1. Nano-channel Creation in a Polymer Thin Film Studied by GISAXS
Xuefa Li, Christopher K. Ober
Sol M. Gruner, Detlef-M Smilgies
Lewis Fetters
Dept. of Materials Science & Engineering
Dept. of Physics
CHESS

2. The Idea C H 2 3 x y n m b 1 2
A two-step strategy was developed to create nano-channels: In step 1 a low-dose
UV was used to crosslink the matrix. In step 2 a high-dose UV was used to
decompose the cylinder phase.

3. AFM Results Poly(isoprene-b--methylstyrene) diblock copolymer: 2 m
Before UV exposure
After UV exposure
Poly(isoprene-b--methylstyrene) diblock copolymer:
Cylinders stand up in the thin film (left). After poly(-methylstyrene) blocks were selectively
decomposed by UV exposure, hydrophobic nano-channels were created (right).

4. GISAXS Scattering Geometry-ID
side view S3 S2 S1
beam
stop
top view
α: incident angle
β: exit angle
ψ: scattering angle

5. GISAXS Scattering Geometry-IIqz
SAXS:
lateral surface
structure
diffuse XR:
normal density profile
q
Scattering plane
Surface plane
thin film

6. Nano-channel Creation-I
Before UV exposure
After UV exposure
Poly(isoprene-b--methylstyrene) diblock copolymer:
Hydrophobic nano-channels form in the thin film and still stand up after poly(-methylstyrene)
blocks were selectively decomposed by UV exposure.

7. Nano-channel Creation-II
Before UV exposure
After UV exposure
Poly(hydroxy-styrene-b--methylstyrene) diblock copolymer:
Hydrophilic nano-channels form in the thin film and stand up after poly(-methylstyrene)
blocks were selectively decomposed by UV exposure.

8. Effect of Photo-crosslinker
Before UV
after UV
A thin film without photo-crosslinker shows standing-up cylinders before expose
to UV. After UV decomposes poly(-methylstyrene) block, the nano-channels
collapse due to the soft matrix. Therefore, a photo-crosslinker is essential.

9. Annealing Effect Fresh film 2 hr annealing 24 hr annealing
Poly(isoprene-b--methylstyrene) block copolymer in freshly spin-coated
thin film forms standing-up cylinders. After annealing, the cylinders tend to lie
parallel to the substrate.

10. Application of GISAXS Mixed lamellar domains Micelles Cylinders
parallel and normal
to substrate
Micelles
on substrate
Cylinders
parallel to substrate

11. Summary Acknowledgement CCMR and NSF for financial support
Poly(isoprene-b--methylstyrene) diblock copolymer forms standing-up
cylinders in the thin films. With added photo-crosslinker, the poly(isoprene)
matrix can be selectively crosslinked and poly(-methylstyrene)
block can be decomposed by using a two-step UV exposure strategy.
The nano-channels were created as proved by both AFM and GISAXS.
Acknowledgement
CCMR and NSF for financial support
CHESS, CNF and CCMR for facility uses.
Prof. Gruner group