An atomic force microscopic investigation of electro-sensitive polymer surface

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Polymer films with tunable properties are crucial for advanced applications.
• Controlling surface characteristics like wettability and phase behavior is a key challenge.
• Electro-responsive polymers offer a pathway to dynamic material control.

Purpose of the Study:

• To fabricate an electro-sensitive polymer film using poly(2-acrylamide-2-methylpropane sulfonic acid) (PAMPS).
• To investigate the influence of external electric fields on the film's microscopic wettability and phase behavior.
• To elucidate the molecular mechanisms behind the observed electro-responsive phenomena.

Main Methods:

• Surface-initiated atom transfer radical polymerization (ATRP) for film fabrication on a silicon substrate.
• Atomic force microscopy (AFM) in contact mode to measure friction and adhesion forces.
• Atomic force microscopy (AFM) in tapping mode to detect phase changes.

Main Results:

• Friction and adhesion forces between the AFM tip and PAMPS film varied with applied negative bias voltage.
• Microscopic wettability of the film was demonstrably adjustable by external electric fields.
• AFM tapping mode revealed corresponding phase changes in the film under electric field influence.

Conclusions:

• The electro-sensitive PAMPS film exhibits tunable microscopic wettability and phase behavior.
• Observed effects are attributed to the conformational overturn of sulfonic groups and alkyl chains in response to electric fields.
• This work highlights the potential of electric fields for controlling polymer film properties at the nanoscale.