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The hydrophobic interaction is significantly responsible for driving protein folding and self-assembly. To understand it, the thermodynamics, the role of water structure, the dewetting process surrounding hydrophobes, and related aspects have undergone extensive investigations. Here, we examine the hypothesis that polymer-solvent interfacial free energy is adequate to describe the energetics of the collapse of a hydrophobic homopolymer chain at fixed temperature, which serves as a much simplified model for studying the hydrophobic collapse of a protein. This implies that changes in polymer-solvent interfacial free energy should be directly proportional to the force to extend a collapsed polymer into a bad solvent. To test this hypothesis, we undertook single-molecule force spectroscopy on a collapsed, single, polystyrene chain in water-ethanol and water-salt mixtures where we measured the monomer solvation free energy from an ensemble average conformations. Different proportions within the binary mixture were used to create solvents with different interfacial free energies with polystyrene. In these mixed solvents, we observed a linear correlation between the interfacial free energy and the force required to extend the chain into solution, which is a direct measure of the solvation free energy per monomer on a single chain at room temperature. A simple analytical model compares favorably with the experimental results. This knowledge supports a common assumption that explicit water solvent may not be necessary for cases whose primary concerns are hydrophobic interactions and hydrophobic hydration. [ABSTRACT FROM AUTHOR]

Organized arrays of anisotropic nanoparticles show electronic and optical properties that originate from the coupling of shape-dependent properties of the individual nanorods. The organization of nanorods in a controllable and predictable way provides a route to the fabrication of new materials and functional devices. So far, significant progress has been achieved in the self-assembly of nanorod arrays, yet the realization of a range of different structures requires changing the surface chemistry of the nanoparticles. We organized metal nanorods in structures with varying geometries by using a striking analogy between amphiphilic ABA triblock copolymers and the hydrophilic nanorods tethered with hydrophobic polymer chains at both ends. The self-assembly was tuneable and reversible and it was achieved solely by changing the solvent quality for the constituent blocks. This approach provides a new route to the organization of anisotropic nanoparticles by using the strategies that are established for the self-assembly of block copolymers. [ABSTRACT FROM AUTHOR]

Solution-based linearself-assembly of metal nanoparticles offersa powerful strategy for creating plasmonic polymers, which, so far,have been formed from spherical nanoparticles and cylindrical nanorods.Here we report linear solution-based self-assembly of metal nanocubes(NCs), examine the structural characteristics of the NC chains, anddemonstrate their advanced optical characteristics. In comparisonwith chains of nanospheres with similar dimensions, composition, andsurface chemistry, predominant face-to-face assembly of large NCscoated with short polymer ligands led to a larger volume of hot spotsin the chains, a nearly uniform E-field enhancement in the gaps betweencolinear NCs, and a new coupling mode for NC chains due to the formationof a Fabry–Perot resonatorstructure formed by face-to-face bonded NCs. The NC chains exhibitedstronger surface-enhanced Raman scattering in comparison with linearassemblies of nanospheres. The experimental results were in agreementwith finite difference time domain simulations. [ABSTRACT FROM AUTHOR]