Journal of Polymer Science Part A: Polymer Chemistry最新文献

Pushing the limits of synthetic polymers in terms of stiffness and strength, aromatic polyamide fibers – like Kevlar® – are used for demanding applications. Damage mechanisms and crack propagation are observed in situ and unveil a widespread damage over the entire length of the fiber. These observations make it possible to draw a novel scenario of fracture. To shed light on the crucial role of microfibril cooperativity in fracture toughness, a slight twist is applied to the single fiber to promote tortuosity and frictional contacts between microfibrils. Statistical fracture analysis demonstrated the beneficial impact of such torsion on early failure events. Alba Marcellan created the cover image. DOI: 10.1002/pol.20230400

The cover image by first author Kosuke Terayama represents nanoparticles composed of conjugated polymers (Pdots). Each monomer unit is a different color, highlighting the bright near-infrared fluorescent polymer due to the electronic interactions of the conjugated monomer units. A vague cellular image is depicted in the background because of the potential application of Pdots for clinical diagnosis and therapeutic evaluation. (DOI: 10.1002/pol.20230421)

The cover by Johannes Berg shows the schematic representation of calcium alginate consisting of mannuronic acid (green) and guluronic acid (red), cross-linked by calcium cations (yellow). An interpenetrating additional polymer is polyethyleneimine (blue), thereby constituting a composite hydrogel. Positively charged methylene blue is selectively adsorbed in the alginate hydrogel due to its negatively charged polymer backbone. Along with that, negatively charged congo red is selectively adsorbed by the positively charged polyethyleneimine. (DOI: 10.1002/pol.20230215)

The cover image by Daisuke Aoki shows how the properties of biobased furan polymers are tuned by the Diels–Alder reaction with the tailor-made modification agents. (DOI: 10.1002/pol.20230316)

Impressions of IPF Dresden: (A) Main building established in 1952 (© Emanuel Richter) (B) Max-Bergmann Center of Biomaterials (2002) (© Emanuel Richter), and (C) IPF Institute of Theory of Polymers with central facilities (2020) (© Jörg Simanowski).

The present Leibniz Institute of Polymer Research Dresden (IPF) has a long and multifaceted history. In 1948, a textile research institute was founded at the spinning mill Mitteldeutsche Spinnhütte in Pirna-Copitz near Dresden to be developed to an institute of the Technische Hochschule (today Technische Universität) Dresden. In January 1950, this Institute of Technology of Fibers became a member of the (East) German Academy of Sciences at Berlin and developed to a well established polymer institute covering various aspects of polymer science including synthesis, characterization and processing, with special expertise in interfacial phenomena of polymer materials. In 1984, the institute was re-named to Institute of Technology of Polymers and with its profile and research quality it was successfully evaluated after the reunification of Germany. In 1992, the institute was re-founded as a member of today's Leibniz Association (with Max Planck Society, Helmholtz Association, and Fraunhofer Society one of the four pillars of Germany's non-university research).

Already in 1952, the institute moved close to Dresden main railway station, to the grounds of the former Kaiser Wilhelm Institute of Leather Research that had been destroyed during the Second World War. The founding director of that Kaiser Wilhelm Institute, Max Bergmann, made pioneering contributions to biomacromolecules synthesis and emigrated to the USA in 1933 were he established a world-leading peptide synthesis laboratory at Rockefeller University in New York. The IPF acknowledged this fact in 2002 by naming a new joint building that houses research activities on biomaterials of IPF and Technische Universität Dresden after him (“Max Bergmann Center of Biomaterials”). In 2020, the IPF was further expanded with a building for the IPF Institute of Theory of Polymers, besides providing central facilities and guest apartments.

Over the years, the IPF has significantly grown and broadened its profile, now covering polymer material science comprehensively. Today it consists of five IPF institutes with about 500 coworkers: Macromolecular Chemistry, Physical Chemistry and Polymers Physics, Polymer Materials, Biofunctional Polymer Materials, and Theory of Polymers. It holds seven joint professorships with TU Dresden in different disciplines comprising chemistry, physics, mechanical engineering and material science, as well as medicine, complemented with a professorship to be established soon in electrical engineering. Central research avenues of IPF cover bioinspired, interactive, and surface-engineered materials and systems, as well as process-engineering of hybrid & multiphase (composit

Microfluidics are key tools for designing uniform polymer microgels via emulsion templates, although usually limited to microliter quantities. 3D printing forms a promising basis to fabricate flow cells in a single process step, enabling the integration of various functional microfluidic units in one device, e.g., to address the demand for large quantities of microgels for particle-based inks in extrusion-based 3D printing or for constructing supragels. Here, parallelized droplet formation and splitting are combined in one reusable 3D-printed flow cell to form polymer microparticles at milliliter-per-hour scale. Cover art designed by Martin Schumann. (DOI: 10.1002/pol.20230213)

Pushing the limits of synthetic polymers in terms of stiffness and strength, aromatic polyamide fibers–like Kevlar®–are used for demanding applications in the form of fiber assemblies as ropes. The unique mechanical performance of aramid fiber is intimately linked to its hierarchical structure and orientation, induced during the spinning process. Surprisingly, after nearly 60 years of heavy use, very little is known about damage mechanisms and rational explanation of such high resistance. We report an experimental investigation of the fiber damage mechanisms at the single fiber scale (diameter ≅ 10 μm) with the aim to establish a link with the microstructure. Damage mechanisms and crack propagation are observed in situ for the first time and unveil a widespread damage over the entire length of the fiber in the form of a network of transverse and longitudinal cracks. These observations make it possible to draw a novel scenario of fracture that mitigates the small strain failure hypothesis. To shed light on the crucial role of microfibril cooperativity in fracture toughness, a slight twist is applied to the single fiber to promote tortuosity and frictional contacts between microfibrils. Statistical fracture analysis demonstrated the beneficial impact of such torsion on early failure events, since lowest fracture stresses are shifted to higher stresses.

Copolymerizing poly(lactide) with other materials to obtain better comprehensive performance is a effective way to expand its application range. In this work, the precursors of hydroxyl terminated (poly(L-lactide) [PLLA], poly(ε-caprolactone) [PCL], poly(D,L-lactide) [PDLLA]) were prepared, and PLLA-PCL-PDLLA copolymer were synthesized by chain extension. The effects of the proportion and molecular weight of each component and the amount of chain extender on crystallization, phase structures, mechanical properties and thermal stabilities of PLLA-PCL-PDLLA copolymer were studied in detail. Based on small-angle X-ray scattering results, the competition between crystallization and microphase separation was regulated by the composition and chain length of prepolymers. As the ratio of PLLA/PDLLA  was 1:1, crystallization was prevailing and no obvious peak was observed in SAXS pattern. The tensile test results showed that as the ratio of PLLA/PDLLA increased from 1:1 to 1:5, the elongation at break of the copolymer changed from 1.8% to 343%. By using shorter length of PCL and PLLA segments in chain extension, improvement in strength and flexibility were obtained due to moderate degree of crystallization and microphase separation. This work used biodegradable materials to prepare extraordinary toughness copolymers without losing the biocompatibility, which may provide a feasible method for obtaining high toughness and biodegradable PLA-based materials.

Fluorescence imaging in the second near-infrared (NIR-II) region has become one of the most powerful tools in clinical diagnosis and therapy assessment because of its high spatial resolution, rapid feedback, radiation safety, and low cost. Conjugated polymer nanoparticles (Pdots) based on donor-acceptor (D-A) polymers are some of the most promising fluorescent probes which have many superior characteristics, such as a high fluorescence brightness, good photostability, facile functionalization, and low cytotoxicity. While there has been tremendous progress in developing fluorescent polymers for use in the NIR-II wavelength range, the types of monomer structures used as building blocks for NIR-II fluorophores are still limited compared to those for organic solar cells and organic transistors. This review summarizes the NIR-II fluorescent polymers reported in the past few decades. The donor/acceptor unit structures of the polymers are systematically classified and discussed, which will provide new insights into the logical molecular design of donor/acceptor units for the development of high-brightness NIR-II Pdots.