Journal of Polymer Science最新文献

The agglomeration of polybutadiene latex (PBL) is a complex process influenced by numerous factors. Up to now, the change of particle size of agglomerated PBL with time under varying conditions remains unclear, and the agglomeration kinetic model of PBL has not been proposed. In this study, the influence of the process parameters on the particle size of agglomerated PBL with time was studied, including the amount of agglomerating agent, temperature, stirring rate, and solid content of PBL. According to the particle size evolution of agglomerated PBL, the agglomeration process of PBL is divided into two stages, including the dispersion of the agglomerating agent and its adsorption and coalescence with PBL (stage I), followed by the shrinkage of agglomerated PBL particles (stage II). It was found that the process of stage I can be accelerated significantly by increasing the amount of agglomerating agent and agglomeration temperature during PBL agglomeration, thereby reducing the total agglomeration time. The mean particle size of agglomerated PBL was also reduced when the agglomeration process reached stability. With the increase of stirring rate, the time required for agglomeration of PBL and the mean particle size of agglomerated PBL decrease. The higher the solid content of pre-agglomerate PBL, the shorter the time for PBL to complete the agglomeration, but it has no obvious effect on the mean particle size of agglomerated PBL. Based on the experimental results, on the one hand, a novel method for expressing the particle size shrinkage of agglomerated PBL was developed. This analysis was based on the change of mean particle size of agglomerated PBL with time. On the other hand, the Boltzmann equation was used to fit the agglomeration kinetics of the whole process of PBL agglomeration. The results showed that the predicted values were in good agreement with the experimental values when PBL was agglomerated under different process parameters. Knowledge obtained from this study will provide insight into the influence of process parameters on the particle size of agglomerated PBL over time, and the establishment of kinetic models can help the industrial development of PBL agglomeration technology.

Fenton-like hydrogels crosslinked with imine bond were prepared for the removal of tetracycline. Initially, the oxidation process of carboxymethyl cellulose (CMC) was performed, and it was named OX-CMC. The confirmations were then obtained using NMR and FTIR analyses. The degree of CMC oxidation was investigated in relation to reaction time, and optimal time of 4 h was selected. In the second part, a pH-sensitive hydrogel with imine bond was prepared from the crosslinking reaction between OX-CMC and chitosan. The formation of the hydrogel through imine crosslinking was confirmed by FTIR spectroscopy. By increasing ratio of OX-CMC to chitosan, the swelling rate for the hydrogel decreased. Turbidity measurements showed that a higher OX-CMC to chitosan weight ratio resulted in slower hydrogel degradation in acidic environments. In the third part, Fe₃O₄ nanoparticles with concentrations of 5 and 10 wt% were incorporated into the hydrogel structure. TEM studies revealed a spherical morphology and uniform distribution of nanoparticles within the hydrogel network. SEM images revealed a porous structure which composed of interconnected pores in the hydrogel. The results of UV–visible spectroscopy indicated that the degradation of magnetic hydrogels would augment as magnetic nanoparticle content increases, pH decreases, and the hydrogen peroxide content increases.

Exhibiting excellent mechanical properties and exceptional vibration reduction performance, polymer composite (PC) has garnered significant research interest in various industries, particularly in ultra-precision machining (UPM) machine tool beds. UPM machine tools have a stringent requirement on the comprehensive performance of the bed materials. Specially, the materials of machine tool bed must possess both high mechanical properties and outstanding damping characteristics. However, a major obstacle hindering the widespread adoption of PC in UPM machine tool beds is the difficulty in achieving optimal mechanical properties and vibration reduction simultaneously with the same material composition and curing process conditions. In this study, the effect of various particulates on the mechanical strength, loss factor and the average thermal expansion coefficient of PC were systematically investigated. The experimental findings revealed that the compressive strength of PC improved by the incorporation of particulates. Nevertheless, the flexural strength and tensile strength of PC display an inverse variation. Subsequently, gradient PC and compound PC were designed based on the aforementioned results to achieve the best overall properties for the machine tool bed material. The experimental results highlighted that the left and right tri-gradients materials (L-R-3) exhibited the outstanding comprehensive performance. Moreover, this study provides beneficial information to improve the comprehensive properties of PC. Furthermore, it is of great significance to improve machining accuracy of UPM and increase the machining stability of UPM.

A Salen-Co(III)-Cl catalyzed copolymerization strategy is developed for the controlled synthesis of polycarbonate-b-polyester block copolymers through a one-pot process involving CO₂, 4-vinyl-1-cyclohexene-1,2-epoxy (VCHO), and ε-caprolactone (ε-CL). This procedure is extended to the copolymerization of CO₂, VCHO, and lactide. The catalytic system is designed and optimized with temperature and CO₂ acting as triggers to switch between CO₂/epoxide copolymerization and ε-CL homopolymerization. In addition, introducing water as the chain transfer agent reduced the polydispersity index (PDI) of the block copolymers. The copolymer composition can be controlled by adjusting the concentration ratio of epoxides and ε-CL, yielding copolymers with carbonate molar ratios ranging from 14% to 67%. The block copolymers exhibit enhanced thermal stability, and the glass transition temperature (T _g) can be controlled by adjusting the block composition.

The building up of chitosan (CS)/gallic acid (GA) films was performed by casting method, thermally pre-processing the reaction mixture at several temperatures and process times. This study focused on the thermal treatment impact on the antioxidant activity, mechanical deformation at break, water vapor diffusion, and surface CS film features. It is found that the thermal energy promotes the diffusion of species through CS chains as well as the GA interaction with the polysaccharide, producing films with different structural organizations. Since the crosslinking degree depends on the energy received by the system, heterogeneous materials with a low chain crosslinking and a high free GA content are generated at 40°C, while homogeneous films with covalently crosslinking are mostly generated from 50°C. The free GA availability within segregated CS film regions favors the antioxidant activity, but also the polyphenol interaction with the polysaccharide decreases the crystallinity and elastic modulus, increasing the tensile strength and elongation at break. Since a threshold of 516 kJ energy received regulates the transition from heterogeneous to homogeneous films can be thermally tuned. This discovery represents a controlling synthetic factor critical to the design of materials with unique characteristics such as those required for food packaging.

Excessive Mn(VII) and Cr(VI) ions threaten environmental safety and public health. As a result, effective environmental water quality monitoring is required, and the development of materials for rapid and precise detection of hazardous ions in aqueous solutions is imperative. In this study, carbon dioxide-based polycarbonates containing tetraphenylethylene skeletons-based groups (herein referred to as PPCTs) were synthesized in an unprecedented one-pot method using 4-(1,2,2-triphenylethenyl) phenol (T) as the monomer with carbon dioxide and propylene oxide. Fluorescence characterization indicated that modified PPCT retained the aggregation-induced luminescence properties of T. A significant overlap was observed between the ultraviolet absorption bands of the polymer and the MnO₄ ²⁻, and Cr₂O₇ ²⁻ ions, inducing an internal filter effect that resulted in fluorescence quenching of the PPCT solution. The probe demonstrated specific selectivity against interference, as well as high sensitivity toward these anions, with limits of detection as low as 47.8 nM, 0.438 μM, and 1.12 μM, respectively. Furthermore, the modified PPCT demonstrated enhanced thermal properties compared with those of conventional PPC materials, which are crucial for its application in harsh environments. This innovative material synthesized using CO₂ offers a new approach to ion detection in real samples and broadens the scope of poly(propylene carbonate) in fluorescence sensing applications.

The abuse of traditional plastic food packaging has caused severe food safety and environmental pollution, urgently necessitating the development of green and sustainable biodegradable packaging materials. Chitosan (CS) belongs to an inexpensive and readily available biopolymer; however, the poor mechanical properties and weak resistance to UV light and water make it unsuitable for the food packaging industry. In this study, a layer-by-layer (LBL) assembly of CS decorated with anthocyanins as a polycationic electrolyte and carboxylated graphene oxide (GO-COOH) as a polyanionic electrolyte is used to fabricate bio-based films with the aim of improving comprehensive properties of CS-based films. The results indicate that the LBL assembly extremely enhanced the UV-blocking ability (the average transmittance in the UV-B region drops to 1.68%), tensile strength (TS) (53.52 MPa), toughness (71.81%), thermal stability, water resistance, hydrophobicity (the water contact angle is up to 109.5°), and antioxidant activities of the films, attributed to hydrogen bonds among CS, anthocyanins, and GO-COOH and electrostatic interactions between GO-COOH and CS along with anthocyanins. In addition, the LBL films show exceptional advantages in the storage application for fresh-cut apples. In general, the study demonstrates that a novel and sustainable CS-based film can be fabricated by the LBL technique for food packaging.

The advancement of therapeutic gas treatment has significantly impacted on the biomaterial field, with nitric oxide (NO) gaining attention for its safety, multifunctionality, and role in regulating biological processes. Thus, this study introduces a novel biocatalytic NO-generating in situ forming hydrogel (GTA/Cu) to address wound-related issues, fabricated through a simple, one-step process by incorporating copper ions (Cu²⁺) into tannic acid-conjugated gelatin (GTA). Herein, Cu²⁺ functions simultaneously as a crosslinking agent, NO-generating catalyst, and antibacterial agent, while the galloyl groups in GTA enable effective tissue adhesion and diverse crosslinking interactions. The hydrogels' mechanical properties are controlled by varying Cu²⁺ concentrations (25, 50, and 100 mg/mL), with higher concentration accelerating gelation and enhancing mechanical strength. At 100 mg/mL Cu²⁺, the hydrogel releases NO for up to 12 days, reaching a cumulative concentration of around 200 μM. It also demonstrated robust antioxidant activity, high tissue adhesion (~20 kPa), and comparable antibacterial effects to Cu-only samples. Interestingly, the released NO facilitates endothelial cell proliferation, accelerates scratch closure within 36 h, and stimulates new tube formation on Matrigel, showing comparable effects to VEGF. Additionally, it clearly promotes new blood vessel formation in vivo following subcutaneous injection, further highlighting its potential for practical wound healing applications.

Using the “grafting through” approach, alternating polymer brushes with different lengths of the backbone and side chains are synthesized. Thermosensitive poly(2-ethyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline) with styrene and maleimide moieties are used as the macromonomers. The prepared polymer brushes are characterized by molar masses in the range of 19,000–52,000 g·mol⁻¹ and have a low dispersity Ð = 1.6–1.9. The number of side chains is from 10 to 20. The LCST behavior of alternating brushes in aqueous solutions is studied by light scattering and turbidimetry. Phase separation temperatures of aqueous solutions of alternating polymer brushes are varied from 37°C to 48°C depending on the length and number of the side chains, as well as on the polymer molar mass. The critical micelle concentrations depend on molar mass and the side chain length, changing from 1.12 × 10⁻⁵ to 9.40 × 10⁻⁴ mol·L⁻¹, as established by the method of solubilization of a hydrophobic dye. Using the Benesi–Hildebrand method, the binding constants for curcumin and polymer brush samples are determined; their values range from 360 to 63,400 L·mol⁻¹. It is shown that curcumin is effectively bound by polymer brush molecules in the aqueous solutions, which ensures the solubilization of hydrophobic curcumin in water.