Self-healing polyacrylic acid hydrogels

Abstract

pH responsive physical gels were prepared by micellar copolymerization of acrylic acid with 2 mol % 5 stearyl methacrylate (C18) in the solution of worm-like sodium dodecyl sulfate micelles. The physical gels are insoluble in water and exhibit time-dependent dynamic moduli, high Young's modulus (6 -53 kPa), high fracture stress (41 -173 kPa), high elongation at break (1800 -5000 %), and self-healing, as evidenced by rheological and mechanical measurements. Cyclic elongation tests show significant hysteresis due to the existence of reversibly breakable bonds (up to 25 %) within the gel network. As the 10 polymer concentration is increased, both the lifetime of hydrophobic associations and the mechanical strength of gels increase while the elongation ratio at break decreases. As compared to the polyacrylamide gels formed under identical conditions, present hydrogels exhibit a much stronger selfhealing effect, which is attributed to the cooperative hydrogen bonding between the carboxyl groups stabilizing the hydrophobic domains. The efficiency of self-healing significantly increases with 15 increasing temperature due to the decrease of the lifetime of hydrophobic associations. 75 55 † Electronic Supplementary Information (ESI) available: Swelling behavior, temperature dependence of the dynamic moduli, and the effect of urea on the self-healing behavior of PAAc hydrogels. See

The self‐healing mechanism of an industrial acrylic elastomer

“…15 Figure 4 35,36 The results obtained confirm the existence of functional groups constituting poly(acrylic acid) in the investigated material.…”

“…12 The self-healing ability of these materials is attributed to the reversible noncovalent interactions in particular such as hydrogen bonding, 6,8,[13][14][15] hydrophobic association, [16][17][18][19][20] ionic bonds, [21][22][23][24] and p-p stacks. 25,26 However, the low mechanical strength has limited the practical application of these materials.…”

Self-Healing Hydrogels Formed via Hydrophobic Interactions

“…7 [37,41]. In contrast, HM PAAc hydrogels formed in SDS solutions exhibit high swelling ratios in water because of the osmotic pressure of the AAc counterions [39]. The equilibrium swelling ratio (m rel,eq ) of these hydrogels formed at C 0 ¼ 20 % (w/v) is around 500, corresponding to a PAAc concentration of 0.04 % (w/v) in the swollen gel.…”

“…Uniaxial compression and tensile measurements on hydrophobically modified hydrogels serve to evaluate their elastic properties such as moduli, fracture stresses, and deformation ratios at break [33][34][35][39][40][41][42]. The stress is presented by its nominal, σ nom , or true values, σ true (equal to λσ nom ), defined as the forces per unit undeformed and deformed area, respectively; λ is the deformation ratio.…”

Self‐Healing Poly(acrylic acid) Hydrogels: Effect of Surfactant

“…In this study, pH responsive physical gels were prepared by micellar copolymerization of hydrophilic monomer acrylic acid (AAc) with large hydrophobic monomer stearyl methacrylate (C18) in solution of worm-like anionic surfactant [15] (sodium dodecyl sulfate, SDS) and cationic surfactant [16] (cetyltrimethyl ammonium bromide, CTAB) micelles. Hydrophobe content of the monomer mixtures was 2 mol.% and total monomer concentration in gels was 20 w/v%.…”