The effect of hydrophobic alkyl chain length on the mechanical properties of latex particle hydrogels

Herein, different long alkyl chains (C1, C6, C12, and C16) were introduced as hydrophobic segments to enhance the performance of hydrogels reinforced by latex particles (LP-Gel). Poly(butyl acrylate) (PBA) latex particles (LPs) were employed as hydrophobic association cross-linking centers. First, the PBA latex particles were prepared via emulsion polymerization, and then, LP-Gel with high mechanical strength was prepared via one-pot free radical polymerization using acrylamide as a monomer, LP as a cross-linking center, and methacrylate as a hydrophobic molecule. It was found that the length of the hydrophobic alkyl chains from methacrylate has a significant effect on the mechanical performance and swelling degree of the hydrogels. The short alkyl chains exhibited weak hydrophobic interactions, and the resulting LP-Gel had a low mechanical strength. However, the long alkyl chains can effectively entangle with LPs through strong hydrophobic interactions, which significantly enhance the mechanical strength of the hydrogels. As a result, the LP-Gel exhibits a maximum fracture stress of 1.2 MPa and elongation of 2336%. This study will have a profound impact on the understanding of hydrogels toughened by hydrophobic alkyl chains of different lengths. The hydrogels with optimal alkyl segments reinforced by LPs exhibited the maximum fracture stress of 1.2 MPa and elongation of 2336%.