TY  - JOUR
A1  - Kopyshev, Alexey
A1  - Galvin, Casey J.
A1  - Genzer, Jan
A1  - Lomadze, Nino
A1  - Santer, Svetlana A.
T1  - Opto-mechanical scission of polymer chains in photosensitive diblock-copolymer brushes
JF  - Langmuir
N2  - In this paper we report on an opto-mechanical scission of polymer chains within photosensitive diblock-copolymer brushes grafted to flat solid substrates. We employ surface-initiated polymerization of methylmethacrylate (MMA) and t-butyl methacrylate (tBMA) to grow diblock-copolymer brushes of poly(methylmethacrylate-b-t-butyl methacrylate) following the atom transfer polymerization (ATRP) scheme. After the synthesis, deprotection of the PtBMA block yields poly(methacrylic acid) (PMAA). To render PMMA-b-PMAA copolymers photosensitive, cationic azobenzene containing surfactants are attached to the negatively charged outer PMAA block. During irradiation with an ultraviolet (UV) interference pattern, the extent of photoisomerization of the azobenzene groups varies spatially and results in a topography change of the brush, i.e., formation of surface relief gratings (SRG). The SRG formation is accompanied by local rupturing of the polymer chains in areas from which the polymer material recedes. This opto-mechanically induced scission of the polymer chains takes place at the interfaces of the two blocks and depends strongly on the UV irradiation intensity. Our results indicate that this process may be explained by employing classical continuum fracture mechanics, which might be important for tailoring the phenomenon for applying it to poststructuring of polymer brushes.
Y1  - 2013
U6  - https://doi.org/10.1021/la403241t
SN  - 0743-7463
VL  - 29
IS  - 45
SP  - 13967
EP  - 13974
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Yadavalli, Nataraja Sekhar
A1  - Saphiannikova, Marina
A1  - Lomadze, Nino
A1  - Goldenberg, Leonid M.
A1  - Santer, Svetlana A.
T1  - Structuring of photosensitive material below diffraction limit using far field irradiation
JF  - Applied physics : A, Materials science & processing
N2  - In this paper, we report on in-situ atomic force microscopy (AFM) studies of topographical changes in azobenzene-containing photosensitive polymer films that are irradiated with light interference patterns. We have developed an experimental setup consisting of an AFM combined with two-beam interferometry that permits us to switch between different polarization states of the two interfering beams while scanning the illuminated area of the polymer film, acquiring corresponding changes in topography in-situ. This way, we are able to analyze how the change in topography is related to the variation of the electrical field vector within the interference pattern. It is for the first time that with a rather simple experimental approach a rigorous assignment can be achieved. By performing in-situ measurements we found that for a certain polarization combination of two interfering beams [namely for the SP (a dagger center dot, a dagger") polarization pattern] the topography forms surface relief grating with only half the period of the interference patterns. Exploiting this phenomenon we are able to fabricate surface relief structures with characteristic features measuring only 140 nm, by using far field optics with a wavelength of 491 nm. We believe that this relatively simple method could be extremely valuable to, for instance, produce structural features below the diffraction limit at high-throughput, and this could significantly contribute to the search of new fabrication strategies in electronics and photonics industry.
Y1  - 2013
U6  - https://doi.org/10.1007/s00339-013-7945-3
SN  - 0947-8396
SN  - 1432-0630
VL  - 113
IS  - 2
SP  - 263
EP  - 272
PB  - Springer
CY  - New York
ER  -