Appropriately designed chemical architectures can fold to adopt well-defined secondary structures without the need for structural motifs of biological origin. We have designed tris(N-salicylideneaniline)-based hyperbranched molecules that spontaneously collapse to compact three-blade propeller geometry of either (P)- or (M)-handedness. For a homologous series of compounds, a direct correlation was established between the absolute screw sense, either (P)- or (M)-, of this helical folding and the absolute configuration, either (R)- or (S)-, of the chiral alcohol groups introducing local asymmetric bias to the conformationally restricted molecular backbone. 1H NMR and CD spectroscopic studies provided significant insights into structural folding and unfolding of these chiral molecules in solution, which proceed via reversible assembly and disassembly of the C3-symmetric hydrogen-bonding network. Notably, solvents profoundly influenced this dynamic process. A strong correlation between the solvent donor number (DN) or solvent basicity (SB) parameters and the change in the Cotton effects pointed toward specific O-H...solvent interactions that drive structural unfolding and eventual refolding to apparently opposite helicity. This unusual chirality inversion process could also be induced by installation of chemical protecting groups that simulate specific solvent-solute interactions. Removal of this covalent mimic of the solvent shell restored the original screw sense of the parent molecule, thus establishing the feasibility of covalently triggered helicity inversion as a new mode of operation for chiroptical molecular switches.

Matrix free assemblies of polymer‐grafted, “hairy” nanoparticles (aHNP) exhibit novel morphology, dielectric, and mechanical properties, as well as providing means to overcome dispersion challenges ubiquitous to conventional polymer‐inorganic nanocomposite blends. Physical aging of the amorphous polymer glass between the close‐packed nanoparticles (NPs) will dominate long‐term stability; however, the energetics of volume recovery within the aHNPs is unknown. Herein, we compare glass transition temperature (Tg) and enthalpy recovery of aHNPs to NP‐polymer blends, across different nano‐silica loadings (0–50 v/v%) and canopy architecture of polystyrene (PS) grafted silica. For aHNPs, the grafting of PS to silica imposes an additional design constraint between silica volume fraction, graft density, and graft molecular weight. At low and intermediate silica volume fraction, the Tg of blended nanocomposites is independent of silica content, reflecting a neutral polymer‐NP interface. For aHNPs, the Tg decreases with silica content, implying that chain tethering decreases local segment density more than the effect of molecular weight or polymer‐NP interactions. Additionally, the Tg of the aHNPs is higher than a linear matrix of comparable molecular weight, implying a complementary effect to local segment density that constrains cooperativity. In contrast, enthalpy recovery rate in the blend or aHNP glass is retarded comparably. In addition, a cross‐over temperature, Tx, emerges deep within the glass where the enthalpy recovery process of all nanocomposites becomes similar to linear unfilled matrices. Differences between structural recovery in aHNP and blended nanocomposites occur only at the highest silica loadings (∼ 50 v/v%), where enthalpy recovery for aHNPs is substantially suppressed relative to the blended counterparts. The absence of physical aging at these loadings is independent of brush architecture (graft density or molecular weight of tethered chains) and indicates that the impact of chain tethering on effective bulk structural relaxation starts to appear at particle‐particle surface separations on the order of the Kuhn length. Overall, these observations can be understood within the context of how three separate structural characteristics impact local segment density and relaxation processes: the dimension and architecture of the tethered polymer chains, the separation between NP surfaces, and the confinement imposed by chain tethering and space filling within the aHNP. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 319–330

Chemical architectures supporting a high degree of electronic conjugation serve as important functional components in devices and materials for advanced electronic and photonic applications. Increasing the spatial dimensionality of such constructs can fundamentally modify their optoelectronic properties and significantly alter intra- and intermolecular interactions that are crucial for understanding and controlling charge/energy-transfer processes. In this article, emerging design principles in the construction of well-defined conjugated platforms beyond molecular wires are highlighted. Both covalent and noncovalent approaches can be strategically employed to position one-dimensional (1D) substructures in a spatially well-defined manner in order to enhance both structural and functional complexity in a two-dimensional (2D) setting. A predictable and controllable switching mechanism can be designed and implemented with mobile 2D electronic conjugation that operates by correlated motions of inherently rigid 1D subunits. This emerging "dynamic" approach complements and challenges the prevailing "static" paradigm of conjugated chemical architectures.

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Cooperative interaction between multiple chiral centers dictates the absolute handedness of structural folding. We have designed and prepared a series of chiral C 3 -symmetric tris(Nsalicylidenamine) derivatives that adopt three-blade propeller-like conformations. Synthetic access to an expanded family of such constructs was aided by enzymatic resolution and C-C cross-coupling reactions of aryl-substituted chiral propargylic alcohol derivatives. These key structural components were integrated into molecular propellers of predetermined helical screw sense. Through comparative studies on a homologous set of molecules, we found that installation of phenylene-ethynylene-derived π-conjugation profoundly affected the stabilities of the helically folded structures, as evi-

The parameter ∆ε (in M -1 cm -1 ) appearing in this article, including figures, to report the CD intensity should be corrected to [θ] Because the experiments were actually carried out at 300 K, the correct value of the viscosity of D 2 O is 1.0465 mPa · s.1 After correction for the presence of salts using the Jones-Dole equation, 2 the final viscosity of the D 2 O solution used to carry out the PFGSE NMR experiments was 1.0586 mPa · s. Because the viscosity is used to convert the diffusion coefficient of the dendrimers, measured by the NMR experiment, into a hydrodynamic radius (R h ) via the Stokes-Einstein equation, this error led to an incorrectly stated value of R h . The incorrect value of R h given in the paper for G4-OH and G4-OH(Pd 55 ) is 1.7 ( 0.2 nm for both species. The actual value of R h for both G4-OH and G4-OH(Pd 55 ), calculated using the proper solution viscosity and temperature, is 2.0 ( 0.2 nm. This latter value agrees very well with previous R h values determined by PFGSE NMR experiments for G4-NH 2 and G4-OH (2.08 ( 0.13 nm 3 and ∼1.85 nm, 4 respectively).The errors discussed herein do not significantly change any of the conclusions or claims made in the original paper.We sincerely regret this error, and we thank Prof. Neer Asherie (Yeshiva University) for pointing it out. Literature Cited(1) http://webbook.nist.gov/.(2) Jones, G.; Dole, M.