Assembling semiconducting molecules by covalent attachment to a lamellar crystalline polymer substrate

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Polymers with precisely spaced side-branches are investigated for thin film applications.
• Side-branches are excluded from the crystalline core upon crystallization, forming a crystal surface layer.
• Carboxyl groups on side-branches enable chemical functionalization with semiconducting molecules.

Purpose of the Study:

• To investigate the potential of functionalizing polymer crystals for organic electronic applications.
• To compare the properties of functionalized small nanocrystals versus large single crystals.
• To explore methods for creating uniform thin films of functionalized polymers.

Main Methods:

• Crystallization of precisely side-branched polymers to form lamellar crystals.
• Functionalization of carboxyl side-branches with semiconducting molecules.
• Assembly of nanocrystals on a Langmuir trough and growth of large-area single crystals via local supersaturation.

Main Results:

• Side-branches were excluded from the crystalline core, creating functionalizable surfaces.
• Nanocrystals were assembled into monolayers, and large-area single crystals were grown.
• Semiconducting molecules were successfully attached to single crystal surfaces after annealing.
• The morphology of the semiconducting layer evolved from patchy to compact with increased grafting time.

Conclusions:

• Precisely side-branched polymers offer a route to functionalized crystalline materials for organic electronics.
• Both nanocrystal assembly and large single crystal growth are viable methods for thin film fabrication.
• Annealing and grafting duration are critical parameters for controlling the morphology of the functionalized layer.