30.5. Tailoring of optical transmittance, reflectance, and hydrophobicity of polymers by micro- and nanoscale structuring

Public examination of a doctoral dissertation in the field of chemistry

Doctoral candidate: M.Sc. Inka Saarikoski 

Date and venue: 30.5.2011, at 12 noon, Auditorium F100, Futura, Joensuu campus



Antireflective and self-cleaning surfaces are increasingly in demand in everyday applications. Many chemical and physical methods exist to produce such antireflective and self-cleaning surfaces. In this work, the optical properties of polycarbonate (PC) and the hydrophobicity of cycloolefin copolymer (COC), polycarbonate, and two acrylic thermoplastic elastomer (TPE) surfaces were modified by micro- and nanoscale structuring. 

The optical transmittance and reflectance properties of polycarbonate were tailored by applying a nanoporous anodized aluminum oxide (AAO) coating to the PC surface and by structuring the surface with nanopillars of different dimensions. The reflectance values for uncoated and smooth PC surfaces were between 5.0 and 6.5%. Both coating and structuring of PC sheet increased the transmittance and decreased the reflectance over the whole wavelength range of visible light. At best, the reflectance decreased to less than 1% with both nanostructuring methods.  

The hydrophobicity of COC, PC, and TPE surfaces was modified by patterning with micro-, nano-, and hierarchical micro-nanostructures. Structured polymer disks were prepared by injection molding with the aid of micro-, nano-, and hierarchically structured mold inserts. COC was also structured by imprinting method. The effects of the different sizes and scales of structures on the properties of polymer surfaces were investigated with contact angle measurements of water and oleic acid. After structuring, all polymer surfaces were clearly hydrophobic. The water contact angle increased most, for all investigated polymers, with the addition of hierarchical micro-nanostructure. A water contact angle of 164° was measured for a TPE surface with nanograss-covered nail-like micropillars: superhydrophobicity with close to zero degree sliding angle was achieved. Relative to the smooth TPE surface the water contact angle was increased by 88°

The doctoral dissertation of Inka Saarikoski entitled “Tailoring of optical transmittance, reflectance, and hydrophobicity of polymers by micro- and nanoscale structuring"  will be examined at the Faculty of Science and Forestry. The opponent in the public examination is Professor Helge Lemmetyinen, Tampere University of Technology and the custos is Professor Tapani Pakkanen of the University of Eastern Finland.

Photo available for download at http://www.uef.fi/vaitoskuvat

Contact: Inka Saarikoski, inka.saarikoski@uef.fi, tel. +358 40 735 7751

Publishing year: 2011

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