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Item type:Publication, Access status: with files , Iron(III) ion reinforced P(NiPAAm-co-AA) beads as tunable smart organogelsP(NiPAAm-co-AA) organogel beads were prepared by UV-induced droplet polymerization and mechanically reinforced through treatment with iron(III) chloride. Energy-dispersive X-ray spectroscopy mapping revealed a structure generation dependent on the amount of iron incorporation: beads with a low iron(III) loading have a core–shell architecture; high loadings result in a more homogeneous distribution of the ions over the particle volume. Fourier transform infrared analysis and proton release indicate coordination of iron(III) ions to formed carboxylic entities in the copolymer. A colorimetric thiocyanate assay allowed us to quantify the iron uptake, identifying a limit at a ratio of Fe3+ to COOH entities of approximately 1:3.8. The compressive Young's modulus of the 5 mm beads increased by a factor of 378 from 6.1 kPa in the parent gel to 2.3 MPa in the Fe3+-saturated beads. The gels show a highly reversible shrinkage and swelling during solvent exchange between ethanol and ethyl acetate. The reinforced beads with a low and a high Fe3+ content conditioned in ethanol undergo a shrinkage of their volume after immersing in ethyl acetate of 38% and 25%, respectively; the time constants for shrinkage increase most significantly with the iron content; the rate of swelling is comparable. No iron(III) leaching was detected over multiple swelling–shrinkage cycles. © 2026 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.Publicationtype: Journal Article15 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Preparation of organogel beads for smart valve components: kinetic study of their chemoresponsiveness(American Chemical Society (ACS), 2026-07-20); ; ; ; Chemoresponsive P(NiPAAm- co -AA) beads (approximately 3 mm radius) were synthesized via UV-light-induced copolymerization of N -isopropylacrylamide (NiPAAm) and acrylic acid (AA) in aqueous droplets suspended in silicone oil. SEM analysis revealed a closed surface for beads with a 3-fold excess of AA; macroporous morphologies appeared for NiPAAm:AA ratios of 1:1 and 3:1. Swelling behavior was mapped across linear alcohols, acids, esters, and their mixtures, revealing a cononsolvency related to ethanol presence. Beads with a 1:1 monomer ratio exhibited the largest swelling difference between ethanol and ethyl acetate or with mixtures of ethyl acetate and ethanol. Their reversible swelling–shrinkage was fitted to two exponential functions. The time constant of the first fast part is on the order of minutes. The extent of shrinkage is negatively correlated with the logarithmic ethanol fraction in ethyl acetate. Beads in a casing were used to halt the flow of ethyl acetate after a switch to ethanol.Publicationtype: Journal Article24 35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Autonomous flow control by a responsive poly(2-hydroxyethyl acrylate) organogel-valve during the aerobic oxidation of benzyl alcohol(American Chemical Society (ACS), 2026-06-05); ; ; Macroscopic poly(2-hydroxyethyl acrylate) organogel beads were synthesized and applied as a chemoresponsive component in a smart valve. Monodisperse round beads of about 3 mm diameter were obtained by cryogenic dripping and subsequent UV photopolymerization of the frozen aqueous monomer solution. The synthesis yields dimensionally stable, soft spheres with a macroporous architecture. The elastic modulus increases from the soft, swollen state in benzyl alcohol to over 250 kPa for high-density networks in the collapsed state in benzaldehyde. They have a degree of swelling in benzaldehyde lower by a factor of 3–7 to that in benzyl alcohol, in dependence of the amount of polyethylene glycol diacrylate cross-linker in the precursor solution. Upon exposure to benzaldehyde, the beads become opaque, indicating a phase transition. Kinetic analysis of the bead volume change for swelling in benzyl alcohol and shrinkage in benzaldehyde gives half-life times in the range of 2–5 min. Beads exhibiting a macroscopic volume change of up to 71% were confined in a casing and acted as a smart valve in a reactor system. The aerobic oxidation of benzyl alcohol to benzaldehyde with a TEMPOL/copper acetate catalyst mixture demonstrated the high efficiency and practical applicability of the self-regulating flow-control component.Publicationtype: Journal Article29 49 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Esterification in an autonomously controlled reactor: exploiting the chemo-mechanical properties of a smart organogel(American Chemical Society (ACS), 2026-06-04); ; ; ; Iron(III)-reinforced poly(N-isopropylacrylamide-co-acrylic acid) organogel beads inside a casing give an intrinsic chemo-mechanical valve. The valve was incorporated in a setup with a stirred reactor for the heterogeneously acid-catalyzed esterification of acetic acid and ethanol. A noninvasive gravimetric control loop was used to validate the autonomous modulation of the hydrodynamic residence time in response to the composition of the reaction mixture. Operating at a 1:1 molar feed ratio, the valve restricted the initial outflow to less than 7 mL·min–1 and autonomously ramped up to a steady state flow of 135 mL·min–1 as the esterification approached thermodynamic equilibrium. The valve opening rate was about half of the reaction rate. The ionically reinforced organogel had enough resilience inside the casing for multiple uses. Soft actuators were thus successfully applied for reaching a self-regulating reactor loop driven by intrinsic chemical feedback of a smart material.Publicationtype: Journal Article77 68 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enhancing swelling kinetics of pNIPAM lyogels: the role of crosslinking, copolymerization, and solvent(Elsevier, 2025-10-01); ; ; ; Stimuli-responsive lyogels are known for their ability to undergo significant macroscopic changes when exposed to external stimuli. While thermo-responsive gels, such as poly-N-isopropylacrylamide (pNIPAM), have been extensively studied across various applications, solvent-induced swelling has predominantly been investigated in aqueous solutions. This study explores the tailoring of lyogel formulations for future applications by controlling their solvent-induced swelling behavior, comparing both homopolymeric and semi-interpenetrating polymer networks (semi-IPNs). It is structured in two parts: the first focuses on characterization techniques, including NMR relaxometry, swelling degree measurements, mechanical testing, and SEM analysis, while the second part delves into swelling kinetic analysis, applying solvent exchange as a stimulus for varying gel formulations and solvents. In contrast to most previous studies, the impact of chemical and physical crosslinking, as well as copolymer inclusion, on the swelling behavior and mechanical properties of lyogels in organic solvents is examined and compared with solvent-induced swelling kinetics measurements. The results demonstrate that increasing chemically crosslinking in homopolymers and physically crosslinking in semi-IPNs enhances mechanical stability, while improving mass transport properties and solvent exchange kinetics. However, increases degree of crosslinking results in a prolonged response time to the solvent exchange stimulus and a reduction in the overall swelling capacity of the lyogels. Furthermore, variations in solvent properties, including molecular size and diffusion rates, significantly influence the swelling kinetics, whereas smaller, faster-diffusing solvents leading to more pronounced solvent spillage effects. Our findings highlight the complex interplay between gel formulation, network structure, and solvent nature in determining the solvent-induced swelling kinetics of lyogels, providing insights into how these materials can be tailored for specific applications especially those requiring short response times and optimized mechanical properties.Publicationtype: Journal Article110 61