Journal of Polymer Science最新文献

Technologies for formation of polymer materials with a given spatial distribution of properties are widely in demand in both scientific and industry applications. Various chemical or physical effects are used to control the formation of polymers and influence their properties, enabling the creation of materials with controlled property gradients. Among the physical effects the use of centrifugal field is one of the most effective ways. Usually it is believed that this mechanism is able to form only a monotonous distribution of properties in the radial direction. In our work, the possibility of obtaining a non-monotonic distribution of optical and mechanical polymer properties during polymerization in centrifuge is demonstrated by the example of acrylamide polymer. The use of interferometry in real-time visualization of the polymerization process allowed us to demonstrate a key role of convective motion in the final distribution of polymer properties. The magnitude of the refractive index inhomogeneity turned out to be on the order of 10⁻³. We propose a physical mechanism responsible for the formation of a non-monotonic distribution of polymer properties based on the competition of several effects at once: free convection, convection in a porous medium, and edge effects.

In this study, we investigate temperature/pH/redox-responsive poly(N-isopropylacrylamide/N-tert-butylacrylamide/N-acrylamido-L-phenylalanine) (P(NIPA/TBA/Aphe)) nanogels cross-linked by N,N′-bis(acryloyl)cystam (BAC) using emulsion precipitation polymerization. The nanogels, denoted as PNTA-BAC, are characterized through nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The hydrogel photonic crystals self-assembled by the PNTA-BAC nanogels demonstrate a stable structural color due to in situ gelation even as the temperature is increased up to the phase transition temperature (Tp) of the nanogels. A large steric hindrance of N-tert-butyl of the TBA side group dramatically slows down the shrinkage of the PNTA-BAC nanogels, leading to the in situ gelation of the hydrogel photonic crystals. Moreover, the synergies of large steric hindrance of the benzene ring and the strongly absorbing water of the carboxyl group of the side groups of the nanogels maintain the structural color of the hydrogel photonic crystals above Tp. When loaded with the drug doxorubicin hydrochloride (DOX), the nanogels exhibit degradability in the strong reducing agent 1,4-dithiothreitol (DTT). Cell toxicity is evaluated using mouse endothelial cells cultured with different concentrations of the nanogel solution. The results indicate that the biodegradable hydrogel photonic crystals composed of the PNTA-BAC nanogels have good biocompatibility, providing a potential nano-platform for drug delivery systems.

In this study, chitosan nanoparticles loaded with laurel essential oil ( Laurus nobilis L.) were produced using the electrospraying method, and the effects of various process parameters were investigated. The morphological, chemical, thermal, and antioxidant properties of the nanoparticles were comprehensively characterized. The addition of laurel essential oil to the solutions resulted in a decrease in electrical conductivity and an increase in viscosity, which led to an increase in particle diameters. Field Emission Scanning Electron Microscopy (FE-SEM) images revealed that the particle morphologies were spherical, with average diameters between 105 and 155 nm. Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed the physical encapsulation of laurel essential oil within the chitosan matrix, while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses revealed an increase in the thermal stability of the laurel essential oil-loaded nanoparticles. In antioxidant activity analyses, 75% essential oil-loaded nanoparticles exhibited significantly higher DPPH (2,2-Diphenyl-1-picrylhydrazyl) (6394.34 μmol TE/g dm) and ABTS (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) (7289.87 μmol TE/g dm) radical scavenging capacities compared to the blank nanoparticles (p < 0.05). The phenolic content also increased proportionally with the essential oil concentration. In conclusion, this study demonstrated the successful encapsulation of laurel essential oil within chitosan nanoparticles. Thus, these findings support potential applications as food preservatives.

AB-type monomers enable a more flexible molecular design of polyurethane synthesis than the conventional methods by the polyaddition of diol and di-isocyanate, that is, various side chain structures can be easily integrated on the former. Meanwhile, the impact of the substituent effect has not been clearly investigated on the synthesis and properties of polyurethanes from AB-type monomers despite its fundamental importance. Herein, we developed four new AB-type monomers exhibiting certain substituents to study the above issue. Interestingly, the introduction of a benzene ring to the side chain moiety did not significantly affect the thermal properties of the polyurethane compared with the corresponding polymer having an n-butyl substituent, while that to the main chain moiety drastically changed the reactivity of the monomer and the thermal properties of the resulting polymer. Moreover, a 2-ethylhexyl side chain structure increased the solubility and flexibility of the polyurethane framework while maintaining the high monomer reactivity at the same time, indicating it would work as a useful comonomer to increase the processability of rigid polymers.

Epoxy resins (EP) have significant application value in the industrial sector; however, their flammability and toxic fume emissions during combustion limit their applications. Bio-based flame retardants provide effective flame-retardant properties, primarily owing to their unique molecular compositions and structural features. In this study, a flame retardant (DAVN) is prepared using vanillin, 5-amino-1H-tetrazole, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). When 6 wt.% DAVN is added to the EP, the EP composite exhibits a residual carbon content of 19.9% at 700°C while achieving a limiting oxygen index (LOI) value of 32.6% and the UL-94V-0 standard. Additionally, compared with pure EP, the peak heat release rate (PHRR), total heat output (THR), total smoke production (TSP), and smoke production rate (SPR) decrease by 49.3%, 44.7%, 35.1%, and 35.1%, respectively. These improvements primarily result from the polyphosphates formed from the DAVN decomposition, which promote the carbonization and cross-linking of EP, thus forming a compact carbon layer that suppresses heat and smoke release. Moreover, the formation of gas during combustion dilutes the combustible gases, thereby enhancing flame retardancy. Additionally, DAVN improves the mechanical properties of EP and increases its tensile strength by 7.1%. This study provides a useful reference for the development of high-performance flame-retardant EP composites.

The replacement of non-recyclable multilayer films with high-performance, monolithic polymer films represents a critical goal for a circular economy. This feasibility study investigates melt mastication (MM), a novel processing technique that utilizes flow-induced crystallization (FIC) to enhance the mechanical and barrier properties of high-density polyethylene (HDPE). The MM process, particularly at low shear rates, fundamentally alters the semicrystalline morphology, increasing the bulk crystallinity to an exceptional level of 85%. This unique, non-spherulitic, granular morphology results in a dramatic enhancement of mechanical properties, with a greater than 240% increase in elastic modulus and a 340% increase in tensile strength compared to conventional controls. A detailed, multi-scale characterization using thermal analysis (DSC), X-ray scattering (WAXS/SAXS), solid-state NMR, and electron microscopy (SEM) elucidates the structure responsible for this performance. The resulting morphology is a direct product of an FIC pathway that occurs above the nominal melting temperature. While the oxygen barrier performance shows a complex dependence on the interplay between crystalline and amorphous structures, the most highly crystalline MM films demonstrate promising properties. This work establishes MM as a powerful pathway for upcycling commodity polymers and provides a model for understanding how chaotic shear can create non-equilibrium structures with enhanced performance.

Smart adsorption material toward both anionic and cationic dyes have been reported rarely, despite bright prospects in dye adsorption. Polyampholyte is a potential ideal candidate. PAAD (copolymer of acrylamide, acrylic acid and [2-(Methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide) is a novel thermo-responsive hydrogel based on polyampholyte, whereas inferior mechanical properties induce fracture during the adsorption process. Herein, we designed a novel cellulose-based crosslinker, which constructs both a robust backbone and reconfigurable physical entanglements in the PAAD-matrix hydrogel to improve the fracture strength and elongation by nearly 195.70% and 360.65%. Meanwhile, the physical entangle is disentangled during deformation and could be re-entangled after deformation, endowing the hydrogel with efficient energy dissipation, fatigue resistance and self-recovery ability, while the highly rigid chemically crosslinked backbone could maintain the shape of the hydrogel under stress. Moreover, the hydrogel can be used as a controllable adsorption material toward both cationic and anionic dyes, which could greatly increase adsorption capacity after reaching UCST due to its temperature-sensitive characteristics.

Thermoplastic elastomers (TPEs) have recently emerged as a class of promising precursors of ordered mesoporous carbons (OMCs) due to their low cost and broad availability. Despite understanding their reaction-induced morphological changes, the fundamental pyrolysis kinetics of crosslinked TPEs remain poorly understood. In this study, we systematically investigate the pyrolysis behavior and pore formation mechanisms of sulfonated polystyrene-block-polybutadiene-block-polystyrene (SBS) using thermogravimetric analysis coupled with mass spectrometry (TGA-MS), nitrogen physisorption measurements, and model-free kinetic analysis. TGA-MS results reveal a multi-stage thermal decomposition process characterized by distinct thermal transitions and volatile product evolution. Nitrogen physisorption measurements demonstrate the development of mesoporosity and surface area with increasing pyrolysis temperature, identifying critical thermal windows for mesopore formation. Furthermore, kinetic modeling of the pyrolysis process was used to determine the apparent activation energies for the cleavage of aromatic and unsaturated moieties. These findings can provide important mechanistic insights for material and process design for producing OMCs via direct pyrolysis of commercially available TPEs.