Journal of Polymer Science最新文献

Poly(L-lactic acid) (PLLA) is one of the most popularly utilized plant-based polymers, as PLLA can be synthesized from renewable sources such as sugar, carbohydrate, etc. In recent several decades, scientists have been interested in PLLA because of its environment-friendly characteristics. However, there exist some big problems with PLLA, which are low crystallization rate and low crystallinity. In order to overcome such drawbacks, nucleation agents have been incorporated into PLLA. On the contrary, we have reported that plasticizers (both of biobased (organic acid mono-glyceride; OMG) and oil-based (dioctylphthalate)) can improve the crystallizability of PLLA [Polymer Journal 2019; 51(2): 283–294]. The results are significant because plasticizers are believed to delay crystallization of polymers by reducing the thermodynamical driving force of crystallization. We now recognize that the lowering of the activation energy for the PLLA crystallization may be the main effect of a plasticizer with small-amount loading. In this study, we confirm that in the presence of the plasticizer molecules, better folding of the PLLA chains results, which has been experimentally confirmed by the fact that the surface free energy (σ _e ) of the crystallites plane, on which the folds of the PLLA chains exist, becomes lower upon the loading of plasticizers. The free energy change upon the formation of a primary nucleus is then drawn as a function of the thickness of the primary nucleus using the values of σ _e (which were evaluated in the framework of the Hoffman-Lauritzen theory through the growth rate of spherulite from the polarizing optical microscopic observation) and it was found that the energy barrier (activation energy) for the crystallization is decreased by the loading of plasticizers. This explains the enhancement of the crystallizability by the presence of plasticizer.

The study investigates the influence of scaffold architecture and postprocessing, specifically heat treatment, on the mechanical and biological effectiveness of 3D-printed polylactic acid (PLA) scaffolds. Cross-patterned PLA scaffolds were printed at infill densities of 50%, 60%, and 70% and heat-treated (HT) at varying temperature–time combinations to enhance crystallinity. The optimum condition was found to be 90°C for 120 min (HT-120), which was chosen for further study. MTT assays using MG 63 osteoblast cells indicated that HT scaffolds, particularly with 70% infill density (HT90(120)-70), showed significantly greater cell viability for 15 days than untreated scaffolds (UT-70). The exchange of growth-promoting nutrients among cells and heat treatment-induced surface roughness enhances biocompatibility and cellular proliferation, crucial for bone regeneration. Mechanical tests showed that HT90(120)-70 had nearly 20% higher yield strength than UT-70 due to its enhanced crystallinity. Immersion of HT90(120)-70 in physiological fluid for 15 days at 37°C did not significantly change yield strength compared to dry conditions, but post-yield softening was observed in immersed scaffolds due to hydrolytic aging. Cyclic unloading-reloading experiments under physiological conditions also demonstrated that HT90(120)-70 shows greater resistance to deformation. The study reveals HT90(120)-70 as a promising alternative scaffold for load-bearing bone tissue engineering.

A multi-component hydrogel was prepared by the sol–gel process of anionic κ-carrageenan to construct a physical cross-linking network and chemical cross-linking of acrylamide (AM), in which polyvinylpyrrolidone (PVP) served as a component of the semi-interpenetrating network, and nano-silver powders were used as conductive particles and antibacterial agents of the hydrogel. XRD confirmed that the hydrogel contained silver nanoparticles, and the homogeneous dispersion of silver nanoparticles made the hydrogel have high conductivity (35.84 S/m) and also improved its sensitivity in strain response. The strain sensitivity gauge factor (GF) of the hydrogel could reach 6.79 in a relatively large strain range (100%–500%), and it also had a high response sensitivity in the weak strain range such as 0.1% to 5% (GF = 1.43). The presence of PVP-Ag improved the mechanical properties of the gel, and its tensile strength, elongation at break, and toughness were 0.345 MPa, 1310%, and 4519.5 kJ/m³, respectively. With the increase in carrageenan content, the thermal reversibility of the hydrogel was dominant, and the composite hydrogel behaved with a certain self-healing ability. Thus, this work could provide a flexible electronic material with biocompatibility, antibacterial properties, high sensitivity, and a wide strain range.

Organic solar cells (OSCs) present a viable, cost-effective, and adaptable substitute for conventional silicon-based photovoltaics. But their power conversion efficiency (PCE), which is frequently constrained by ineffective photocurrent collection, continues to be a major obstacle to broad commercialization. In this study, the synergistic effect of solvent additives and quantum dots (QDs) on the performance of thin-film polymer solar cells (TFPSCs) was investigated. Tellurium-based QD at optimum concentration and chloronaphthalene (CN) solvent additive were used in the hole transport layer (HTL) and the solar absorber layer of TFPSC separately and simultaneously to improve the performance of the devices. The performance of the TFPSCs with only CN additives in the active layer and that of the QD only in the HTL were very close to each other. However, better device performance was observed when the solvent additive and the QD were used simultaneously in the bulk heterojunction (BHJ) photoactive layer and the HTLs, respectively. However, increasing the concentration of the QD in the HTL led to a reduction in device performance. The TFPSC with both additive and QD doping displays an over 50% enhancement of the PCE when compared to the pristine devices.

Hydrogels plug high-permeability zones by swelling in profile control, redirecting water to low-permeability areas. This study developed a novel 3D composite hydrogel using acrylamide, flyash, and sodium carboxymethyl cellulose for enhanced swelling under extreme conditions. Swelling behavior was optimized under varying salinity, pH, temperature, and particle size. Under optimal conditions (8% NaCl, pH 12.0, 120°C, particle size ≤ 0.125 mm), the hydrogel achieved a remarkable swelling ratio of 158.90 g g⁻¹, surpassing conventional PAM's 108.60 g g⁻¹. In contrast, the salt-tolerant swelling capacity of the hydrogel was only 39.80 g g⁻¹ under pH 6.0 conditions. Core flooding tests showed 93.3% plugging efficiency in sand packs, with excellent profile control and water shutoff. Notably, the hydrogel showed significantly enhanced salt-resistant swelling at pH 12.0. This performance improvement primarily stems from the targeted hydrolysis reaction of flyash in strong alkaline environments. During this hydrolysis process, the generated anions effectively reduce Na⁺ concentration and mitigate osmotic pressure, while the hydrolysis of CONH₂ groups produces COO⁻ under alkaline conditions. This enhances the electrostatic repulsion between polymer chains, expanding the 3D network and thereby greatly increasing swelling. This study promotes a circular economy by repurposing industrial waste into smart hydrogels for practical oilfield water control applications.

Poly(methyl methacrylate) (PMMA) with different content of unsaturated end (UE, 42.6%–56.6%) structure was prepared by high-temperature free radical polymerization. The influence of UE structure on the thermal stability of PMMA was quantitatively elucidated. The innovative method of bromine addition-iodometric titration with ¹H-NMR complementary validation system was used for the precise quantification of UE. Thermogravimetric analysis results showed that under nitrogen atmosphere, the increasing content of UE significantly decreased the thermal stability of PMMA, and for every 1% increasing content of UE, the initial degradation temperature (T_i) decreased by 3.14°C ± 0.38°C, the low-temperature peak temperature (T_d1) decreased by 2.38°C ± 0.16°C, the apparent activation energy (Ea) decreased by 4.18 ± 0.49 kJ mol⁻¹; under air atmosphere, oxygen showed a stabilization effect in the initial stage by inhibiting the “unzipping” degradation triggered by UE with a positive correlation between ΔT_i and UE (ΔT_i = 3.05UE–125.15). The dual role of oxygen (stabilization at low temperature and promotion at high temperature) and modulation of stabilization effect by UE resolved the controversy in the literature. This study provided a quantitative framework for the optimization of PMMA thermal stability.

Covalent organic polymers (COPs) with tunable functionality hold strong potential for pollutant capture and drug delivery. We report the synthesis of a benzene-cored COP (BeTz-COP) via a metal- and catalyst-free inverse electron-demand Diels–Alder (IEDDA) reaction between a tetra-norbornene-functionalized benzene monomer and a bifunctional tetrazine linker. This modular approach enables access to multifunctional materials under mild conditions. BeTz-COP was characterized using FTIR, SEM, EDX, TEM, and TGA, confirming its robustness. UV–Vis diffuse reflectance spectroscopy revealed a band gap of 2.01 eV for BeTz-COP, compared to 1.66 eV for the porphyrin-based PoTz-COP, as we previously reported, highlighting the impact of core structure on optoelectronic properties. Both polymers are semiconducting in optoelectronic behavior and hold promise for photocatalysis, biosensing, and light-triggered drug delivery. In cyclohexane, BeTz-COP exhibited an iodine uptake of 547 mg·g⁻¹, surpassing PoTz-COP (462 mg·g⁻¹), underscoring the aromatic core's effect on adsorption. At pH 8.50, drug loading efficiencies were 23.0% for BeTz-COP and 31.0% for PoTz-COP. Both materials showed pH-responsive doxorubicin release, with faster release under acidic conditions (pH 5.50, mimicking tumor pH) and prolonged release at physiological pH (7.40), supporting targeted drug delivery. IEDDA chemistry offers a versatile platform for designing adaptive COPs for environmental and biomedical applications.

Salting-out method has been widely employed to enhance the mechanical properties of hydrogels. Unfortunately, the enhancement in mechanical properties is still unsatisfactory for many applications. Here we report a modified salting-out method for preparing polyvinyl alcohol (PVA) hydrogels with dramatically enhanced mechanical properties by soaking a weakly cross-linked PVA hydrogel in a mixed aqueous solution of sodium citrate (Na₃Cit) and polyacrylic acid (PAA). Compared with the PVA hydrogel prepared with the common salting-out method, the PVA/Na₃Cit/PAA hydrogels show dramatically enhanced tensile strengths, elastic moduli, and elongations at break up to 21.8 MPa, 4.6 MPa, and 1200%, respectively. The mechanical properties of the hydrogels can be adjusted by controlling the concentrations of Na₃Cit and PAA. The use of a mixed solution of an inorganic salt and a polymer capable of forming hydrogen bonds enables the simultaneous introduction of additional components into the hydrogel network and the formation of more and stronger hydrogen bonds with PVA chains during the salting-out process, resulting in the increased cross-linking density and enhanced mechanical properties of the hydrogel. This work provides a simple yet novel method for improving the mechanical properties of hydrogels.