Macromolecular Rapid Communications最新文献

In recent years, the growing problem of antibiotic resistance has highlighted the need for antibacterial materials to prevent the development of infections. Different types of tests exist to certify the antibacterial properties of materials. Variations in results can occur due to the unique requirements of each test technique. The antibacterial test result may be influenced, in particular, by the distinct modes of action of leaching and non-leaching compounds. Using antibacterial materials prepared by the dispersion of an amphiphilic cationic synthetic copolymer in a polyurethane matrix, the influence of the reaction medium and the contact time on the results obtained by two well-established tests: ISO 22196 and CERTIKA is investigated. This shows that the kinetics of killing is bacteria dependent and depending on the test conditions (concentration of salt, time of contact, or media), contradictory results could be obtained. Moreover, the influence of the ionic strength (called salt effect) in both free solution and antibacterial surface is highlighted.

Protein function results from the precise folding of polypeptides into bespoke architectures. Taking inspiration from nature, the field of single-chain nanoparticles (SCNPs), intramolecularly crosslinked synthetic polymers, emerged. In contrast to nature, the function of SCNPs is generally defined by the parent polymer or the applied crosslinker, rather than by the crosslinking process itself. This work explores the cyanopyridine-aminothiol click reaction to crosslink peptide-decorated polymers intra-macromolecularly to endow the resulting SCNPs with emerging functionality, resulting from the conversion of N-terminal cysteine units into pyridine-thiazolines. Dimethylacrylamide based polymers with different cysteine-terminated amino acid sequences tethered to their sidechains are investigated (P1 (C), P2 (GDHC), P3 (GDSC)) and intramolecularly crosslinked into SCNPs. Since the deprotection of the parent polymers yields disulfide-based SCNPs, a direct comparison between disulfide and pyridine-thiazolines crosslinked SCNPs is possible. This comparison revealed two emerging properties of the pyridine-thiazoline crosslinked SCNPs: 1) The formation of pyridine-thiazolines gave rise to metal binding sites within the SCNP, which complexed iron. 2) Depending on the peptide sequence in the precursor polymer, the hydrolytic activity of the peptide sequences is either increased (GDHC) or decreased (GDSC) upon pyridine-thiazoline formation compared to identical SCNPs based on disulfide crosslinks.

The origin of stereocontrol in ring opening polymerization (ROP) of racemic lactide (rac-LA) promoted by achiral aluminium-based catalysts has been explained through DFT calculations combined with a molecular descriptor (%V_Bur) and the activation strain model (ASM-NEDA) analysis. The proposed chain end control (CEC) model suggests that the ligand framework adopts a chiral configuration mimicking the enantiomorphic site control (ESC) while also incorporating control of the last inserted monomer unit. It is found that the ligand wrapping mode around the aluminium centre is dictated by the monomer configuration (R,R-LA and S,S-LA). A good correlation with experimental data is achieved only when accounting for the ligand dynamic features and its steric influences, as highlighted by %V_Bur steric maps and ASM-NEDA analysis. Understanding the ESC and CEC interplay is an important target for obtaining stereoselective ROP polymerization for the synthesis of biodegradable materials with tailored properties.

An atomic-level understanding of radiation-induced damage in simple polymers like polyethylene is essential for determining how these chemical changes can alter the physical and mechanical properties of important technological materials such as plastics. Ensembles of quantum simulations of radiation damage in a polyethylene analog are performed using the Density Functional Tight Binding method to help bind its radiolysis and subsequent degradation as a function of radiation dose. Chemical degradation products are categorized with a graph theory approach, and occurrence rates of unsaturated carbon bond formation, crosslinking, cycle formation, chain scission reactions, and out-gassing products are computed. Statistical correlations between product pairs show significant correlations between chain scission reactions, unsaturated carbon bond formation, and out-gassing products, though these correlations decrease with increasing atom recoil energy. The results present relatively simple chemical descriptors as possible indications of network rearrangements in the middle range of excitation energies. Ultimately, the work provides a computational framework for determining the coupling between nonequilibrium chemistry in polymers and potential changes to macro-scale properties that can aid in the interpretation of future radiation damage experiments on plastic materials.

Front Cover: Synthesis and property evaluation of cyclodextrin (CD)-based polyurethane-type poly[3]rotaxane is studied. The polyaddition between acetylated CD-based [3]rotaxane diol and various di-isocyanates affords polyurethanes, and the subsequent deprotection of acetyl groups on CD units generate hydroxyl groups, inducing drastic property change. More details can be found in article 2400441 by Yosuke Akae and Patrick Theato.

Front Cover: The molecular-level interaction mechanisms between versatile mussel-inspired chemistries, including 3,4-dihydroxyphenylalanine (DOPA) and polydopamine (PDA), and lubricant-infused slippery surfaces are investigated using nanomechanical techniques based on atomic force microscopy (AFM). The cover image depicts force measurements of mussel-derived adhesives using an AFM probe, symbolizing this investigation. More details can be found in article 2400276 by Hongbo Zeng and co-workers.

Rapid, nondestructive characterization techniques for evaluating the degree of crystallinity and phase segregation of organic semiconductor blend thin films are highly desired for in-line, automated optoelectronic device fabrication facilities. Here, it is demonstrated that reflection polarized optical microscopy (POM), a simple technique capable of imaging local anisotropy of materials, is capable of determining the relative degree of crystallinity and phase segregation of thin films of polymer:fullerene blends. While previous works on POM of organic semiconductors have largely employed the transmission geometry, it is demonstrated that reflection POM provides 3× greater contrast. The optimal configuration is described to maximize contrast from POM images of polymer:fullerene films, which requires Köhler illumination and slightly uncrossed polarizers, with an uncrossing angle of ±3°. It is quantitatively demonstrated that contrast in POM images directly correlates with 1) the degree of polymer crystallinity and 2) the degree of phase segregation between polymer and fullerene domains. The origin of the bright and dark domains in POM is identified as arising from symmetry-broken liquid crystalline phases (i.e., dark conglomerates), and it is proven that they have no correlation with surface topography. The use of reflection POM as a rapid diagnostic tool for automated device fabrication facilities is discussed.

Polymer gels are fascinating soft materials and have become excellent candidates for wearable electronics, biomedicine, sensors, etc. Synthetic gels usually suffer from poor mechanical properties, and integrating good mechanical properties, adhesiveness, stability, and self-healing performances in one gel is more difficult. Herein, polymerization-induced self-assembly (PISA) providing PEG-gels with an overall improvement in their comprehensive performances is reported. PISA synthesis is carried out in PEG (solvent) to efficiently produce various nanoparticles, which are used as the nanofillers in the subsequent synthesis of PEG-gels with dynamic micelle-crosslinked hierarchical structures. Compared to hydrogels, PEG-gels show excellent long-term stability due to the nonvolatile feature of PEG solvent. The hierarchical PEG-gels (with nanofillers) exhibit better mechanical and adhesive properties than the homogeneous-gels (without nanofillers). The energy dissipation mechanism of the PEG-gels is analyzed via stress relaxation and cyclic mechanical tests. High-density hydrogen bonds between the micelles and PAA matrix can be broken and reformed, endowing better self-healing properties of the dynamic micelle-crosslinked PEG gels. This work provides a simple strategy for producing hierarchical structural gels with enhanced properties, which offers fundamentals and inspirations for the designing of various advanced functional materials.

Thermal conductivity coefficient κ measures the ability of a material to conduct a heat current. In particular, κ is an important property that often dictates the usefulness of a material over a wide range of environmental conditions. For example, while a low κ is desirable for the thermoelectric applications, a large κ is needed when a material is used under the high temperature conditions. These materials range from common crystals to commodity amorphous polymers. The latter is of particular importance because of their use in designing light weight high performance functional materials. In this context, however, one of the major limitations of the amorphous polymers is their low κ, reaching a maximum value of ≈0.4 W/Km that is 2-3 orders of magnitude smaller than the standard crystals. Moreover, when energy is predominantly transferred through the bonded connections, κ ⩾ 100 W/Km. Recently, extensive efforts have been devoted to attain a tunability in κ via macromolecular engineering. In this work, an overview of the recent results on the κ behavior in polymers and polymeric solids is presented. In particular, computational and theoretical results are discussed within the context of complimentary experiments. Future directions are also highlighted.