Macromolecular Materials and Engineering最新文献

Natural rubber (NR) films with different natural networks—concentrated NR (CNR), deproteinized NR (DPNR), and small rubber particles (SRP)—are investigated to explore the relationship between network structure and film properties using atomic force microscopy (AFM) in PeakForce Quantitative Nanomechanics (QNM) mode. Nitrogen content, gel content, and particle size distribution analyses reveal distinct network topologies in each latex type. Mechanical testing shows variations in tensile strength and crosslink density. AFM analysis provides insights into the crosslink network structures within the pre-vulcanized latex film. It is found that DPNR and CNR films have a uniform distribution of crosslink networks, with DPNR exhibiting higher Young's modulus values. In contrast, SRP shows varying Young's modulus values, suggesting poor coalescence arising from a harder particle surface and a softer rubber core in an inhomogeneous network structure intrinsic to the non-rubber components (NRCs) make-up of SRP latex. This study highlights the pivotal role of natural network structures formed by NRCs in determining the ultimate properties of latex films, which has significant implications for the rubber industry, particularly in the production of latex-dipped products, medical devices, and bioengineering applications.

In this study, two green extraction methods are explored to valorize rice straw into cellulose fibers (CFs), namely subcritical water extraction (SWE) and combined ultrasound-heating treatment (USHT). The resultant fibers are, thereafter, successfully pretreated with (3-glycidyloxypropyl) trimethoxysilane (GPS) and incorporated at 3% wt into poly(butylene succinate) (PBS) by melt-mixing. The green composites are shaped into films by thermo-compression and characterized in terms of their performance for food packaging applications. The chemical analysis of the fibers reveals that SWE is more effective to selectively remove hemicelluloses than USHT, whereas silanization promotes the removal of lignin in both fiber types. Fiber incorporation, more notably in the case of the silanized fibers, restricts the movement of the PBS chains, indicating good interaction with the biopolyester matrix. In particular, CFs act as antinucleating agents in PBS, delaying both glass transition and crystallization from the melt phenomena and hindering crystal formation. Furthermore, the fibers mechanically reinforce and improve the oxygen barrier of the PBS films. The highest barrier enhancement is obtained for the thermo-compressed composite film with silanized fibers obtained by SWE, yielding a decrease of nearly 20% in the permeability to oxygen versus the unfilled PBS film.

Alternative anode materials with increased theoretical specific capacities are under scrutinity as a replacement to graphite in lithium-ion batteries (LiBs). Silicon oxides offer increased capacities compared to graphite and do not suffer the same level of material expansion as pure Si. Consequently, they are an intermediate commercial anode material, on the pathway toward pure Si anodes. In this study, stable Silica/carbon (SiO₂/C) nanofibers are successfully developed from tetraethyl orthosilicate (TEOS) using poly(vinylpyrrolidone) (PVP). The fibers show excellent stability after calcination, with silica evenly dispersed within the fibers exhibiting a surface area of 327 m² g⁻¹. This study demonstrates that the electrochemical performance of SiO₂/C composite anodes is significantly influenced by the silica content. SiO₂/C composites with ≈68 at% SiO₂ achieve reversible capacities of 315.6 and 300.9 mAh g⁻¹, after the 2nd, and 800th cycles, respectively, at a specific current of 100 mA g⁻¹, with a remarkable capacity retention of 95.3%. In a second stage, lignin is added as a potential nanostructuring agent. The addition of lignin to the sample reduces the amount of silica without significantly impacting its performance and stability. Tailoring the composition of SiO₂/C composite anodes enables stable capacity retention over the course of hundreds of cycles.

With this issue of Macromolecular Materials and Engineering, celebrating 25 years of the journal, the editors, friends, and colleagues congratulate Prof. Rolf Mülhaupt on the occasion of his 70th birthday in September 2024. The broad range of topics assembled in this volume reflects the impressive scope of topics, Rolf Mülhaupt's research has addressed. It was briefly sketched how these have evolved from the different stations of his career in a previous editorial in a sister journal.^[1]

The ten years that have passed since this review of Rolf Mülhaupt's outstanding and unconventional scientific career have certainly held unexpected developments. Only a few days after the conference “Makromolekulares Kolloquium” in Freiburg in February 2020 honored him on the occasion of his upcoming formal retirement from his chair position at the Institute of Macromolecular Chemistry, public and academic life were shut down by a pandemic. Also, he was not spared from “remote teaching” in the following. His scientific curiosity and productivity are, of course, uncompromised, as also evidenced by his published oeuvre. Within the breadth of Rolf Mülhaupt's contributions, as an example of his interests in the past decade, it is certainly appropriate to highlight additive manufacturing, reflected in a review article that has been cited already more than 2500 times since its appearance in 2017.^[2] This topic—in which he was active very early on actually—has moved on to—among others—3D printing of polyolefins with his team. This again takes advantage of his development of “all-polyethylene” composites, which achieve outstanding material performance yet are also well processable, thereby providing improved circularity. Concerning the intensely discussed issue of polymer materials' circularity, the scientific community continues to benefit from Rolf Mülhaupt's to-the-point and sometimes sobering assessments of reality, for instance in “Green Polymer Chemistry and Bio-based Plastics: Dreams and Reality”,^[3] a highly cited perspective on this research area and its future options.

Together with all other authors that have contributed to this volume, and with the entire team of the Macromolecular journals, I congratulate Rolf Mülhaupt on the occasion of his anniversary and wish him continued delight in science in the years to come!

In the present study, a method is proposed for preparing novel ductile-sticky materials that can be used as bone void fillers using hydrolyzed wool-keratin (WK) and silk fibroin (SF). This methodology uses citric acid as a cross-linking agent in preparing keratin paste (KP) owing to its non-toxicity and plasticizing properties. The Keratin paste-silk fibroin structure (KPSF) is obtained by adding SF, which possesses biocompatible and superior mechanical properties. Methanol treatment is employed on the KPSF mixture to convert the Silk I structure in the SF to Silk II, resulting in a water-insoluble and tightly packed proteinaceous structure. The physicochemical properties of both bioscaffolds are investigated and discussed in detail by comparison. Based on the findings, the presence of SF in the KPSF structure contributed to properties such as flexibility and porosity. In ovo CAM analysis reveals that both materials exhibit proangiogenic properties and are biocompatible. KP and KPSF bioscaffolds can be converted into ductile-sticky forms by adding water. It believes that these forms can easily apply to bone defect areas, particularly cavitary bone defects. Furthermore, KPSF bioscaffolds, with better mechanical properties, can be considered candidates for use in non-load-bearing bone tissue engineering applications.

Electrohydrodynamic processes have emerged as promising methods for fabricating polymetric fiber-based artificial tubular tissues. Existing review articles focus on the biological applications and processing materials associated with electrohydrodynamic processes in artificial tubular constructs, while overlooking the design and fabrication of these constructs. To address this gap, this review article emphasizes the design and fabrication of tubular tissue constructs enabled by employing electrohydrodynamic processes. This article begins by presenting an overview of two electrohydrodynamic processes: solution electrospinning (SE) and melt electrowriting (MEW). It then delves into the control of the fiber diameter enabled by SE and MEW, offering insights into the manipulation of processing parameters to achieve desired fiber diameters. Additionally, the review highlights cutting-edge strategies for electrohydrodynamic processes to create tubular structures with customized microarchitectures. This includes fiber alignment control for SE and pore morphology design for MEW. Moreover, the review covers the creation of customized macroscale tubular geometries through collector geometry design. Lastly, a comprehensive survey is presented for designing multiphasic tubular structures specifically for electrohydrodynamic techniques or in tandem with other techniques. The objective of this review is to offer a thorough understanding of the design considerations and potential applications of tubular structures fabricated by electrohydrodynamic processes.

The use of high electric fields, as well as pre-stressing, are the two main obstacles to the widespread use of poly(vinylidene fluoride (PVDF)-based actuators. In response, a new double-sided multilayer device has been developed which, coupled with a polarization procedure, enables high bending performance at low voltages. The actuator's symmetry allows zero bending at rest, while the high number of layers enables a strong field to be maintained while reducing the applied voltage. X-ray and permittivity studies reveal the ultimate links between the microscopic material displacement and the actuator deflection. These results, coupled with the analytical model developed in this work, demonstrate that the optimization of complex multilayer systems requires a detailed understanding of mechanics, design, and microstructure. Experimental, analytical and finite element results confirm that such a double-sided multilayer actuator is of 50% more efficient than a conventional single-sided actuator, up to 40 V µm⁻¹. These achievements open up new prospects for PVDF-based actuators in application of healthcare, such as arterial navigation.

The introduction of biobased carbon sources in intumescent flame retardant formulations is extensively explored, particularly for biopolymers such as poly(lactic acid) (PLA). In this work, the flame retardant efficiency of alginate, a favorable renewable charring agent candidate, is enhanced by chemical modification with a phosphorus- and silicon-containing compound and subsequent coagulation in the presence of Ca²⁺ ions. The simultaneous presence of P and Si atoms in the reactive compound is shown to be an effective way to avoid thermal stability issues related to the biobased carbohydrate. The newly synthesized PSilAlg additive boosts the flame-retardant effectiveness of ammonium-polyphosphate (APP) at low loadings. Adding 5 wt% PSilAlg to 15 wt% APP containing PLA composite increases the limiting oxygen index from 26.0 to 34.0 vol% and decreases the total heat emission during combustion by 46%, accompanied by significantly (by 66%) reduced smoke production. The outstanding flame retardant performance of PSilAlg is attributed to the high amount and thermally stable carbonaceous fire-protecting layer that forms as a result of the enhanced charring, catalyzed by the high oxidation state P, and the strengthening mechanism of inorganic silicates and calcium salts.

This work investigates the hybrid nanocomposites manufactured by direct mixing by dispersing varying weight percentages (wt.%) of graphene nanoparticles (GNPs) and Al₂O₃ NPs in epoxy resin. Their properties are then obtained using various mechanical (tensile, flexural, impact, and hardness) and thermal (thermogravimetric) analyses. Furthermore, their microstructure and functional groups are studied by SEM and FTIR, respectively. The hybrid nanocomposite, which contains 1.5 wt.% GNPs and 8.5 wt.% Al₂O₃ NPs, has excellent mechanical properties. Compared to a composite without GNPs, the tensile strength, flexural strength, impact strength, and shore D hardness improve by 95.12, 90.01, 171.43, and 19.75%, respectively. It is also found that hybrid nanocomposite exhibits enhanced thermal stability as GNPs increase, particularly at lower wt.% of Al₂O₃. The SEM of tensile fractured specimens of GNPs/Al₂O₃ epoxy hybrid nanocomposites reveals prominent failure mechanisms, including agglomeration of GNPs and debonding between the GNPs/Al₂O₃ and epoxy. The FTIR spectroscopy analysis reveals distinctive spectral peaks indicating successful incorporation of Al₂O₃ and GNPs into the epoxy-based composite, with observed peaks corresponding to functional groups and bonds characteristic of each component. These findings suggest that the manufactured nanocomposite holds promise as a component in structural applications, particularly in automobiles, aerospace components, and sports equipment.

Front Cover: In this study, nanoparticle dust filters are prepared by electrospinning method by mixing different polymers or polymer blends with ionic liquids. The performance of the filters is evaluated using a sensitive gravimetric method. CTAB modified chitosan fibers retain 96.37 and 96.64 % of Fe₂O₃ and ZnO nanoparticles. More details can be found in article 2400062 by Zeki Tok and Kadriye Ertekin.