Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

Area of Science:

• Polymer Science
• Materials Science
• Crystallization Science

Background:

• Self-assembly of block copolymers is crucial for nanomaterials.
• Controlling crystal morphology and structure is essential for material properties.
• Existing methods lack precise control over crystal formation parameters.

Purpose of the Study:

• To investigate the formation of self-seeded platelet-like crystals from PS-b-PEO diblock copolymers.
• To establish control over crystal number, size, and lamellar stacking using a self-seeding procedure.
• To elucidate the influence of polymer concentration, crystallization temperature, and self-seeding temperature on crystal formation.

Main Methods:

• Utilized a self-seeding technique to circumvent homogeneous nucleation.
• Systematically varied polymer concentration (c), crystallization temperature (TC), and self-seeding temperature (TSS).
• Quantified crystal number (N), mean lateral size (L), and number of stacked lamellae (η).

Main Results:

• The number of crystals (N) increased linearly with polymer concentration (c) and decayed exponentially with self-seeding temperature (TSS).
• Homogeneous nucleation was avoided, making N independent of crystallization temperature (TC).
• Crystal size (L) was controlled by N, η, and the difference between polymer concentration and solubility limit (Δc = c - c*).

Conclusions:

• The self-seeding procedure offers predictable control over the number and size of platelet-like crystals.
• This method also enables control over the number of stacked lamellae within these crystals.
• The solubility limit (c*) was found to be dependent on the crystallization temperature (TC).