Materials:Unless otherwise noted, all solvents and reagents were purchased from VWR or Sigma-Aldrich.The ruthenium-based metathesis catalyst was obtained from Materia Inc. and stored in a drybox prior to use, and the RuO4 SEM staining agent was obtained from Polysciences, Inc and stored at 4 ºC. The ruthenium metathesis catalyst ((H2IMes)(pyr)2(Cl)2RuCHPh) and PLA macromonomer initiator (N-(hydroxyethanyl)-cis-5-norbornene-exo-2,3-dicarboximide) were prepared as described previously (1). Dry solvents were purified by passing them through solvent purification columns, and 3,6-dimethyl-1,4-dioxane-2,5-dione was purified by sublimation under vacuum. All other solvents and chemicals were used without further purification unless otherwise noted. General Information:NMR spectra were recorded at room temperature on a Varian Inova 500 (at 500 MHz), and analyzed on MestReNova software. Gel permeation chromatography (GPC) was carried out in THF on two Plgel 10 μm mixed-B LS columns (Polymer Laboratories) connected in series with a miniDAWN TREOS multiangle laser light scattering (MALLS) detector, a ViscoStar viscometer and Optilab rex differential refractometer (all from Wyatt Technology). The dn/dc values used for the polylactide and polystyrene macromonomers were 0.050 and 0.180 respectively, and dn/dc values for the brush polymers and random copolymers were obtained for each injection by assuming 100% mass elution from the columns. SEM images were taken on a ZEISS 1550 VP

We investigate the relationship between inherent secondary structure and aggregation propensity of peptides containing chameleon sequences (i.e., sequences that can adopt either α or β structure depending on context) using a combination of replica exchange molecular dynamics simulations, ion-mobility mass spectrometry, circular dichroism and transmission electron microscopy. We focus on an eight-residue long chameleon sequence that can adopt an α-helical structure in the context of the iron-binding protein from Bacillus anthracis (PDB id 1JIG) and a β-strand in the context of the baculovirus P35 protein (PDB id 1P35). We show that the isolated chameleon sequence is intrinsically disordered, interconverting between α-helical and β-rich conformations. The inherent conformational plasticity of the sequence can be constrained by addition of flanking residues with a given secondary structure propensity. Intriguingly, we show that the chameleon sequence with helical flanking residues aggregates rapidly into fibrils, whereas the chameleon sequence with flanking residues that favor β-conformations has weak aggregation propensity. This work sheds new insights into the possible role of α-helical intermediates in fibril formation.

We use self‐consistent field theory to calculate the energy of defect formation in cylinder‐forming diblock copolymers in laterally confining thin channels. We focus on two isolated defects, dislocations and disclinations and explore a wide range of polymer and channel characteristics. Our findings suggest appropriate conditions for the design of optimized graphoepitaxial processes, where defects are limited to very low concentrations. Using the string method, we also investigate the energy barriers and kinetic pathways of the transition from defective to perfect states. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40790.

We use self‐consistent field theory to study the self‐assembly of cylinder‐forming diblock copolymers confined in a cylindrical prepattern. This situation arises in contact holes—the hole shrink problem—where the goal is to produce a cylindrical hole with reduced dimensions relative to a guiding prepattern. In this study, we focus on systems with a critical prepattern dimension ranging from 50 nm to 100 nm that consequently lead to the formation of a single cylinder in the middle of the hole. We find that a variety of defect morphologies arise from the self‐assembly process and are strongly governed by the prepattern dimensions, wetting conditions as well as the polymer molecular weight. We also consider blends of diblock copolymers and homopolymers and determine optimal blending configurations that not only favor the formation of the desired cylindrical morphology but also extend the processing window relative to the pure diblock case. When defective structures form inside the prepattern, we compute their formation energy and use the string method to examine the kinetic pathways for the transition from the defective state to the perfect cylindrical state. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 142–153

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