Zwitterion-Modified Nanogel Responding to Temperature and Ionic Strength: A Dissipative Particle Dynamics Simulation

Area of Science:

• Polymer Science
• Materials Science
• Computational Chemistry

Background:

• Poly(n-isopropylacrylamide) (p(NIPAm)) nanogels exhibit thermoresponsive behavior.
• Stimuli-responsive materials are crucial for advanced applications.
• Understanding nanogel self-assembly and response is key for material design.

Purpose of the Study:

• To investigate the self-assembly and stimuli-responsive properties of p(NIPAm) and zwitterion-modified p(NIPAm-co-SBMA) nanogels.
• To explore the influence of polymer concentration, chain length, temperature, and ionic strength on nanogel behavior.
• To provide molecular-level insights into the design of antifouling nanogels.

Main Methods:

• Dissipative particle dynamics (DPD) simulations were employed.
• The study analyzed nanogel formation at varying polymer concentrations (5-10%).
• The effect of chain length (L=10 to 40) on nanogel size was examined.

Main Results:

• Spherical nanogels form optimally at 5-10% polymer concentration.
• Nanogel size increases with chain length.
• p(NIPAm) nanogels show thermoresponsiveness (swelling/shrinking with temperature).
• p(NIPAm-co-SBMA) nanogels exhibit concurrent thermoresponsiveness and ionic strength responsiveness.
• At higher temperatures (318 K), superhydrophilic pSBMA covers the hydrophobic p(NIPAm) core, maintaining antifouling properties.
• Ionic strength influences nanogel volume, with larger volumes in saline systems due to inhibited zwitterionic shrinkage.

Conclusions:

• Zwitterion-modified pNIPAm nanogels demonstrate dual temperature and salt responsiveness.
• Simulation results offer molecular-level understanding of these behaviors.
• The findings guide the design of effective antifouling nanogel materials.