https://doi.org/10.1140/epje/i2009-10474-x
Regular Article
Spreading of diblock copolymer droplets: A probe of polymer micro-rheology
Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, Canada
* e-mail: dalnoki@mcmaster.ca
Received:
4
March
2009
Revised:
4
May
2009
Accepted:
12
May
2009
Published online:
24
June
2009
We present an experimental study of the spreading dynamics of symmetric diblock copolymer droplets above and below the order-disorder transition. Disordered diblock droplets are found to spread as a homopolymer and follow Tanner’s law (the radius grows as R ∼ t m , where t is time and m = 1/10 . However, droplets that are in the ordered phase are found to be frustrated by the imposed lamellar microstructure. This frustration is likely at the root of the observed deviation from Tanner’s law: droplet spreading has a much slower power law ( m ∼ 0.05±0.01 . We show that the different spreading dynamics can be reconciled with conventional theory if a strain-rate-dependent viscosity is taken into account.
PACS: 83.80.Uv Block copolymers – / 68.08.Bc Wetting – / 82.35.Gh Polymers on surfaces; adhesion – / 47.55.D- Drops and bubbles –
© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg, 2009