Orientation Control of Molecular Chains in Polymers Using Atomic Force Microscopy

Abstract

We successfully controlled the molecular orientation of flat-on lamellar crystals of the ferroelectric copolymer, vinylidenefluoride and trifluoroethylene (P(VDF-TrFE)), on Pt and Au surfaces utilizing atomic force microscopy (AFM). The orientation was controlled by scanning a cantilever tip in contact with the film surface whose temperature was kept at just below its melting point (Tm). The molecules were stretched in the scan direction and new edge-on crystals were subsequently formed, whose lamellar planes were perpendicular to the scan direction. We also attempted to modify an isotactic poly-1-butene (IPB) thin film and a polyaniline emeraldine base (PANI-EB) thin film utilizing AFM. In the case of IPB film, structures similar to edge-on crystals of P(VDF-TrFE) were obtained when modified with the film temperature kept at just below its Tm. The result strongly suggests that this orientation control technique is also applicable to IPB. On the other hand, in the case of PANI-EB film, we could obtain many ellipsoidal grains in the scanned area. One possible mechanism is that PANI-EB molecular chains were stretched parallel to the modification scan to form fibrils or bundles.