Modifying Properties of Polymer Films by Solvent Swelling

Ophelia Tsui, Trustees of Boston University, DMR 0908651

Solvated film

Polymer film

Swell with the vapor of a

near- solvent

10 20 300

100

200

300

Temperature (oC)

Rel

axat

ion

Tim

e (h

rs)

Polymer film

Quench to ambience

Under the support of this MWN award, we have found that polymer films prepared at different temperatures near the theta temperature () may exhibit noticeably different physical properties as revealed from their relaxation time and long-time viscosity. These are attributable to the different degrees of overlap between polymer chains at different temperatures during spin-coating that may get frozen in when the films dry and settle. While this result suggests that one may adjust the properties of polymer films by spin-coating them at different temperatures near , this strategy may not work well sometimes. For example, it has been found difficult to produce thick films by spin-coating the films at or below . In this study, we find that the properties of polymer films can be similarly tuned by swelling a previously spin-coated polymer film with a solvent at different temperatures near followed by rapid quenching to ambience. The graph at right clearly shows the (aging) relaxation time of these films varies notably with the swelling temperature and so demonstrates swelling may provide a simple route to adjust the properties of polymer films. This work has been accepted for publication in Macromolecules.

Publications:1. “Equilibration of Polymer Films Cast from Solutions with Different Solvent Qualities”, Nancy R. Li, A. Clough, Z. Yang, O.

K. C. Tsui, Macromolecules, 45, 1085-1089 (2012).2. “Spreading of Liquids on Substrates”, G. Reiter, In Handbook of Adhesion Technology. Eds. L. F. M. da Silva, A. Öchsner,

R. Adams. Springer 2011.3. “Processes of Ordered Structure Formation in Polypeptide Thin Film Solutions”, I. Botiz, H. Schlaad, G. Reiter, Adv. in

Polymer Science, 242, 117-149 (2011).4. “Probing Properties of Polymers in Thin Films Via Dewetting”, Günter Reiter, Adv. Polym. Sci., 2012 (DOI:

10.1007/12_2012_174).5. “Thin Polymer Films Out of Thermodynamic Equilibrium”, Mithun Chowdhury. Inaugural-Dissertation zur Erlangung des

Doktorgrades der Fakultät für Mathematik und Physik der Albert-Ludwigs-Universität Freiburg, 2012.6. “Swelling with a Near-Theta Solvent as a Means to Modify the Properties of Polymer Thin Films", A. Clough, M.

Chowdhury, K. Jahanshahi, G. Reiter, O. K. C. Tsui, Macromolecules (accepted). 7. “Consequences of varying adsorption strength and adding steric hindrance on self-assembly of supra-molecular

polymers on carbon substrates”, R. Shokri, F. Vonau, M. Cranney, D. Aubel, A. Narladkar, B. Isare, L. Bouteiller, L. Simon, G. Reiter (submitted).

8. “Segmental Relaxations Have Macroscopic Consequences in Glassy Polymer Films”, M. Chowdhury, P. Freyberg, F. Ziebert, A. C.-M. Yang, U. Steiner and G. Reiter (submitted).

Education:Training of 4 graduate students (two in the US and two in Germany), one visiting researcher from China and one high-school student.

PhD graduate student, Mithum Chowdhury (Germany) is graduating this August, but has already started a postdoctoral fellowship in Trinity College, Dublin. PhD graduate students, Andrew Clough and R. Nancy Li (USA) passed their prospectus oral examination this April. Mithun, Andrew and Nancy have each given two oral presentations at professional meetings this year. In addition, Mithun has given three poster presentations and Paul Freyberg given one. High-school intern, Lawrence Arney gave a poster presentation at a local workshop organized by Boston University. Outreach: Eight items were published1-6 or submitted7-8 as research papers, handbook contribution or PhD thesis. Twelve presentations were given in professional meetings or academic institutions.

High-school intern, Lawrence Arney of Randolph School, Huntsville, Alamaba is visiting Tsui’s lab. this summer. The background shows the ellipsometer and optical microscope in her lab.

Ophelia Tsui, Trustees of Boston University, DMR 0908651