Dresden 2009 – scientific programme
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SYSO: Symposium Self-organizing Surfaces and Interfaces
SYSO 4: Self-Organizing Surfaces and Interfaces III
SYSO 4.3: Talk
Thursday, March 26, 2009, 10:00–10:15, GÖR 226
Structural changes in thin block copolymer films during vapor treatment — •Zhenyu Di1, Christine M. Papadakis1, Dorthe Posselt2, Ruipeng Li3, and Detlef-M. Smilgies3 — 1TU München, Physikdepartment E13, Garching — 2Roskilde University, Denmark — 3Cornell University, USA
Vapor treatment is a powerful alternative to thermal annealing of block copolymer thin films. The processes going on during structural rearrangements are complex. Solvent not only swells the polymers, but also increases the chain mobility and reduces the effective Flory-Huggins interaction parameter between the blocks [1].
We have investigated a thin film of lamellar poly(styrene-b-butadiene) which was vapor treated with toluene, a good and non-selective solvent [2] or with cyclohexane, a slightly selective solvent, both in saturated and in non-saturated vapor. Grazing-incidence small-angle x-ray scattering with a time resolution of a few sec enable us to follow the changes of the inner film structure in-situ. In all cases, an overshoot of the lamellar thickness and a subsequent decrease are observed which we attribute to non-equilibrium swelling and the tendency to more coiled block conformations in the solvent. Also, the transient state is characterized by improved long-range order. We assign this behavior to the interplay of the rapid increase in chain mobility and the (slower) decrease of the interaction parameter.
[1] J. Noolandi, K.-M. Hong, Ferroelectrics 1980, 30, 117
[2] C. M. Papadakis, Z. Di, D. Posselt, D-M. Smilgies, Langmuir 2008, ASAP