Polymer Science, Series A最新文献

Sealant materials serve as the primary waterproof barrier for the external walls of prefabricated concrete buildings. Their durability is a crucial performance indicator, directly influencing the effectiveness of waterproofing and service lifespan of buildings. Therefore, the assessment of sealant durability is a critical area of research with substantial practical implications. This study evaluates the durability characteristics of three commercially available sealant types: one-component modified silicone, two-component modified silicone, and polyurethane sealants. A comprehensive testing program was conducted, involving specimen preparation and subsequent exposure to four distinct aging conditions: natural aging, thermal aging, UV aging, and accelerated artificial climate aging. This study aimed to effectively assess the influence of various aging conditions on the evolution of the physical and mechanical properties of the abovementioned sealant materials. The aged sealants were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and volumetric swelling tests to analyze the aging mechanisms of the different sealant structures. Furthermore, the coefficient of variation method was employed to assess the durability performance of the three sealants. Testing results revealed distinct sensitivity patterns to aging conditions among the different sealant structures. The one-component modified silicone sealant demonstrated comparable sensitivity to thermal aging, UV aging, and artificial climate aging, exhibiting superior durability performance. By contrast, both two-component modified silicone and polyurethane sealants showed increased sensitivity to UV aging and artificial climate aging conditions.

Natural polymers are of great interest as soil ameliorants capable of biodegradation at the end of growing season. The synthesis of interpolyelectrolyte complex (IPEC) of anionic xanthan and cationic chitosan is described, and their physico-chemical, water-retaining, anti-erosion and biological properties are compared with the properties of the individual xanthan. A combination of methods: gravimetric analysis, FTIR spectroscopy, electron microscopy, equilibrium centrifugation, mechanical strength assessment and cell-mediated hydrolysis allowed the following main results: (a) Addition of a xanthan aqueous solution to a chitosan aqueous solution result in spherical capsules with a chitosan–xanthan IPEC shell and a xanthan solution inside. (b) Destruction of the capsules, washing with water and lyophilization yields the stoichiometric IPEC with a porous structure, stabilized by electrostatic and hydrophobic interactions. (c) The swelling degree of IPEC in water is 65 and decreases to 32 after mixing IPEC with sand. (d) Addition of IPEC and xanthan to sand increases the maximum water capacity from 27% up to 59–62% while a substantial part of water in the modified sand retains available to plants. (e) Application of IPEC and xanthan over sand leads to the protective polymer-sand coatings, resistant to water erosion; the IPEC-sand coating provides only 1.4 wt % sand loss versus 16 wt % sand loss for the xanthan-sand coating. (f) Field trails have shown that IPEC has a longer service life. (g) Soil microorganisms utilize xanthan and IPEC, with the former being consumed much faster than the latter. The obtained results indicate the potential of using biodegradable IPEC as a combined eco-friendly soil ameliorant.

The piezoelectric properties of thin polyvinylidene fluoride films with a thickness of 9 μm were studied after irradiation with fast heavy ions Ne, Xe, and Bi with a fluence of about 10⁹ ions/cm². The effect of Xe ion fluence in the range from 10⁵ to 10¹⁰ ions/cm² on the piezoelectric characteristics of PVDF was also studied. The results showed that irradiation with high-energy ions promotes the formation of the piezoelectric module d₃₃ in PVDF films. This effect is due to thermal and structural transformations caused by heavy ions. Additional polarization in the electric field of a negative corona discharge leads to an enhancement of the piezoelectric response. At the same time, chemical etching causes an exponential decrease in the value of d₃₃, which may be associated with the destruction of β-phase areas and an increase in conductivity along ion tracks, leading to charge leakage and a decrease in residual polarization.

The conformational behavior of a single polymer chain with polar groups is studied using molecular dynamics simulations under the combined action of a mechanical stretching force and an external electric field. The polar groups are uniformly distributed along the chain and modeled as dipolar units composed of two oppositely charged beads that are covalently bonded together. One of the beads is incorporated into the backbone chain, while the other forms a side group. Special attention is paid to the chain behavior in low-polarity environments, where the polymer forms a polyelectrolyte globule. It is demonstrated that an external electric field aligned with the stretching force F promotes chain extension at small values of F. At higher extensions, however, the application of the field leads to partial contraction of the chain due to electrostatic attraction between dipoles, which tend to align along the field direction and form linear aggregates. The structure of ionic aggregates and the degree of orientational ordering of dipoles are analyzed as functions of solvent polarity, the field strength, and the relative orientation of the electric field and the stretching force.

In this work, flexible poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLA-PEG-PLA) composites incorporated with non-activated coconut-shell biochar (BC) and activated coconut-shell biochar (ABC) were successfully prepared through melt blending. Scanning electron microscopy (SEM) indicates that all the composites showed good phase compatibility, suggesting strong interfacial adhesion between the PLA-PEG-PLA matrix and both the biochar types. Differential scanning calorimetry (DSC) demonstrated that the composites containing 0.5 wt % biochar exhibited the highest crystallinity for both BC and ABC. When the biochar content exceeded 0.5 wt %, the effectiveness of biochar as a nucleating agent diminished due to the restriction of chain mobility in PLA-PEG-PLA. Thermal stability from thermogravimetric analysis (TGA) and mechanical properties from tensile tests of the composites were improved by the addition of these biochars. The 0.5 wt % biochar yielded the highest maximum tensile strength and Young’s modulus values of the composites. The DSC, TGA, and tensile results indicate that BC has a high potential to be used as nucleating, thermal stabilizing, and reinforcing agents for PLA-PEG-PLA compared to the ABC.

Poly((sulfobetaine methacrylate)-co-N-isopropylacrylamide) (P(SPE-co-NIPAM)) is a hydrogel with LCST and UCST types of thermoresponsive behavior that can be used as a drug delivery system. The hydrogel has been successfully synthesized via free radical polymerization, using the N,N'-methylene-bisacrylamide (MBA) as the crosslinker and ammonium persulfate (APS) as the initiator. The hydrogel was then characterized using Fourier transform infrared (FTIR), which showed the disappearance of the C=C vinyl group from both monomers in the hydrogels which confirmed the success of the synthesis. The gel content showed that increasing the concentration of MBA caused the increase of gel content of the hydrogel, while the ESR was decreased. The swelling test was conducted to study the thermoresponsive behavior of the hydrogels and revealed that the swelling decreases as the temperature increases. Additionally, increasing the concentration of APS and the composition of NIPAM would lead to a higher swelling ratio. The deswelling test indicated that a greater SPE monomer composition resulted in a lower deswelling rate. The P(SPE-co-NIPAM) hydrogel was investigated for its performance as an active agent delivery. It was found that the P(SPE₂₀-co-NIPAM₈₀) with sample code S20N80-4-1 and S20N80-2-2, were able to load 2.75 and 4.8% of the metformin-HCl, respectively. The in vitro release test of these hydrogels showed the cumulative release from metformin-HCl of 26.33 and 19.34% in phosphate buffer solution pH 7.4 at 37°C within 15 h.

Gelatin-core/poly(ethyleneglycol)-shell structured nanoparticles were synthesized via soap-free emulsion polymerization, gelatin and poly(ethylene glycol) were modified with methacrylic anhydride into methacrylated gelatin (GelMA) and poly(ethyleneglycol) dimethacrylate (PEGDMA), characterized by different techniques and used as macro-comonomers. Nanoparticles were prepared using different macro-comonomer ratios which translated into different sizes as revealed by dynamic light scattering measurements. Nanoparticles were then loaded with clioquinol as model drug for Alzheimer’s treatment, and their drug release behavior was studied, finding that nanogels impart a controlled release directly correlated with the amount of PEGDMA in relation to GelMA in them. Nanoparticles were found to be biocompatible when tested by the MTT assay on human skin fibroblasts. These characteristics make the synthesized nanogels prime candidates for their potential use as drug carriers for neurodegenerative disease treatment.

The article shows the influence of the type and composition of commercial grade compatibilizers on the degree of compatibility difficult mix polypropylene random copolymer/aluminum hydroxide (PP‑R/Al(OH)₃) systems. The influence of the compatibilizer type and the aluminum hydroxide content on the properties of the PP-R/Al(OH)₃ composite was investigated. For this purpose, PP-R/Al(OH)₃ and PP‑R/compatibilizer /Al(OH)₃ composites were obtained by mixing them on hot rollers in the melt mode. Three kinds of compatibilizer were used: maleic anhydride functionalized polypropylene copolymer, maleic anhydride functionalized homopolypropylene, blend of fatty acid metal soap and amide. The influence of compatibilizers on the properties and compatibility of PP-R/Al(OH)₃ composites was studied. Compatibilization was compared from the physical and mechanical properties, morphology, and melt properties of the blends. The morphology and dispersion of Al(OH)₃ in PP-R composites evaluated using scanning electron microscope (SEM). It was shown that relatively uniform dispersion of Al(OH)₃ in the PP-R matrix was achieved in the presence of compatibilizers. Studies showed that the compatibilizers not only improved the compatibility of the mixed components of the mixture but also the interfacial adhesion between Al(OH)₃ and PP-R. Composites with a compatibilizer showed a more homogeneous morphological structure, which has a positive effect on improving their main physical and mechanical characteristics.

A series of nonequilibrium-swollen biopolymer materials based on N-(1,2-dicarboxyethyl) chitosan (DCEC), N,O-(carboxymethyl) chitosan (CMC), N-(2-carboxyethyl) chitosan (CEC) and hyaluronic acid (HA) as carboxyl-containing polysaccharides were obtained. Evaluation of the mechanical strength of the swollen materials under compression showed that the samples of biopolymers based on N-(1,2-dicarboxyethyl) chitosan with a functionalization degree of 0.35, 0.5 and N,O-(carboxymethyl) chitosan with a functionalization degree of 1, were destroyed, probably due to the formation of a denser network of intermolecular interactions. Materials based on hyaluronic acid and N-(2-carboxyethyl) chitosan showed high elasticity and plasticity. However, the biopolymer material based on hyaluronic acid has lower mechanical strength due to its low molecular weight. A sample based on N-(2-carboxyethyl) chitosan with a functionalization degree of 1 is characterized by high mechanical strength and elasticity, with a true stress of 1.24 MPa. This opens the possibility of developing new medical materials based on these biopolymers.