Synthesis and characterization of hydrophobic association hydrogels with tunable mechanical strength

Abstract

Designing hydrogels with tunable mechanical properties and self-healing effects is crucial to a variety of applications, such as bioremediation carriers. Here, we synthesized a series of hydrophobic associated hydrogels (HA-gels) through micellar copolymerization in sodium dodecyl sulfate (SDS) aqueous solution. The hydrophobic monomer used is fatty alcohol polyoxyethylene acrylate (AEO-AC), which is significantly more eco-friendly than the traditional octylphenol polyoxyethylene acrylate (OP-AC) hydrophobic monomer. Interestingly, the mechanical properties of HA-gels can be tuned controllably by varying the ratio of AEO-AC-10-5 to AEO-AC-13-5 (AEO-AC-n-5: C_nH_2n+1(OCH₂CH₂)₅O–C(O)CHCH₂; n = 10, 13). The longer and sheer straight carbon chain of AEO-AC-13-5 leads to stronger hydrophobic association point, while the shorter and branched carbon chain of AEO-AC-10-5 results in weaker hydrophobic association point. The resulting AEO-AC-13-5-AM gels possess tough mechanical strength (maximum broken stress is 318 kPa) and high elongation (1000–3000%). Then, we could tune the swelling and stress relaxation behaviors by varying the ratio of SDS to AEO-AC and obtain HA-gels that maintain their shapes in water nearly half a year, with low content of SDS. Lastly, our HA-gels also exhibit good self-healing capability, and offer great opportunities for a lot of prospective biomaterials.