Xuanxuan Chen

Directed self-assembly of block copolymers in the Nealey Group has focused on the behavior of thin films (< 150 nm). However, for many applications, thicker films with similar structures are preferred, but the extension of the process from thin to thick films is nontrivial. Block copolymers in thin films are subject to confinement effects, which play a large role in their assembly; these effects fall off as the film thickness increases and the BCP system behavior more closely mirrors that of the bulk. Xuanxuan is investigating this transition as well as methods to control and direct the BCP assembly at various film thicknesses. She characterizes the polymer behavior using in situ X-ray scattering experiments as well as cross-sectional SEM imaging to gather new insight into polymer assembly behavior at the critical film thickness where orientation transition occurs. Additionally, she is researching the formation of through-film structures and methods to direct their development.