TY - JOUR
T1 - Structural details and digital memory performances of difluorene-containing diblock copolymers in nanoscale thin films
AU - Wi, Dongwoo
AU - Ree, Brian J.
AU - Ahn, Byungcheol
AU - Hsu, Jung Ching
AU - Kim, Jehan
AU - Chen, Wen Chang
AU - Ree, Moonhor
N1 - Publisher Copyright:
© 2015 Elsevier Ltd
PY - 2016/8/1
Y1 - 2016/8/1
N2 - Amphiphilic poly(4-di(9,9-dihexylfluoren-2-yl)styrene)-b-poly(2-vinylpyridine)s (PStFl2m-b-P2VPn) in two different compositions and their homopolymers were synthesized: PStFl211-b-P2VP89 (50/50, volume ratio), PStFl212-b-P2VP33 (75/25), PStFl2, and P2VP. They were thermally stable up to around 350 °C. In nanoscale thin films, the diblock copolymers exhibited various phase-separated nanostructures depending on the composition and film process condition: random two phases, horizontal hexagonal P2VP cylinders, and hexagonally-close packed (HCP) P2VP spheres. Surprisingly, the hexagonal cylinder and HCP sphere structures are quite different from those of common diblock copolymers with similar compositions. The structural details of these thin film morphologies were investigated by synchrotron grazing incidence X-ray scattering. The thin film morphologies were found to make influences on the electrical memory performances of the polymers. In particular, the switching-ON voltage was influenced by the nanostructures and the film layer thickness as well as by the composition. Overall, the diblock copolymer films demonstrated excellent p-type permanent digital memory behaviors with unipolarity, long retention time, high ON/OFF current ratio and low power consumption. These memory behaviors were governed by a trap-limited space charge limited conduction mechanism combined with ohmic conduction and a hopping process.
AB - Amphiphilic poly(4-di(9,9-dihexylfluoren-2-yl)styrene)-b-poly(2-vinylpyridine)s (PStFl2m-b-P2VPn) in two different compositions and their homopolymers were synthesized: PStFl211-b-P2VP89 (50/50, volume ratio), PStFl212-b-P2VP33 (75/25), PStFl2, and P2VP. They were thermally stable up to around 350 °C. In nanoscale thin films, the diblock copolymers exhibited various phase-separated nanostructures depending on the composition and film process condition: random two phases, horizontal hexagonal P2VP cylinders, and hexagonally-close packed (HCP) P2VP spheres. Surprisingly, the hexagonal cylinder and HCP sphere structures are quite different from those of common diblock copolymers with similar compositions. The structural details of these thin film morphologies were investigated by synchrotron grazing incidence X-ray scattering. The thin film morphologies were found to make influences on the electrical memory performances of the polymers. In particular, the switching-ON voltage was influenced by the nanostructures and the film layer thickness as well as by the composition. Overall, the diblock copolymer films demonstrated excellent p-type permanent digital memory behaviors with unipolarity, long retention time, high ON/OFF current ratio and low power consumption. These memory behaviors were governed by a trap-limited space charge limited conduction mechanism combined with ohmic conduction and a hopping process.
KW - Composition dependency
KW - Diblock copolymers
KW - Electrical memory behavior
KW - Film thickness dependency
KW - Grazing incidence X-ray scattering
KW - Morphology dependency
KW - Phase-separated nanostructures
KW - Switching mechanism
UR - http://www.scopus.com/inward/record.url?scp=84950291664&partnerID=8YFLogxK
U2 - 10.1016/j.eurpolymj.2015.12.011
DO - 10.1016/j.eurpolymj.2015.12.011
M3 - Article
AN - SCOPUS:84950291664
SN - 0014-3057
VL - 81
SP - 582
EP - 597
JO - European Polymer Journal
JF - European Polymer Journal
ER -