Statistical Thermodynamics

Asymmetric composites

Structurally asymmetric mixtures, such as mixtures of linear polymers with branched polymers or nanop../reprints/articles can be used to create novel nanostructures. We are developing a general thermodynamic theory of asymmetric mixtures and testing it by computer simulations and experiments.

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1. "Flory Theorem for Structurally Asymmetric Mixtures" by F. C. Sun, A. V. Dobrynin, D. Shirvanyants, H.-B. Lee, K. Matyjaszewski, G. J. Rubinstein, M. Rubinstein, and S. Sheiko, Physical Review Letters 99, 137801 (2007).

 

Universality of polymer size in various solvents

We found that polymer conformations do not obey the predictions of classical theories. We are developing models that take into account long-range correlations and predict the dependence of polymer size on degree of polymerization.

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1. "Long-Range Correlations in a Polymer Chain Due to Its Connectivity" by D. Shirvanyants, S. Panyukov, Q. Liao, and M. Rubinstein, Macromolecules 41, 1475-1485 (2008).

 

Block polyampholytes

Block polyampholytes, charged polymers containing acidic and basic blocks, can self-assemble into organized structures. Our aim is to understand the dependence of their conformations and self-organization on composition of blocks, ionic environment, and temperature.

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1. "Scaling Theory of Polyelectrolyte and Polyampholyte Micelles" by N. Shusharina and M. Rubinstein in , Nanostructured Soft Matter: Experiment, Theory, Simulation and Prospectives. Series: NanoSciene ant Technology, Edited by A.V. Zvelindovski, Springer (2007).

2.. "Regimes of Conformational Transitions of a Diblock Polyampholyte" by Z. Wang and M. Rubinstein, Macromolecules 39, 5897-5912 (2006).

3. "Scaling Theory of Diblock Polyampholyte Solutions" by N. P. Shusharina, E. B. Zhulina, A. V. Dobrynin, and M. Rubinstein, Macromolecules 38, 8870-8881 (2005).

 

Functionalized nanop../reprints/articles

Nanop../reprints/articles with surfaces modified by polymers can self-assemble to particular structures under various concentrations. In collaboration with Dr. Kumacheva we are designing experiments to investiage possible structures that could be formed by those nanop../reprints/articles and developing thermodynamic theories to describe the mechanisms of the self-assembly process.

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1. "Supermolecular Assembbly of Gold Nanorods End-Terminated with Polymer Pom-Poms: Effect of Pom-Pom Structure on the Association Modes" by Z. Nie, D. Fava, M. Rubinstein, and E. Kumacheva, J. Am. Chem. Soc. 130, 3683-3689 (2008).

2. "Self-Assembly of Metal-Polymer Analogues of Amphiphilic Triblock Copolymers" by Z. Nie, D. Fava, E. Kumacheva, S. Zou, G. C. Walker and M. Rubinstein, Nature Materials 6, 609-614 (2007).

 

Tension amplification in a branched macromolecule

Amplification of tension in molecular bonds can be self-generated in highly branched macromolecules by focusing tension from many arms to a specific strand. We study the tension generated in branched macromolecules with different architectures and design strategy to amplify and focus tension onto a particular bond.

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1. "Amplification of Tension in Branched Macromolecules" by Panyukov, S.V., S.S. Sheiko, and M. Rubinstein, Physical Review Letters, 2009. 102(14).

 

Tension in Bonds

Tension in individual bonds is important because it changes the chemical reactivity, lifetime of materials, and electronic and optical properties of materials. Tension can be applied externally to single molecules by means of atomic force microscopy, magnetic tweezers, or biomembrane force probes, to name a few techniques. Also, tension can be generated internally as a result of molecular architecture and the focusing of forces due to excluded volume repulsion, such as in bottle-brush and pom-pom polymers. We use theory and simulations to quantitatively determine tension in individual bonds of complex molecules. Applications for this research include development of novel materials, single molecule force probes, finding new mechanochemistry, and better understanding mechanical coupling to chemistry in biological systems.

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1. “Bond Tension in Tethered Macromolecules” " by S. S. Sheiko, S. Panyukov, and M. Rubinstein, Macromolecules 44, 4520-4529 (2011).
2. “Chains Are More Flexible Under Tension” " by A. V. Dobrynin, J.-M. Y. Carrillo, and M. Rubinstein, Macromolecules 43, 9181–9190(2010).
3. "Tension Amplification in Molecular Brushes in Solutions and on Surfaces" by S. Panyukov, E. B. Zhulina, S. S. Sheiko, G. C. Randall, J. Brock, and M. Rubinstein, J. Phys. Chem. 113, 3750-3768 (2009).