Solvent and Substrate Induced Synergistic Ordering in Block Copolymer Thin Films

Direct observation of morphological transition for an adsorbed single polymer chain

A better understanding of the structure of polymers at solid interfaces is crucial for designing various polymer nano-composite materials from structural materials to nanomaterials for use in industry. To this end, the first step is to obtain information on how synthetic polymer chains adsorb onto a solid surface. We closely followed the trajectory of a single polymer chain on the surface as a function of temperature using atomic force microscopy. Combining the results with a full-atomistic molecular dynamics simulation revealed that the chain became more rigid on the way to reaching a pseudo-equilibrium state, accompanied by a change in its local conformation from mainly loops to trains. This information will be useful for regulating the physical properties of polymers at the interface.

Mesoscopic simulation study on the structural transition of comb-shaped block copolymer lamellae on chemically patterned substrates: from vertical to lateral

Directed self-assembly of polymers on chemically homogeneous and heterogeneous patterns is of considerable interest for nanolithography and nanofluidic devices. By employing dissipative particle dynamics (DPD) technology, we explore the nanoscale phase separation of comb-like block copolymers (CBCPs) confined at chemically homogeneous and heterogeneous substrates. Herein, the geometric and energetic influences of striped substrates on the microphases are firstly studied using various geometries of annular stripes for the heterogeneous substrates. Different parameters including the stripe geometry, substrate selectivity, and film thickness are studied systematically. T-Junction lamellae and acclivitous alignment are achieved on the heterogeneous substrates because of the synergy of geometrical effects of the striped pattern from heterogeneous substrates together with weak preference of the substrates toward one of the CBCP components. In this study, we provide a detailed understanding of microphase separation of CBCPs on the heterogeneous substrates, and the approach outlined in the present study offers a crucial tool for experimentalists to design CBCP thin films with complex device-oriented structures.