title: PVP-b-PEO block copolymers for stable aqueous and ethanolic graphene dispersions.
abstract: The ability to disperse pristine (unfunctionalized) graphene is important for various applications, coating, nanocomposites, and energy related systems. Herein we report that amphiphilic copolymers of poly(4-vinyl pyridine)-block-poly(ethylene oxide) (PVP-b-PEO) are able to disperse graphene with high concentrations about 2.6mg/mL via sonication and centrifugation. Ethanolic and aqueous highly-ordered pyrolytic graphite (HOPG) dispersions with block copolymers were prepared and they were compared with the dispersions stabilized by P-123 Pluronic® (P123) and poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) synthesized. Transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman and UV-visible spectroscopic studies confirmed that PVP-b-PEO block copolymers are better stabilizers for HOPG graphene than P123 and PS-b-PEO. X-ray photoelectron spectroscopy and force-distance (F-d) curve analyses revealed that the nitrogen of vinyl pyridine plays a vital role in better attractive interaction with surface of graphene sheet. Thermogravimetric analysis showed that larger amount of PVP-b-PEO was adsorbed onto graphene with longer poly(4-vinyl pyridine) (PVP) block length and in aqueous medium, respectively, and which was consistent with electrical conductivity decreases. This study presents the dispersion efficiency of graphene using PVP-b-PEO varies substantially depending on the lengths of their hydrophobic (PVP) domains.
authors.affiliation: Department of Applied Chemistry, Kyungpook National University, Buk-gu, Daehak-ro 80, Daegu 702-701, South Korea.
authors.forename: Suguna
authors.initials: S
authors.lastname: Perumal
authors.affiliation: Department of Applied Chemistry, Kyungpook National University, Buk-gu, Daehak-ro 80, Daegu 702-701, South Korea.
authors.forename: Kyung Tae
authors.initials: KT
authors.lastname: Park
authors.affiliation: Department of Applied Chemistry, Kyungpook National University, Buk-gu, Daehak-ro 80, Daegu 702-701, South Korea.
authors.forename: Hyang Moo
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Applied Chemistry, Kyungpook National University, Buk-gu, Daehak-ro 80, Daegu 702-701, South Korea. Electronic address: inwoo@knu.ac.kr.
authors.forename: In Woo
authors.initials: IW
authors.lastname: Cheong
keywords: Amphiphilic; Block copolymers; Dispersions; Graphene; Stabilizers