Crystallization behavior of single isotactic poly(methyl methacrylate) chains visualized by atomic force microscopy

Area of Science:

• Polymer Science
• Materials Science
• Nanotechnology

Background:

• Previous work visualized 2D folded chain crystals of isotactic poly(methyl methacrylate) (it-PMMA) using AFM.
• Understanding polymer crystallization at the single-chain level remains a challenge.

Purpose of the Study:

• To visualize the crystallization behavior of a single isolated polymer chain at the molecular level.
• To investigate the influence of compression and molecular weight on single-chain crystallization.

Main Methods:

• Utilized atomic force microscopy (AFM) to observe polymer chains.
• Employed a Langmuir monolayer technique with high-molecular-weight it-PMMA diluted in an it-PMMA oligomer monolayer.
• Controlled surface pressure and compression rates to study crystallization.

Main Results:

• Isolated high-molecular-weight it-PMMA chains were observed to crystallize into single-chain crystals upon compression.
• Crystalline nuclei preferentially formed at chain ends, resembling a necklace structure.
• Slow compression promoted whole-chain crystallization, with nucleus size largely independent of molecular weight.

Conclusions:

• The study provides the first molecular-level visualization of single isolated polymer chain crystallization.
• Findings offer novel insights into the fundamental mechanisms of polymer crystallization.
• This work paves the way for understanding and controlling polymer self-assembly at the nanoscale.