Aligned Cellulose Nanocrystals and Directed Nanoscale Deposition of Colloidal Spheres

Supporting Information

Aligned Cellulose Nanocrystals and Directed Nanoscale Deposition of Colloidal Spheres

Gustav Nyström, Andreas B. Fall, Linn Carlsson and Lars Wågberg

G. Nyström, A. B. Fall, L. Carlsson, L. Wågberg

KTH Royal Institute of Technology, School of Chemical Science and Engineering, Dept. of Fibre and Polymer Technology and Wallenberg Wood Science CentreTeknikringen 56-58, SE-100 44 Stockholm, Sweden.

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Contents

1. Photograph of PDMS template

2. Atomicforce micrograph of pristine colloidal spheres

3. Water contact angle measurements on surfaces with aligned cellulose nanocrystals

1. Photograph of PDMS template

In Figure S1 a photograph of wrinkled PDMS is shown. The stamp measures 60*20 mm2 and the area exposed to the air plasma is clearly seen as blue and green color shifts due to interference. This qualitatively confirms the presence of wrinkled features with similar wavelengths as visible light. For analysis convenience, in the alignment experiments smaller pieces of wrinkled PDMS (5*2 mm2) was cut from the larger stamp. Scale up, using the whole area of the stamp below or even larger stamps, should however be possible.

Figure S1. Photograph showing a 60*20 mm2 piece of wrinkled PDMS template.

2. Atomicforce micrographs of pristine colloidal spheres

Figure S2 shows atomicforce microscopy (AFM) micrographs of the cationic latex particles used in this study. Individual particles are seen and they are relatively monodisperse in size. From z profiles across the surfaces a rough estimate of the particle diameter of 75 nm was found. This corresponds well to values obtained from dynamic light scattering (not shown).

Figure S2.AFM height images showing spherical cationic latex nanoparticles deposited on a cellulose model surface (spin casted from NMMO cellulose solution). The scale bars correspond to 1 micrometer in both images and the height scale also applies for both images.

3. Water contact angle measurements on surfaces with aligned cellulose nanocrystals

Figure S3a shows water contact angle on a freshly printed surface with CNC onto a Si-PEI substrate. A contact angle of 23.4° ± 6.7° was found which is slightly lower than the contact angle found for the pristine Si-PEI substrate (35.3° ± 1.2°) and slightly higher than that for the pristine cellulose CNC particle film (14.9° ± 2.0°), see Figure S3b,c (all values are expressed as mean ± standard deviation for n=3). This shows that the surface is not made more hydrophobic as a result of the printing process as could have been anticipated from the contact with the PDMS stamp during particle transfer.S1 The slightly lower contact angle found for the CNC printed surface (Figure S3a) most likely results from the transferred highly hydrophilic CNC (Figure S3c).

Figure S3. Water contact angles on freshly prepared surfaces of printed CNC on Si-PEI (a), pristine Si-PEI (b) and thin cellulose CNC films casted from dispersion onto silica surface (c).

References

S1J. A. Wigenius, M. Hamedi, O. Inganäs, Adv Funct. Mater.2008, 18, 2563.