Temperature-Dependent Chain Structures during Solution-Grown Crystallization via Atomic Force Microscopy

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Semi-crystalline polymers like Polyethylene Oxide (PEO) are cost-effective and widely used.
• Polymer crystallization behavior is highly sensitive to crystallization temperature (Tc).
• Understanding single-chain folding is crucial for controlling polymer properties.

Purpose of the Study:

• To investigate the effect of crystallization temperature on single-chain folding structures in PEO.
• To elucidate the relationship between temperature, chain folding, and aggregation structures.
• To introduce a novel AFM-based single-molecule force spectroscopy (SMFS) method for studying polymer crystallization.

Main Methods:

• Atomic Force Microscopy (AFM)-based Single-Molecule Force Spectroscopy (SMFS) was employed.
• Force-Volume (FV) mode enabled simultaneous measurement of single-chain forces and surface morphology.
• Analysis of force-extension curves and morphological changes before/after SMFS provided molecular-level insights.

Main Results:

• Crystallization temperature influences the type of chain folding structures formed in PEO.
• Low temperatures favor intermediate structures, while high temperatures promote adjacent reentry structures.
• Temperature does not alter the degree of chain folding (number of adjacent reentry folds) but affects aggregation structures due to surface free energy changes.

Conclusions:

• AFM-based SMFS offers a new approach to study single-chain structural dynamics during polymer crystallization.
• The findings provide insights into how crystallization temperature dictates molecular-level organization in semi-crystalline polymers.
• Understanding these structures is key to tailoring polymer material properties.