Synthesis of Oligosaccharide-Based Block Copolymers with Pendent Conjugated Oligofluorene Moieties and Their Electrical Device Applications
Journal
Macromolecules
Journal Volume
48
Journal Issue
12
Pages
3907-3917
Date Issued
2015
Author(s)
Abstract
We report the synthesis and electric device applications of oligosaccharide-based diblock copolymers consisting of a maltoheptaose (MH) block and a poly(4-oligofluorenylstyrene) block (PStFln, n = 1 or 2), referred to as MH-b-PStFln. MH-b-PStFln was prepared by the Cu(I)-catalyzed click reaction of azido-terminated PStFln (PStFln-N3), which was obtained from the azidation reaction of the bromo-terminated PStFln (PStFln-Br), with excess ethynyl-terminated MH in the THF/DMF mixture solvent. The resulting diblock copolymers self-assembled to spherical microdomains with sub-10 nm sizes in both bulk and thin film state after annealing process. Thereafter, the MH-b-PStFln thin film (50 nm) with the self-assembled nanoscale spherical aggregates was used as the charge storage layer for the pentacene-based field-effect transistor type memory devices. The MH-b-PStFln-based devices had the excellent hole mobility (0.25-0.52 cm2 V-1 s-1) and the high ON/OFF current (ION/IOFF) ratio of 107-108, of which the MH-b-PStFl1-based one had the higher mobility than that of the MH-b-PStFl2-based one because the pentacene crystal in the former device possessed the larger grain size and fewer boundaries. On the other hand, the MH-b-PStFl2-based device showed a larger memory window than the MH-b-PStFl1-based one because the stronger electron-donating effect of the difluorenyl group in MH-b-PStFl2 increased the charge storage capability of its related device. All the memory devices showed a long-term retention time over 104 s with the high ION/IOFF ratio of 106-108. Among these devices, the MH-b-PStFl1-based device showed a good WRER endurance over 180 cycles. This work not only demonstrates the tunable electrical memory characteristics by adjusting the conjugation length of the oligofluorenyl side chain in the polymer electret but also provides a promising approach for developing the next-generation green electronics using natural materials.
SDGs
Type
journal article