Thermoresponsive PEG-based polymer layers: surface characterization with AFM force measurements

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Thermoresponsive polymers enable dynamic control over surface properties.
• Poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate) [P(MEO(2)MA-co-OEGMA)] exhibits tunable phase transitions.
• Understanding polymer-surface interactions is crucial for biomaterial design.

Purpose of the Study:

• To investigate temperature-dependent surface interactions of P(MEO(2)MA-co-OEGMA) with a colloidal probe.
• To characterize the transition from repulsive to attractive forces at different temperatures.
• To assess the reproducibility and kinetics of surface property switching.

Main Methods:

• Atomic Force Microscopy (AFM) force-distance measurements in aqueous medium.
• Analysis of adhesion forces from AFM retraction curves.
• Temperature cycling experiments (heating/cooling) and time-dependent measurements.

Main Results:

• Two distinct regimes of surface interaction were identified below and above the lower critical solution temperature (LCST).
• At 25°C (swollen state), repulsive forces dominated.
• At 37°C, attractive forces and stronger adhesion were observed.
• Reproducible adhesion force values were obtained across multiple heating/cooling cycles.
• Switching kinetics were found to be coupled to polymer kinetics, potentially limited by cellular rearrangements.

Conclusions:

• P(MEO(2)MA-co-OEGMA) surfaces exhibit switchable interactions from repulsive to attractive forces with temperature changes.
• The observed reversible and reproducible adhesion force modulation is suitable for controlled cell attachment and detachment.
• AFM force measurements provide valuable insights into the dynamic behavior of thermoresponsive polymer surfaces for biomaterial applications.