TY  - JOUR
A1  - Pester, Christian W.
A1  - Schmidt, Kristin
A1  - Ruppel, Markus
A1  - Schoberth, Heiko G.
A1  - Böker, Alexander
T1  - Electric-Field-Induced Order-Order Transition from Hexagonally Perforated Lamellae to Lamellae
JF  - Macromolecules : a publication of the American Chemical Society
N2  - Block copolymers form a variety of microphase morphologies due to their ability to phase separate. The hexagonally perforated lamellar (HPL) morphology represents an unusually long-lived, nonequilibrium transient structure between lamellar and cylindrical phases. We present a detailed study of a concentrated, HPL-forming poly(styrene-b-isoprene) diblock copolymer solution in toluene in the presence of an electric field. We will show that this phase is readily aligned by a moderate electric field and provide experimental evidence for an electric-field-induced order order transition toward the lamellar phase under sufficiently strong fields. This process is shown to be fully reversible as lamellar perforations reconnect immediately upon secession of the external stimulus, recovering highly aligned perforated lamellae.
Y1  - 2015
U6  - https://doi.org/10.1021/acs.macromol.5b01336
SN  - 0024-9297
SN  - 1520-5835
VL  - 48
IS  - 17
SP  - 6206
EP  - 6213
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kathrein, Christine C.
A1  - Pester, Christian
A1  - Ruppel, Markus
A1  - Jung, Maike
A1  - Zimmermann, Marc
A1  - Böker, Alexander
T1  - Reorientation mechanisms of block copolymer/CdSe quantum dot composites under application of an electric field
JF  - Soft matter
N2  - Time- and temperature-resolved in situ birefringence measurements were applied to analyze the effect of nanoparticles on the electric field-induced alignment of a microphase separated solution of poly(styrene)-block-poly(isoprene) in toluene. Through the incorporation of isoprene-confined CdSe quantum dots the reorientation behavior is altered. Particle loading lowers the order-disorder transition temperature, and increases the defect density, favoring nucleation and growth as an alignment mechanism over rotation of grains. The temperature dependent alteration in the reorientation mechanism is analyzed via a combination of birefringence and synchrotron SAXS. The detailed understanding of the effect of nanoparticles on the reorientation mechanism is an important prerequisite for optimization of electricfield-induced alignment of block copolymer/nanoparticle composites where the block copolymer guides the nanoparticle self-assembly into anisotropic structures.
Y1  - 2016
U6  - https://doi.org/10.1039/c6sm01073c
SN  - 1744-683X
SN  - 1744-6848
VL  - 12
SP  - 8417
EP  - 8424
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -