Distribution of block copolymers in drying polymer films

Area of Science:

• Polymer Science
• Materials Science
• Surface Chemistry

Background:

• Block copolymers (BCP) with polar and apolar blocks are key for polymer film surface functionalization.
• BCP characteristics dictate surface segregation and phase separation in bulk mixtures.
• Understanding these phenomena is crucial for optimizing BCP composition for desired surface properties.

Purpose of the Study:

• To systematically investigate the distribution of poly(ethylene oxide)-polydimethylsiloxane (PEO-PDMS) BCP in coating formulations.
• To determine the optimal BCP composition for high surface enrichment without bulk phase separation.
• To compare experimental findings with self-consistent field (SCF) computations.

Main Methods:

• Surface tension measurements for liquid formulations.
• X-ray photoelectron spectroscopy (XPS) for dried films.
• Turbidity measurements for phase separation quantification.
• Scheutjens-Fleer self-consistent field (SF-SCF) computations.

Main Results:

• Longer polydimethylsiloxane (PDMS) blocks reduced liquid mixture interfacial tension.
• Intermediate PDMS block lengths yielded the highest PDMS concentration at the interface in cured films.
• Phase separation occurred at low BCP concentrations for long PDMS blocks.
• SCF predictions qualitatively matched experimental results and showed drying effects on BCP distribution.

Conclusions:

• BCP composition critically influences surface segregation and phase separation.
• Intermediate PDMS block lengths are optimal for achieving high surface concentration without bulk phase separation.
• Film drying significantly alters BCP distribution and stability.