Lower Critical Solution Temperature Phase Transition of Poly(PEGMA) Hydrogel Thin Films

Area of Science:

• Polymer Science
• Materials Science
• Biotechnology

Background:

• Surface-attached hydrogel films offer tunable thickness and stimuli-responsive properties, serving as alternatives to polymer brushes and layer-by-layer assemblies.
• Poly(N-isopropylacrylamide) (PNIPAM) is a common temperature-responsive polymer, but there's a need for polymers responding at various temperatures while maintaining biocompatibility.

Purpose of the Study:

• To synthesize and characterize temperature-responsive poly[oligo(ethylene glycol) methacrylate] (PEGMA) hydrogel thin films.
• To demonstrate tunable transition temperatures and stability in physiological conditions for potential biomedical applications.

Main Methods:

• Synthesis of surface-attached poly(PEGMA) hydrogel films utilizing a versatile thiol-ene click reaction (cross-linking and grafting).
• Characterization of hydrogel film thickness, temperature-responsive properties (swelling-to-collapse transition), and transition temperature tuning based on PEGMA composition.

Main Results:

• Poly(PEGMA) hydrogel films exhibited tunable transition temperatures ranging from 15 to 60 °C by adjusting the number of oligo(ethylene glycol) units (2 to 5).
• Transition temperatures could be further fine-tuned using copolymers or polymer blends of PEGMA.
• The hydrogel films demonstrated robust lower critical solution temperature (LCST) properties, including swelling-to-collapse amplitude and transition temperature, which were unaffected by salt, including phosphate-buffered saline.

Conclusions:

• Surface-attached poly(PEGMA) hydrogel films provide a versatile platform for tunable temperature-responsive materials.
• The stability in physiological buffers makes these hydrogel films highly promising for advanced biomedical applications such as injectable hydrogels and drug delivery systems.