Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)—A Critical Review

Abstract

Hydrogels made of cross-linked polyacrlyamides (cPAM) and conducting materials made of polyanilines (PANIs) are both the most widely used materials in each category. This is due to their accessible monomers, easy synthesis and excellent properties. Therefore, the combination of these materials produces composites which show enhanced properties and also synergy between the cPAM properties (e.g., elasticity) and those of PANIs (e.g., conductivity). The most common way to produce the composites is to form the gel by radical polymerization (usually by redox initiators) then incorporate the PANIs into the network by oxidative polymerization of anilines. It is often claimed that the product is a semi-interpenetrated network (s-IPN) made of linear PANIs penetrating the cPAM network. However, there is evidence that the nanopores of the hydrogel become filled with PANIs nanoparticles, producing a composite. On the other hand, swelling the cPAM in true solutions of PANIs macromolecules renders s-IPN with different properties. Technological applications of the composites have been developed, such as photothermal (PTA)/electromechanical actuators, supercapacitors, movement/pressure sensors, etc. PTA devices rely on the absorption of electromagnetic radiation (light, microwaves, radiofrequency) by PANIs, which heats up the composite, triggering the phase transition of a thermosensitive cPAM. Therefore, the synergy of properties of both polymers is beneficial.

Biomaterials-based hydrogels for therapeutic applications

“…Free radical polymerization: Free radical polymerization is a commonly used method for synthesizing hydrogels from monomers such as acrylic acid, acrylamide, or methacrylate derivatives. Initiators such as ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) are used to initiate polymerization, leading to the formation of crosslinked polymer networks [56].…”

Polymer-Based Hydrogels Applied in Drug Delivery: An Overview

“…Natural polymers commonly used include alginate [179,180], chitosan [181,182], collagen [64], hyaluronic acid [17,23], and gelatin [183,184]. Synthetic polymers such as polyethylene glycol (PEG) [185,186], polyacrylamide (PAAm) [179,187], and poly(N-isopropylacrylamide) (PNIPAAm) [17,23] are also widely employed in hydrogel synthesis. The choice of polymer depends on the desired properties and intended applications of the hydrogel.…”

“…This can be accomplished by introducing crosslinking agents during the polymerization process or by post-polymerization crosslinking reactions. Examples of chemically crosslinked homopolymer hydrogels include polyacrylamide (PAAm) hydrogels [179,187], polyethylene glycol (PEG) hydrogels [185,186], and poly(N-isopropylacrylamide) (PNIPAAm) hydrogels [17,23]. For physically crosslinked homopolymer hydrogels, the crosslinking is based on physical interactions, such as entanglements, hydrogen bonding, or hydrophobic interactions between the polymer chains.…”

Revolutionizing biomedicine: advancements, applications, and prospects of nanocomposite macromolecular carbohydrate-based hydrogel biomaterials: a review

“…This method involves mixing the carbon nanoparticles with a polymer solution and then crosslinking the mixture to form a hydrogel. 25 Freeze-drying : freeze-drying is a technique that can synthesize carbon-based nanocomposite hydrogels. 26 This method involves freezing a solution containing carbon nanoparticles and a polymer, then drying the mixture under a vacuum to form a hydrogel.…”