Poly(N-isopropylacrylamide) Microgels under Alcoholic Intoxication: When a LCST Polymer Shows Swelling with...

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Poly(N-isopropylacrylamide) (PNIPAM) microgels are known as smart polymers.
• PNIPAM exhibits a volume phase transition temperature (VPTT) around 32°C in aqueous solutions, leading to collapse above this temperature.

Purpose of the Study:

• To investigate the conformational behavior of PNIPAM microgels in aqueous alcohol mixtures.
• To determine if PNIPAM microgels always collapse above their VPTT.
• To elucidate the factors governing the microgel's structural transitions.

Main Methods:

• Experimental studies on PNIPAM microgels.
• Molecular simulations of PNIPAM in solution.
• Analysis of microscopic interactions and bulk solution properties.

Main Results:

• PNIPAM microgels do not exclusively collapse above the VPTT in aqueous alcohol mixtures.
• A two-step conformational transition is observed: collapse below 32°C and reswelling above 50°C.
• Microscopic interactions and solution properties critically influence the reswelling behavior.

Conclusions:

• The reswelling of PNIPAM microgels at higher temperatures in aqueous alcohol mixtures is not a typical upper critical solution behavior.
• Delicate interactions govern the complex phase transitions of PNIPAM microgels.
• Understanding these transitions is crucial for designing advanced smart materials.