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<p>Dynamic changes in the nanostructure and rheology during the hydrolysis of poly(<i>D</i>,<i>L</i>-lactic acid) (PLA)-bearing hydrogels were investigated using synchronized NMR, small-angle neutron scattering (SANS), and small-amplitude oscillatory shear (SAOS). Here, the hydrogels were prepared from the amphiphilic self-assembly of a symmetric triblock copolymer, PLA-<i>b</i>-polyethylene oxide (PEO)-<i>b</i>-PLA. For accelerated hydrolysis, the gels were prepared in a basic buffer and monitored at 37 °C. Since carboxylic acid end groups are produced from the hydrolysis of PLA, the observed hydrolysis has autodecelerating characteristics because of the reduction in the concentration of hydroxyl ions (i.e., the catalytic species of hydrolysis). The degree of hydrolysis, measured by time-slice NMR, followed first-order kinetics in a constant pH region near the buffer’s p<i>K</i><sub>a</sub>, but the hydrolysis was faster at higher pH. In situ SANS revealed that the PLA core was swollen with increasing fractions of water as hydrolysis progressed. In situ SAOS showed that the gel remained an elastic material during hydrolysis but with a rapid decrease in <i>G</i>’ over the incubation time. Moreover, <i>G</i>’ had a power-law relationship with the fraction of unhydrolyzed carbonyls in PLA. The close correlations between chemical, structural, and rheological kinetics established in this work clearly demonstrate how hydrolysis drives the structural and mechanical disintegration of biodegradable gels.</p>

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Hydrolytic evolution of the structure and rheology of a biodegradable hydrogel bearing poly(D,L-lactic acid)

  • 期刊论文

  • 发表日期：

    2026年7月10日

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  • Seonhye Hwang,
  • Junho Lee,
  • Hye Jin Oh,
  • Seon Yeop Jung,
  • Seyoung Kim

摘要

Dynamic changes in the nanostructure and rheology during the hydrolysis of poly(D,L-lactic acid) (PLA)-bearing hydrogels were investigated using synchronized NMR, small-angle neutron scattering (SANS), and small-amplitude oscillatory shear (SAOS). Here, the hydrogels were prepared from the amphiphilic self-assembly of a symmetric triblock copolymer, PLA-b-polyethylene oxide (PEO)-b-PLA. For accelerated hydrolysis, the gels were prepared in a basic buffer and monitored at 37 °C. Since carboxylic acid end groups are produced from the hydrolysis of PLA, the observed hydrolysis has autodecelerating characteristics because of the reduction in the concentration of hydroxyl ions (i.e., the catalytic species of hydrolysis). The degree of hydrolysis, measured by time-slice NMR, followed first-order kinetics in a constant pH region near the buffer’s pKa, but the hydrolysis was faster at higher pH. In situ SANS revealed that the PLA core was swollen with increasing fractions of water as hydrolysis progressed. In situ SAOS showed that the gel remained an elastic material during hydrolysis but with a rapid decrease in G’ over the incubation time. Moreover, G’ had a power-law relationship with the fraction of unhydrolyzed carbonyls in PLA. The close correlations between chemical, structural, and rheological kinetics established in this work clearly demonstrate how hydrolysis drives the structural and mechanical disintegration of biodegradable gels.