Preparation of High-Density Polymer Brushes with a Multihelical Structure

Area of Science:

• Polymer Science
• Materials Science
• Supramolecular Chemistry

Background:

• Polymethyl methacrylate (PMMA) stereocomplexes are known to form multihelical structures.
• These structures typically involve isotactic chains surrounded by syndiotactic chains.
• Previous research has not extensively explored stereocomplex formation within high-density polymer brushes under geometric confinement.

Purpose of the Study:

• To investigate the structure of stereocomplexes formed by syndiotactic PMMA polymer brushes tethered to a silicon substrate.
• To understand the influence of geometric confinement (flat vs. spherical substrates) on stereocomplex formation.
• To characterize the crystalline nature and orientation of the formed stereocomplexes.

Main Methods:

• Preparation of high-density syndiotactic PMMA polymer brushes on flat and spherical silicon substrates.
• Mixing tethered syndiotactic PMMA with untethered isotactic PMMA.
• Static contact angle measurements to assess surface mobility.
• Grazing incidence wide-angle X-ray diffraction (GIWAXD) using fluoroalkyl-substituted brushes for enhanced contrast.

Main Results:

• Stereocomplex formation with a multihelical structure was confirmed for both flat and spherical substrates.
• Static contact angle measurements indicated hindered surface mobility, suggesting a crystalline stereocomplex structure.
• GIWAXD analysis verified the formation of a crystalline stereocomplex oriented perpendicular to the substrate, with a moderate degree of orientation.

Conclusions:

• Stereocomplex formation in PMMA polymer brushes is achievable even under geometric confinement.
• The resulting stereocomplexes exhibit a crystalline, multihelical structure oriented perpendicular to the substrate.
• Surface properties and structural orientation are influenced by the tethered polymer brush architecture.