Experimental data

Figureset containing experimental data for each Figure presented in the PLOS One article.<br

Brownian motion of nanofilaments

Dataset presenting Brownian motion of single filament with the code for persistence length calculation.<br

In-Situ Platinum Deposition on Nitrogen-Doped Carbon Films as a Source of Catalytic Activity in a Hydrogen Evolution Reaction

Copolymer-templated nitrogen-doped carbon (CTNC) films deposited on glassy carbon were used as electrodes to study electrochemically driven hydrogen evolution reaction (HER) in 0.5 M H₂SO₄. The activity of these materials was extremely enhanced when a platinum counter electrode was used instead of a graphite rod and reached the level of commercial Pt/C electrodes. Postreaction scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) measurements of electrode surfaces revealed that incorporation of even extremely low amounts of Pt resulted in this considerable gain of HER activity. High resolution XPS analysis and density functional theory (DFT) calculations confirmed that pyridinic nitrogen atoms act as active sites for Pt coordination and deposition. The Pt can be incorporated in both molecular (Pt²⁺) and metallic (Pt⁰) form. This study shows that great caution must be taken when designing “metal-free” HER catalysts based on N-doped carbons

Transformable Materials: Structurally Tailored and Engineered Macromolecular (STEM) Gels by Controlled Radical Polymerization

Structurally tailored and engineered macromolecular (STEM) gels constitute part of an emerging field of smart materials. STEM gels are polymer networks containing latent initiator sites available for postsynthesis modification. STEM gels synthesized by controlled radical polymerization (CRP) are presented. First, reversible addition–fragmentation chain transfer (RAFT) polymerization was used to copolymerize (meth)­acrylate monomer, di­(meth)­acrylate cross-linker, and inimer for the subsequent atom transfer radical polymerization (ATRP) grafting-from process. The resulting STEM gels were infiltrated with a second monomer, which formed side chains grafted from the inimer sites by photoactivated ATRP. This approach permits significant spatial and temporal control over the structure of the resulting material. Here, the technique was used to transform primary STEM gels into single-piece amphiphilic and hard/soft materials

Conjugated Polymers with Repeated Sequences of Group 16 Heterocycles Synthesized through Catalyst-Transfer Polycondensation

Periodic π-conjugated polymers of the group 16 heterocycles (furan, thiophene, and selenophene) were synthesized with controlled chain lengths and relatively low dispersities using catalyst-transfer polycondensation. The optical gap and redox potentials of these copolymers were fine-tuned by altering the heterocycle sequence, and atomic force microscopy revealed nanofibrillar morphologies for all the materials. Grazing incidence wide-angle X-ray scattering of the thiophene-selenophene copolymers indicated that the π-stacking distance increased with incorporation of the larger heteroatom (from ∼3.7–4.0 Å), while the lamellar spacing decreased (from ∼15.8–15.2 Å). The study also revealed that periodic sequences allow electronic properties to be tuned while retaining nanofibrillar morphologies similar to those observed for poly­(3-hexylthiophene)

Preparation of Polymeric Nanoscale Networks from Cylindrical Molecular Bottlebrushes

The design and control of polymeric nanoscale network structures at the molecular level remains a challenging issue. Here we construct a novel type of polymeric nanoscale networks with a unique microporous nanofiber unit employing the intra/interbrush carbonyl cross-linking of polystyrene side chains for well-defined cylindrical polystyrene molecular bottlebrushes. The size of the side chains plays a vital role in the tuning of nanostructure of networks at the molecular level. We also show that the as-prepared polymeric nanoscale networks exhibit high specific adsorption capacity per unit surface area because of the synergistic effect of their unique hierarchical porous structures. Our strategy represents a new avenue for the network unit topology and provides a new application for molecular bottlebrushes in nanotechnology

Synthesis of Polyfuran and Thiophene-Furan Alternating Copolymers Using Catalyst-Transfer Polycondensation

There is intense interest in the rational design of semiconducting materials to improve organic electronics. Furan is a particularly attractive monomer for building biorenewable and biodegradable π-conjugated frameworks. In this report, regioregular head-to-tail and head-to-head poly­(3-hexylfuran) were synthesized using chain-growth polycondensation. The resultant polyfurans have relatively low molecular weights but also low dispersities. The head-to-head polyfuran adopted a nearly identical coplanar backbone conformation as its head-to-tail analog in the solid state, as determined by UV–visible spectroscopy and atomic force microscopy. Extensive aggregation of the furan homopolymer during polymerization led to the investigation of an alternating furan-thiophene copolymer, confirming that furyl-based monomers can polymerize in a chain-growth manner. All of the synthesized polymers are sensitive when exposed to both oxygen and light

Self-Healing Polymer Films Based on Thiol–Disulfide Exchange Reactions and Self-Healing Kinetics Measured Using Atomic Force Microscopy

Self-healing polymeric materials with branched architectures and reversible cross-linking functionalities at the periphery of branches were synthesized by atom transfer radical polymerization (ATRP). Poly(<i>n</i>-butyl acrylate) grafted star polymers were prepared by chain extension ATRP from cross-linked cores comprised of poly(ethylene glycol diacrylate). These polymers were further used as macroinitiators for the consecutive chain extension ATRP of bis(2-methacryloyloxyethyl disulfide) (DSDMA), in which way disulfide reversible cross-links (SS) were introduced at the branch peripheries. The SS cross-linked polymers were then cleaved under reducing conditions to form thiol (SH)-functionalized soluble star polymers. The SH-functionalized star polymer solutions were deposited on silicon wafer substrates and converted to insoluble SS re-cross-linked films via oxidation. The self-healing of prepared polymer films was studied by continuous atomic force microscopy (AFM) imaging of cuts micromachined with the AFM tip and by optical microscopy. The re-cross-linked star polymer (X3) showed a rapid spontaneous self-healing behavior, with the extent of healing dependent on the initial film thickness and the width of the cut. The self-healing behavior observed for this sample was attributed to the regeneration of SS bonds via thiol–disulfide exchange reactions. This study demonstrated the suitability of grafted multiarm polymer architectures as building blocks of self-healing polymeric materials and pointed to the importance of low intrinsic viscosity of material and high accessibility of functional groups responsible for healing

Systematic Investigation of Benzodithiophene-Benzothiadiazole Isomers for Organic Photovoltaics

Two new donor–acceptor small molecules based on benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene (BDT) and benzo­[<i>c</i>]­[1,2,5]­thiadiazole (BT) were designed and synthesized. Small molecules 4,4′-[(4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)­benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene-2,6-diyl)­bis­(2,2′-bithiophene)-5,5′-diyl]­bis­(benzo­[<i>c</i>]­[1,2,5]­thiadiazole) (BDT-TT-BT) and 4,4′-(4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)­benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene-2,6-diyl)­bis­[7-(2,2′-bithiophene-5-yl)­benzo­[<i>c</i>]­[1,2,5]­thiadiazole] (BDT-BT-TT) are structural isomers with the 2,2-bithiophene unit placed either between the BDT and BT units or at the end of the BT units. This work is targeted toward finding the effect of structural variation on optoelectronic properties, morphology, and photovoltaic performance. On the basis of theoretical calculations, the molecular geometry and energy levels are different for these two molecules when the position of the 2,2-bithiophene unit is changed. Optical and electrochemical properties of these two small molecules were characterized using UV–vis and cyclic voltammetry. The results showed that BDT-BT-TT has broader absorption and an elevated HOMO energy level when compared with those of BDT-TT-BT. The performance of these two isomers in solar cell devices was tested by blending with [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). Power conversion efficiencies as high as 3.22 and 3.71% were obtained in conventional solar cell structures for BDT-TT-BT and BDT-BT-TT, respectively. The morphology was studied using grazing incident wide-angle X-ray scattering and transmission electron microscopy, which revealed different phase separations of these two molecules when blended with PC₇₁BM

Polyacrylonitrile‑<i>b</i>‑poly(butyl acrylate) Block Copolymers as Precursors to Mesoporous Nitrogen-Doped Carbons: Synthesis and Nanostructure

A series of polyacrylonitrile-<i>block</i>-poly­(butyl acrylate) (PAN-<i>b</i>-PBA) copolymers were prepared by supplemental activator reducing agent atom transfer radical polymerization (SARA ATRP). These copolymers were then used as precursors to pyrolytic nanostructured carbons with the PAN block serving as a nitrogen-rich carbon precursors and the PBA block acting as a sacrificial porogen. The study revealed that while the size of mesopores can be controlled by the size of the porogenic block, the connectivity of pores diminishes with the decrease of the overall molecular weight of the precursor. This partial loss of mesopore connectivity was attributed to the weaker phase segregation between the blocks of shorter lengths inferred from the shape of small-angle X-ray scattering profiles and from the crystallinity of polyacrylonitrile phase