3D printing of solvent-free supramolecular polymers

Rupp, H., et al. Frontiers in Chemistry, 2021, DOI:https://doi.org/10.3389/fchem.2021.771974

Additive manufacturing has significantly changed polymer science and technology by engineering complex material shapes and compositions. With the advent of dynamic properties in polymeric materials as a fundamental principle to achieve, e.g., self-healing properties, the use of supramolecular chemistry as a tool for molecular ordering has become important. We here review recent progress in the 3D printing of supramolecular polymers, with a focus on fused deposition modelling (FDM) to overcome some of its limitations still being present up to date and open perspectives for their application.

Nanoscale structure and dynamics of thermoresponsive single-chain nanoparticles investigated by EPR spectroscopy

Roos, A. H., et al. Soft Matter, 2021, DOI:https://doi.org/10.1039/D1SM00582K

We characterize temperature-dependent macroscopic and nanoscopic phase transitions and nanoscopic pre-transitions of water-soluble single chain nanoparticles (SCNPs). We analyze the temperature-dependent phase transitions of spin-labeled SCNPs by rigorous spectral simulations of a series of multicomponent EPR-spectra that derive from the nanoinhomogeneities (1) that are due to the single-chain compartmentation in SCNPs and (2) the transformation upon temperature change due to the LCST behavior. These transitions of the SCNPs and their respective polymer precursors can be monitored and understood on the nanoscale by following EPR-spectroscopic parameters like hyperfine couplings that depend on the surrounding solvent molecules or Heisenberg spin exchange.

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

Wang, H., et. al. J. Polymer Chemistry, 2021, 12, 6300-6306, https://doi.org/10.1039/D1PY01061A

Giant vesicles represent an extremely useful system to mimick biomembranes. By designing a hydrogen-bonding (H-bonding) amphiphilic ABA triblock copolymer and introducing 2,6-diaminopyridine (DAP) moieties as pendant groups within 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. This study provides a new opportunity for the design of supramolecular polymers, serving as polymeric vesicle scaffolds in material design and may act as red-blood-cell-like container in delivery and microreactor applications. Published with a permission of the Polymer Chemistry 2021.

Fluorescent and water dispersible single-chain nanoparticles: core-shell structured compartmentation

Hoffmann, J.F., et al. Angewandte Chemie, International Edition, 2021, accepted, https://doi.org/10.1002/anie.202015179

The internal structure of single-chain nanoparticles (SCNPs) has been investigated, forming nanosized domains preformed during the crosslinking process. We present proof for the presence of nano-compartments within SCNPs via a combination of electron paramagnetic resonance (EPR) and fluorescence spectroscopy. A novel strategy to encapsulate labels within such water dispersible SCNPs is presented.

Multicomponent stress-sensing materials fabricated by 3D-printing-methodologies

Rupp, H., et. al. Macromolecular Rapid Communications, 2021https://doi.org/10.1002/marc.202000450

The preparation and characterization of mechanoresponsive, 3D-printed composites is reported using a dual-printing setup for both, liquid dispensing and fused-deposition-modeling. The here reported stress‐sensing materials are based on high- and low molecular weight mechanophores, including  poly(e-caprolactone)-, polyurethane-, and alkyl(C11)-based latent copper(I)bis(N‐heterocyclic carbenes), which can be activated by compression to trigger a fluorogenic, copper(I)-catalyzed azide/alkyne “click”-reaction (CuAAC) of  an azide-functionalized fluorescent dye inside a bulk polymeric material. The low-molecular weight mechanophores bearing the alkyl-C11 chains displayed the best printability, yielding a useful mechanochemical response after the 3D-printing process. © 2020 The Authors. Published by Wiley‐VCH GmbH

Tuning the Self-Healing Response of Poly(dimethylsiloxane)-Based Elastomers

Döhler, D., et. al. ACS Applied Polymer Materials, 2020, 4127, https://dx.doi.org/10.1021/acsapm.0c00755

We present a comprehensive investigation of mechanical properties of supramolecular polymer networks with rationally developed multistrength hydrogen-bonding interactions. Self-healing poly(dimethylsiloxane) (PDMS)-based elastomers with varying elasticity, fracture toughness, and the ability to dissipate strain energy through the reversible breakage and re-formation of the supramolecular interactions were obtained. By changing the ratio between isophorone diisocyanate (IU), 4,4′-methylenebis(cyclohexyl isocyanate) (MCU), and 4,4′-methylenebis(phenyl isocyanate) (MPU) and by varying the molecular weight of the PDMS precursor, we obtained a library of poly(urea)s to study the interplay of mechanical performance and self-healability. Selected poly(urea)s could be processed via 3D printing by the conventional extrusion method, obtaining dimensionally stable and freestanding objects. Copyright © 2020, American Chemical Society

3D-printing of core-shell capsule composites for post-reactive and damage sensing applications

Rupp, H., et al. Advanced Materials Technology, 2020, 2000509, https://doi.org/10.1002/admt.202000509

3D-printing of multi-component materials as an advantageous method over traditional mold casting methods is demonstrated, developing small core-shell capsule composites fabricated by a two-step 3D-printing process. We here report the 3D-printing of a capsule-based multicomponent material using a two print-head system (fused deposition modeling extruder and a liquid inkjet print head), to embed micro-sized capsules in sizes ranging from 100 – 800 µm, located within the thermoplastic polymer poly(ε-caprolactone) (PCL) As a proof of concept novel “click”-reaction systems, used in self-healing and stress-detection applications, are manufactured, in which PCL composites with nano- and micro-fillers are combined with reactive, encapsulated liquids. Copyright © 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim

3D Printing of Supramolecular Polymers: Impact of Nanoparticles and Phase Separation on Printability.

Rupp, H., et al. Macromolecular Rapid Communications 2019,1900467, DOI: https://doi.org/10.1002/marc.201900467.

3D printing of linear and three-arm star supramolecular polymers with attached hydrogen bonds and their nanocomposites is reported. The linear and three-arm star poly(isobutylene)s PIB-B2 (Mn = 8500 g mol -1), PIB-B3 (Mn = 16 000 g mol -1), and linear poly(ethylene glycol)s PEG-B2 (Mn = 900 g mol-1, 8500 g mol -1) are prepared and then probed by melt-rheology to adjust the viscosity to address the proper printing window. A blend of the linear polymer PIB-B2 and the three-arm star polymer PIB-B3 (ratio ≈ 3/1 mol) reaches an even higher structural stability, able to build free-standing structures. Reproduced by permission. Copyright © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mixed Hybrid Lipid/Polymer Vesicles as a Novel Membrane Platform.

Schulz, M., et al. Macromolecular Rapid Communications 2015,36 (23), 2031-2041, DOI: http://dx.doi.org/10.1002/marc.201500344.

Vesicles can be individually fabricated from naturally occurring lipid or synthetic block copolymer molecules via self-assembly in aqueous solutions. Upon merging the best properties of lipo- and polymersomal membranes, hybrid lipid/polymer vesicles represent a new scaffold for medical applications combining, e.g., combining the biocompatibility of liposomes with the high thermal and mechanical stability and functional variability of polymersomes within a single vesicle type. Reproduced by permission. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlling the Localization of Polymer-Functionalized Nanoparticles in Mixed Lipid/Polymer Membranes.

Olubummo, A., et al. ACS Nano 2012,6 (10), 8713–8727, DOI: http://dx.doi.org/10.1021/nn3023602.

In this paper, we demonstrate the preparation and characterization of polymer-functionalized CdSe NPs, tuning their interaction with mixed lipid/polymer membranes from 1, 2-dipalmitoyl-sn-glycero-3-phophocholine (DPPC) and PIB87-b-PEO17 block copolymer by varying their surface-hydrophobicity. Reproduced with permission. Copyright 2012©, American Chemical Society.