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The friction behaviour of new chitosan derivative coatings obtained by chemical modification of chitosan with fatty acids (linoleic and dilinoleic acid) has been investigated in order to explore their potential as endovascular catheter coatings and to benchmark them against commercially available coatings used in endovascular catheter applications. An in vitro tribological system was developed that was intended to represent to a limited extent the in vivo tribological conditions of a typical endovascular catheterization procedure. Continuous reciprocating sliding tests were carried out with uncoated and coated polymer specimens. The results showed that all of the coatings tested decreased the coefficient of friction compared to the uncoated polymer. Compared to a neat chitosan coating, the chitosan derivative coatings showed a clear reduction in the coefficient of friction to levels similar to those of the commercially-available coatings. A comparison between the friction results and contact angle measurements carried out on the coatings indicated that a range of contact angle values exists for which the friction coefficient is at a minimum. The reason for this is unclear and further studies are required in order to confirm and investigate the trend, especially within the context of hydrophilic lubricious coating development. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present the results of comparative dynamic stress relaxation studies performed with poly(styrene-b-isobutylene-b-styrene) (SIBS), polyurethane (PU) and polyester (PED) biomaterials in air and simulated body fluid (SBF) at 24°C and 37°C. SIBS showed the highest value of relieved stress under constant strain (24.1% after 100,000 cycles in air) with PED and PU having similar relative change (12.2% and 10.5%). In spite of its softness (Shore A 56 vs. 80), the dynamic modulus (E dyn) and stiffness of SIBS were in between PED and PU. The behavior of the materials was correlated to their structure: SIBS is an amorphous block copolymer with a long elastomer midblock, while PU and PED are semicrystalline segmented copolymers with much shorter soft blocks, and hydrogen bonding. SIBS and PED were relatively insensitive to SBF and temperature changes, while PU experienced the largest changes in physical properties in vitro (simulated body fluid, 37°C). [Copyright &y& Elsevier]

Abstract: The morphology of hydrogels based on poly(vinyl alcohol) (PVA) in their frozen hydrated state, modified with biologically active di- and multifunctional molecules was studied by scanning electron microscopy (SEM) with cryo-attachment. The porosity of samples was found to be more regular and ordered in the case of samples containing difunctional, and especially multifunctional carboxylic acids as compared to the neat PVA hydrogel. The morphology is dependent not only from the hydrogel composition but also the number of freezing–thawing cycles. Resulted highly porous and oriented structure has significant influence on materials properties, such as compressive stress and crosslinking density. [Copyright &y& Elsevier]

The effects of simulated body fluid (SBF) on the surface and mechanical properties of poly(aliphatic/aromatic-ester) (PED) copolymers were investigated. PED copolymers containing different hard (aromatic) and soft (aliphatic) segment weight ratios were exposed to SBF for 52 days, and afterwards their mechanical properties were evaluated. A quasi-static tensile test estimating relaxation and fatigue properties from the hysteresis method was performed. The surface properties were monitored with scanning electron microscopy and energy-dispersive X-ray spectrometry. PED copolymers showed various susceptibilities to apatite layer formation on the surface. This was ascribed to the hard/soft segment ratios of PED materials. Polymers containing higher amounts of amorphous soft segments showed a better deposition with the apatite layer, which provided improved mechanical properties, especially fatigue (improved dynamic creep resistance). [Copyright &y& Elsevier]

This study was undertaken to evaluate the biocompatibility of new multiblock poly(ester–ester)s proposed as an alternative to Hunter silastic prosthesis used in a two-stage tendon reconstruction. Methanol-extracted polymeric material retained its weight, demonstrating the absence of leachable particles (e.g. low-molecular weight oligomers). Implantation tests indicated that the observed tissue changes were similar to those obtained with silicone, no evidence of contact necrosis being observed. The unchanged morphology of rat liver hepatocytes and the lack of parenchymal necrosis also indicated that exposure to the investigated polymers did not cause any cytotoxic reactions. [Copyright &y& Elsevier]

In this study a degradation process of flexible polymer networks fabricated from telechelic macromonomers comprising methacrylic functionalities and dimer fatty acid derivatives were discussed. Hydrolytic degradation in simulated body fluid (SBF) as well as enzymatic degradation with a lipase of six different systems comprising ester, anhydride and urethane bonds was investigated. In parallel, in order to make a comparison with other analogous polymeric systems, reference materials were also considered. The degradation process was monitored by determining the weight loss and water uptake, FT-IR analysis and changes in pH of degradation medium as a function of time. A rapid progress of degradation of the network containing anhydride bonds was observed. Furthermore, polymer networks showed low water absorption from 10 to 2 wt.%. Polymer networks did not release acidic degradation products in an amount that causes acidification of the medium except the anhydride network. The IR analysis of characteristic bands showed degradation of specific bonds leading to formation of possible hydrolysis products of these networks such as poly(methacrylic acid), macromonomer precursor molecules and derivatives of the macromonomers having terminal carboxylic and hydroxyl groups. We demonstrated that the referred polymeric networks undergo a controlled gradual degradation in the presence of lipase. This study provides an example of how the susceptibility of cross-linked polymers to degradation can be tailored by varying their molecular structure, depending on the needs. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of PVA-chitosan-NiO, PVA-chitosan-TiO 2 , and PVA-chitosan-TiO 2 @NiO films have opened avenues for tailoring materials with specific electrical, dielectric, and optical properties. The synergistic effects arising from the combination of polymers and metal oxides offer a platform for further optimization and application-specific tuning. The synthesis process successfully incorporated NiO and TiO 2 nanoparticles into the PVA-chitosan matrix, creating three distinct films: PVA-chitosan-NiO, PVA-chitosan-TiO 2 , and PVA-chitosan-TiO 2 @NiO. Structural analyses, including X-ray diffraction (XRD) and scanning electron microscopy (SEM), revealed well-defined nanostructures with crystalline metal oxide dispersions. Dielectric characterization demonstrated frequency-dependent behavior, elucidating the influence of metal oxides on dielectric constants and loss tangents. Cole–Cole plots provide insights into relaxation processes and can guide applications in capacitors and energy storage devices. Conductivity measurements highlight the enhanced electrical performance of NiO and TiO 2. This study provides a foundation for future research on the development of advanced functional materials for a wide range of technological applications. The insights gained from this work contribute to the growing body of knowledge on polymer-metal oxide composites and pave the way for innovations in electronic, optoelectronic, and energy-related technologies. • Developed PVA-chitosan hybrid films incorporating TiO 2 and NiO nanoparticles for advanced functional material applications were prepared. • Employed X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm well-defined nanostructures and homogeneous dispersion of metal oxide nanoparticles within the polymer matrix. • Performance including higher dielectric constants and reduced loss tangents, highlighting potential in capacitive and energy storage applications were improved. • Enhanced electrical conductivity in PVA-chitosan-TiO 2 @NiO films compared to individual PVA-chitosan-NiO and PVA-chitosan-TiO 2 films was observed. [ABSTRACT FROM AUTHOR]

• Enzyme catalyzed PBS copolyesters were synthesized in solution. • Kinetic studies revealed formation of segmented copolymers with random to ordered segments distribution. • MALDI-ToF evidenced presence of cyclic structures. • Thermal properties strongly depend on the degree of randomness, sequence length and hard to soft segments ratio. A series of segmented bio-copolyesters based on crystallizable hard segments of poly(butylene succinate) (PBS) and fully bio-based dilinoleic diol (DLAOH), creating dilinoleic succinate (DLS) soft segments, were prepared by enzymatically catalyzed polycondensation. The kinetic studies performed with 1H NMR and SEC have proved incorporation of highly hydrophobic DLAOH into the polymer backbone. We found that the efficacy of DLAOH incorporation was limited by the catalytic pocket size of the enzyme and its hydrophobic nature favouring the formation of long PBS sequences, especially at the early synthesis stages and having an effect on final content of soft segments compared to feed ratio. Based on quantitative 13C NMR analysis we found that copolymers had R- values lower than 1, that is low degree of randomness. Differential scanning calorimetry (DSC) revealed changes in degree of crystallinity and the presence of a phase mixed system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Three carbon nanofillers were used to produce nanocomposites in situ during polymerization. • The chemical structure of the nanocomposites was studied by NMR and IR spectroscopy. • Aspect ratio of nanofiller had a marked effect on thermal and mechanical properties. • Cytocompatibility tests did not show any adverse effect of carbon black/graphene. Abstract Nanocomposites based on poly(ethylene terephthalate-ethylene dilinoleate) (PET-DLA) copolymers of different hard to soft segment ratios (40:60 and 60:40) and three different carbon nanofillers of different aspect ratios (dimensions), as 0D carbon black, 1D multiwalled carbon nanotubes, and 2D graphene, have been prepared in situ during two-stage polymerization. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize the chemical structures of the obtained nanocomposites. Scanning electron microscopy (SEM) indicated very good dispersions of all carbon nanofillers in both polymer matrices. Differential scanning calorimetry (DSC) results revealed that the addition of nano-sized fillers eliminated cold crystallization of materials containing 40% hard segments in polymer matrix. We found that the high aspect ratio, 1D nano-filler (multiwalled carbon nanotubes) strongly nucleated crystallization of materials containing 60% of hard segments. This nanofiller also yielded the greatest improvement in the Young's modulus as assessed by tensile tests, both at 24 °C and 37 °C. We did not observe reduced bacterial adhesion to nanocomposites, likely due to increased roughness. Importantly, in vitro cytocompatibility tests with L929 murine fibroblasts demonstrated cell viability and growth on all materials except those containing carbon nanotubes. Finally, both high aspect ratio nanofillers markedly improved the barrier properties of obtained nanocomposites. New materials were successfully used for manufacturing of prototype of heart assist device, with pneumatic membrane made of graphene nanocomposite. [ABSTRACT FROM AUTHOR]

The solid state properties of segmented polyurethanes (TPU) are determined to a great extent by their microphase-separated structure thus making them attractive for several technological applications. In addition to microphase separation, hydrogen bonding and partial crystallization of the soft segments often contribute to the thermoplastic elastomeric behavior of TPUs. In this work, we applied infrared spectroscopy to determine the degree of microphase separation and quantitative analysis of H-bonds formation between functional groups of hard and soft segments in poly(carbonate-urethane)s (PCUs) with a narrow weight ratio from 35 to 41 wt% of hard segments. Using the Gaussian deconvolution of infrared spectroscopy peaks we determined the degree of microphase separation in synthesized PCUs, indicating for the first time, the significant contribution of the H-bonds present in mixed phase of hard and soft segments. Moreover, high content of mixed phase and additional physical carbonyl groups interactions of carbonate macrodiol resulted in the highest elastic modulus for PCU containing only 41 wt% of hard segments. The results demonstrated that the newly introduced deconvolution formula and detailed analysis of infrared spectra are a precise tool in determining the degree of microphase separation in segmented polyurethanes even at narrow segments ratio. [ABSTRACT FROM AUTHOR]

In this work, we present novel, sustainable filters based on bacterial cellulose (BC) functionalized with low-pressure argon plasma (LPP-Ar). The "green" production process involved BC biosynthesis by Komagataeibacter xylinus , followed by simple purification, homogenization, lyophilization, and finally LPP-Ar treatment. The obtained LPP-Ar-functionalized BC-based material (LPP-Ar-BC-bM) showed excellent antimicrobial and antiviral properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, and an enveloped bacteriophage phage Φ6, with no cytotoxicity versus murine fibroblasts in vitro. Further, filters consisting of three layers of LPP-Ar-BC-bM had >99 % bacterial and viral filtration efficiency, while maintaining sufficiently low airflow resistance (6 mbar at an airflow of 95 L/min). Finally, as a proof-of-concept, we were able to prepare 80 masks with LPP-Ar-BC-bM filter and ~85 % of volunteer medical staff assessed them as "good" or "very good" in terms of comfort. We conclude that our novel sustainable, biobased, biodegradable filters are suitable for respiratory personal protective equipment (PPE), such as surgical masks and respirators. [Display omitted] [ABSTRACT FROM AUTHOR]

A new copolymer poly(butylene succinate-dilinoleic succinate) (PBS-DLS) has been successfully synthesized and its suitability for the fabrication of electrospun fiber mats has been investigated for the obtaining both electrospun scaffolds of neat PBS-DLS and also in blend with poly(glycerol sebacate) (PGS). After optimizing the electrospinning process for both neat and PGS/PBS-DLS (ratio 1:2) blend materials, homogeneous fiber mats have been obtained with an average fiber diameter of 2.5 ± 0.5 μm and 2.0 ± 0.2 μm, for neat and blend mats, respectively. Mechanical properties and degradation behavior in PBS were investigated to evaluate their suitability for soft tissue engineering applications. A feasibility study of the obtained electrospun mats functionalization was performed and positive results were obtained, demonstrating the versatility and suitability of PGS/PBS-DLS electrospun fibers as candidate for soft tissue engineering applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fatty acid derived ester-urethane telechelic macromonomers were synthesized with Bi and Zn catalysts. • Syntheses were performed in ethyl acetate (a green solvent) • Reaction kinetics of non-toxic Bi and Zn catalysts were compared to organotin catalyst. • Elastomeric films were created in air and argon by photopolymerization. • The use of non-toxic solvent and catalysts increased cell viability in vitro. Photocurable materials that can be delivered as liquids and rapidly (within seconds) cured in situ using UV light are gaining increased interest in advanced minimally invasive procedures. The aim of this work was to synthesize and characterize fatty-acid-derived ester-urethane telechelic (methacrylate) macromonomers, suitable for photopolymerization. The commonly used dibutyltin dilaurate catalyst was replaced with bismuth neodecanoate, bismuth tris(2-ethylhexanoate), and zinc (II) acetyloacetonate as less-toxic alternative catalysts. Additionally, ethyl acetate was used as a "green" solvent. The progress of the two-step synthesis was monitored with infrared spectroscopy. The chemical structure and molecular weight of the obtained viscous materials was characterized with nuclear magnetic resonance spectroscopy and gel permeation chromatography. Photocrosslinking of the macromonomers into elastomeric films was achieved using 150 s per spot of UV light (20 mW/cm2) exposure. Mechanical tensile testing of the films indicated their elasticity up to 120% and low modulus typical for soft and elastomeric materials. Finally, in vitro cytotoxicity tests showed high cell viability for the case of materials synthesized using bismuth and zinc catalysts. Overall, our results indicate that bismuth and zinc catalysts are excellent alternatives to organotin compounds in the synthesis of photocurable methacrylate ester-urethanes with improved environmental and safety profile, and for potential biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present the first results on the effect of specimen size and branching on the fatigue properties of polyisobutylene-based thermoplastic elastomers measured by the hysteresis method. It was verified that smaller specimens were inherently stronger as expected; at the same loading rate microdumbbells induced higher strain rates so they can be considered as the “worst case” scenario. Microdumbbells, which can be implanted into small animals for in vivo studies, were used for dynamic fatigue testing of linear poly(styrene-b-isobutylene-b-styrene) triblock copolymers (L_SIBS) in comparison with long-chain branched (tree-like or dendritic) versions (D_SIBS). In dynamic stress relaxation studies, D_SIBS performed better than L_SIBS. Simulated physiological conditions had negligible effect on the dynamic properties. [Copyright &y& Elsevier]

• Chitosan modified with fatty acids (CHFA) was characterized with IR, NMR and XPS. • Amphiphilic CHFA coatings exhibited self-organization and reduced bacterial growth. • Easily-prepared CHFA coatings were lubricious, non-toxic, and non-hemolytic. • The developed strategy is particularly promising for biofunctinal catheter coatings. Multifunctional and biofunctional coatings for medical devices are an attractive strategy towards tailoring the interactions of the device with the body, thereby influencing the host response, and the susceptibility to microbial colonization. Here we describe the development of a coating process to yield amphiphilic, lubricious coatings, resistant to bacterial colonization, based on chitosan. Chitosan-fatty acid derivatives were obtained by simultaneous N,O -acylation of chitosan with either linoleic, α-linolenic, or dilinoleic acid. Chemical characterization of new materials was carried out using 1H NMR, FTIR, and XPS. Surface properties of coated polyester samples were studied using SEM and contact angle measurements, which indicated that the incorporation of hydrophobic constituents into chitosan macromolecules led to a decrease of both surface roughness and water contact angle. Importantly, tribological testing demonstrated that these new coatings decrease the coefficient of friction due to the self-organization of fatty acid (from 0.53 for the neat chitosan to 0.35 for chitosan-fatty acid derivative). Meanwhile, preliminary bacterial colonization tests indicated significant—over 80%—reduction in E. coli colonization following coating with chitosan-linoleic and chitosan-α-linolenic derivatives. Finally, cytotoxicity and hemocompatibility studies confirmed that all amphiphilic chitosan-fatty acid derivatives were non-toxic and non-hemolytic. Collectively, our results demonstrate the potential of the developed coating strategy, particularly the chitosan-linoleic and chitosan-α-linolenic acid derivatives, for applications as biofunctional catheter coatings. [ABSTRACT FROM AUTHOR]