Single-Chain Folding of Diblock Copolymers Driven by Orthogonal H‑Donor and Acceptor Units

We report the precision single-chain folding of narrow dispersity diblock copolymers via pairwise orthogonal multiple hydrogen bonding motifs and single chain selected point folding. Well-defined linear polystyrene (PS) and poly­(<i>n</i>-butyl acrylate) (P<i>n</i>BA) carrying complementary recognition units have been synthesized via activators regenerated by electron transfer/atom transfer radical polymerization (ARGET ATRP) utilizing functional initiators yielding molecular weights of <i>M</i>_n,SEC = 10900 Da, <i><i>Đ</i> =</i> 1.09 and <i>M</i>_n,SEC = 3900 Da, <i><i>Đ</i> =</i> 1.10, respectively. The orthogonal hydrogen bonding recognition motifs were incorporated into the polymer chain ends of the respective building blocks (to yield an eight shaped single chain folded polymers). Diblock copolymer formation was achieved via the Cu­(I) catalyzed azide–alkyne cycloaddition (CuAAC) reaction, while the single-chain folding of the prepared linear diblock copolymer–at low concentrations–was driven by orthogonal multiple hydrogen bonds via three-point thymine–diaminopyridine and six-point cyanuric acid–Hamilton wedge self-association. The self-folding process was followed by proton nuclear magnetic resonance (¹H NMR) spectroscopy focused on the respective recognition pairs at low temperature. In addition, the single-chain folding of the diblock copolymer was analyzed by dynamic light scattering (DLS) and concentration dependent diffusion ordered NMR spectroscopy (DOSY) as well as atomic force microscopy (AFM), providing a limiting concentration for self-folding (in dichloromethane at ambient temperature) of close to 10 mg mL^–1

A Mild and Efficient Approach to Functional Single-Chain Polymeric Nanoparticles via Photoinduced Diels–Alder Ligation

We present a new ambient temperature synthetic approach for the preparation of single-chain polymeric nanoparticles (SCNPs) under mild conditions using a UV-light-triggered Diels–Alder (DA) reaction for the intramolecular cross-linking of single polymer chains. Well-defined random copolymers with varying contents of styrene (S) and 4-chloromethylstyrene (CMS) were synthesized employing a nitroxide-mediated radical polymerization (NMP) initiator functionalized with a terminal alkyne moiety. Postpolymerization modification with 4-hydroxy-2,5-dimethylbenzophenone (DMBP) and an <i>N</i>-maleimide (Mal) derivative led to the functional linear precursor copolymers. The intramolecular cross-linking was performed by activating the DMBP groups via irradiation with UV light of 320 nm for 30 min in diluted solution (<i>c</i>_Polymer = 0.017 mg mL^–1). The ensuing DA reaction between the activated DMBP and the Mal groups resulted in well-defined single-chain polymeric nanoparticles. To control the size of the SCNPs, random copolymers with varying CMS contents (i.e., different functional group densities (FGD)) were employed for the single-chain collapse. Additionally, monotethered nanoparticles were prepared via the copper-catalyzed azide–alkyne cycloaddition between the alkyne bearing copolymer with the highest FGD and an azide-terminated poly­(ethylene glycol) (PEG) prior to UV-induced cross-linking. The formation of SCNPs was followed by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), and atomic force microscopy (AFM)

Preparation of Freestanding Conjugated Microporous Polymer Nanomembranes for Gas Separation

Conjugated microporous polymers (CMPs) have attracted much interest due to their intrinsic porosity, outstanding stability, and high variability. However, the processing of these materials for membrane application has been limited due to their insoluble nature when synthesized as bulk material. Here we report the synthesis of freestanding CMP-nanomembranes via layer-by-layer growth of a “click” based conjugated microporous polymer on a sacrificial substrate. After dissolution of the substrate the CMP-nanomembrane can be transferred to porous substrates and continuously cover holes of up to 50 μm diameter. The CMP-nanomembranes appear defect-free as inferred from high selectivity values obtained from gas permeation experiments and from electrochemical investigation in the presence of ferrocene. The presented synthesis method represents a versatile strategy to incorporate CMP materials in functional devices for membrane separation, catalysis, or organic electronics