Thin Film Morphologies of Block Copolymers Complexed with Wedge-Shaped Liquid Crystalline Amphiphilic Molecules

Abstract

Wedge-shaped molecules with a sulfonic group at the tip have been incorporated into a poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer via proton transfer at different degrees of neutralization. The protonation of P2VP was monitored by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The thin film morphology of the complexed block copolymers has been studied by scanning force microscopy and X-ray reflectivity. The complexes exhibit strongly microphase-segregated patterns comprising smectic layers of the complexed P2VP blocks, oriented parallel to the substrate throughout the whole film with the embedded PEO domains. For the complex with a degree of neutralization of 0.50 ordered amorphous PEO cylinders are observed oriented perpendicular to the substrate. For a degree of neutralization equal to 0.25 initially also perpendicular PEO cylinders are formed, but upon solvent-vapor annealing they partially merge, resulting in a mixed lamellar-cylindrical morphology. In all cases an extra surface layer is formed at the substrate. Thus, for the first time we have demonstrated that a block copolymer thin film structure can easily be controlled by the degree of neutralization of one of the blocks.

Nanostructured Organic Semiconductors via Directed Supramolecular Assembly

“…Thus, solvent-annealed PS-b-P4VP(4T) 1.5 does not form a well-ordered lamellae-within-lamellae morphology in thin films as previously found with other BCPbased supramolecules. 41,43 We speculate that, after solvent annealing, PS-b-P4VP(4T) 1.5 may form morphologies similar to that shown in Figure 4b, where a significant fraction of 4Ts organize into lamellae bridging the BCP lamellae in different grains to provide a pathway to transport charges between P4VP(4T) r lamellae. Upon thermal annealing, 4Ts are incorporated within P4VP(4T) r microdomains, which resulted in an increase in BCP periodicity.…”

“…39Ϫ43 Experimentally, by adjusting the loading of the small molecules, the BCP microdomains can be aligned perpendicular to the surface. 41,43 Within BCP microdomains, lamellar assemblies from the comb block, several nanometers in size, are oriented parallel to the surface and small molecules are aligned perpendicular to the surface. 41,43 Blending organic semiconductors with inert polymers was shown to be effective for improving the solution processability of the semiconductor.…”

Block copolymer–nanoparticle composites: Structure, functional properties, and processing

“…Annealing of nanocomposites by applying heat or solvent treatment can also be useful in achieving equilibrium structure [145,311,312]. BCP domains can be oriented by applying external fields such as shear and electric [262][263][264]301].…”

Hierarchical Assemblies of Block-Copolymer-Based Supramolecules in Thin Films

“…Moeller et al investigated the thin film morphologies of wedgeshaped liquid crystalline amphiphilic molecules complexed with poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) diblock copolymer via proton transfer. 28 The complex microphase separated with parallel smectic layers of the complexed P2VP blocks throughout the thin films. By varying the degree of neutralization, namely the stoichiometry of the wedge-shaped molecule to 2VP, the block copolymer thin film structures can be controlled.…”