Research Field 1

Gloger, D. et. al. ACS Applied Polymer Materials, 2024, 6, 10824-10841, https://doi.org/10.1021/acsapm.4c01938

In this study, we report the coupling of high-density polyethylene (HDPE) and isotactic polypropylene (iPP) into grafted block copolymers (HDPE-g-iPP) from HDPE and iPP precursors subjected to reactive extrusion with an organic peroxide, however, without a cross-linker. Coupling of macroradicals in the melt state is confined to a small interfacial volume at the HDPE/iPP domain interfaces of this immiscible two-phase blend system. The tendency of HDPE macroradicals to branch and cross-link into a solid-like network, together with the tendency of iPP macroradicals to simply cleave, is a common problem to overcome. Moreover, to prove HDPE-g-iPP molecules in reactive HDPE/iPP blends is difficult due to the low grafting yields and the additional challenge to analytically distinguish HDPE-g-iPP molecules from the HDPE/iPP matrix. In this study, we work with a low-viscosity blend system, which, combined with the low unsaturation content of the HDPE, made cross-linking negligible. We identify HDPE-g-iPP molecules via interaction chromatography by iPP components in the HDPE elution range and by analytical temperature-rising elution fractionation, where we find HDPE in the iPP elution range. Physical characterization by thermal, dynamic mechanical, and morphological analyses confirmed that the reactive blend is compatibilized by HDPE-g-iPP molecules, seen by shifts in crystallization temperature and glass transition, and by diffuse domain interfaces. With improved grafting yields, reactive blends could potentially be used directly as compatibilizers. Copyright © 2024, American Chemical Society.

Cai, Y. et. al. Macromolular Chemistry & Physics, 2024, 2400177, https://doi.org/10.1002/macp.202400177

Semi-interpenetrating polymer networks (semi-IPNs), composed of two or more polymers, forming intertwined network-architectures, represent a significant type of polymer combination in modern industry, especially in automotive and medical devices. An initiator-free synthesis of semi-interpenetrating polymer networks via Bergman cyclization (BC) is reported here, acting as a trigger to embed a second polymer via its reactive enediyne (EDY) moiety, then embedded into the first network. (Z)-oct-4-ene-2,6-diyne-1,8-diol (diol-EDY) is targeted as the precursor of the second polymer, swollen into the first polyurethane network (PU), followed by a radical polymerization induced by the radicals formed by the BC. The formation of the semi-IPN is monitored via electron paramagnetic resonance (EPR) spectroscopy, infrared-spectroscopy (FT-IR), and thermal methods (DSC), proving the activation of the EDY-moiety and its subsequent polymerization to form the second polymer. Stress−strain characterization and cyclic stress−strain investigations, together with TGA and DTG analysis, illustrate improved mechanical properties and thermal stability of the formed semi-IPN compared to the initial PU-network. The method presented here is a novel and broadly applicable approach to generate semi-IPNs, triggered by the EDY-activation via Bergman cyclization. © 2024 The Author(s). Macromolecular Chemistry and Physics published by Wiley‐VCH GmbH.

Alqaisi, M. et. al., Polymer Chemistry, 2024, 15, 2949 – 2958, https://doi.org/10.1039/D4PY00355A

The generation of nanosized compartments in single chain nanoparticles (SCNPs) is a promising approach to generate individualized confinement-zones on a small scale for drug-encapsulation or catalysis. We here report the synthesis and characterization of compartmented, fluorinated SCNPs generated by single-chain collapse of amphiphilic copolymers. Polyethylene glycol (PEG) functionalized monomers were utilized as hydrophilic moieties, while hydrophobic residues were introduced using different mole fractions of either aliphatic or fluorinated monomers. Single chain collapse and subsequently crosslinking via copper-catalyzed azide–alkyne click reactions in selective and non-selective solvents yields internally structured SCNPs with hydrodynamic radii of 2.5–5.8 nm. Reproduced with permission from the Royal Society of Chemistry

Cai, Y. et.al., Macromol. Rapid Commun., 2023, 202300440,  https://doi.org/10.1002/marc.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

Li, C. et. al., Macromol. Raid Commun., 2023,  2300464,  https://doi.org/10.1002/marc.202300464 

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

Cai, Y., et al. Polym. Chem., 2022, DOI:https://doi.org/10.1039/D2PY00259K

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.

Chen, S., et al. Angew. Chem. Int. Ed., 2022, DOI:https://doi.org/10.1002/anie.202203876   

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.

Li, C., et al. Int. J. Macromol. Sci., 2021, DOI:https://www.mdpi.com/1422-0067/22/23/12679

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.

Chen, S. P., et al. J. Macromol. Rapid Commun., 2022, DOI:https://doi.org/10.1002/marc.202200168

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.

Wang, H., et al. Polym. Chem., 2021, DOI:https://doi.org/10.1039/D1PY01061A

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.