Multifunctional, Degradable Wearable Sensors Prepared with an Initiator and Crosslinker-Free Method

The present zwitterionic hydrogel-based wearable sensor exhibits various limitations, such as limited degradation capacity, unavoidable toxicity resulting from initiators, and poor mechanical properties that cannot satisfy practical demands. Herein, we present an initiator and crosslinker-free approach to prepare polyethylene glycol (PEG)@poly[2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) (PSBMA) interpenetrating polymer network (IPN) hydrogels that are self-polymerized via sunlight-induced and non-covalent crosslinking through electrostatic interaction and hydrogen bonding among polymer chains. The PEG@PSBMA IPN hydrogel possesses tissue-like softness, superior stretchability (∼2344.6% elongation), enhanced fracture strength (∼39.5 kPa), excellent biocompatibility, antibacterial property, reliable adhesion, and ionic conductivity. Furthermore, the sensor based on the IPN hydrogel demonstrates good sensitivity and cyclic stability, enabling effective real-time monitoring of human body activities. Moreover, it is worth noting that the excellent degradability in the saline solution within 8 h makes the prepared hydrogel-based wearable sensor free from the electronic device contamination. We believe that the proposed strategy for preparing physical zwitterionic hydrogels will pave the way for fabricating eco-friendly wearable devices.

Kinetic Study of the Diels-Alder Reaction between Maleimide and Furan-Containing Polystyrene Using Infrared Spectroscopy

The Diels-Alder (D-A) reaction between furan and maleimide is a thermally reversible reaction that has become a vital chemical technique for designing polymer structures and functions. The kinetics of this reaction, particularly in polymer bulk states, have significant practical implications. In this study, we investigated the feasibility of utilizing infrared spectroscopy to measure the D-A reaction kinetics in bulk-state polymer. Specifically, we synthesized furan-functionalized polystyrene and added a maleimide small-molecule compound to form a D-A adduct. The intensity of the characteristic absorption peak of the D-A adduct was quantitatively measured by infrared spectroscopy, and the dependence of conversion of the D-A reaction on time was obtained at different temperatures. Subsequently, the D-A reaction apparent kinetic coefficient kapp and the Arrhenius activation energy Ea,D-A were calculated. These results were compared with those determined from 1H-NMR in the polymer solution states.

Advancements in gelatin-based hydrogel systems for biomedical applications: A state-of-the-art review

A gelatin-based hydrogel system is a stimulus-responsive, biocompatible, and biodegradable polymeric system with solid-like rheology that entangles moisture in its porous network that gradually protrudes to assemble a hierarchical crosslinked arrangement. The hydrolysis of collagen directs gelatin construction, which retains arginyl glycyl aspartic acid and matrix metalloproteinase-sensitive degeneration sites, further confining access to chemicals entangled within the gel (e.g., cell encapsulation), modulating the release of encapsulated payloads and providing mechanical signals to the adjoining cells. The utilization of various types of functional tunable biopolymers as scaffold materials in hydrogels has become highly attractive due to their higher porosity and mechanical ability; thus, higher loading of proteins, peptides, therapeutic molecules, etc., can be further modulated. Furthermore, a stimulus-mediated gelatin-based hydrogel with an impaired concentration of gellan demonstrated great shear thinning and self-recovering characteristics in biomedical and tissue engineering applications. Therefore, this contemporary review presents a concise version of the gelatin-based hydrogel as a conceivable biomaterial for various biomedical applications. In addition, the article has recapped the multiple sources of gelatin and their structural characteristics concerning stimulating hydrogel development and delivery approaches of therapeutic molecules (e.g., proteins, peptides, genes, drugs, etc.), existing challenges, and overcoming designs, particularly from drug delivery perspectives.

Tough thermoplastic hydrogels with re-processability and recyclability for strain sensors

Tough hydrogels with the ability to be repeatedly processed into various shapes as thermoplastics are highly desired in advanced medical devices and tissue engineering. Here, we have developed a kind of versatile supramolecular hydrogel with a network cross-linked by double hydrogen bonds from poly(N-acryloyl glycinamide) (PNAGA). The resulting PNAGA-30 hydrogels (30 wt% solid content) are tough, re-processable, and recyclable similar to thermoplastics. The hydrogels in the form of fragments can be easily re-processed into various shapes including sheet, filament, cylinder and other complex shapes by using simple stamping and injection methods. The mechanical properties of the re-programed hydrogels are comparable to the properties of the original hydrogels. The re-processability and robust mechanical properties of the PNAGA hydrogels are promising for practical applications in soft materials, tissue engineering and wearable devices. Furthermore, the PNAGA-30&LiCl ionic hydrogels can be fabricated by simply compositing LiCl into thermoplastic hydrogels. The PNAGA-30&LiCl hydrogels can function as multifunctional strain sensors to monitor large human movements and tiny vibrations, thereby showing great application potential in robotics, biomedical prosthetics, personal healthcare monitoring and so on.

Copolymerization of Propylene with Higher α-Olefins by a Pyridylamidohafnium Catalyst: An Effective Approach to Polypropylene-Based Elastomer

In this contribution, we explored the copolymerization of propylene with higher α-olefins, including 1-octene (C8) 1-dodecene (C12), 1-hexadecene (C16) and 1-eicosene (C20), by using a dimethyl pyridylamidohafnium catalyst. A series of copolymers with varied comonomer incorporation, high molecular weight and narrow molecular weight distribution were obtained at mild conditions. The effects of the insertion of the comonomers on the microstructure, thermal and final mechanical properties were systemically studied by 13C NMR, wide-angle X-ray scattering, DSC and tensile test. Excellent mechanical performances were achieved by tuning the incorporation and chain length of the higher α-olefins. When the comonomer content reached above 12 mol.%, polypropylene-based elastomers were obtained with high ductility. A combination of excellent elastic recovery and flexibility was achieved for the P/C16 copolymers with about 20 mol.% monomer incorporation. The monomer incorporation and side chain length played a crucial role in determining the mechanical property of the outstanding polypropylene-based elastomers.

Synthesis and properties investigation of hydroxyl functionalized polyisoprene prepared by cobalt catalyzed co-polymerization of isoprene and hydroxylmyrcene

Controlled copolymerization of isoprene and hydroxylmyrcene afforded well-defined hydroxyl functionalized polyisoprene. Blends of functionalized polyisoprene/SiO₂ displayed enhanced miscibility, and remarkable vulcanization and mechanical properties.

Thermoreversible cross-linking of ethylene/propylene copolymers based on Diels–Alder chemistry: the cross-linking reaction kinetics

The kinetics of the cross-linking reaction of ethylene/propylene rubbers based on Diels–Alder chemistry was detected by the rheological method.