Triggered Crosslinking of Main-Chain Enediyne Polyurethanes via Bergman-Cyclization

Cai, Y., Macromol. Rapid Commun., 2023, 202300440,

Crosslinking chemistries occupy an important position in polymer modification with a particular importance when triggered in response to external stimuli. Enediyne (EDY) moieties are used as functional entities in this work, known to undergo a pericyclic Bergman cyclization (BC) to induce a triggered crosslinking of polyurethanes (PU) via the intermediately formed diradicals. Diamino-EDYs, where the distance between the enyne-moieties is known to be critical to induce a BC, are placed repetitively as main-chain structural elements in isophorone-based PUs to induce reinforcement upon heating, compression, or stretching. A 7-day compression under room temperature results in a ≈69% activation of the BC, together with the observation of an increase in tensile strength by 62% after 25 stretching cycles. Purely heat-induced crosslinking contributes to 191% of the maximum tensile strength in comparison to the virgin PU. The BC herein forms an excellent crosslinking strategy, triggered by heat or force in PU materials. © 2023 The Authors. Macromolecular Rapid Communications published by Wiley‐VCH GmbH

Stability of Quadruple Hydrogen Bonds in an Ionic Liquid Environment

Li, C. et. al., Macromol. Raid Commun., 2023,  2300464 

Hydrogen bonds (H-bonds) are highly sensitive to the surrounding environments owing to their dipolar nature, with polar solvents kown to significantly weaken H-bonds. Herein, the stability of the H-bonding motif ureidopyrimidinone (UPy) is investigated, embedded into a highly polar polymeric ionic liquid (PIL) consisting of pendant pyrrolidinium bis(trifluoromethylsulfonyl)imide (IL) moieties, to study the influence of such ionic environments on the UPy H-bonds. The content of the surrounding IL is changed by addition of an additional low molecular weight IL to further boost the IL content around the UPy moieties in molar ratios of UPy/IL ranging from 1/4 up to 1/113, thereby promoting the polar microenvironment around the UPy-H-bonds. Variable-temperature solid-state MAS NMR spectroscopy and FT-IR spectroscopy demonstrate that the UPy H-bonds are largely present as (UPy-) dimers, but sensitive to elevated temperatures (>70 °C). Subsequent rheology and DSC studies reveal that the ILs only solvate the polymeric chains but do not interfere with the UPy-dimer H-bonds, thus accounting for their high stability and applicability in many material systems. © 2023 The Authors. Macromolecular Rapid Communications published by Wiley‐VCH GmbH

Bergman cyclization of main-chain enediyne polymers for enhanced DNA cleavage

Cai, Y., et al. Polym. Chem., 2022, DOI:

Since the discovery of the role of enediynes in natural antibiotics (such as calicheamicines) via in situ diradical-induced DNA strand cleavage, Bergman cyclization has attracted fervent attention for decades. The synthesis of main-chain enediyne polymers was accomplished, allowing to embed and control the reactivity of the diamino enediynes via polycondensation into polyimines inside their main-chain. These polymers exert a chain-length dependent DNA cleavage activity under physiological conditions, additionally tunable by modulating the stereoelectronic environment via their substitution patterns.

Hydrogen-Bonded Supramolecular Polymer Adhesives: Straightforward Synthesis and Strong Substrate Interaction

Chen, S., et al. Angew. Chem. Int. Ed., 2022, DOI:   

High-performance adhesives are important in view of reversible bonding/debonding chemistries, allowing to efficiently recycle and separate polymer blends and composites. We herein identify a straightforward synthetic strategy towards universal hydrogen-bonded (H-bonded) polymeric adhesives, using a side-chain barbiturate (Ba) and Hamilton wedge (HW) functionalized copolymer. Starting from a rubbery copolymer containing thiolactone derivatives, Ba and HW moieties are tethered as pendant groups via an efficient one-pot two-step amine-thiol-bromo conjugation. The presence of individual Ba or HW moieties enables strong binding to a range of substrates, outstanding compared to commercial glues and reported adhesives.

Comparing C2=O and C2=S Barbiturates: Different Hydrogen Bonding Patterns of Thiobarbiturates in Solution and the Solid State

Li, C., et al. Int. J. Macromol. Sci., 2021, DOI:

Carbonyl-centered hydrogen bonds with various strength and geometries are often exploited in materials to embed dynamic and adaptive properties, with the use of thiocarbonyl groups as hydrogen-bonding acceptors remaining only scarcely investigated. We herein report a comparative study of C2=O and C2=S barbiturates in view of their differing hydrogen bonds, using the 5,5-disubstituted barbiturate B and the thiobarbiturate TB as model compounds. Differences in their association in solution were extracted via concentration- and temperature-dependent NMR experiments, as well as in Langmuir films, and Brewster angle microscopy. When embedded into a hydrophobic polymer such as polyisobutylene, a largely different rheological behavior was observed for the barbiturate-bearing PB compared to the thiobarbiturate-bearing PTB polymers, indicative of a stronger hydrogen bonding in the thioanalogue PTB.

Hydrogen-Bonds Mediated Nanomedicine: Design, Synthesis and Applications

Chen, S. P., et al. J. Macromol. Rapid Commun., 2022, DOI:

Hydrogen-bonds (H-bonds) bridge artificial and biological sciences, implementing dynamic properties into materials and (macro)molecules, which cannot be achieved via purely covalent bonds. In this review, the current state-of-the-art for designing novel H-bonded nanomedicines for precise diagnosis, and targeted therapeutic drugs delivery are highlighted.

Hydrogen-bonding mediated self-assembly of amphiphilic ABA triblock copolymers into well defined giant vesicles

Wang, H., et al. Polym. Chem., 2021, DOI:

Giant vesicles represent an extremely useful system to mimic biomembranes. By designing a hydrogen-bonding (H-bonding) amphiphilic ABA triblock copolymer and introducing 2,6-diaminopyridine (DAP) moieties as pendant groups into the middle hydrophobic block, we demonstrate a straightforward and effective self-assembly strategy to form giant vesicles (∼3 μm in diameter) via a combination of H-bonding and amphiphilic interactions. Atomic force microscopy (AFM) studies further prove the hollow interior of these vesicular morphologies. This study provides a new opportunity for the design of supramolecular polymers, serving as polymeric vesicle scaffolds in materials design and may act as red-blood-cell-like containers in delivery and microreactor applications.

Synthesis and self-aggregated nanostructures of hydrogen-bonding polydimethylsiloxane

Chen,* S.,et al. Polymer Chemistry, 2021, 28(12), 4111-4119,

Gaining control over assembled nanostructures is an important aspect in nanotechnology and materials. We investigate nanostructures, including lamellae (LAM), hexagonally packed cylinders (HPC), body-centered cubic spheres (BCC) and disordered micelles (DIM), primarily influenced by the nature of H-bonding moieties (e.g., Ba, TAP, HW) attached to the PDMS polymers, proving that the immiscibility parameter and volume fraction between nonpolar PDMS and polar H-bonding moieties both are determining the final structures. We report the precise synthesis of tailored polydimethylsiloxanes (PDMS) at their α-ends, bearing a series of H-bonding moieties (e.g., barbiturate (Ba), 2,4,6-triaminopyrimidine (TAP) and Hamilton wedge (HW)), using robust copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Self-aggregated H-bonds are formed in the solid state from the obtained H-bonding PDMS, as evidenced by the temperature dependent solid-state 1H MAS NMR. We also demonstrate a thermally reversible order-disorder transition (ODT) of the observed nanostructures, induced by the H-bonding self-aggregation as observed via temperature-dependent SAXS investigations. Published with a permission of the Royal Society of Chemistry 2021.

Halogen-Bond Mediated 3D Confined Assembly of AB Diblock Copolymer and C Homopolymer Blends

Zheng, X. et al. Small, 2021, 2007570,

Halogen-bond driven assembly, a world parallel to hydrogen-bond, has emerged as an attractive tool for constructing (macro)molecular arrangement. An I….N bond mediated confined-assembly pathway to enable order-order phase transitions is reported here. Polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) AB diblock copolymers are chosen as halogen acceptor, while an iodotetrafluorophenoxy substituted C-type homopolymer, (poly(3-(2,3,5,6-tetrafluoro-4-iodophenoxy)propyl acrylate), PTFIPA) is designed as halogen donor, synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Formation of halogen bonding donor–acceptor pairs induce an order-to-order morphology transition sequence changing from spherical cylindrical lamellar inverse cylindrical. Subsequent selective swelling/deswelling of the P4VP domains gives rise to further internal morphology transitions, creating tailored mesoporous microparticles, disassembled nanodiscs, and superaggregates. © 2021 Wiley‐VCH GmbH

Cyclopropanation of Poly(isoprene) Using NHC-Cu(I) Catalysts: IntroducingCarboxylates

Shinde, K.S., et al. Journal of Polymer Science, 2020, 58 (20), 2864-2874,

The incorporation of functional groups into unsaturated polyolefine-polymers often represent a challenging task. We in this paper develop an approach to decorate the polymer backbone of poly(diene)s with ester as well as carboxylic groups via cyclopropanation. Predominantly cis-1,4-poly(isoprene)s are converted with ethyl or tert-butyl diazoacetate using copper(I) N-heterocyclic carbene (NHC) catalysts in modification degrees of 4 – 5 %, displaying potential for up-scaling for manufacturing of modified synthetic rubbers. Copyright 2020©, The Authors. Journal of Polymer Science published by Wiley Periodicals LLC