Macromolecular Chemistry and Physics最新文献

This research presents the optical limiting properties of a novel axially linked D-A type compound, LaPc-C60(OH)n, where lanthanide phthalocyanine serves as the donor and fullerenol as the acceptor. The incorporation of fullerenol expands the π-conjugated system, decreases the aggregation of the phthalocyanine, and significantly increases the solubility of the compound. The establishment of this D-A system promotes intramolecular electron transfer, effectively improving both the non-linear optical (NLO) response and optical limiting properties. In addition, homogeneous poly(methyl methacrylate) (PMMA) composite films (LaPc-C60(OH)n/PMMA) are prepared using a simple solution casting method. Compared to fullerenol or lanthanum phthalocyanine individually, LaPc-C60(OH)n exhibited a superior NLO response both in solution and in the solid composite film. In particular, LaPc-C60(OH)n/PMMA demonstrated an increase in the non-linear absorption coefficient (2050 cm GW⁻¹) and a larger third-order magnetization (1.84 × 10⁻⁸ esu). In addition to exhibiting an excellent NLO response at 532 nm, LaPc-C60(OH)n also shows significant NLO enhancement at 1064 nm, extending the limiting range into the near-infrared region. This behavior is attributed to different nonlinear absorption mechanisms and the synergistic effect that arise from the photo-induced electron transfer process between the fullerenol and LaPc.

Carbon-based materials are extensively used in fuel cell applications due to their crucial role in maintaining high performance. Particularly, carbon black (CB) stands out as a preferred electrode material for fuel cells, owing to its high electrical conductivity and large surface area. This review focuses on the functionalization of CB and its use as a support for Pt-based catalysts in proton exchange membrane fuel cells. Functionalization strategies include oxidation, covalent functionalization, as well as polymer grafting or impregnation. Various approaches to functionalize the CB surface are discussed that effectively tailor the surface properties of electrodes, leading to improved fuel cell performance. The improvements are seen in enhanced dispersibility of catalyst particles, better ionomer distribution, increased catalyst stability, and reduced carbon corrosion. This review provides an overview of various modifications applied to CB to enhance their structural and electrochemical properties, thereby boosting fuel cell performance.

Mechanistic understanding of free radical polymerization (FRP) in aqueous solution is hindered by the lack of kinetic coefficient data. Here, we investigated the propagation rate coefficient (k_p) for FRP of HEMA in aqueous solution. The k_p at 80 °C increased by 6 times as the monomer weight fraction in aqueous system decreases from 100 wt.% to 6 wt.%, that is., from 6.0 × 10³ to 3.3 × 10⁴ L·moL⁻¹·s⁻¹. This increase in k_p is associated with the increase in pre-exponential factor (A), which suggests an increase in entropy with increasing water molecules in the polymerization system. To investigate the effect of solvent on k_p, pulse-laser polymerization in solvents of different hydrogen bonding affinity, that is, 50 wt.% butyl propionate (BP) and dimethyl formamide (DMF), are conducted. The k_p obtained are in order of k_p,bulk∼k_p,BP > k_p,DMF, suggesting that the intermolecular hydrogen bonding at carbonyl moieties critically affects the geometry of transition state quasi-equilibrium in propagation. We underpinned this observation by analyzing the carbonyl and alkene moieties of HEMA in different solvents using infrared (IR) spectroscopy. The mechanistic analyses and insights relating to hydrogen bonding and functional moieties can be relevant for future studies involving non-aqueous solvents promoting hydrogen bonds.

Harnessing data to discover the underlying constitutive relation of phase-separated polymers can significantly advance the fabrication of high-performance materials. This work introduces a novel data-driven method to learn the constitutive equation of diffusional transport of polymers from spatiotemporal density field. In particular, the data-driven method seamlessly integrated physics-informed neural networks for inference of approximate solution of diffusivity, and symbolic regression that form explicit expressions of diffusivity. The efficacy and robustness of this method are demonstrated by learning the distinct forms of diffusivity for the phase separation of homopolymer blends with various compositions. In addition, the data-driven method is generalized to extract the constitutive relation of homogenous chemical potential in the phase separation of homopolymer blends. The data-driven framework shows the potential for model discovery of nonlinear dynamic system from the spatiotemporal state variables.

In this study, it is attempted to enhance the properties and biodegradability of poly(butylene adipate terephthalate) (PBAT) using nanocomposite technology to meet the demand for sustainable packaging applications. Two nanoclays containing PBAT composites are reactively processed and integrated into the multilayered films. Reactive processing facilitates the dispersion and distribution of nanoclay particles in the PBAT matrix. The multilayered films comprising reactively processed PBAT composites exhibited a 24.5%–31.5% reduction in the oxygen transmission rate and improved dimensional stability and tensile properties. Moreover, the degradability of the multilayered film comprising reactively processed PBAT composites reached 82% in 180 days. In contrast, a neat PBAT film of similar thickness attained only 53% degradation in the same period. The biodegradation mechanism is proposed based on the topology of the disintegrated films studied using scanning electron microscopy, chemical bond vibrations determined by Fourier-transform infrared spectroscopy, and structural evolution by small- and wide-angle X-ray scattering (SWAXS). The SWAXS analysis is used to understand the changes in the degree of crystallinity, long-range periodic order, and crystalline and amorphous layer thickness of the multilayered films before and after degradation. Such multilayered films can find applications where packaging or biomedical devices cannot be recycled.

Magnetic nanomaterials have emerged as an effective drug-delivery platform for targeted imaging and therapy. However, it remains challenging to fabricate biodegradable magnetic nanoparticles with controllable drug release behaviors and strong magnetic responsiveness. Here an asiaticoside-loaded biodegradable magnetic vesicle is developed based on the self-assembly of amphiphilic block copolymer tethered superparamagnetic iron oxide nanoparticles. Thanks to the collective properties, the magnetic vesicles show stronger magnetic responsiveness than individual nanoparticles. Additionally, the magnetic vesicles are dissociated within weeks owing to the biodegradable polymer backbone, which can significantly improve the long-term biocompatibility of the nanomaterials. The asiaticoside-loaded magnetic vesicles can readily release the payloads in an alternating magnetic field, likely due to the rising local temperature over the phase transition temperature of the polymers attached on nanoparticles. This work provides new insights into the design and construction of biodegradable magnetic nanomedicines for targeted drug delivery.

This study focuses on the helical conformation of the main chain of syndiotactic poly(substituted methylene)s with 4-cyanobiphenyl (CB) moieties incorporated at the ends of the alkyloxycarbonyl side chains. The polymers are designated as PCBn, where n is the number of methylene units in the spacer between the main chain and CB. PCB6 and PCB8 assemble the side chains into layers without positional order within the layers. Meanwhile, PCB10 and PCB12 assemble the side chains into layers with a short-range positional order. Each CB moiety at a side chain end is bonded to a carbon atom, which is arranged along the helical main chain contour, and its position correlates with that of the carbon atom. As the temperature increases, PCB10 undergoes a phase transition, losing the positional order of the side chains within a layer, which alters the main chain conformation. Consequently, the positions of the side-chain CB moieties affect the helical conformation of the main chain. In contrast, PCB12 maintains the main chain conformation when undergoing a phase transition similar to that of PCB10. PCB12 with the longer spacer allows the main chain to adopt a helix conformation, which is independent of the positions of side-chain CB moieties.

Front Cover: The picture on the cover of the article 2300444 by Yong Zhang, Lizhai Pei, and co-workers is the elemental map of polyaniline/copper vanadate composite nanomaterials under high power transmission electron microscope, red represents element C, orange represents element N, yellow represents element V, blue represents element Cu. The spatial distribution of C, N, V, and Cu is uniform, confirming the polymerization of polyaniline on the copper vanadate nanomaterials.