Macromolecular Rapid Communications最新文献

This study investigates the crystallization behavior of electrospun coaxial fibers composed of crystalline poly(ethylene oxide) (PEO) in the core and crystalline poly(L-lactide) (PLLA) in the sheath. The influence of cold crystallization temperature and premelting temperature on the crystallization of PEO and PLLA is investigated. At a cold crystallization temperature of ≤60 °C, PLLA remained immobile. PEO crystallization is hard-confined, leading to a low degree of crystallinity. At a cold crystallization temperature of >60 °C, PEO melted, whereas PLLA crystallized. An increase in cold crystallization temperature results in an increase in the crystallite size and crystallinity of PLLA. Furthermore, the melt crystallization behavior of PEO in the coaxial fibers is strongly influenced by its premelting temperature and crystallization temperature. A higher premelting temperature leads to enhanced interdiffusion between PEO and PLLA. This increased confinement results in a decrease in PEO's crystallizability. Additionally, premelting relaxes the PEO chains, causing a shift in crystal orientation from parallel to the fiber axis (observed in as-electrospun fibers) to perpendicular to the fiber axis (observed in melt-crystallized fibers). Moreover, at a low melt crystallization temperature, demixing between PEO and PLLA is observed. This, coupled with a higher degree of supercooling, leads to an increase in PEO's crystallizability.

Bacterial biofilms and intracellular pathogens pose significant challenges in eradication, often leading to persistent infections that are difficult to treat. To address this issue, the hydrophobic biofilm dispersant D-tyrosine is encapsulated within protein-polycation nanoparticles, designed using a mannose-terminated cationic polymer and concanavalin through electrostatic interactions. Thermodynamic studies reveal that free mannosyl groups on the nanoparticle surface promote spontaneous binding to receptor molecules mimicking those on bacterial biofilms and host cells. Under mildly acidic conditions, the nanoparticles reduce in size from 550 to ≈48 nm within 2 h, releasing 76% of encapsulated D-tyrosine. The combination of mannose targeting, particle size reduction, and controlled D-tyrosine release enable the nanoparticles to eliminate 70%-80% of the Pseudomonas aeruginosa and Staphylococcus aureus biofilm biomass at minimum bactericidal concentration (MBC) and 2MBC while eradicating 8 log of bacteria embedded within the biofilm. In an intracellular Pseudomonas aeruginosa infection model using RAW 264.7 macrophages, the nanoparticles at 2MBC eliminate over 95% of the intracellular bacteria without inducing an increase in the inflammatory cytokine interleukin-6. These protein-polycation nanoparticles, which activate their antimicrobial properties under acidic conditions, efficiently penetrate bacterial biofilms and host cell barriers via their mannose-rich surface, offering a promising strategy for the treatment of persistent infections.

The advancement of stereoregular polymerization techniques for linear 1,3-dienes has enabled the production of polymers with precise stereocontrol, influencing their physical and chemical properties significantly. While 1,3-butadiene and isoprene yield diverse stereoregular polymers, cyclic dienes have received less attention due to catalyst challenges and limited application in the rubber industry. However, the growing interest in bio-based monomers, particularly those derived from terpenes and terpenoids, has revitalized interest in cyclic monomers with conjugated double bonds. This study investigates 1-vinylcyclohexene (VCH) polymerization using [OSSO]-type titanium complexes 1-2, revealing significant regio- and stereoselectivity. Catalyst 2, incorporating cumyl substituents, demonstrates superior performance, yielding highly isotactic poly(VCH) with 3,4-insertion predominance. It is also shown that the polymerization of S-4-isopropenyl-1-vinyl-1-cyclohexene (IVC), a bio-based monomer, results in a highly isotactic polymer. Finally, the copolymerization results of IVC with two linear terpenes to obtain copolymers derived entirely from renewable sources are also reported.

The formation of a robust, self-healing hydrogel of a novel pyrene-appended dipeptide, Py-E-A (L-Glutamic acid short as E; L-Alanine short as A) is demonstrated. Detailed studies suggest that nanoscopic fibers with a length of several micrometers have formed by chiral self-organization of Py-E-A gelators. Additionally, live human PBMCs imaging is shown using the Py-E-A fluorophore. Interestingly, electron-rich Py-E-A couples with electron-deficient NDI-β-A (β-Alanine short as β-A) by charge transfer (CT) complexation and forms stable deep violet-colored CT super-hydrogel. X-ray diffraction, DFT, and 2D ROESY NMR studies suggest lamellar packing of both Py-E-A and the alternating CT stack in its hydrogel matrixes. Supramolecular chirality of the Py-E-A donor can be altered by adding an achiral acceptor NDI-β-A. Notably, the fibers of the CT hydrogel are found to be even thinner than the Py-E-A fibers, which, in turn, makes the CT hydrogel more tolerant to the applied strain. Further, the self-healing and injectable properties of the hydrogels are shown. Finally, the magneto-responsive behavior of the Py-E-A and CT hydrogels loaded with spin-canted Cu-ferrite (Cu_0.6Zn_0.4Fe₂O₄) nanoparticles (NPs) is demonstrated. The presence of magnetic NPs within the hydrogels has changed the fibrous morphology to rod-like nanoclusters.

Polymerizable deep eutectic solvents (PDES) represent a novel class of ionic liquids characterized by the presence of polymerizable groups in their hydrogen-bond donor or acceptor components. Within the realm of flexible electronics, PDES is emerged as a promising material for the fabrication of sensors that exhibit both flexibility and stretchability. This research employs the UV-initiated photocopolymerization of a ternary PDES composed of choline chloride (ChCl), 2-hydroxyethyl acrylate (HEA), and itaconic acid (IA), to synthesize an ionic conductive elastomer (ICE) that boasts desirable comprehensive performances, which can be controlled by meticulously adjusting the ratios of these components. The fabrication process is streamlined and efficient, utilizing cost-effective and eco-friendly materials. This elastomer exhibits favorable ionic conductivity (1.70 × 10^-2-5.45 × 10^-2 S m^-1), mechanical strength (0.48-1.21 MPa stress at break, 395-701% elongation at break), adhesion capacity (49-120 kPa adhesion strength), and sensing sensitivity toward human motions.

A bio-based benzoxazine monomer, diphenolic methyl ester hexafluoro diamino benzoxazine (DPME-HFBz), was successfully synthesized from diphenolic acid (DPA), and the chemical structure was successfully verified. The curing kinetics were studied via non-isothermal differential scanning calorimetry (DSC). The activation energies of DPME-HFBz were calculated by Kissinger and Ozawa methods to be 136.15 and 139.92 kJ/mol, respectively, and the reaction order was calculated to be first order. Owing to the large number of hydrogen bonds after polymerization, poly(DPME-HFBz) presented an ultra-high glass transition temperature of 312 °C and a high initial decomposition temperature (350 °C under air and 345 °C under nitrogen). Because of the excellent charring ability (50.2% residue under nitrogen), the LOI value of poly(DPME-HFBz) was as high as 38%. Poly(DPME-HFBz) also exhibited a very low heat release capacity (HRC) of 90 J/(g·K). In addition, poly(DPME-HFBz) had a dielectric constant (Dk) of 1.88 at 1.5 MHz, which was much lower than the Dk of the reported low-dielectric polymers. This work provides an efficient and sustainable strategy for the synthesis of benzoxazine thermosetting materials with excellent comprehensive properties.

Luminescent materials that respond to changes in microscopic chemical conditions are essential for visualizing and evaluating molecular environments. Boron complexes are often employed as robust scaffolds for constructing such responsive systems because of their inherent stimuli-responsive properties. However, in the case of nonresponsive luminophores, the absence of these intrinsic features limits their range of applications. In this study, environment-responsive luminescent homopolymers based on the boron β-dialdiminate complex are developed, which is intrinsically less responsive, by introducing optimized side chains. As a key finding, the triethylene glycol-decorated polymer exhibits more intense luminescence in chloroform but weaker luminescence in N,N-dimethylformamide. Structural analyses using NMR and size-exclusion chromatography suggest that this polymer forms larger aggregates in polar solvents because of the solvophobicity of its main chain, while the polar side chains assist in maintaining adequate dispersibility of these aggregates. Photophysical measurements indicate that interchromophore interactions within the aggregates should be responsible for the reduced luminescence in polar solvents. These findings suggest that side-chain engineering should be an effective strategy for creating stimuli-responsive polymers from otherwise nonresponsive luminophores.

Weakly anionic semi-interpenetrating polymer networks (semi-IPNs), comprised of copolymer poly(N-isopropylacrylamide-co-methacrylic acid) P(NIPA-MA) and linear poly(acrylamide) (LPA) chains as macromolecular crowding agent, are designed to evaluate pH-induced swelling and elasticity. Uniaxial compression testing after swelling in various pH-conditions is used to analyze the compressive elasticity as a function of swelling pH and LPA-content. The swelling of P(NIPA-MA)/LPA semi-IPNs is strongly pH-dependent due to MA units incorporated into the copolymer network which already exhibits temperature-sensitivity by presence of PNIPA counterpart. Since the behavior of semi-IPNs is a combination of PMA, LPA, and PNIPA moieties, the sensitivity of swelling to external pH can be modified with increasing swelling temperature. At high pH conditions, LPA-doped semi-IPNs show elasticity representing soft and loosely cross-linked structure. Elastic modulus is higher in acidic pH condition due to the less swelling tendency, while in basic pH, the modulus decreases significantly in coordination with swelling. Oscillatory swelling reveals how fast semi-IPNs can respond to environmental pH change (2.1-10.7). By describing adsorption potential of semi-IPNs for cationic methylene blue uptake by pseudo-first-order and Freundlich model, the designed poly(NIPA-MA)/LPA semi-IPNs emerge as promising smart materials in applications requiring rapid response to changes in temperature and pH via diffusional properties.

Natural silk nanofibers (SNF) are attractive conductive substrates due to their high aspect ratio, outstanding mechanical strength, excellent biocompatibility, and controllable degradability. However, the inherently non-conductivity severely restricts the potential sensor application of SNF-based aerogels. In this work, the conductive nanofibrous aerogels with low-density achieved through freeze-drying by dispersing carbon nanotubes (CNT) into SNF suspension. The addition of CNT significantly increases the conductivity with improved mechanical properties of composite aerogels. SEM results reveal that the distinct hierarchical structure comprising micropores and nanofibrous networks within the pores is formed when CNT content reached 30%. Furthermore, increased cell viability suggested the excellent biocompatibility of SNF-CNT-based conductive aerogel for tissue-engineering applications. Subsequently, the elastic water-borne polyurethane (WPU) is incorporated to SNF-CNT system to construct aerogel with good sensing properties. The introduction of WPU demonstrates enhanced compressive performances and an exceptionally high elastic recovery ratio of 99.8%, thereby exhibiting a stable and lossless strain-sensing signal output at 5% strain. This study provides a feasible choice and strategy for exploring the potential application of SNF in functional aerogels.

Living tissues span a remarkable spectrum of modulus ranging from the level of Pa to GPa in a water-rich environment. Constructing soft and hard materials that match the mechanics of tissues and researching mechanical transition in water, are beneficial for their biological applications. Here, using polyelectrolyte complex fiber as a model system and reinforcing the fiber by stepwisely introducing additional coordination and covalent bonds, this investigated that the water effect on mechanical transition behaviors. Alginate/chitosan fiber (AC fiber) has a single electrostatic bond and shows continuous mechanical transition containing a glassy state, rubbery state, and terminal relaxation (initial modulus lower than 10 MPa) in aqueous solution. Alginate/chitosan/calcium fiber (ACC fiber) has both electrostatic and coordination bonds, which shows the behavior of hard rubber (initial modulus 100 MPa) when water reaches equilibrium. Alginate/chitosan/calcium/polydopamine fiber (ACCP fiber) with triple bonds, including electrostatic, coordination, and covalent bonds, exhibits the behavior like ductile plastics in aqueous solution (initial modulus 1000 MPa). This work not only provides important insight into the toughening mechanism of polyelectrolyte complexes in water but also contributes to the preparation of tissue adaptive implantations.