Studies of the Sulfonated Hydrogenated Styrene-Isoprene-Styrene Block Copolymer and Its Surface Properties, Cytotoxicity, and Platelet-Contacting Characteristics

Styrenic thermoplastic elastomers (TPEs) consist of styrenic blocks. They are connected with other soft segments by a covalent linkage and are widely used in human life. However, in biomedical applications, TPEs need to be chemically hydrogenated in advance to enhance their properties such as strong UV/ozone resistance and thermal-oxidative stability. In this study, films composed of sulfonated hydrogenated TPEs were evaluated. Hydrogenated tert-butyl styrene–styrene–isoprene block copolymers were synthesized and selectively sulfonated to different degrees by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tert-butyl styrene–styrene–isoprene block copolymer and acetyl sulfate, sulfonated films were optimized to demonstrate sufficient mechanical integrity in water as well as good biocompatibility. The thermal plastic sulfonated films were found to be free of cytotoxicity and platelet-compatible and could be potential candidates in biomedical film applications such as wound dressings.

Sulfonic SiO2 nanocolloid doped perfluorosulfonic acid films with enhanced water uptake and inner channel for IPMC actuators

This study provides a facile and effective strategy to fabricate sulfonic SiO₂ nanocolloid (HSO₃-SiO₂) doped perfluorosulfonic acid (PFSA) films with enhanced water uptake and inner channel for high-performance and cost-effective ionic exchange polymer metal composite (IPMC) actuators. A commercial precursor of mercaptopropyl trimethoxysilane was hydrolyzed to form thiol functionalized SiO₂ nanocolloids (SH-SiO₂, ∼25 nm in diameter), which were further oxidized into sulfonic SiO₂ nanocolloids (HSO₃-SiO₂, ∼14 nm in diameter). Both SiO₂ nanocolloids were used as additives to dope PFSA film for fabricating IPMC-used matrix films. Due to difference of compatibility, the SH-SiO₂ nanocolloids take phase separation in the cocrystallization course, and aggregate into huge, regular spherical particles with a mean diameter of ∼690 μm; while the HSO₃-SiO₂ nanocolloids are completely compatible with PFSA, forming a very homogeneous hybrid matrix film. Related physiochemical investigations by analytical tools revealed that, the resultant HSO₃-SiO₂ hybrid film shows better IPMC-related properties compared to the SH-SiO₂ hybrid film: 1.59 folds in water uptake, and 2.37 folds in ion exchanging capacity, thus contains an increased number of cations and possesses larger and better interconnected inner channels for IPMC bending. Consequently, the HSO₃-SiO₂ hybrid IPMC actuator exhibits remarkably higher levels of actuation behaviours such as higher force output, higher displacement output, and longer stable working time, which could be used as a valuable artificial muscle for flexible actuators or displacement/vibration sensors at low cost.

Incorporation of Metallic Species into Midblock-Sulfonated Block Ionomers

Block ionomers can, in the same fashion as their neutral block copolymer analogs, microphase-order into various nanoscale morphologies. The added benefit of a copolymer possessing a charged species is that the resultant block ionomer becomes amphiphilic and capable of imbibing polar liquids, including water. This characteristic facilitates incorporation of metallic species into the soft nanostructure for a wide range of target applications. In this study, the nonpolar and polar constituents of solvent-templated midblock-sulfonated block ionomers (SBIs) are first selectively metallated for complementary morphological analysis. Next, four different salts, with cationic charges ranging from +1 to +3, are introduced into three hydrated SBIs varying in their degree of sulfonation (DOS), and cation uptake is measured as a function of immersion time. These results indicate that uptake generally increases with increasing salt concentration, cationic charge, and specimen DOS. Swelling and nanoindentation measurements conducted at ambient temperature demonstrate that water uptake decreases, while the surface modulus increases, with increasing cationic charge. Chemical spectra acquired from energy-dispersive X-ray spectroscopy (EDS) confirm the presence of each of the ion-exchanged species, and corresponding EDS chemical maps reveal that the spatial distribution of these species is relatively uniform throughout the block ionomer films.

Single vial sample preparation of markers of nerve agents by dispersive solid-phase extraction using magnetic strong anion exchange resins

A sample preparation method involving extraction, enrichment and derivatization of acidic degradation products of nerve agents was developed using magnetic strong anion exchange resins (MSAX). The method was performed in a single vial involving magnetic dispersive solid phase extraction (MDSPE). Analytes were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) in the presence of resins. MSAX were custom synthesized using Fe3O4 nanoparticles as core, 4-vinylpyridine-co-divinylbenzene as polymer shell and quaternary pyridinium function as anion-exchanger. Hydroxide ions were the counter-anions of MSAX to effectively capture the acidic alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs). Quantitative measurements of analytes were performed in the selected ion monitoring mode of GC-MS. Full scan mode of analysis was followed for identifications. Under the optimized conditions analytes were recovered in the range of 39.7-98.8% (n=3, relative standard deviations (RSD) from 0.3 to 6.5%). Limits of detection (LODs) were in the range of 0.1-1.1ngmL(-1); and the linear dynamic range was 5-1000ngmL(-1) with r(2) of 0.9977-0.9769. Applicability of the method was tested with rain-, tap-, muddy-water and Organization for Prohibition of Chemical Weapons (OPCW) Proficiency Test samples.

Morphological investigation of midblock-sulfonated block ionomers prepared from solvents differing in polarity

Recent developments regarding charged multiblock copolymers that can form physical networks and exhibit robust mechanical properties herald new and exciting opportunities for contemporary technologies requiring amphiphilic attributes. Due to the presence of strong interactions, however, control over the phase behavior of such materials remains challenging, especially since their morphologies can be solvent-templated. In this study, transmission electron microscopy and microtomography are employed to examine the morphological characteristics of midblock-sulfonated pentablock ionomers prepared from solvents differing in polarity. Resultant images confirm that discrete, spherical ion-rich microdomains form in films cast from a relatively nonpolar solvent, whereas an apparently mixed morphology with a continuous ion-rich pathway is generated when the casting solvent is more highly polar. Detailed 3D analysis of the morphological characteristics confirms the coexistence of hexagonally-packed nonpolar cylinders and lamellae, which facilitates the diffusion of ions and/or other polar species through the nanostructured medium.