Doped photo-crosslinked polyesteramide hydrogels as solid electrolytes for supercapacitors

Synthesis and Mass Spectrometry Structural Assessment of Polyesteramides Based on ε-Caprolactone and L-Phenylalanine

L-Phenylalanine-ε-caprolactone-based polyesteramides (PCPs) were synthesized via melt polycondensation across a diverse range of molar compositions. The copolymer structure was extensively characterized using nuclear magnetic resonance (NMR) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). NMR analysis confirmed the intercalation of the L-Phenylalanine comonomer units within the polyester backbone. MALDI MS characterization further demonstrated the formation of linear PCP chains with carboxyl end groups. A detailed structural analysis through MALDI MS/MS fragmentation indicated that ester bond scission was the predominant fragmentation mechanism, depicting the polyesteramide sequence in the copolymers. The resulting copolymers were primarily amorphous, except for those with molar compositions of 90/10 and 80/20, which exhibited semi-crystalline structures. Additionally, these PCPs showed an increase in glass transition temperatures with higher amino acid contents and demonstrated good thermal stabilities, as evidenced by a 10% mass loss at elevated temperatures.

Tough and Recyclable Phase-Separated Supramolecular Gels via a Dehydration-Hydration Cycle

Hydrogels are compelling materials for emerging applications including soft robotics and autonomous sensing. Mechanical stability over an extensive range of environmental conditions and considerations of sustainability, both environmentally benign processing and end-of-life use, are enduring challenges. To make progress on these challenges, we designed a dehydration-hydration approach to transform soft and weak hydrogels into tough and recyclable supramolecular phase-separated gels (PSGs) using water as the only solvent. The dehydration-hydration approach led to phase separation and the formation of domains consisting of strong polymer-polymer interactions that are critical for forming PSGs. The phase-separated segments acted as robust, physical cross-links to strengthen PSGs, which exhibited enhanced toughness and stretchability in its fully swollen state. PSGs are not prone to overswelling or severe shrinkage in wet conditions and show environmental tolerance in harsh conditions, e.g., solutions with pH between 1 and 14. Finally, we demonstrate the use of PSGs as strain sensors in air and aqueous environments.

Stimuli-Responsive Electrochemical Energy Storage Devices

Electrochemical energy storage (EES) devices have been swiftly developed in recent years. Stimuli-responsive EES devices that respond to different external stimuli are considered the most advanced EES devices. The stimuli-responsive EES devices enhanced the performance and applications of the EES devices. The capability of the EES devices to respond to the various external stimuli due to produced advanced EES devices that distinguished the best performance and interactions in different situations. The stimuli-responsive EES devices have responsive behavior to different external stimuli including chemical compounds, electricity, photons, mechanical tensions, and temperature. All of these advanced responsiveness behaviors have originated from the functionality and specific structure of the EES devices. The multi-responsive EES devices have been recognized as the next generation of stimuli-responsive EES devices. There are two main steps in developing stimuli-responsive EES devices in the future. The first step is the combination of the economical, environmental, electrochemical, and multi-responsiveness priorities in an EES device. The second step is obtaining some advanced properties such as biocompatibility, flexibility, stretchability, transparency, and wearability in novel stimuli-responsive EES devices. Future studies on stimuli-responsive EES devices will be allocated to merging these significant two steps to improve the performance of the stimuli-responsive EES devices to challenge complicated situations.

Itaconic-Acid-Based Sustainable Poly(ester amide) Resin for Stereolithography

Material science is recognized as a frontrunner in achieving a sustainable future, owing to its primary reliance upon petroleum-based chemical raw materials. Several efforts are made to implement common renewable feedstocks as an alternative to common fossil resources. For this purpose, additive manufacturing (AM) represents promising and effective know-how for the replacement of high energy- and resource-demanding processes with more environmentally friendly practices. This work presents a novel biobased ink for stereolithography, which has been formulated by mixing a photocurable poly(ester amide) (PEA) obtained from renewable resources with citrate and itaconate cross-linkers and appropriate photopolymerization initiators, terminators, and dyes. The mechanical features and the relative biocompatibility of 3D-printed objects have been carefully studied to evaluate the possible resin implementation in the field of the textile fashion industry.

Free-Standing, Flexible Nanofeatured Polymeric Films Prepared by Spin-Coating and Anodic Polymerization as Electrodes for Supercapacitors

Flexible and self-standing multilayered films made of nanoperforated poly(lactic acid) (PLA) layers separated by anodically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) conducting layers have been prepared and used as electrodes for supercapacitors. The influence of the external layer has been evaluated by comparing the charge storage capacity of four- and five-layered films in which the external layer is made of PEDOT (PLA/PEDOT/PLA/PEDOT) and nanoperforated PLA (PLA/PEDOT/PLA/PEDOT/PLA), respectively. In spite of the amount of conducting polymer is the same for both four- and five-layered films, they exhibit significant differences. The electrochemical response in terms of electroactivity, areal specific capacitance, stability, and coulombic efficiency was greater for the four-layered electrodes than for the five-layered ones. Furthermore, the response in terms of leakage current and self-discharge was significantly better for the former electrodes than for the latter ones.

Electrical and Capacitive Response of Hydrogel Solid-Like Electrolytes for Supercapacitors

Flexible hydrogels are attracting significant interest as solid-like electrolytes for energy storage devices, especially for supercapacitors, because of their lightweight and anti-deformation features. Here, we present a comparative study of four ionic conductive hydrogels derived from biopolymers and doped with 0.1 M NaCl. More specifically, such hydrogels are constituted by κ-carrageenan (κC), carboxymethyl cellulose (CMC), poly-γ-glutamic acid (PGGA) or a phenylalanine-containing polyesteramide (PEA). After examining the morphology and the swelling ratio of the four hydrogels, which varies between 483% and 2356%, their electrical and capacitive behaviors were examined using electrochemical impedance spectroscopy. Measurements were conducted on devices where a hydrogel film was sandwiched between two identical poly(3,4-ethylenedioxythiophene) electrodes. The bulk conductivity of the prepared doped hydrogels is 76, 48, 36 and 34 mS/cm for PEA, PGGA, κC and CMC, respectively. Overall, the polyesteramide hydrogel exhibits the most adequate properties (i.e., low electrical resistance and high capacitance) to be used as semi-solid electrolyte for supercapacitors, which has been attributed to its distinctive structure based on the homogeneous and abundant distribution of both micro- and nanopores. Indeed, the morphology of the polyestermide hydrogel reduces the hydrogel resistance, enhances the transport of ions, and results in a better interfacial contact between the electrodes and solid electrolyte. The correlation between the supercapacitor performance and the hydrogel porous morphology is presented as an important design feature for the next generation of light and flexible energy storage devices for wearable electronics.