Polymer Solvent Research Articles

Chemical Resistance of Hydrogenated Nitrile Butadiene Rubber and Nitrile Butadiene Rubber in Propylene

Abstract The chemical resistance of hydrogenated nitrile butadiene rubber (HNBR) and nitrile butadiene rubber (NBR) in propylene is considered as no resistance (NR) by many chemical compatibility handbooks and industry chemical resistance tables and charts. This situation drives the change of the elastomer compounds from cheap HNBR/NBR to expensive fluoroelastomer (FKM) for applications involving propylene. However, in the literature, NBR and HNBR are rated as having good or excellent chemical resistance to all other hydrocarbons, such as ethylene, ethane, propane, butane, butylene. It seems that there are some special or unknown characters of propylene that make it is very harsh to both NBR and HNBR, and therefore it is important to investigate the chemical resistance of NBR and HNBR in propylene. In this study, the chemical resistance of HNBR and NBR in propylene is investigated according to ISO 23936-2 and ASTM D471. The test results are crucially important for the applications of HNBR/NBR in contact with propylene. Based on the tests, we investigated the changes of physical properties such as tensile properties, volume changes and glass transition temperatures and chemical structure of HNBR/NBR after aging in high-pressure propylene at an elevated temperature. The Hansen solubility parameters (HSP) of HNBR and NBR and many hydrocarbons such as ethylene, ethane, propylene, propane, butane, and butylene were estimated. Based on the HSP, the polymer solvent interaction parameters between HNBR/NBR and hydrocarbons were also estimated to explain the chemical resistance of HNBR/NBR in propylene. An aging mechanism was also proposed to explain the changes of HNBR and NBR in propylene aging. This study provided an even better guidance on chemical resistance of HNBR/NBR in propylene to the elastomer industry.

Solvent and additive-controlled supramolecular isomerism in zinc coordination polymers.

A new series of Zn(II) supramolecular isomers containing ditopic 1,3-di(pyridin-4-yl)urea (4bpu) ligand were synthesized and characterized by infrared analysis, elemental analysis and TGA as well as single-crystal X-ray diffraction analysis. Four solvent-induced pseudopolymorphic zinc (II) coordination polymers (CPs), namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1), {[Zn(4bpu)(OAc)2](C2H5OH)}n (2), {[Zn(4bpu)(OAc)2](HOCH2CH2OH)}n (3), and {[Zn(4bpu)(OAc)2](0.5H2O)}n (4), were prepared by the reaction of Zn(OAc)2.2H2O and 4bpu via self-assembly under varying solvent systems. Also, a pair of polymorphic coordination polymers namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1α) and {[Zn3(4bpu)3(OAc)6](CH3OH)2}n(1β), was prepared in the presence of different organic additives. Single-crystal X-ray diffraction confirmed that 1-4 and 1α display 1D polymeric zig-zag chains and 1β exhibits 1D triple-stranded ladders that were self-assembled through various supramolecular interactions. In addition, a series of dissolution-recrystallization structural transformations (DRST) were performed on these supramolecular isomers.

Folding behaviors of two-dimensional flexible polymers.

Unlike one-dimensional polymers, the theoretical framework on the behaviors of two-dimensional (2D) polymers is far from completeness. In this study, we model single-layer flexible 2D polymers of different sizes and examine their scaling behaviors in solution, represented by Rg ∼ Lν, where Rg is the radius of gyration and L is the side length of a 2D polymer. We find that the scaling exponent ν is 0.96 for a good solvent and 0.64 for under poor solvent condition. Interestingly, we observe a previously unnoticed phenomenon: under intermediate solvent conditions, the 2D polymer folds to maintain a flat structure, and as L becomes larger, multiple folded structures emerge. We introduce a shape parameter Q to diagram the relationship of folded structures with the polymer size and solvent condition. Theoretically, we explain the folding transitions by the competition between bending and solvophobic free energies.

Quantitative Macromolecular Modeling Assay of Biopolymer-Based Hydrogels

The rubber elasticity theory has been lengthily applied to several polymeric hydrogel substances and upgraded from idealistic models to consider imperfections in the polymer network. The theory relies solely on hyperelastic material models in order to provide a description of the elastic polymer network. While this is also applicable to polymer gels, such hydrogels are rather characterized by their water content and visco-elastic mechanical properties. In this work, we applied rubber elasticity constitutive models through hyperelastic parameter identification of hydrogels based on their stress–strain response to compression. We further performed swelling experiments and determined the intrinsic properties, i.e., density, of the specimens and their components. Additionally, we estimated their equilibrium swelling and employed it in the swelling-equilibrium theory in order to determine the polymer–solvent interaction parameter of each hydrogel with regard to cross-linking. Our results show that the average mesh size obtained from the rubber elasticity theory can be regarded as a concentration-dependent characteristic length of the hydrogel’s network and couples the non-linear elastic response to the specimens’ inherent visco-elasticity through hysteresis as a quantifier of energy dissipation under large deformation.

Methodical evaluation of Boyle temperatures using Mayer sampling Monte Carlo with application to polymers in implicit solvent.

The Boyle temperature, TB, for an n-segment polymer in solution is the temperature where the second osmotic virial coefficient, A2, is zero. This characteristic is of interest for its connection to the polymer condensation critical temperature, particularly for n → ∞. TB can be measured experimentally or computed for a given model macromolecule. For the latter, we present and examine two approaches, both based on the Mayer-sampling Monte Carlo (MSMC) method, to calculate Boyle temperatures as a function of model parameters. In one approach, we use MSMC calculations to search for TB, as guided by the evaluation of temperature derivatives of A2. The second approach involves numerical integration of an ordinary differential equation describing how TB varies with a model parameter, starting from a known TB. Unlike general MSMC calculations, these adaptations are appealing because they neither invoke a reference for the calculation nor use special averages needed to avoid bias when computing A2 directly. We demonstrate these methods by computing TB lines for off-lattice linear Lennard-Jones polymers as a function of chain stiffness, considering chains of length n ranging from 2 to 512 monomers. We additionally perform calculations of single-molecule radius of gyration Rg and determine the temperatures Tθ, where linear scaling of Rg2 with n is observed, as if the polymers were long random-walk chains. We find that Tθ and TB seem to differ by 6% in the n → ∞ limit, which is beyond the statistical uncertainties of our computational methodology. However, we cannot rule out systematic error relating to our extrapolation procedure as being the source of this discrepancy.

Mechanical Design Principles of Conductive Gels Applied for Flexible Electronics

AbstractReaping the benefits of the burgeoning investigation of gels in recent decades, flexible electronics based on conductive gels have been extensively explored. Gels consisting of polymer networks and solvents provide ideal platforms for fabricating flexible electronics due to their soft mechanical nature, excellent biocompatibility, water‐like environment, and ease of processing. The majority of investigations of flexible electronics primarily focus on functionalities such as sensing capability, energy density, luminance, fluctuating frequency, and so on, whereas the distinguishing feature of flexible electronics lies in its inherent deformable mechanics in comparison to metal‐ or semiconductor‐based stiff electronics. However, the comprehensive design and investigation of the mechanical properties of deformable conductive gels have not received sufficient attention to improve the overall performance of flexible electronics. A comprehensive summary is provided, listing six crucial mechanical parameters—stretchability, modulus, strength, elasticity, hysteresis, and fatigue—which exert significant influence on the functionalities of flexible electronics. This review aims to direct researchers’ attention toward the mechanical design of deformable conductive gels and presents representative strategies for their mechanical modulation.

Effect of concentration and electrical charge of maltodextrin, and packing factor on electrospinning processing

The power law ηrel ∼ Ca of maltodextrins with higher entanglement concentrations (Ce) of dextrose equivalent (DE) 4, 10, and 18 exhibits an unusually high exponent a, ranging from 10.34 to 14.38 in congested solutions where particles occupy significant space. This contrasts with the dilute exponents (a ∼2) typically observed in polymer–solvent systems. To address this issue, several viscosity factors were evaluated using the Einstein–Roscoe and Mooney equations, which demonstrated viscosity dependence due to volume fraction (ϕ) > 0.35, shape, crowding factor (k) packing factor (1/k∼0.5) and centered cubic cell (CC), particularly for larger chain sizes (>20 glucoses) in DE-4. Chain electrical charges significantly stiffen the chain and increase its length beyond the theoretically predicted Kuhn persistent length (Lp), which seems to be responsible for the exponential increase in viscosity. Normalizing the viscosity/charge data revealed a log–log plot consistent with the exponent a of the general power law theory. In addition to concentration, electrospinning processing is influenced by strong particle–particle charge interactions, (ϕ), packing factor (1/k), CC, and chain sizes. The Maxwell model demonstrated poor interaction for DE-4 (modulus ∼286 Pa at maximum ϕ due to loose packing of CC, in contrast to DE-18, which exhibited a modulus of 994 Pa for a solution with maximum ϕ> 0.5 and a congested solution of 52% w/v, packing factor of 0.68, and high particle–particle interaction of the body-centered cubic (BCC) cell, favoring electrospun fiber formation. The packing factor, ϕ, and cell type, are highly sensitive and have potential applications in food systems, 3D bioprinting, among many other scientific domains.

Deep Eutectic Solvent as a New Zeta Potential Altering Chemical for Sand Agglomeration.

Fines migration can cause various issues, such as plugging of the sand screen and damage to tubings. There are two chemical sand control methods: consolidation and agglomeration. Consolidation works by injection of a solvent into the formation to harden over time and hold the sand in place, while agglomeration works by altering chemical properties of the sand surface to attract and clump up sand. Various chemicals have been used for research in sand control. Some chemicals for consolidation, mostly resins, have been effective in consolidating sand but may cause permeability impairment, which will reduce production. Some chemicals for agglomeration such as a polymer with amines have been less effective or are nonbiodegradable. In this work, a novel deep eutectic solvent (DES) and ionic polymer combination as a fines stabilizer is formulated in-house and tested through extensive experimental study. The development of chemicals is based on agglomeration principles which determine the range of zeta potential reduction that can be achieved to destabilize, coagulate, and flocculate the fine particles together with different combinations of DESs and ionic polymers tested systematically using the design of experiment (DoE) method. The chemicals are then tested for compatibility with reservoir fluids in the jar test. The optimized formulation is characterized by thermogravimetric analysis (TGA) for limit of temperature degradation and laser particle size analysis (LPSA) for the extent of particle size. The novelty of this work is the development of a greener and more cost-saving in-house DES and ionic polymer combination as a fines stabilizer chemical, which is effective for both injection or production wells after stimulation or enhanced oil recovery (EOR) treatments. Due to the tunable nature of the DES, the formulated chemical can be tailored for various reservoir conditions to cater to specific requirements.

Approach for concurrent detection and removal of diclofenac in wastewater: Integration of MOF with Poly(deep eutectic solvent) imprinting method

Diclofenac in medical wastewater poses a significant threat to the environment and human health. A simple and efficient enrichment strategy has been established for the selective identification and removal for diclofenac in environmental water samples applying MOF based polymeric deep eutectic solvent (Poly(DES)@MOF). Poly(DES)@MOF was synthesized using a surface imprinting method. The components included MOF-199 as the support material, diclofenac as the template, and a deep eutectic solvent (DES) composed of choline chloride and methacrylate (1:2) as the functional monomer. Density functional theory calculated the Gibbs free energy change during the reaction process, confirming that DES improved the binding performance and selectivity of polymer. Related experiments have shown that Poly (DES) @ MOF has high adsorption capacity, reaching equilibrium within 2 h. In real sample experiments, the maximum adsorption capacity of diclofenac in lake water by the extraction device was 19.39 mg·g−1, with an average recovery rate between 99.4 % and 105.8 %. After 5 repeated uses, the performance did not show significant degradation. After evaluating the principles of green analytical chemistry using agree software, the total score was 0.68, reflecting the high greenness of this study. This study combined molecular imprinting technology and computer theory simulation of MOF based and DES mediated polymerization processes to construct an extraction device that was easy to operate and could extract diclofenac from environmental water samples with high selectivity and adsorption capacity. It showed great potential in the field of environmental monitoring and provided a new approach for the detection of other pollutants in the environment.

Analytical and Numerical Investigation of Star Polymers in Confined Geometries.

The analysis of the impact of the star polymer topology on depletion interaction potentials, depletion forces, and monomer density profiles is carried out analytically using field theory methods and techniques as well as molecular dynamic simulations. The dimensionless depletion interaction potentials and the dimensionless depletion forces for a dilute solution of ideal star polymers with three and five legs (arms) in a Θ-solvent confined in a slit between two parallel walls with repulsive surfaces and for the case where one of the surfaces is repulsive and the other inert are obtained. Furthermore, the dimensionless layer monomer density profiles for ideal star polymers with an odd number (f˜ = 3, 5) of arms immersed in a dilute solution of big colloidal particles with different adsorbing or repelling properties in respect of polymers are calculated, bearing in mind the Derjaguin approximation. Molecular dynamic simulations of a dilute solution of star-shaped polymers in a good solvent with N = 901 (3 × 300 + 1 -star polymer with three arms) and 1501 (5 × 300 + 1 -star polymer with five arms) beads accordingly confined in a slit with different boundary conditions are performed, and the results of the monomer density profiles for the above-mentioned cases are obtained. The numerical calculation of the radius of gyration for star polymers with f˜ = 3, 5 arms and the ratio of the perpendicular to parallel components of the radius of gyration with respect to the wall orientation for the above-mentioned cases is performed. The obtained analytical and numerical results for star polymers with an odd number (f˜ = 3, 5) of arms are compared with our previous results for linear polymers in confined geometries. The acquired results show that a dilute solution of star polymer chains can be applied in the production of new functional materials, because the behavior of these solutions is strictly correlated with the topology of polymers and also with the nature and geometry of confined surfaces. The above-mentioned properties can find extensive practical application in materials engineering, as well as in biotechnology and medicine for drug and gene transmission.

FLIM nanoscopy resolves the structure and preferential adsorption in the co-nonsolvency of PNIPAM microgels in methanol-water

Polymer microgels are swollen macromolecular networks with a typical size of hundred of nanometers to several microns that show an extraordinary open and responsive architecture to different external stimuli, being therefore important candidates for nanobiotechnology and nanomedical applications such as biocatalysis, sensing and drug delivery. It is therefore crucial to understand the delicate balance of physical-chemical interactions between the polymer backbone and solvent molecules that to a high extent determine their responsivity.In particular, the co-nonsolvency effect of poly(N-isopropylacrylamide) in aqueous alcohols is highly discussed, and there is a disagreement between molecular dynamics (MD) simulations (from literature) of the preferential adsorption of alcohol on the polymer chains and the values obtained by several empirical methods that mostly probe the bulk solvent properties.It is our contention that the most efficacious method for addressing this problem requires a nanoscopic method that can be combined with spectroscopy and record fluorescence spectra and super-resolved fluorescence lifetime images of microgels labeled covalently with the solvatochromic dye Nile Red. By employing this approach, we could simultaneously resolve the structure of sub-micron size objects in the swollen and in the collapsed state and estimate the solvent composition inside of them in ▪–▪ mixtures for two very different polymer architectures. We found an outstanding agreement between the MD simulations and our results that estimate a co-solvent molar fraction excess of approximately 3 with a very flat profile in the lateral direction of the microgel.

Cleaner and Sustainable Production of Core-Sheath Polymer Fibres.

The amalgamation of sustainable practises throughout the fabrication process with advanced material engineering holds promise not only for eco-conscious manufacturing but also for promoting technological advancements in versatile material design and application. Moreover, technological innovation serves as a catalyst for sustainability initiatives, driving innovation and enabling the adoption of greener practises across industries. This study investigates redefining the production protocol of pressure spinning to produce core-sheath polymer fibres, deepening sustainable practises. It aims to explore innovative approaches such as modifying spinning parameters, optimising polymer solvent configurations and understanding fluid behaviour to curtail material wastage and maintain minimal energy consumption without compromising production efficiency. Utilising Polyvinylpyrrolidone (PVP) for the core and Polyethylene oxide (PEO) for the sheath, production rates of up to 64 g/h were achieved with a fibre diameter range of 3.2 ± 1.7 µm to 4.6 ± 2.0 µm. Energy consumption per mass of fibres produced showed a decreasing trend overall with increasing applied gas pressure. These findings highlight the potential for the efficient and scalable production of core-sheath fibres with applications in various advanced materials fields.

Impact of the alkyl side-chain length on solubility, interchain packing, and charge-transport properties of amorphous π-conjugated polymers

Increasing the length of alkyl side chains is a typical way to improve the solubility of π-conjugated polymers designed for use in solution-processed devices. However, these modifications have also been reported to alter the film morphology. Given that the mechanism leading to improved solubility is not well documented yet and the nanoscale (local) morphologies of amorphous π-conjugated polymer films are difficult to characterize experimentally, here, we combine molecular dynamics simulations and long-range corrected density functional theory calculations to examine at the molecular scale the impact that the alkyl side-chain length has on polymer solubility and film morphologies. As a representative example, we consider poly(thieno[3,4-c]pyrrole-4,6-dione-alt-3,4-difluorothiophene) (PTPD[2F]T) with two different lengths of the alkyl side chains on the thieno[3,4-c]pyrrole-4,6-dione (TPD) moieties, i.e., 2-hexyldecyl (2HD) and 2-decyltetradecyl (2DT). A detailed analysis of polymer–solvent and polymer–polymer interactions provides a picture that describes the underlying mechanism for improved solubility in going from 2HD to 2DT. We then underline an intrinsic characteristic that decreasing the side-chain length brings a greater extent of backbone planarity and lesser side chain-TPD interactions, which leads to higher interchain π-π packing density and order, while the interchain π-π packing patterns remain similar in the two films. These morphologies are discussed in terms of the charge-transport properties between neighboring PTPD[2F]T chains, which point to a higher electron mobility in the PTPD[2F]T films with shorter alkyl side chains. Overall, our findings offer guidance in the field of solution-processed electronic devices by pointing out that the polymer alkyl side-chain length could be minimized to improve carrier mobility while ensuring polymer solubility.

(Invited) Engineering Porous Electrodes for Redox Flow Batteries – Leveraging Computational and Synthetic Platforms

Porous electrodes are critical components in redox flow batteries where they are responsible for multiple critical functions in the cell, such as providing surfaces for electrochemical reactions, an open structure for fluid flow and mass transport, and the conductive scaffold for electronic and thermal conduction. However, our current portfolio of materials is limited to carbon-fiber-based electrodes which are assembled using various mechanical methods (e.g., paper making, weaving, hydro-entangling) resulting in distinct structures such as papers, cloths, and felts (1). These fabrication methods involve multiple complex subprocessing steps impacting the final product cost and limiting the achievable range of electrode properties, which ultimately restricts device performance (2). Thus, there is a need to develop new material sets with precise control over microstructure and surface composition while employing synthetic methods that are compatible with large-scale manufacturing.In this lecture, I will discuss our efforts to design tailored electrodes for redox flow batteries, which hold promise for long-duration stationary energy storage (3). First, I will introduce a pore network modeling framework that captures electrochemical performance in complex microstructures with low computational requirements (4), and then show the coupling of this framework with a genetic algorithm to enable bottom-up electrode design (5). In our most recent effort, we are building topology optimization models of porous electrodes using multi-scale modeling of redox flow batteries, coupling computational macro- and meso-scale models of transport processes constructed using finite element and finite volume methods. We then couple these approaches with upscaling strategies that enable manufacturability of the structures. Second, I will describe a new approach to synthesizing porous electrodes based on non-solvent induced phase separation (NIPS) (6). NIPS is a simple and versatile fabrication method that can be used to synthesize morphologically-diverse electrode microstructures (e.g., isoporous, pore-size gradients, and multimodal porosity) by tuning simple parameters in the polymer solution, such as polymer concentration, solvent type, and temperature. Using a suite of microscopic, spectroscopic, and electrochemical diagnostic tools, I will present synthesis-property-performance relationships of the NIPS electrodes (7). Third and finally, I will highlight our efforts to functionalize porous electrode interfaces with organic molecules to impart targeted functional properties including hydrophilicity, kinetic activity (8), and selectivity (e.g. H2 evolution suppression). References A. Forner-Cuenca, F. R. Brushett, Curr. Opin. Electrochem. 18, 113–122 (2019).C. Minke, U. Kunz, T. Turek, J. Power Sources. 342, 116–124 (2017).M. L. Perry, K. E. Rodby, F. R. Brushett, ACS Energy Lett. 7, 659–667 (2022).M. van der Heijden, R. van Gorp, M. A. Sadeghi, J. Gostick, A. Forner-Cuenca, J. Electrochem. Soc. 169, 040505 (2022).R. van Gorp, M. van der Heijden, M. A. Sadeghi, J. Gostick, A. Forner-Cuenca, Chem. Eng. J. 455, 139947 (2023).C. T. Wan et al., Adv. Mater. 33, 2006716 (2021).R. R. Jacquemond et al., Cell Reports Phys. Sci. 3, 100943 (2022).E. B. Boz, P. Boillat, A. Forner-Cuenca, ACS Appl. Mater. Interfaces. 14, 41883–41895 (2022).

Starch nanoparticle preparation by the nanoprecipitation technique: Effects of formulation parameters

This study investigates how key formulation parameters influence the formation of starch nanoparticles using the nanoprecipitation technique. When loaded with different compounds, starch nanoparticles present a promising option for controlled drug delivery in food, biomedical, and pharmaceutical applications. The work thoroughly examines factors such as polymer concentration, NaOH concentration, solvent ratios, stirring speed, injection flow, and properties of the non-solvent phase. Characterization is conducted using dynamic light scattering, laser Doppler electrophoresis, and scanning electron microscopy, followed by statistical analysis. Increasing the stirring speed notably decreases nanoparticle size, yielding dimensions of 161.5±2.1 nm, 157.6±2.5 nm, and 136.0±0.8 nm at 500, 700, and 900 rpm, respectively. Higher starch concentrations slightly increase the zeta potential of starch nanoparticles to values of −1.97±0.4 mV, −3.1±0.7 mV, and −3.9±1.5 mV for concentrations of 0.5 %, 1 %, and 2 %, respectively. This charge can be attributed to the hydroxyl functional groups in starch monomers. The study also assesses the stability of starch nanoparticles at different pH levels (4, 7.4, and 9) and explores the use of cryoprotectants during freeze-drying. Remarkably, nanoparticles show enhanced stability at pH 7.4, maintaining their initial sizes over six weeks. Cryoprotectants, even in small amounts, effectively preserve nanoparticle size post-freeze-drying. By adjusting formulation parameters, researchers can tailor the physicochemical characteristics of nanoparticles to achieve specific sizes and ensure stability.

Preferential Solvation of Cyclosporin in Aqueous Mixtures of Some Polymeric Cosolvents

Background: Cyclosporin is a cyclic peptide-drug used as immunosuppressant for the prophylaxisof transplant rejection whose physicochemical properties in mixed aqueous solvent systems isstill not well understood. The preferential solvation parameters of cyclosporin in aqueous binarymixtures of diethylene glycol monoethyl ether (DEGME), polyethylene glycol 200 (PEG 200) andpolyethylene glycol 400 (PEG 400) were computed. Methods: Reported mole fraction solubilities of cyclosporin in DEGME-aqueous mixtures,PEG 200-aqueous mixtures, and PEG 400-aqueous mixtures were processed by following theinverse Kirkwood-Buff integrals (IKBI) method as suggested by Marcus and Ben-Naim using somethermodynamic parameters reported in the literature for these aqueous-polymeric mixtures at298.15 K. Results: It is observed that cyclosporin is sensitive to preferential solvation effects in theseaqueous-polymeric binary solvent systems. The preferential solvation parameter by DEGME (δx1,3)is negative in water-rich mixtures but positive in mixtures of 0.12<x1<1.00. It is conjecturablethat hydrophobic hydration around the non-polar methyl and methylene groups of this drug thatcould be present in water-rich mixtures can significantly impact the drug solvation. Otherwise,in mixtures of 0.12<x1<1.00 in DEGME-aqueous mixtures, as well as in almost all the mixtureswith PEGs, the preferential solvation by polymeric cosolvents could be due to the acidic behaviorof cyclosporin in front of ether and hydroxyl oxygen atoms of these polymeric cosolvents. Conclusion: Cyclosporin is preferentially solvated by the polymeric solvents in almost all thestudied mixtures of these aqueous-polymeric binary solvent systems.

Enabling low molecular weight electrospinning through binary solutions of polymer blends

The formation of nanofibrous membranes via electrospinning is typically restricted to high molecular weight polymers in an appropriate solvent, correlated with the necessary formation of polymer chain entanglements that are needed to achieve successful production of electrospun fibers. The present work extends the electrospinning of low molecular weight polymers by investigating the electrospinning of a binary solution system consisting of two different low molecular weight polymers, using as a model system polycaprolactone (PCL) and gelatin in different ratios. The viscosities of the polymer solutions were characterized as a proxy for polymer chain entanglement and the resulting fibers were morphologically characterized by SEM imaging and further assessed water contact angle and molecular composition to determine the impact and homogeneity of the binary mixtures. We found that unitary solutions of either PCL or gelatin failed to generate proper fibers despite indications of chain entanglement. In contrast, binary solutions of low molecular weight PCL and gelatin generated different fiber quality and size distributions, depending on the ratio used, with direct correlations between fiber properties and the PCL:Gelatin ratio. It was discovered that the ratio of PCL to gelation was most predictive for successful fiber generation, with effective electrospinning occurring only for a define intermediate range of high blend ratios while both low and high blended binary solutions resulted in poor fiber production. Our study confirmed that this behavior was independent from absolute polymer concentration, indicating a unique interaction between these binary species which exists only under specific ratio concentrations and indicates promising new avenues to process low molecular weight polymers solutions.

Multi-Stimuli-Responsive Fluorescent Molecule with AIE and TICT Properties Based on 1,8-Naphthalimide.

A multi-stimuli responsive fluorophore, named NBDNI, was developed by constructing a 1,8-naphthalimide derivative in which a rotatable electron-donating N,N-dimethylaniline group attached to its 4-position. This molecular structure endowed NBDNI with aggregate-induced emission (AIE) and twisted intramolecular charge transfer (TICT) properties, enabling remarkable fluorescence changes in response to multiple external stimuli: (i) sensitivity to polarity in various solvent systems and polymer matrix; (ii) significant fluorescence response and excellent linearity towards temperature changes in solution; (iii) distinct switch of fluorescence color upon acid and base treatments; (iv) reversible mechanochromism behavior in the solid state. Moreover, the mechanisms underlying the aforementioned stimuli-responsive phenomena have been proposed based on comprehensive systematic measurements. Furthermore, preliminary applications such as fluorescence thermometry and acid/base test paper have been demonstrated. This research will bring about new opportunities for the development of novel stimuli-responsive luminescent materials.

Electrospun Cellulose Acetate/Maleic Acid Functionalized Gold Nanoparticles as Pb(II) Ions Colorimeter Senser Strip

This study investigates the synthesis of gold nanoparticles and surface modifications to enable their utilization as a colorimetric sensor strip on electrospun nanofibrous. Additionally, it utilizes cellulose acetate electrospun fiber preparations as substrates for loading the gold nanoparticles. In order to produce gold nanoparticles, citrate reduction was employed, followed by modification with maleic acid (MA-GNPs). MA-GNPs were significantly more selective for Pb2+ than for other ions (Co2+, Cu2+, Hg2+, Ni+), according to the results. Following the introduction of Pb2+, the solutions exhibited a color change from red to blue or purple, which was attributed to the aggregation of nanoparticles, as determined by UV-Vis spectrometry. An optical band indicative of GNPs and MA-GNPs was detected at an estimated wavelength of 520 nm. Approximately 600 nanometers after the addition of Pb2+, the intensity of the solution progressively decreased to 520 nanometers, and a new band emerged. To fabricate cellulose acetate nanofibrous via electrospinning, the impact of solvent ratios, polymer concentrations, and process conditions were investigated. The ideal parameters for the fabrication of the substrate were as follows: 15%w/w polymer solution, 15 kV electrospinning voltage, 15 cm needle-to-collector distance, and 48 hours of collecting time. In order to examine the color change of the prepared strip, it is observed that the strip transforms from red to blue upon exposure to Pb2+ ions of varying concentrations, just as it does in solution form. An examination of water samples indicated that the strip remained colorless when tested with DI water. However, testing with wastewater sourced from a battery facility identified a transformation of the strip from red to purplish blue. This is equivalent to an estimated lead concentration of 40 parts per million. The outcomes showcased the capacity of the discolored strips to identify the preliminary concentration of lead ions, suggesting potential for future advancements in this area.

Advanced microfluidic techniques for in situ PLGA microparticle formation: A dynamic solvent extraction approach

Microencapsulation processes often use the "solvent extraction/evaporation" technique, which involves (i) dissolving a polymer in an organic solvent (optionally with a bioactive component), (ii) forming microdroplets, (iii) removing the solvent, and finally (iv) harvesting and drying the particles ex situ. These last two steps lack control over the solidification processes, which adversely affects the morphology and size distribution of the final microparticles. In this study, we present a continuous production process for solid PLGA microparticles within a microfluidic chip, covering droplet formation, solvent extraction, and solidification. This method offers the advantage of enhanced control over the solidification process within a closed system, leading to morphologically uniform particles. The setup includes a co-axial junction integrated into a chip with an 80 cm long serpentine channel. We generated droplets with various PLGA/ethyl acetate concentrations and tracked their shrinkage until solidification. Results showed that all droplets underwent identical shrinkage processes with consistent rates, velocity profiles, and sizes. The shrinkage rate was linear and unaffected by PLGA concentration, which only influenced final particle size.To demonstrate our setup's advantages, we compared it with the conventional off-chip method, where droplets shrink in a beaker. Off-chip shrinkage was non-linear and inconsistent, influenced by factors such as the number of surrounding droplets and production time. Droplets produced within a 10-s difference had solidification delays up to 250 s. In contrast, on-chip production was uniform, predictable, and 4–10 times faster. SEM imaging confirmed that on-chip particles were consistently spherical with a rough, wrinkled surface, unlike the irregular, bumpy off-chip particles.In summary, on-chip production and shrinkage of PLGA particles is faster and produces more uniformly shaped particles compared to off-chip methods. This study suggests that on-chip production could significantly enhance the efficiency and quality of drug-loaded microparticles, particularly for drug delivery applications.