Pentablock Copolymers Research Articles

Development of Tailored Hydrocarbon‐based Pentablock Copolymer Membranes for Sodium‐Polysulfide Flow Batteries

Development of Tailored Hydrocarbon‐based Pentablock Copolymer Membranes for Sodium‐Polysulfide Flow Batteries

Development of Pentablock Copolymer Membranes for a Sodium Polysulfide Hybrid Redox Flow Battery

Long duration energy storage devices, such as redox flow batteries (RFBs), are critical for enabling the widespread adoption of renewable energy sources such as wind and solar on the electric grid. Non-aqueous RFBs (NARFBs) have emerged as a possible alternative to aqueous RFBs (e.g., all-vanadium and Zn/Br systems), as they have the potential to use supporting electrolytes with wide operating voltage windows (>3 V) and a variety of redox couples. One NARFB of interest is a hybrid RFB that utilizes an alkali metal anode, such as sodium, and a polysulfide catholyte. However, the realization of a hybrid NARFB for long duration energy storage requires the development of new membranes with robust mechanical properties, good (electro)chemical stability, high ionic conductivity, and low polysulfide permeability. In this work, we have utilized a cation exchange pentablock copolymer membrane with sodium sulfonate and sodium trifluoromethanesulfonimide (TFSI) functionalities. We studied various crosslinking methods with the goal of reducing electrolyte uptake and polysulfide crossover of the membrane, while maintaining high ion transport. One lightly crosslinked membrane exhibits a 40% reduction in electrolyte uptake compared to the uncrosslinked membrane, but at the expense of a reduction in ionic conductivity from 2.5 x 10-4 S/cm to 4.2 x 10-5 S/cm at 20 °C. Our continued efforts in developing techniques to improve membrane properties will also be discussed.

Solid-Phase Synthesis of Well-Defined Multiblock Copolymers by Atom Transfer Radical Polymerization.

Solid-phase polymer synthesis, historically rooted in peptide synthesis, has evolved into a powerful method for achieving sequence-controlled macromolecules. This study explores solid-phase polymer synthesis by covalently immobilizing growing polymer chains onto a poly(ethylene glycol) (PEG)-based resin, known as ChemMatrix (CM) resin. In contrast to traditional hydrophobic supports, CM resin's amphiphilic properties enable swelling in both polar and nonpolar solvents, simplifying filtration, washing, and drying processes. Combining atom transfer radical polymerization (ATRP) with solid-phase techniques allowed for the grafting of well-defined block copolymers in high yields. This approach is attractive for sequence-controlled polymer synthesis, successfully synthesizing di-, tri-, tetra-, and penta-block copolymers with excellent control over the molecular weight and dispersity. The study also delves into the limitations of achieving high molecular weights due to confinement within resin pores. Moreover, the versatility of the method is demonstrated through its applicability to various monomers in organic and aqueous media. This straightforward approach offers a rapid route to developing tailored block copolymers with unique structures and functionalities.

Sulfonated Pentablock Copolymer (NexarTM) for Water Remediation and Other Applications.

This review focuses on the use of a sulfonated pentablock copolymer commercialized as NexarTM in water purification applications. The properties and the use of sulfonated copolymers, in general, and of NexarTM, in particular, are described within a brief reference focusing on the problem of different water contaminants, purification technologies, and the use of nanomaterials and nanocomposites for water treatment. In addition to desalination and pervaporation processes, adsorption and photocatalytic processes are also considered here. The reported results confirm the possibility of using NexarTM as a matrix for embedded nanoparticles, exploiting their performance in adsorption and photocatalytic processes and preventing their dispersion in the environment. Furthermore, the reported antimicrobial and antibiofouling properties of NexarTM make it a promising material for achieving active coatings that are able to enhance commercial filter lifetime and performance. The coated filters show selective and efficient removal of cationic contaminants in filtration processes, which is not observed with a bare commercial filter. The UV surface treatment and/or the addition of nanostructures such as graphene oxide (GO) flakes confer NexarTM with coating additional functionalities and activity. Finally, other application fields of this polymer are reported, i.e., energy and/or gas separation, suggesting its possible use as an efficient and economical alternative to the more well-known Nafion polymer.

Metallosupramolecular Multiblock Copolymers of Lanthanide Complexes by Seeded Living Polymerization.

Supramolecular block copolymers, derived via seeded living polymerization, are increasingly recognized for their rich structural and functional diversity, marking them as cutting-edge materials. The use of metal complexes in supramolecular block copolymerization not only offers a broad range of block copolymers through the structural similarity in the coordination geometry of the central metal ion but also controls spectroscopic properties, such as emission wavelength, emission strength, and fluorescence lifetime. However, the exploration of metallosupramolecular multiblock copolymerization based on metal complexes remains quite limited. In this work, we present a pioneering synthesis of metallosupramolecular multiblock copolymers utilizing Eu3+ and Tb3+ complexes as building blocks. This is achieved through the strategic manipulation of nonequilibrium self-assemblies via a living supramolecular polymerization approach. Our comprehensive exploration of both thermodynamically and kinetically regulated metallosupramolecular polymerizations, centered around Eu3+ and Tb3+ complexes with bisterpyridine-modified ligands containing R-alanine units and a long alkyl group, has highlighted intriguing behaviors. The monomeric [R-L1Eu(NO3)3] complex generates a spherical structure as the kinetic product. In contrast, the monomeric [R-L1Eu2(NO3)6] complex generates fiber aggregates as a thermodynamic product through intermolecular interactions such as π-π stacking, hydrophobic interaction, and H-bonds. Utilizing the Eu3+ complex, we successfully conducted seed-induced living polymerization of the monomeric building unit under kinetically regulated conditions. This yielded a metallosupramolecular polymer of precisely controlled length with minimal polydispersity. Moreover, by copolymerizing the kinetically confined Tb3+ complex state ("A" species) with a seed derived from the Eu3+ complex ("B" species), we were able to fabricate metallosupramolecular tri- and pentablock copolymers with A-B-A, and B-A-B-A-B types, respectively, through a seed-end chain-growth mechanism.

Preparation and characterization of the injectable pH- and temperature-sensitive pentablock hydrogel containing human growth hormone-loaded chitosan nanoparticles via electrospraying

This research investigated the in vivo gelation, biodegradation, and drug release efficiency of a novel injectable sensitive drug delivery system for human growth hormone (HGh). This composite system comprises pH- and temperature-sensitive hydrogel, designated as oligomer serine-b-poly(lactide)-b-poly(ethylene glycol)-b-poly(lactide)-b-oligomer serine (OS-PLA-PEG-PLA-OS) pentablock copolymer, as matrix and electrosprayed HGh-loaded chitosan (HGh@CS) nanoparticles (NPs) as principal material. The proton nuclear magnetic resonance spectrum of the pH- and temperature-sensitive OS-PLA-PEG-PLA-OS pentablock copolymer hydrogel proved that this copolymer was successfully synthesized. The HGh was encapsulated in chitosan (CS) NPs by an electrospraying system in acetic acid with appropriate granulation parameters. The scanning electron microscopy images and size distribution showed that the HGh@CS NPs formed had an average diameter of 366.1 ± 214.5 nm with a discrete spherical shape and dispersed morphology. The sol–gel transition of complex gel based on HGh@CS NPs and OS-PLA-PEG-PLA-OS pentablock hydrogel was investigated at 15 °C and pH 7.8 in the sol state and gelled at 37 °C and pH 7.4, which is suitable for the physiological conditions of the human body. The HGh release experiment of the composite system was performed in an in vivo environment, which demonstrated the ability to release HGh, and underwent biodegradation within 32 days. The findings of the investigation revealed that the distribution of HGh@CS NPs into the hydrogel matrix not only improved the mechanical properties of the gel matrix but also controlled the drug release kinetics into the systematic bloodstream, which ultimately promotes the desired therapeutic body growth depending on the distinct concentration used.

Amphiphilic hot-melt pressure sensitive adhesives for transdermal administration made from low melt-processing temperature OSISO copolymers

Herein, an anionic polymerization method was employed to synthesize a series of amphiphilic poly(ethylene oxide-b-styrene-b-isoprene-b-styrene-b-ethylene oxide) penta-block copolymers (OSISO). Their molecular structure and properties were comprehensively characterized using GPC,1H-NMR, thermodynamic rheological testing and water contact angle test. Notably, the hydrophilic characteristics exhibited a proportional increase with the rise in poly(ethylene oxide) (PEO) content, ranging from 1.3 to 12.6 wt%. The polystyrene blocks with low number-average molecular weight (2000–3500) reduced the copolymer melt viscosity, surpassing a tenfold decrease than the control sample within the temperature range of 50–150 °C. Resultantly, this series of OSISO copolymers could be used to develop amphiphilic hot-melt pressure-sensitive adhesives (HMPSAs) by low temperature hot-melt processing method (<120 °C). HMPSAs loaded with 2 wt% of geniposide, prepared by an optimized composition formula of OSISO copolymers, tackifiers, and plasticizers (in a ratio of 5:5:2), displayed excellent in vitro drug release performance. Additionally, these adhesives presented impressive 180° peeling strength (0.05–0.14 kN/m) without residues left on the substrate in the 180° peeling tests. The incorporation of PEO block significantly enhanced both the adhesive properties and accumulative drug release. Geniposide showed a burst release behavior with a moderate accumulative drug release (15–30 wt%), attributed to the PEO phase without crystallization behavior of long PEO chains.

Tailoring pore size of mesoporous silica and organosilica using biodegradable pentablock copolymer templates via EISA process

In this work, we have designed unique poly(lactic acid-co-glycolic acid)-b-poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(lactic acid-co-glycolic acid) pentablock copolymers using Pluronic F68 and F108 triblock copolymers as macroinitiators. The poly(lactic acid-co-glycolic acid) (PLGA) blocks were attached as glycolide and lactide monomers at the both ends of each F68 and F108 triblock copolymer. The molecular weights and the block fractions were confirmed by gel permeation chromatography (GPC) and proton nuclear magnetic resonance (1H NMR) for the four kinds of pentablock copolymers. Using these pentablock copolymers as templates, we synthesized mesoporous ethane-silicas as well as silicas by the evaporation-induced self-assembly (EISA) method. 1,2-bis(triethoxysily)ethane (BTEE) were used as an organosilica precursor. The mesoporous ethane-silica samples were characterized using synchrotron small angle X-ray scattering (SAXS), nitrogen sorption experiments, transmission electron microscopy (TEM), and solid-state 29Si CP-MAS NMR. Based on the experimental results, it was confirmed that the porosity and pore diameter can be varied with the PLGA weight fraction of the pentablock copolymer. It is due to the PLGA block in polymer forming the hydrophobic domain in micelles, which leads to the formation of increased pore size over 20 nm without any additive pore expander. In addition, it seems that as the organosilica precursor increases, the association number of block copolymers forming one micelle decreases, resulting in a decrease in pore size. In summary, the polymer template plays a vital part in tuning the structure of the mesoporous ethane-silica samples. Thus, the development of synthetic method of mesoporous organosilica materials using polymer templates with different topology is still challenging and can endow the unique structure and property for mesoporous organosilica for future applications.

Block Sequence Effects on the Self-Assembly Behaviors of Polypeptide-Based Penta-Block Copolymer Hydrogels.

Peptide-based hydrogels have great potential for applications in tissue engineering, drug delivery, and so on. We systematically synthesize, characterize, and investigate the self-assembly behaviors of a series of polypeptide-based penta-block copolymers by varying block sequences and lengths. The copolymers contain hydrophobic blocks of poly(γ-benzyl-l-glutamate) (PBG, Bx) and two kinds of hydrophilic blocks, poly(l-lysine) (PLL, Ky) and poly(ethylene glycol) (PEG, EG34), where x and y are the number of repeating units of each block, where PBG and PLL blocks have unique functions for nerve regeneration and cell adhesion. It shows that a sufficient length of the middle hydrophilic segment capped with hydrophobic end PBG blocks is required. They first self-assemble into flower-like micelles and sequentially form transparent hydrogels (as low as 2.3 wt %) with increased polymer concentration. The hydrogels contain a microscale porous structure, a desired property for tissue engineering to facilitate the access of nutrient flow for cell growth and drug delivery systems with high efficiency of drug storage. We hypothesize that the structure of Bx-Ky-EG34-Ky-Bx agglomerates is beyond micron size (transparent), while that of Ky-Bx-EG34-Bx-Ky is on the submicron scale (opaque). We establish a working strategy to synthesize a polypeptide-based block copolymer with a wide window of sol-gel transition. The study offers insight into rational polypeptide hydrogel design with specific morphology, exploring the novel materials as potential candidates for neural tissue engineering.

Self-consistent field theory and coarse-grained molecular dynamics simulations of pentablock copolymer melt phase behavior

Using a combined theory-simulation approach we rapidly screen a large polymer design space to identify rules for desired morphologies as well as the chain conformations associated with the theory-predicted phase behavior.

Poly(lactic acid) block improves ambient-temperature ionic conductivity of pentablock copolymer electrolyte

A polystyrene-b-poly(lactic acid)-b-poly(ethylene oxide)-b-poly(lactic acid)-b-polystyrene pentablock copolymer electrolyte (PSLE) is successfully prepared by ring-opening polymerization (ROP) of DL-lactide (DL-LA) with poly(ethylene oxide) (PEO) followed by atom transfer radical polymerization (ATRP) with styrene. Poly(lactic acid) (PLA) block made by the polymerization of DL-LA can not only reduce the crystallinity of PEO, but also balance the coordination properties of Li+, while polystyrene (PS) block acts as a hard block to improve the mechanical properties of PSLE. Here, the obtained PSLE achieves high ionic conductivity (1.3 × 10−4 S cm−1) under ambient temperature and wide electrochemical stable window (4.2 V). In addition, the PSLE shows outstanding stability, allowing the Li/PSLE/Li cell to cycle stably for more than 600 h at 0.1 mA cm−2 without an increase in polarization voltage. And LiFePO4/PSLE/Li cell shows an initial discharge capacity of 159 mA h g−1 and keeps a capacity retention of 94.6 % after 200 cycles at 0.1C under ambient temperature. The LiNi0.6Co0.2Mn0.2O2/PSLE/Li cell also delivers good cycling performance. These results suggest that multiblock copolymer electrolyte is very promising material for the preparation of solid polymer electrolytes (SPEs) suitable for lithium metal batteries.

Tailoring surface and bulk morphologies to control transport properties of sulfonated block copolymer films

We examine the effects of solvent composition and solution-casting protocol on the structure of a lamellar sulfonated pentablock copolymer (SPC) membrane. Films are prepared by a layering process, wherein the film is built up through sequential bar-coating steps. Process variables include bar gap height, which controls drying time and layer thickness, and solvent selectivity toward each block in the SPC, which controls solution-state structure and biases the domain orientations at the surface. We find that irrespective of solvent selectivity, one-layer films have poorly ordered structures in the bulk with minimal restructuring near the surface. However, when the process involves sequential deposition of two or more layers, then the bulk structure of dry films can be well-predicted by the solution-state structure, and domain orientations at the surface are templated by polymer-solvent interactions. Consequently, processing conditions strongly influence through-plane transport properties of the SPC films. When the casting process generates disordered lamellae in bulk with a perpendicular lamellar orientation at the surface, both water and protons can move across the film. However, when the process generates highly ordered lamellae in bulk and parallel lamellar orientations at the surface, transport of both water and protons is inhibited by limited pathways. Significantly, the methodology outlined in this work can be extended to other ionic block copolymer platforms, allowing researchers to tailor bulk and surface morphologies for optimization of critical transport properties.

Visible Light Photoiniferter Polymerization for Dispersity Control in High Molecular Weight Polymers

AbstractThe synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible‐light controlled photoiniferter reversible addition‐fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain‐transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol−1). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. Tg was lowered for high‐dispersity polymers of similar MWs due to the existence of more low‐MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.

Visible Light Photoiniferter Polymerization for Dispersity Control in High Molecular Weight Polymers.

The synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible-light controlled photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain-transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol-1 ). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. Tg was lowered for high-dispersity polymers of similar MWs due to the existence of more low-MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.

Synthesis and Optimization of Next-Generation Low-Molecular-Weight Pentablock Copolymer Nanoadjuvants.

Polymeric nanomaterials such as Pluronic®-based pentablock copolymers offer important advantages over traditional vaccine adjuvants and have been increasingly investigated in an effort to develop more efficacious vaccines. Previous work with Pluronic® F127-based pentablock copolymers, functionalized with poly(diethyl aminoethyl methacrylate) (PDEAEM) blocks, demonstrated adjuvant capabilities through the antigen presentation and crosslinking of B cell receptors. In this work, we describe the synthesis and optimization of a new family of low-molecular-weight Pluronic®-based pentablock copolymer nanoadjuvants with high biocompatibility and improved adjuvanticity at low doses. We synthesized low-molecular-weight Pluronic® P123-based pentablock copolymers with PDEAEM blocks and investigated the relationship between polymer concentration, micellar size, and zeta potential, and measured the release kinetics of a model antigen, ovalbumin, from these nanomaterials. The Pluronic® P123-based pentablock copolymer nanoadjuvants showed higher biocompatibility than the first-generation Pluronic® F127-based pentablock copolymer nanoadjuvants. We assessed the adjuvant capabilities of the ovalbumin-containing Pluronic® P123-based pentablock copolymer-based nanovaccines in mice, and showed that animals immunized with these nanovaccines elicited high antibody titers, even when used at significantly reduced doses compared to Pluronic® F127-based pentablock copolymers. Collectively, these studies demonstrate the synthesis, self-assembly, biocompatibility, and adjuvant properties of a new family of low-molecular-weight Pluronic® P123-based pentablock copolymer nanomaterials, with the added benefits of more efficient renal clearance, high biocompatibility, and enhanced adjuvanticity at low polymer concentrations.

Sulfonated Pentablock Copolymer with Graphene Oxide for Co2+ Ions Removal: Efficiency, Interaction Mechanisms and Secondary Reaction Products

In this work, sulfonated pentablock copolymer (s-PBC) and s-PBC mixed with graphene oxide (s-PBC_GO) layers were deposited on polypropylene (PP) fibrous filters and tested as active coatings for the removal of cobalt ions from water using adsorption and filtration processes. Some of the coated filters were treated by UV light irradiation to modify their hydrophilic properties. The filters were characterized, before and after the processes, by energy-dispersive X-ray (EDX) analysis and Fourier transform infrared spectroscopy (FT-IR). The Qt (mg/g) values, defined as the weight ratio between the removed ions and the coating layer, were evaluated. In the case of adsorption processes, the best results for the removal of Co2+ ions were achieved by the s-PBC_GO coating, with a Qt of 37 mg/g compared to 21 mg/g obtained by the s-PBC. This was ascribed to the presence of GO, which contains more favorable sites able to adsorb positive ions from the solution. Vice versa, for filtration processes, the s-PBC coated filters show similar or slightly better results than the s-PBC_GO coated ones. Such differences can be ascribed to the shorter contact time between the solution and the coating layer in the case of filtration, with respect to adsorption processes, thus reducing the chance for the ions to be adsorbed on the GO layers before passing through the filter. A collateral effect, observed in this study and enhanced in the case of UV-treated coatings, is the release of radical oxysulfur species. The mechanisms involved in this effect are discussed and identified as a consequence of the interaction between the coating layers and metal ions. In order to identify the mechanism of oxysulfur radicals formation and considering a water sample closer to real water, the Co2+ ions adsorption experiments were conducted in the presence of a competitive organic contaminant (i.e., methyl orange, MO).

Nonequilibrium Colloids: Temperature-Induced Bouquet Formation of Flower-like Micelles as a Time-Domain-Shifting Macromolecular Heat Alert.

Climate change requires enhanced autonomous temperature monitoring during logistics/transport. A cheap approach comprises the use of temperature-sensitive copolymers that undergo temperature-induced irreversible coagulation. The synthesis/characterization of pentablock copolymers (PBCP) starting from poloxamer PEO130-b-PPO44-b-PEO130 (poly(ethylene oxide)130-b-poly(propylene oxide)44-b-poly(ethylene oxide)130) and adding two terminal qPDMAEMA85 (quaternized poly[(2-dimethylamino)ethyl methacrylate]85) blocks is presented. Mixing of PBCP solutions with hexacyanoferrate(III)/ferricyanide solutions leads to a reduction of the decane/water interfacial tension accompanied by a co/self-assembly toward flower-like micelles in cold water because of the formation of an insoluble/hydrophobic qPDMAEMA/ferricyanide complex. In cold water, the PEO/PPO blocks provide colloidal stability over months. In hot water, the temperature-responsive PPO block is dehydrated, leading to a pronounced temperature dependence of the oil-water interfacial tension. In solution, the sticky PPO segments exposed at the micellar corona cause a colloidal clustering above a certain threshold temperature, which follows Smoluchowski-type kinetics. This coagulation remains for months even after cooling, indicating the presence of a kinetically trapped nonequilibrium state for at least one of the observed micellar structures. Therefore, the system memorizes a previous suffering of heat. This phenomenon is linked to an exchange of qPDMAEMA-blocks bridging the micellar cores after PPO-induced clustering. The addition of ferrous ions hampers the exchange, leading to the reversible coagulation of Prussian blue loaded micelles. Hence, the Fe2+ addition causes a shift from history monitoring to the sensing of the present temperature. Presumably, the system can be adapted for different temperatures in order to monitor transport and storage in a simple way. Hence, these polymeric "flowers" could contribute to preventing waste and sustaining the quality of goods (e.g., food) by temperature-induced bouquet formation, where an irreversible exchange of "tentacles" between the flowers stabilizes the bouquet at other temperatures as well.

Pentablock Copolymer Membranes for Non-Aqueous Redox Flow Batteries

Long duration energy storage devices, such as redox flow batteries, are needed to enable smart grids and widespread adoption of renewable energy sources. Sodium based electrochemical energy storage is of interest for large-scale applications due to sodium’s low cost and high abundance compared to lithium and vanadium. The membrane plays a critical role in flow batteries by providing counterion transport while separating the catholyte and anolyte. Considering that the membrane is a significant source of internal resistance and capacity fade (e.g., due to crossover) in an operating battery, developing membranes with controlled swelling, high ionic conductivity, and low active species crossover is imperative. In this work, we studied electrolyte uptake and ion transport in cation exchange pentablock copolymer membranes with sodium sulfonate and sodium trifluoromethanesulfonimide (TFSI) functionality for nonaqueous flow battery applications. The TFSI Na membranes exhibit an ionic conductivity of 7.2 x 10-5 S/cm at room temperature and a cation transport number of 0.75 in 0.5 M sodium triflate/tetraethylene glycol dimethyl ether (TEGDME) electrolyte. Methods improve the ionic conductivity and limit electrolyte uptake of the membranes, such as crosslinking will be discussed. Acknowledgements This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program in the Office of Electricity.

Synthesis and Analysis of Well‐Defined Copolymers via by Combination ROP Technique

AbstractHerein, the poly(ɛ‐caprolactone)‐poly(ethylene glycol)‐poly(ɛ‐caprolactone) (PCL‐PEG‐PCL) macro xanthate reversible addition–fragmentation chain‐transfer agent is obtained on the polyethylene glycol (PEG) (600, 1000, and 1500 g mol−1) block, after the addition of ɛ‐caprolactone via ring‐opening polymerization. Then, poly (styrene‐b‐ɛ‐caprolactone‐b‐PEG‐b‐ɛ‐caprolactone‐b‐styrene) pentablock copolymer is synthesized reversible addition–fragmentation chain‐transfer (RAFT) solution polymerization technique via mediated PCL‐PEG‐PCL xanthate macro‐RAFT agents and 2,2′‐azobisisobutyronitrile as initiator. The products are demonstrated using Fourier transform infrared spectrophotometer (FT‐IR), proton nuclear magnetic resonance (1H‐NMR), carbon nuclear magnetic resonance (13C‐NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) analyses. First‐order linear kinetic graphs of the reaction mechanism are observed with an increase in molecular weights (MW) between 16 000 and 36 000 g mol−1. The narrow dispersity (Đ = 1.40–1.48) polymer formation of styrene (St) controlled by RAFT polymerization confirms the increase in molecular weight according to the polymerization time. The reaction kinetics are first order and the rate constants are found to be k1 = 6.16 × 10−4s−1, k2 = 6.91 × 10−4 s−1 and k3 = 7.33 × 10−4 s−1. Thermal and spectroscopic analyses prove that the reactions are carried out successfully.

PH-temperature Responsive Hydrogel-Mediated Delivery of Exendin-4 Encapsulated Chitosan Nanospheres for Sustained Therapeutic Efficacy in Type 2 Diabetes Mellitus.

Type 2 Diabetes Mellitus (T2D) is a chronic, obesity-related, and inflammatory disorder characterize by insulin resistance, inadequate insulin secretion, hyperglycemia, and excessive glucagon secretion. Exendin-4 (EX), a clinically established antidiabetic medication that acts as a glucagon-like peptide-1 receptor agonist, is effective in lowering glucose levels and stimulating insulin secretion while significantly reducing hunger. However, the requirement for multiple daily injections due to EX's short half-life is a significant limitation in its clinical application, leading to high treatment costs and patient inconvenience. To address this issue, an injectable hydrogel system is developed that can provide sustained EX release at the injection site, reducing the need for daily injections. In this study, the electrospray technique is examine to form EX@CS nanospheres by electrostatic interaction between cationic chitosan (CS) and negatively charged EX. These nanospheres are uniformly dispersed in a pH-temperature responsive pentablock copolymer, which forms micelles and undergoes sol-to-gel transition at physiological conditions. Following injection, the hydrogel gradually degraded, exhibiting excellent biocompatibility. The EX@CS nanospheres are subsequently released, maintaining therapeutic levels for over 72h compared to free EX solution. The findings demonstrate that the pH-temperature responsive hydrogel system containing EX@CS nanospheres can be a promising platform for the treatment of T2D.