Polymer Systems Research Articles

Mechanical and Thermal Properties of Epoxy Resin upon Addition of Low-Viscosity Modifier.

Thermoset-based polymer composites containing functional fillers are promising materials for a variety of applications, such as in the aerospace and medical fields. However, the resin viscosity is often unsuitably high and thus impedes a successful filler dispersion in the matrix. This challenge can be overcome by incorporating suitable low-viscosity modifiers into the prepolymer. While modifiers can aptly influence the prepolymer rheology, they can also affect the prepolymer curing behavior and the mechanical and thermal properties of the resulting matrix material. Therefore, this study investigates the effects that a commercial-grade low-viscosity additive (butyl glycidyl ether) has on a common epoxy polymer system (diglycidyl ether of bisphenol-A epoxy with a methylene dianiline curative). The weight percentage of the modifier inside the epoxy was varied from 0 to 20%. The rheological properties and cure kinetics of the resulting materials were investigated. The prepolymer viscosity decreased by 97% with 20 wt% modifier content at room temperature. Upon curing, 20 wt% modifier addition reduced the exothermic peak temperature by 12% and prolonged the time to reach the peak by 60%. For cured material samples, physical and thermo-mechanical properties were characterized. A moderate reduction in glass transition temperature and an increase in elastic modulus was observed with 20 wt% modifier content (in the order of 10%). Based on these findings, the selected material system is seen as an expedient base for material design due to the ease of processing and material availability. The present study thus provides guidance to researchers developing polymer composites requiring reduced prepolymer viscosity for successful functional filler addition.

Model for predicting oil testing fluid rheological parameters of Bohai Bay oilfield in wide temperature and pressure range

The rheological parameters of oil testing fluids play a crucial role in safely conducting oil testing operations, protecting reservoirs, and maintaining wellbore integrity, which are greatly influenced by temperature and pressure. This article conducted rheological experiments on commonly used potassium salt polymer systems and organic salt systems for oil testing fluids in the Bohai Bay Oilfield under 4–200 °C and 30–150 MPa. The experiments revealed the variation of rheological parameters with temperature and pressure. Nine commonly used rheological models were evaluated for their applicability to the two types of oil testing fluids. It was found that the Ross model was suitable for the potassium salt polymer system, while the power-law model was suitable for organic salt oil testing fluids. A new rheological parameter prediction model suitable for wide range of temperature and pressure and different testing fluid systems was proposed based on the optimized results. The average error for the potassium salt polymer system for oil testing fluids was 0.101%, and the error for the organic salt system for oil testing fluids was 0.113%. Both were superior to known rheological models and can meet the requirements of oil testing operations within the wide temperature and pressure range in the Bohai Bay Oilfield.

Direct In Situ Polymer Modification of Titania Nanomaterial Surfaces via UV‐irradiated Radical Polymerization

AbstractPolymer modification of titania nanomaterials can provide media dispersibility and various functionalities onto the titania surface. Herein, we report the direct in situ polymer modification of the surface of titania nanotubes (TNTs) and titania nanoparticles (TNPs) via ultraviolet (UV)‐irradiated radical polymerization without any pretreatment of titania. The resulting polymer‐modified TNTs and TNPs dispersed well in solvents. The characterization of the products using various techniques including Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy‐energy dispersive X‐ray spectroscopy confirmed the successful modification of the TNT and TNP surfaces by the polymers produced via UV‐irradiated radical polymerization. The polymers on the titania surface were isolated by dissolving titania using hydrofluoric acid and analyzed by means of size exclusion chromatography and matrix‐assisted laser desorption/ionization‐time of flight‐mass spectrometry. The polymer‐modified TNTs and TNPs maintained their photocatalytic activity in dye degradation under UV irradiation. Moreover, glycopolymer‐modified TNTs were successfully prepared using the UV‐irradiated polymerization system. The glycopolymer retained its lectin biding affinity on the TNT surface.

Upcycling of polyethylene/polypropylene mixtures promoted by well-controlled multiblock olefin copolymers

Polyethylene (PE) and isotactic polypropylene (iPP) are two of the most widely used polymer materials, whose huge consumptions urge people to tackle their recycling problem. The incompatibility of PEs and PPs has resulted in their waste streams being recycled into low-value products with poor mechanical properties. Herein, a series of iPP-based olefin block copolymers (OBC) with up to five alternating hard/soft blocks were prepared via coordinative chain transfer polymerization. The facile synthetic strategy of multiblock OBCs not only overcame the inefficiency and diseconomy of living coordination polymerization, but also avoided the critical requirements of complex dual-catalyst systems for chain shuttling polymerization, making it suitable for low-cost and large-scale production of OBCs. These well-designed OBCs provided excellent elastomeric properties combining high strength, high elongation, and high elastic recovery. More importantly, they also demonstrated a strong ability in the upcycling of PE/PP mixtures, transforming brittle blends into tough materials. The PE/PP blends compatibilized with OBCs exhibited greatly improved interfacial adhesion and mechanical properties, with up to 25 times higher elongation at break compared to uncompatibilized blends. It was further demonstrated by the extruding-blow-molded bottles prepared using post-consumer PE/PP products, where recycled bottles containing OBCs exhibited much better mechanical properties than those without OBC. The synthetic strategy of OBCs and the upcycling route of PE/PP blends in this work are not only of great academic value, but also of substantial economic and environmental significance, providing insights into the sustainable development of plastics.

Analysis of Structural Changes of pH-Thermo-Responsive Nanoparticles in Polymeric Hydrogels.

The pH- and thermo-responsive behavior of polymeric hydrogels MC-co-MA have been studied in detail using dynamic light scattering DLS, scanning electron microscopy SEM, nuclear magnetic resonance (1H NMR) and rheology to evaluate the conformational changes, swelling-shrinkage, stability, the ability to flow and the diffusion process of nanoparticles at several temperatures. Furthermore, polymeric systems functionalized with acrylic acid MC and acrylamide MA were subjected to a titration process with a calcium chloride CaCl2 solution to analyze its effect on the average particle diameter Dz, polymer structure and the intra- and intermolecular interactions in order to provide a responsive polymer network that can be used as a possible nanocarrier for drug delivery with several benefits. The results confirmed that the structural changes in the sensitive hydrogels are highly dependent on the corresponding critical solution temperature CST of the carboxylic (-COOH) and amide (-CONH2) functional groups and the influence of calcium ions Ca2+ on the formation or breaking of hydrogen bonds, as well as the decrease in electrostatic repulsions generated between the polymer chains contributing to a particle agglomeration phenomenon. The temperature leads to a re-arrangement of the polymer chains, affecting the viscoelastic properties of the hydrogels. In addition, the diffusion coefficients D of nanoparticles were evaluated, showing a closeness among with the morphology, shape, size and temperature, resulting in slower diffusions for larger particles size and, conversely, the diffusion in the medium increasing as the polymer size is reduced. Therefore, the hydrogels exhibited a remarkable response to pH and temperature variations in the environment. During this research, the functionality and behavior of the polymeric nanoparticles were observed under different analysis conditions, which revealed notable structural changes and further demonstrated the nanoparticles promising high potential for drug delivery applications. Hence, these results have sparked significant interest in various scientific, industrial and technological fields.

Unraveling the Complexities of Silica Nanoparticle Adsorption onto Polymer Latexes in Pickering Emulsion Polymerization.

Incorporating unmodified silica nanoparticles onto polymer latexes to fabricate aqueous polymer dispersions without relying on electrostatic attraction during the Pickering emulsion polymerization process still faces challenges. For negatively charged silica nanoparticles to successfully adsorb onto polymer latexes, particularly in an anionic initiator emulsion polymerization system, they have remained elusive without the use of auxiliary monomers and cationic initiators. This study investigates various experimental parameters, such as emulsion polymerization temperature, monomer solubility, salt concentration, and cation type, to elucidate the factors influencing the adsorption of unmodified silica nanoparticles in Pickering emulsion polymerization. While poly(methyl methacrylate) (PMMA)/SiO2 hybrid latexes can be obtained under pH conditions of 5-6 and at temperatures of 65 °C or below, the loading rate of silica nanoparticles decreases as the reaction temperature increases, resulting in bare PMMA latexes without silica nanoparticle adsorption at temperatures exceeding 70 °C. Introducing styrene (St) into the monomer mixture with methyl methacrylate in a ratio of up to 10 wt % leads to a gradual decrease in silica nanoparticle loading rate, from 27.3 to 8.2 wt %, attributed to the low solubility of St in water. Furthermore, the presence of sodium ions (Na+) is found to be crucial for silica nanoparticle adsorption onto PMMA latexes, as the sodium ions have a stabilizing effect on both the silica nanoparticles and the silica nanoparticle-armored latexes. These findings highlight the complex nature of Pickering emulsion polymerization in the presence of unmodified silica nanoparticles, demonstrating that the loading rate of silica nanoparticles onto polymer latexes is influenced by various factors. These insights pave the way for developing aqueous polymer dispersions with high silica nanoparticle loading rates onto polymer latexes, which is a desirable trait in the coating industry.

Hierarchical Dual‐Mode Efficient Tunable Afterglow via J‐Aggregates in Single‐Phosphor‐Doped Polymer

AbstractThe development of polymer‐based persistent luminescence materials with color‐tunable organic afterglow and multiple responses is highly desirable for applications in anti‐counterfeiting, flexible displays, and data‐storage. However, achieving efficient persistent luminescence from a single‐phosphor system with multiple responses remains a challenging task. Herein, by doping 9H‐pyrido[3,4‐b]indole (PI2) into an amorphous polyacrylamide matrix, a hierarchical dual‐mode emission system is developed, which exhibits color‐tunable afterglow due to excitation‐, temperature‐, and humidity‐dependence. Notably, the coexistence of the isolated state and J‐aggregate state of the guest molecule not only provides an excitation‐dependent afterglow color, but also leads to a hierarchical temperature‐dependent afterglow color resulting from different thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) behaviors of the isolated and aggregated states. The complex responsiveness based on the hierarchical dual‐mode emission can serve for security features through inkjet printing and ink‐writing. These findings may provide further insight into the regulated persistent luminescence by isolated and aggregated phosphors in doped polymer systems and expand the scope of stimuli‐responsive organic afterglow materials for broader applications.

Hierarchical Dual-Mode Efficient Tunable Afterglow via J-Aggregates in Single-Phosphor-Doped Polymer.

The development of polymer-based persistent luminescence materials with color-tunable organic afterglow and multiple responses is highly desirable for applications in anti-counterfeiting, flexible displays, and data-storage. However, achieving efficient persistent luminescence from a single-phosphor system with multiple responses remains a challenging task. Herein, by doping 9H-pyrido[3,4-b]indole (PI2) into an amorphous polyacrylamide matrix, a hierarchical dual-mode emission system is developed, which exhibits color-tunable afterglow due to excitation-, temperature-, and humidity-dependence. Notably, the coexistence of the isolated state and J-aggregate state of the guest molecule not only provides an excitation-dependent afterglow color, but also leads to a hierarchical temperature-dependent afterglow color resulting from different thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) behaviors of the isolated and aggregated states. The complex responsiveness based on the hierarchical dual-mode emission can serve for security features through inkjet printing and ink-writing. These findings may provide further insight into the regulated persistent luminescence by isolated and aggregated phosphors in doped polymer systems and expand the scope of stimuli-responsive organic afterglow materials for broader applications.

General Relations between Stress Fluctuations and Viscoelasticity in Amorphous Polymer and Glass-Forming Systems.

Mechanical stress governs the dynamics of viscoelastic polymer systems and supercooled glass-forming fluids. It was recently established that liquids with long terminal relaxation times are characterized by transiently frozen stress fields, which, moreover, exhibit long-range correlations contributing to the dynamically heterogeneous nature of such systems. Recent studies show that stress correlations and relaxation elastic moduli are intimately related in isotropic viscoelastic systems. However, the origin of these relations (involving spatially resolved material relaxation functions) is non-trivial: some relations are based on the fluctuation-dissipation theorem (FDT), while others involve approximations. Generalizing our recent results on 2D systems, we here rigorously derive three exact FDT relations (already established in our recent investigations and, partially, in classical studies) between spatio-temporal stress correlations and generalized relaxation moduli, and a couple of new exact relations. We also derive several new approximate relations valid in the hydrodynamic regime, taking into account the effects of thermal conductivity and composition fluctuations for arbitrary space dimension. One approximate relation was heuristically obtained in our previous studies and verified using our extended simulation data on two-dimensional (2D) glass-forming systems. As a result, we provide the means to obtain, in any spatial dimension, all stress-correlation functions in terms of relaxation moduli and vice versa. The new approximate relations are tested using simulation data on 2D systems of polydisperse Lennard-Jones particles.

Noncovalent Interactions Define Global Properties of HTPB Isomers.

Commercially available hydroxyl-terminated polybutadiene (HTPB) variants [containing various percentages of its isomers (cis, trans, and vinyl) and utilized in numerous applications ranging from rocket propellant binders to automobile tires] exhibit differences in their thermomechanical properties. Observed thermomechanical response variation between two isomers of HTPB (based upon simulation work at the molecular dynamic level) has been shown to be associated with noncovalent interaction between the isomers. Even though the study has been presented for a specific polymeric system, it could be of interest to the broader polymer chemistry community concerned with the reasons behind the property variation of different isomers of a specific molecule.

Polymer-Based Room-Temperature Phosphorescence Materials Exhibiting Emission Lifetimes up to 4.6 s under Ambient Conditions.

The long-emission-lifetime nature of room-temperature phosphorescence (RTP) materials lays the foundation of their applications in diverse areas. Despite the advantage of mechanical property, processability and solvent dispersity, the emission lifetimes of polymer-based room-temperature phosphorescence materials remain not particularly long because of the labile nature of organic triplet excited states under ambient conditions. Specifically, ambient phosphorescence lifetime (τP) longer than 2 s and even 4 s have rarely been reported in polymer systems. Here, luminescent compounds with small phosphorescence rate on the order of approximately 10-1 s-1 are designed, ethylene-vinyl alcohol copolymer (EVOH) as polymer matrix and antioxidant 1010 to protect organic triplets are employed, and ultralong phosphorescence lifetime up to 4.6 s under ambient conditions by short-term and low-power excitation are achieved. The resultant materials exhibit high afterglow brightness, long afterglow duration, excellent processability into large area thin films, high transparency and thermal stability, which display promising anticounterfeiting and data encryption functions.

Proton transfer induced persistent triplet charge transfer phosphorescence in molecule-doped polymer systems

The intermolecular interactions between small molecules and the matrix in a highly polar environment could easily lead to non-radiative transitions, which significantly hampers the development of high-performance persistent room-temperature phosphorescence (pRTP) materials in such condition. Herein, we introduce a novel strategy that integrates consecutive proton transfer and photo-induced charge transfer to facilitate triplet charge transfer emission in highly polar polymer matrix. In particular, doping aza-arene guests including 1,10-phenanthroline (1,10-Phen), 2,9-dimethyl-1,10-phenanthroline (DM-Phen), and 7,8-benzoquinoline (7,8-BQ) into polyacrylic acid (PAA) resulted in superior pRTP properties compared to other polymer hosts. Spectroscopic investigations and theoretical calculations elucidate that this is attributed to the proton transfer and triplet charge transfer characteristics between the host and guest. Moreover, due to the rigid environment and space confinement provided by PAA, pRTP with the lifetime up to 841 ms is achieved. Capitalizing on the excellent water solubility of the doped PAA films, the inkjet printings have been executed, and showcasing the promising the potential applications of these pRTP materials in the field of information encryption.

Fast and efficient synthesis of polymers driven by solar radiation. New insights on dye/dendrimer photoinitiating systems

The performance of a series of visible-light driven photoinitiating systems (Vis-PIs) for radical polymerization was evaluated. The Vis-PIs formulations consisted of aqueous solutions containing xanthene dyes as sensitizers, while polyamido-amine (PAMAM) dendrimers were tested as alternative co-initiators of lower toxicity than the traditional amines. Acrylamide and HEMA were used as probe monomers and the respective polymers were characterized by FTIR, DSC and viscosimmetry. In order to elucidate the mechanism of photopolymerization, the triplet excited-states and semirreduced forms of the dyes were characterized by transient spectroscopy. Photophysical parameters as intersystem crossing and radical quantum yields were also determined for each dye/dendrimer couple. All Vis-PIs operated successfully under solar irradiation, achieving high monomer conversions after short exposure times. Interestingly, formulations with partially halogenated dyes showed the highest efficiency, which correlates inversely with the affinity and the electron transfer capability between the reactants. This study demonstrates the usefulness of dye/dendrimer combinations to operate as efficient aqueous Vis-PIs under an inexpensive, unlimited and natural energy source such as sunlight.

Novel Anion Exchange Membrane Design Strategies Toward Improved Water Electrolysis Performance

Long-term energy storage is crucial for transitioning from fossil fuels to renewable energies due to the fluctuating energy generation of renewable energy sources such as solar or wind.[1,2] Water electrolysis could produce hydrogen from water and electricity from renewable energy resources, thus solving the energy storage problem.[3] Recent research aims to combine the advantages of alkaline water electrolysis (AWE) and the zero-gap architecture of proton exchange membrane water electrolysis (PEMWE). Limitations of this so-called AEMWE are the lower hydroxide conductivity compared to proton conductivity and, consequently, lower current densities. Furthermore, the chemical stability of AEMs still limits their technical applicability.[4–6] Sustainion®, a commercially available AEM, is a 4-vinylbenzyl chloride styrene copolymer quaternized with 1,2,4,5-tetramethylimidazole.[5,7] Sustainion® shows excellent performance in AEMWE and CO2 electrolysis.[7–9] However, on other polymer systems, it was found that the conductivity and alkaline stability could be increased if the cationic group is separated from the backbone by an alkyl spacer.[10–12] Furthermore, other cationic groups or polymer backbones also offer several advantages. In this study, we demonstrate some new membrane synthesis approaches aiming to enhance the performance of AEMs in electrochemical water-splitting devices. The demonstrated approaches involve attaching different side chains, which may vary in length or the presence of heteroatoms like oxygen. Furthermore, cationic groups like sterically protected imidazoliums are attached to these side chains to study their influence on long-term stability. Finally, our synthetic approaches comprise different membrane preparation strategies such as blending, crosslinking, or applying block-copolymers. The novel polymers are characterized by state-of-the-art methods of polymer chemistry and are further investigated regarding their applicability in AEMWE. Finally, their ionic conductivity, alkaline stability, ion exchange capacity, and the respective performance in AEMWE are investigated.[1] G. A. Lindquist, Q. Xu, S. Z. Oener, S. W. Boettcher, Joule 2020, 4, 2549.[2] A. Kiessling, J. C. Fornaciari, G. Anderson, X. Peng, A. Gerstmayr, M. Gerhardt, S. McKinney, A. Serov, A. Z. Weber, Y. S. Kim, B. Zulevi, N. Danilovic, J. Electrochem. Soc. 2022, 169, 24510.[3] N. Du, C. Roy, R. Peach, M. Turnbull, S. Thiele, C. Bock, Chemical reviews 2022, 122, 11830.[4] S. Gottesfeld, D. R. Dekel, M. Page, C. Bae, Y. Yan, P. Zelenay, Y. S. Kim, J. Power Sources 2018, 375, 170.[5] D. Henkensmeier, M. Najibah, C. Harms, J. Žitka, J. Hnát, K. Bouzek, J. Electrochem. Energy Convers. Storage 2021, 18.[6] N. Chen, Y. M. Lee, Prog. Polym. Sci. 2021, 113, 101345.[7] Z. Liu, S. D. Sajjad, Y. Gao, H. Yang, J. J. Kaczur, R. I. Masel, Int. J. Hydrog. Energy 2017, 42, 29661.[8] J. J. Kaczur, H. Yang, Z. Liu, S. D. Sajjad, R. I. Masel, Front. Chem. 2018, 6, 263.[9] R. I. Masel, Z. Liu, S. Sajjad, ECS Trans. 2016, 75, 1143.[10] H.-S. Dang, P. Jannasch, Macromolecules 2015, 48, 5742.[11] S. Miyanishi, T. Yamaguchi, Polym. Chem. 2020, 11, 3812.[12] S. P. Ertem, E. B. Coughlin, Macromol. Rapid Commun. 2022, 43, e2100610.

Advancements in Cancer Therapeutics: Current Paradigms in Applying Biodegradable Polymer Nanoparticles for Enhanced Management

Abstract: The development of novel colloidal formulations that can regulate the pharmacological and biological properties of medications has been made possible by the developments of nanotechnology. Biodegradable nanoparticles were exploited as drug delivery methods because of their high bioavailability, improved encapsulation, controlled release, and less toxic characteristics. Over the past few decades, a variety of synthetic polymers have been investigated for application in nanomedicine, particularly in drug delivery systems. Drug delivery polymers need to be environmentally friendly, biodegradable, and biocompatible. As they have the ability to provide targeted delivery to a specified site, polymeric nanoparticles have the potential to increase the effectiveness of cancer therapies significantly. It is possible to modify the physical and chemical characteristics of polymers to provide delivery across the many biological barriers needed to reach different cell subsets. The use of biodegradable polymers as nanocarriers is particularly appealing since these materials can be developed to show triggered functionality at certain locations or activated by an external source in addition to degrading under physiological circumstances. Biodegradable polymers can be developed as easy drug-delivery systems that specifically target the tumour microenvironment. This is because these nanomedicines can directly target cancer cells, as well as blood vessels that supply the nutrition and oxygen required for tumour growth and immune cells that support anti-cancer immunotherapy. With the advancements in nanotechnology-based drug delivery systems for pharmaceutical applications, it is exciting to examine and highlight the significance of polymeric nanocarrier systems for drug delivery in chemotherapy.

Enabling Downstream Processing of Lignin Effluent from Cosolvent Enhanced Lignocellulosic Fractionation (CELF) Process through Controlled Electrocatalytic Oxidation and Reduction

Lignin which is a complex organic polymer is abundant in nature. But due to its recalcitrant nature, it can't be converted to value added products easily. Previous studies have found that 40–60 million tons of lignin wastes are generated from the pulp and paper industry globally [1]. The sustainability of these industries can be ensured by converting these wastes into valuable products through environmentally friendly processes. Currently, there are many prevalent catalytic technologies for converting lignin to valuable fuels and chemicals. But these technologies use large amounts of energy and harsh reaction conditions. As a result, catalyst recovery and decomposition often become difficult under such harsh conditions. Besides, bonds between lignin precursors are cleaved unselectively and the selectivity of aromatic products is reduced. An electrocatalytic approach may allow improved control, and few studies have evaluated the electrocatalytic oxidation and reduction of lignin in organic solvents.Organic solvents like tetrahydrofuran (THF) are of interest for lignin electrocatalysis due to their use in the promising cosolvent enhanced lignocellulosic fractionation (CELF) process. Also, THF is a renewable solvent as it can be produced sustainably from the conversion of lignocellulosic biomass. In CELF process, high purity technical lignin can be produced at milder temperatures (1800C) from a mixture of THF and sulfuric acid. Thus, this process has the capability to overcome biomass recalcitrance by breaking β-O-4 aryl ether interunit linkages. Using electrocatalytic conversion processes, additional β-O-4, interunit linkages can be broken down selectively. As a result, if these two processes are integrated, a high amount of phenolic hydroxyl groups with low-content aryl ether linkages will be produced, making the product suitable for the development of biofuels and other chemicals. This study shows that by using controlled electrocatalytic oxidation and reduction in THF/aqueous acidic electrolytes in the ratio of 2:1, nonpolar β-O-4 linkages can be cleaved [2]. This ratio was chosen to mimic the electrolyte composition environment of the CELF pretreatment. The results from both attenuated total reflection-infrared spectroscopy (ATR-IR) and NMR characterization are consistent and show that β-O-4 interlinkage bonds were broken. Quantitative calculations from NMR show that during controlled oxidative potential holds (constant potential oxidation), the presence of aromatic structural components of the lignin polymer increased by 28.67% and aliphatic structural components decreased by 32.73%. On the other hand, during controlled reductive potential holds (constant potential reduction), the presence of aromatic structural compounds decreased by 33.50% and aliphatic structural compounds decreased by 78.43%. These results indicate that electrooxidation and electroreduction may be used strategically to cleave interunit linkages. Finally, it can be said, if electrochemical degradation of lignin is used as a secondary treatment along with the CELF process, it will substantially increase the possibility of transforming lignin into value-added products.References Collins, M. N., Nechifor, M., Tanasă, F., Zănoagă, M., McLoughlin, A., Stróżyk, M. A., Culebras,M., & Teacă, C. A. (2019). Valorization of lignin in polymer and composite systems for advanced engineering applications–a review. International journal of biological macromolecules, 131, 828-849.Hasan, M., Akbari, A., & Greenlee, L. F. (2023). Combined Electrocatalytic Oxidation and Reduction to Selectively Cleave β-O-4 Linkage of Lignin over Platinum Electrode in Organic Solvent: Secondary Treatment Opportunity for CELF Process. ACS Sustainable Chemistry & Engineering. Figure 1

Development of Epoxy-Resin Based Solid Electrolytes for Multifunctional Structural Batteries

A structural battery is defined as being multifunctional; it is a load bearing system with some electrochemical energy storing capability. The electrolyte system is the key enabler for a multifunctional structural battery as it must possess sufficient ionic conductivity (~10-4S/cm) and mechanical strength (Youngs’s modulus ~ 600-900 MPa) simultaneously. Polymeric systems offer the best possible scenario for practical realization of multifunctional structural batteries due to a set of favorable properties, such as reasonable ionic conductivity, easy processability etc. In the present work, we focus on the development of a dual-phase structural battery electrolyte to optimize ionic conductivity and mechanical performance simultaneously. An epoxy resin-based system is chosen due to its high mechanical strength and its ability for in-situ polymerization that leads to a unique microstructure promoting multi-functionality. Diglycidyl ether of Bisphenol A (DGEBA) accounts for the epoxy to provide hard segments in the matrix and is cured by an amine compound (Jeffamine T-403). A liquid electrolyte is added to the system for improving ionic conductivity without compromising its mechanical strength substantially. Multiple liquid components consisting of lithium salt and solvents are considered -lithium bis(trifluoromethanesulfonyl)imide (LITFSI) dissolved in a solution of ethylene carbonate (EC) and dimethyl methyl phosphonate (DMMP) and LiTFSI dissolved in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI). Ionic conductivity of the electrolyte systems as a function of temperature is measured utilizing electrochemical impedance spectroscopy. Uniaxial load tests are performed to evaluate the mechanical properties (e.g., Young’s modulus, Yield strength) of the epoxy-based electrolyte systems with and without the addition of the ion conducting liquids. Comparative data on the epoxy-based systems containing varying amounts of liquid components will be presented.

Changing the Linking Functionality in a Triblock Co-Polymer for Electrolyzer or Fuel Cell Membrane or Ionomer for Chemical Stability Improvements and Potentially Other Consequences.

We have developed a versatile scalable triblock polymer system for anion exchange membrane (AEM) based electrochemical energy conversion devices. This system is uniquely suited to solving both the membrane and ionomer challenges for the commercialization of AEM water electrolysis or fuel cells. Using our advanced fundamental understanding of AEMs based on our work which began in 2010, we can design systems from first principles to match the needs of the device. A triblock ABA polymer is readily fabricated that has both chemical and mechanical stability. The synthesis of these systems is robust, high yield and amenable to high volume production. It utilizes a novel dual chain transfer agent to mediate the chain-transfer ring-opening metathesis polymerization (ROMP) of cyclooctene (COE) or the polymerization of isoprene (IP) to give the hydrophobic B block of the polymer. This is followed by the reversible addition-fragmentation chain transfer radial polymerization of chloromethylstyrene (CMS). The polyCMS (pCMS) blocks are then quaternized with an amine to give the cationic hydrophilic A block. Before quaternization the B block is hydrogenated to give either semi-crystalline polyethylene (pE) or amorphous polymethylbutylene (pMB) from pCOE and pIP respectively. The obvious achilles heal in this system from a chemical durability standpoint is the linking ether functionality between the hydrophobic and hydrophilic blocks. The material we have synthesized to date have exceptional chemical and mechanical stability. It performs very well in ex-situ testing with KOH solutions and in device testing we have demonstrated >500 h at 50°C in water electrolysis in 5 cm2 cells in 1M carbonate electrolyte at 0.5 A cm-2. We attribute the chemical stability to the fact that we post quaternize the membrane to give methylpipiridinium cations and we assume that this reaction does not fully penetrate down the hydrophilic chain. This leaves a hydrophobic un-quaternized region close to the hydrophobic block that does not allow access to the ether linkage by the hydrated hydroxide anion. Recently a new approach to the telehelic mid block pCOE has been reported that has no ether linkages and allows the hydrophobic outer blocks to be linked by a methylene linker. This gives use an opportunity to directly contrast the chemical stability of two identical triblock co-polymers one with an ether linkage and one with a methylene linkage between blocks. In this presentation we will show the results from ex-situ chemical stability test one at low temperatures and higher hydroxide concentration and one at higher temperature and lower hydroxide concentration. There are many examples in polymer electrolyte chemistry where a simple change leads to unintended consequences. The geometry of the ether linkage versus the methylene linkage will change the way that the polymer chains will organize and entangle in ways that are not currently predictable. To probe the mechanical, chemical and morphological difference between these two polymers we will fully characterize and contrast both polymers physical chemical properties including water uptake, ionic conductivity, DSC, TGA, tensile strength and morphology through SAXS, WAXS and HRTEM. Data for the two polymer membranes will also be contrasted and compared in small laboratory 5 cm2 single cells for both electrolysis in dilute carbonate and H2/O2 fuel cells using conventional catalysts.

Mucin incorporated electrospun fibrous matrix of zein and PVP: Towards transmucosal propranolol hydrochloride delivery

Mucoadhesive drug delivery systems are being widely explored as a substitute for conventional drug delivery devices. Several polymers and their functional modifications are under investigations. In that scenario, the cohesive influence of mucin in the polymer system itself to the biologically available mucin in the mucosa is a novel approach. The added advantage of mucin in augmenting mucoadhesion was explored. A two-fold increase in the force of adhesion and an eight-fold increase in the work of adhesion were intriguing observations to be noted. Mucin incorporation in the matrix was done via EDC crosslinker. The results of the TNBS assay confirmed 39 % of mucin binding. A three-fold decrease of elongation at break (%) after mucin binding is a piece of quantitative information to corroborate the same. This work also investigates the efficiency of the mucoadhesive matrix towards the release of Propranolol Hydrochloride (PL). Low oral bioavailability of PL demands its administration via mucosal route to avoid hepatic first-pass metabolism. The release study of PL in PBS and permeation through RPMI 2650 cells revealed a burst release followed by a sustained release profile and best fitted with Korsmeyer Peppas model. PL permeation through the cell monolayer without a cell junction opening pursued a transcellular transport mechanism. Drug permeation through porcine buccal mucosa also assured adequate permeation in ex-vivo conditions. The sustained release of PL from MUZPVP and prolonged residence time of the matrix over mucosa due to increased mucoadhesion guarantees an optimistic drug delivery device to the biomedical discipline.

A Minimalist Method for Fully Oxygen-Tolerant RAFT Polymerization through Sulfur-Centered Trithiocarbonate Radical Initiation.

In recent years, the fully oxygen-tolerant reversible deactivation radical polymerization (RDRP) has become a highly researched area. In this contribution, a new and minimalist method is successfully employed to accomplish fully oxygen-tolerant reversible addition-fragmentation chain transfer (RAFT) polymerization using bis(trithiocarbonate) disulfides (BisTTC) as an iniferter agent, where the released sulfur-centered trithiocarbonate (TTC) radical can initiate monomer. Furthermore, polymerization kinetics revealed the typical "living" features of this polymerization system. More importantly, by high-throughput screening, it is found that dodecyl-substituted TTC is responsible for the fully oxygen-tolerant RAFT polymerization though trithiocarbonate radical initiation and R radical deoxygenation. It is believed that trithiocarbonate radical initiation strategy provides a powerful and minimalist tool for fully oxygen-tolerant RDRPs.