Hydrogels are conductive and stretchable, allowing for their use in flexible electronic devices, such as electronic skins, sensors, human motion monitoring, brain–computer interface, and so on. Herein, we synthesized the copolymers having various molar ratios of 3,4-ethylenedioxythiophene (EDOT) to thiophene (Th), which served as conductive additives. With doping engineering and incorporation with P(EDOT-co-Th) copolymers, hydrogels have presented excellent physical/chemical/electrical properties. It was found that the mechanical strength, adhesion ability, and conductivity of hydrogels were highly dependent on the molar ratio of EDOT to Th of the copolymers. The more the EDOT, the stronger the tensile strength and the greater the conductivity, but the lower the elongation break tends to be. By comprehensively evaluating the physical/chemical/electrical properties and cost of material use, the hydrogel incorporated with a 7:3 molar ratio P(EDOT-co-Th) copolymer was an optimal formulation for soft electronic devices.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.2c07368

Electroactive and Stretchable Hydrogels of 3,4-Ethylenedioxythiophene/thiophene Copolymers

In this paper, macroporous antimicrobial polymeric gels (MAPGs) functionalized with active quaternary ammonium cations attached to varying hydrocarbon chain lengths have been fabricated. Apart from the change in the alkyl chain length attached to the quaternary ammonium cation, the amount of crosslinker was also varied during the fabrication of the macroporous gels. The prepared gels were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy (FE-SEM) and swelling studies. In addition, the mechanical properties of the fabricated macroporous gels were studied using compression and tensile testing. The antimicrobial activity of the gels has been determined for Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) as well as Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus). Antimicrobial activity, as well as the mechanical properties of the macroporous gels, was found to be influenced by the alkyl chain length attached to the quaternary ammonium cations as well as by the amount of crosslinker used for the fabrication of the gel. In addition, on increasing the alkyl chain length from C4 (butyl) to C8 (octyl), the effectiveness of the polymeric gels increased. It was observed that the gels derived using a tertiary amine (NMe2) containing monomer showed relatively low antimicrobial activity as compared to the gels obtained using quaternized monomers (C4 (butyl), C6 (hexyl), and C8 (octyl)). The gels based on the quaternized C8 monomer displayed the highest antimicrobial activity and mechanical stability as compared to the gels based on the C4 and C6 monomers. 

Mechanically robust and highly bactericidal macroporous polymeric gels based on quaternized <i>N</i>,<i>N</i>-(dimethylamino)ethyl methacrylate possessing varying alkyl chain lengths

Conductive hydrogels with stretchable, flexible and wearable properties have made significant contributions in the area of modern electronics. The polyacrylamide/alginate hydrogels are one of the potential emerging materials for application in a diverse range of fields because of their high stretch and toughness. However, most researchers focus on the investigation of their mechanical and swelling behaviors, and the adhesion and effects of the ionic liquids on the conductivities of polyacrylamide/alginate hydrogels are much less explored. Herein, methacrylated lysine and different alkyl chain substituted imidazole-based monomers (IMCx, x = 2, 4, 6 and 8) were introduced to prepare a series of novel pAMAL-IMCx-Ca hydrogels. We systematically investigated their macroscopic and microscopic properties through tensile tests, electrochemical impedance spectra and scanning electron microscopy, as well as Fourier transform infrared spectroscopy, and demonstrated that an alkyl chain length of the IMCx plays an important role in the designing of hydrogel strain sensors. The experiment result shows that the hexyl chains of IMC6 can effectively entangle with LysMA through hydrophobic and electrostatic interactions, which significantly enhance the mechanical strength of the hydrogels. Furthermore, the different strain rates and the durability of the pAMAL-IMC6-Ca hydrogel were investigated and the relative resistance responses remain almost the same in both conditions, making it a potential candidate for wearable strain sensors.

Mei-Yu Yeh

Papers

Alkyl Chain Length Effects of Imidazolium Ionic Liquids on Electrical and Mechanical Performances of Polyacrylamide/Alginate-Based Hydrogels