ACS polymers Au最新文献

As the scale and variety of plastics produced continue to grow, plastics recycling will require innovative solutions. The industrial state-of-the-art sorting technology, near-infrared (NIR) spectroscopy, as currently used, cannot effectively differentiate polyolefins, the single largest class of polymers by volume. Chemical similarity combined with architectural diversity in polyolefins stymies subclass delineation, such as differentiating low-density polyethylene from high-density polyethylene, due to their spectral similarity and chemical overlap. To address this challenge, we use machine learning (ML) to directly predict density, crystallinity, and short-chain branching from NIR spectra, enabling property-based sorting for more effective recycling. After testing a variety of ML models, we find that partial least squares regression provides high prediction accuracy with model simplicity. Since the resulting model leverages the correlated intensities, we develop a method to enhance interpretability by identifying the most important wavenumbers for property prediction, which we then relate to known polyolefin CH₃ NIR vibrational absorption bands. This approach provides a linkage between ML model predictions and the underlying polyolefin chemistry and confirms that our models effectively capture spectrum-structure-property relationships in polyolefins, reinforcing the fundamental role of polymer chain structure in determining properties. These findings significantly contribute to the understanding of polyolefin differentiation using NIR spectroscopy, which could inform future advancements in property-based sorting strategies for plastic recycling efficiency.

For accelerating the shift from fossil-derived plastics toward biopolymers, there is an urgent need to develop efficient and versatile biobased plasticizers to improve biopolymer performance without compromising biodegradability and/or safety. This study explores the versatility of the emerging triphenylacetic glyceroate (TPAG) bioplasticizer by incorporating it into a range of biobased and conventional polymers. An increasing content of TPAG, from 5 to 20 parts per hundred of resin (phr), has been compounded with polyhydroxybutyrate (PHB), polyhydroxybutyrate-co-valerate (PHBV), polyvinyl chloride (PVC), and polybutylene succinate (PBS), which present complicated processability and/or limited mechanical properties as bare polymers. Differential scanning calorimetry reveals a clear reduction in glass-transition temperatures (T _g) for PHB, PHBV, and PVC, with the most significant drop observed for PVC (ΔT _g = -25 °C at 20 phr TPAG), confirming the significant plasticizing efficiency of TPAG. A melting temperature decrease is also noted for PHB and PBS, with PHB exhibiting β-crystalline phase formation at high TPAG contents, which is attributed to enhanced chain mobility. Mechanical tests demonstrate that only 10 phr TPAG reduces Young's modulus across all polymers, importantly enhancing their flexibility. Furthermore, 20 phr of TPAG increases the elongation at break of PVC and PHBV up to 349% and 22%, respectively. Volatility and migration studies demonstrate minimal plasticizer loss with values remaining well below safety limits. Moreover, TPAG addition also tailors both water contact angle and UV-blocking activity of the tested polymers, clearly indicating the versatility and multifunctionality of TPAG as a potentially suitable additive for consumer-facing applications.

Significant reliance on petroleum-based plastics remains due to their attractive properties and wide-ranging applications. Driven by environmental concerns, recent research has increasingly focused on utilizing naturally occurring plant-derived molecules and environmentally friendly processes for the synthesis of novel polymeric materials with adequate properties to replace petroleum-based materials. Within this context, limonene has gained unusual prominence as an abundant citrus byproduct. This terpene can be functionalized through a variety of classical organic reactions, e.g., epoxidation, (meth)-acrylation, lactam formation, and thiol-ene click chemistry, opening distinct pathways toward structurally diverse polymers. These routes span traditional radical and ionic processes, as well as coordination systems and ring-opening polymerizations. Together, they have enabled materials that range from poly-(limonene carbonates) and semiaromatic polyesters to polyethers, biobased polyamides, thermosets, and photo-cross-linkable resins suitable for 3D and 4D printing. Many of these polymers have demonstrated promising optical, mechanical, or thermal performance, although important challenges persist, particularly regarding dispersity control and the integration of recycling strategies into circular economy cycles. By bringing these developments into a single narrative, this review highlights how limonene is gradually shifting from a fragrance molecule to a versatile precursor for advanced, renewable polymeric materials.

Environmental concerns and the global shift toward a more sustainable and circular economy have increased the demand for economically viable materials derived from industrial waste. In this study, high-value engineering materials discarded from different industries were repurposed to develop new multifunctional hybrid composites. The selected postindustrial waste included polyamide 6 (rPA6) from automotive plastic washers, recycled graphite (rGra), and recycled carbon fiber reinforced polymer (rCFRP) epoxy-based composites originating from the aerospace sector. These materials were separately ground using a knife mill and subsequently compounded via extrusion. The fillers (rGra and rCFRP) were incorporated individually and as hybrids (rCFRP:rGra, 1:1 wt %) at total loadings of 5, 10, and 20 wt % in the rPA6 matrix. The composites were characterized in terms of morphology, rheology, mechanical performance (tensile test), thermal behavior (differential scanning calorimetryDSC), electrical conductivity, and electromagnetic properties. The mechanical results revealed a notably high ultimate tensile strength of 126 MPa and an elastic modulus of 4.8 GPa for the rPA6/rCFRP (20 wt %) composition, suggesting strong interfacial adhesion promoted by secondary interactions between the epoxy resin coating on the rCFRP and the rPA6 matrix. Electrical conductivity measurements on composite films showed values from 10^-5 to 10^-1 S.cm^-1 for the hybrid and rCFRP-filled compositions, indicating their potential for antistatic (anti-ESD) applications. Although rGra exhibited lower mechanical and electrical performance than rCFRP at the evaluated contents, it was less detrimental to processability, making the hybrid formulations more balanced candidates for real-world applications. Overall, this study demonstrates a promising strategy for upcycling industrial waste into high-value, multifunctional composites, thereby contributing to resource efficiency and waste minimization across various industrial sectors.

Herein, we describe the design, synthesis, and analysis of anhydrous fuel cell membranes that can operate at temperatures above 100 °C, in view of enhanced performance and stability. Traditional polymer electrolyte membrane fuel cells (PEMFCs) do not operate efficiently above 100 °C because water is used as a proton-conductive medium through the Grotthuss hopping mechanism. By substitution of water with heterocyclic amine monomers and use of ionizing radiation to graft them onto fluoropolymer films, proton-conductive network solid-state polymer electrolyte membranes (PEMs) were developed. PEMs were synthesized using indirect radiation grafting of the following heterocyclic amine monomers: 4-vinylpyridine and 5-vinylpyrimidine onto fluorocarbon substrates. The resulting PEMs have proton conductivities greater than 10^-2 S/cm above 100 °C and perform independent of humidity conditions. These PEMs also demonstrate a positive correlation of increased proton conductivity with increasing temperatures above 100 °C. The chemical properties and structures of the grafted monomers affect the proton-conductive mechanism and performance of the PEMs. The data generated through this research will further the development of anhydrous PEMs through radiation grafting to achieve higher proton conductivity, enhanced performance, and stability.

In this study, a novel photoresponsive poly-(ethylene glycol)-peptide (PEG-peptide) diblock copolymer capable of promoting pheochromocytoma cell (PC12) growth is developed, and the corresponding hydrogels with tunable mechanical properties for nerve tissue engineering are constructed via bridge-micelle architectures. The PEG-peptide forms core-shell micelles in the precursor solution, in which the core peptide segment contains γ-benzyl-l-glutamate moieties to stimulate nerve cell growth and coumarin moieties to provide photoresponsivity, while the hydrophilic PEG shell could enhance stable dispersion of micelles. Meanwhile, coumarin-containing water-soluble random copolymers poly-(N,N-dimethylacrylamide-random-acrylic-(7-(2-acryloyloxyethoxy)-4-methylcoumarin)) (PDA) are incorporated to function as bridges. The coumarin moieties in both polymers undergo [2 + 2] cycloaddition upon 365 nm UV irradiation, resulting in the coexistence of three different types of cross-linking: intramicelle, micelle-bridge, and interbridge cross-linking. By adjusting the composition and concentration of the precursor solutions as well as 365 nm UV irradiation time to delicately balance these cross-linkings, hydrogels with a wide range of mechanical strengths, swelling ratios, and viscoelastic behaviors are feasibly fabricated. This construction not only expands the gelation window but also exerts an effective approach to precisely modulate mechanical properties and water absorption of hydrogels, which could further optimize the environment for cell growth. The complex modulus of the hydrogels is tunable between 238 and 1448 Pa, aligned with the mechanical strength of native extracellular matrix for PC12 cell growth. It is noteworthy that a high complex modulus and high swelling ratio could be concurrently achieved, enabling excellent PC12 cell growth performance in cell cytotoxicity and 3.2 times cell viability with respect to the control group. Additionally, upon 30 min of 254 nm UV irradiation, the hydrogels can be un-cross-linked into solutions via dedimerization of coumarin, offering a great potential for clean scaffold removal. These achievements demonstrate that the hydrogel system provides a cytocompatible and supportive biochemical environment, offering promising potential as a foundational platform for nerve-regeneration scaffold design.

Gene delivery lies at the heart of many approaches for treating a host of different diseases. Promising candidates for the delivery of genetic material are polycationic vectors; however, managing toxicity arising from adverse interactions with the lipid bilayer remains a challenge. In this work, photoiniferter reversible addition-fragmentation chain-transfer (PI-RAFT) polymerization was used to synthesize statistical copolymers of N-vinyl formamide (NVF) and N-vinyl pyrrolidone (NVP). Subsequent selective hydrolysis of NVF was used to introduce polyvinyl amine (PVAm) repeats. The resulting library of polymers with varying charge densities and molar masses was probed for biocompatibility with erythrocytes and MDA-MB-468 cells, revealing substantially reduced cytotoxicity compared with linear polyethylene imine (lPEI) and Lipofectamine 2000. Using an ethidium bromide (EtBr) replacement assay, PVAm copolymers were shown to replace EtBr at low N/P-ratios. The transfection conditions were optimized in terms of the N/P-ratio and polyplex concentration by a Renilla luciferase reporter assay. This revealed 30-fold less cytotoxicity, a much wider viable concentration range, and a 2-fold greater transfection efficiency for the PVAm copolymer compared to lPEI. This study provides insights into the PI-RAFT copolymerization of the less activated monomers NVF and NVP and highlights the potential of polyvinyl amine copolymers resulting from selective hydrolysis for the transfection of genetic material compared with lPEI.

Dendrimers, constituting a prominent class of monodisperse and multivalent macromolecular compounds with outstanding properties, are characterized by regular and highly branched three-dimensional architectures and well-defined chemical structures. Within each structural type, the skeletal diversity is typically limited to the range of generations. Here, we introduce a novel modular synthetic strategy enabling an increase in the diversity of the dendrimer interior while maintaining its chemical nature. Resulting poly-(amide-carbosilane) (PAMCAS) dendrimers can be fine-tuned within one generation in terms of size, number, and density of end groups, as well as interior free volume. Using a tetravalent core and two building blocksdendritic wedges with branching degrees 3 and 6we demonstrate the potency of this strategy by producing a family of dendrimers through a controlled iterative process that combines highly chemoselective amidic coupling and thiol-ene click reaction (TEC). Within three generations, we prepared 14 structural analogs of PAMCAS dendrimers, systematically varying the order of building blocks and thus their structural profile. The solution properties of the obtained materials were studied by DLS, A4F, diffusion NMR, and molecular modeling. When using exclusively the AB₆ module, the dendritic growth is accelerated and allows straightforward access to structures with extremely high valency in a given generation. As the modular synthetic strategy poses a considerable purification challenge, we implemented organic solvent nanofiltration (OSN) as the main separation tool. Herein, we demonstrate proof-of-principle experiments to evaluate the scope and limits of the use of OSN as an effective separation method in synthetic macromolecular chemistry.

Core-sheathed inverted nozzle pressurized gyration (CsINPG) is a novel fiber manufacturing process based on gas blowing-assisted rotary coaxial spinning technology, capable of large-scale manufacture of core-sheathed, micropolymeric structures. The CsINPG spinning vessel is constructed from polycarbonate and has a unique nozzle arrangement, which increases uniformity and facilitates the formation of core-sheathed fibers. The CsINPG apparatus functions as a jet generator, ejecting the spinning feedstock under the combined forces of centrifugal force and pressure differentials. The centrifugal force, which is generated by the spinning of the vessel, is powered by a connected electrical motor. This enables the loaded polymeric feedstock to overcome its surface tension, facilitating fluid ejection through the external nozzles on the vessel wall to form spinning jets. These polymeric jets undergo further stretching through the assimilation of the pressure differential, which is powered by introducing nitrogen flows. This further increases the initial velocity and acceleration. In core-sheathed pressurized gyration, the feedstock is present in two different chambers of the core and the sheath. Furthermore, during "inverted" nozzle-pressurized gyration, the entire manufacturing process is carried out on a horizontal axis, facilitating the controlled streaming of these spinning jets into a water bath. This facilitates the usage of "green polymers" such as alginate and cellulose, which require water baths to be converted from soluble streams to insoluble fibrous structures. These fabricated core-sheathed fibers, manufactured under the optimum parameters in this study, produced fibers with average diameters measuring <10 μm. This paper will delve into the development of the novel CsINPG manufacturing process, focusing on the design of the spinning vessel, the parameters used, the optimization of parameters and their consequences, and the potential future applications of the manufactured core-sheathed fibers.