Microphase separation of diblock copolymer with moving walls

• Autor(a) principal: Daud Júnior,Antonio
• Data de Publicação: 2004
• Outros Autores: Morais,Flavio Moretti, Martins,Sílvia, Coimbra,Débora, Morgado,Welles A. M.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Brazilian Journal of Physics
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97332004000300014

Diblock copolymers are linear chain molecules consisting of two subchains A and B grafted covalently to each other. Below some critical temperature Tc these two blocks tend to segregate, but due to the covalent bond they can segregate at best locally to form periodic structures (microdomains). For molecules whose subchains have the same length, the equilibrium pattern is lamellar. In the bulk regime, these microdomains are ordered at random. To obtain an oriented lamellar pattern it is necessary to consider some asymmetry. In the presence of an external field, the lamellae will align to it. Directional quenching also can lead to the growth of oriented microphase separation. The effect of boundary conditions (confinement between parallel walls) also generates well-aligned lamellae, parallel to the walls. If the distance between the walls is comparable to the molecular sizes, another constraint is imposed on the system since the domains are forced to accommodate between the walls and, for certain conditions we will see a frustration phenomenon. If we allow the walls to move with a certain velocity during phase segregation, the accommodation of the lamellae can be changed. We use a cell dynamical system, which is a very efficient computational method, in order to investigate the effect of moving walls in lamellae formation.