles

We use computer simulations and experiments to study the interactions between nanoparticles (NPs) grafted with self-complementary DNA strands. Each strand ends with a sticky palindromic single-stranded sequence, allowing it to associate equally favorably with strands grafted on the same particle or on different NPs. Surprisingly we find an attractive interaction between a pair of NPs, and we demonstrate that at low temperature it arises purely from a combinatorial-entropy contribution. We evaluate theoretically and verify numerically this entropic contribution originating from the number of distinct bonding patterns associated with intra- and interparticle binding. This entropic attraction becomes more favorable with decreasing inter-NP distance because more sticky ends can participate in making this choice

A coarse-grained protein model in a water-like solvent

Simulations employing an explicit atom description of proteins in solvent can be computationally expensive. On the other hand, coarse-grained protein models in implicit solvent miss essential features of the hydrophobic effect, especially its temperature dependence and have limited ability to capture the kinetics of protein folding. We propose a free space two-letter protein (“H-P”) model in a simple, but qualitatively accurate description for water, the Jagla model, which coarse-grains water into an isotropically interacting sphere. Using Monte Carlo simulations, we design protein-like sequences that can undergo a collapse, exposing the “Jagla-philic” monomers to the solvent, while maintaining a “hydrophobic” core. This protein-like model manifests heat and cold denaturation in a manner that is reminiscent of proteins. While this protein-like model lacks the details that would introduce secondary structure formation, we believe that these ideas represent a first step in developing a useful, but computationally expedient, means of modeling proteins.We thank C. A. Angell, M. Marques, S. Sastry, and Z. Yan for helpful discussions. S. S. and S. K. K. acknowledge the DOE - Basic Engineering Sciences for funding this research. P. G. D. gratefully acknowledges the support of the National Science Foundation (Grant CHE-1213343). P.J.R. gratefully acknowledges the support of the National Science Foundation (Collaborative Research Grants CHE-0908265 and CHE-0910615). Additional support from the R.A. Welch Foundation (F-0019) to P.J.R. is also gratefully acknowledged. HES thanks the NSF Chemistry Division for support through grants CHE 0911389, CHE 0908218 and CHE-1213217. S. V. B. acknowledges the partial support of this research through the Dr Bernard W. Gamson Computational Science Center at Yeshiva College. (DOE - Basic Engineering Sciences; CHE-1213343 - National Science Foundation; CHE-0908265 - National Science Foundation; CHE-0910615 - National Science Foundation; F-0019 - R.A. Welch Foundation; CHE 0911389 - NSF Chemistry Division; CHE 0908218 - NSF Chemistry Division; CHE-1213217 - NSF Chemistry Division; Dr Bernard W. Gamson Computational Science Center at Yeshiva College)Published versio

Drug utilization pattern of psychotropic medicines in tertiary care centre of Bastar Region, Chhattisgarh, India

Background: With the changing lifestyle, the incidence of psychiatric illness is increasing day by day. And the mental illnesses not only affect the social and personal life but also adds additional economic burden affecting quality of life of the person. So, proper diagnosis and management of psychiatric illnesses is utmost important. So, keeping this in mind, the present study has been conducted to evaluate drug utilization pattern of psychotropic medicines in tertiary care centre of Bastar region.Methods: After obtaining approval from Institutional Ethics Committee, present study was conducted in 237 patients for a period of 3 months from February 2019 to April 2019. The data of patients attending psychiatry OPD was collected in a structured case record form. The data were analysed using graph pad prism version 6.0.Results: Out of total 237 patients, males 136(57.38%) outnumbered females 101 (42.62%). The major psychiatric illness reported was schizophrenia (45.99%) followed by bipolar affective disorder (16%) and generalized anxiety disorder (14.35%). Average number of psychotropic drugs per prescription was 1.74±1.02. The percentage of drugs prescribed from state Essential drug List (EDL) was 93.05%.Conclusions: Overall, the principles of rational prescribing was tried to be maintained, as polypharmacy has been avoided and most of the drugs were prescribed from the state EDL. The use of generic drugs should be increased to make prescriptions more rational and to cut down the cost of the therapy which may be helpful in increasing the quality of life of the patients

Nature of the Breakdown in the Stokes-Einstein Relationship in a Hard Sphere Fluid

Molecular Dynamics simulations of high density hard sphere fluids clearly show a breakdown of the Stokes-Einstein equation (SE). This result has been conjectured to be due to the presence of mobile particles, i.e., ones which have the propensity to "hop" distances which are integer multiples of the interparticle distance. We conclusively show that, even though the whole liquid violates the SE equation at high densities, the sedentary particles, i.e., ones complementary to the "hoppers", obey the SE relationship. These results strongly support the notion that the unusual dynamics of fluids near vitrification are caused exclusively by the presence of hopping particles

Crazing of nanocomposites with polymer-tethered nanoparticles

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