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<p>Chemical fuel-driven hydrogels characterized by a controllable phase transition, have garnered significant attention over the past decades due to their tunable lifetimes. Here, we introduced a novel temporally programmed hydrogel synthesized from polyvinyl alcohol (PVA) and boric acid (B(OH)<sub>3</sub>) using sodium hydroxide (NaOH) and methyl lactate as chemical fuels. The introduction of these fuels triggers the formation of dynamic covalent borate ester bonds between PVA and B(OH)<sub>3</sub> under alkaline conditions, resulting in the development of an elastic hydrogel with a storage modulus of ~ 130&#xa0;Pa and a peak apparent viscosity exceeding 10<sup>7</sup> mPa·s at low shear rates, accompanied by pronounced shear-thinning behavior. As ML gradually hydrolyzes, NaOH is consumed, leading to a controlled decrease in pH from 9.03 to 5.26 over 3200&#xa0;min. This pH reduction induces the dissociation of borate ester bonds, reverting the hydrogel back to its sol state. The phase transition is highly programmable, with its lifetime (ranging from 1 to 80&#xa0;h) precisely adjustable by varying the concentrations of NaOH and ML, as well as the temperature. Specifically, the duration of the gel phase increases with higher NaOH concentrations, while it decreases with greater ML content or elevated temperatures. Notably, the sol-to-gel-to-sol transition can be programmed by modifying the composition of the chemical fuels or by adjusting the temperature. Moreover, the hydrogel demonstrates remarkable reversibility and mechanical stability, retaining over 90% of its initial modulus after three cycles of fuel regeneration. Given these unique characteristics, this polymer hydrogel holds significant promise for applications in information security and the immobilization of quartz sand.</p>

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Temporal programmed PVA/boric acid hydrogel based on the hydrolysis of methyl lactate

  • 期刊论文

  • 发表日期：

    2025年11月29日

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  • Xingyao Li,
  • Meng Mu,
  • Jiace Li,
  • Heng Liu,
  • Yongmin Zhang

摘要

Chemical fuel-driven hydrogels characterized by a controllable phase transition, have garnered significant attention over the past decades due to their tunable lifetimes. Here, we introduced a novel temporally programmed hydrogel synthesized from polyvinyl alcohol (PVA) and boric acid (B(OH)3) using sodium hydroxide (NaOH) and methyl lactate as chemical fuels. The introduction of these fuels triggers the formation of dynamic covalent borate ester bonds between PVA and B(OH)3 under alkaline conditions, resulting in the development of an elastic hydrogel with a storage modulus of ~ 130 Pa and a peak apparent viscosity exceeding 107 mPa·s at low shear rates, accompanied by pronounced shear-thinning behavior. As ML gradually hydrolyzes, NaOH is consumed, leading to a controlled decrease in pH from 9.03 to 5.26 over 3200 min. This pH reduction induces the dissociation of borate ester bonds, reverting the hydrogel back to its sol state. The phase transition is highly programmable, with its lifetime (ranging from 1 to 80 h) precisely adjustable by varying the concentrations of NaOH and ML, as well as the temperature. Specifically, the duration of the gel phase increases with higher NaOH concentrations, while it decreases with greater ML content or elevated temperatures. Notably, the sol-to-gel-to-sol transition can be programmed by modifying the composition of the chemical fuels or by adjusting the temperature. Moreover, the hydrogel demonstrates remarkable reversibility and mechanical stability, retaining over 90% of its initial modulus after three cycles of fuel regeneration. Given these unique characteristics, this polymer hydrogel holds significant promise for applications in information security and the immobilization of quartz sand.