Cyan Ni1-xAl2+2x/3□x/3O4 single phase pigments synthesis and modification for electrophoretic inks formulation

Béatrice Serment (1, 2, 3) , Manuel Gaudon (1) , Alain Demourgues (1) , Amélie Noël (3, 2) , Guillaume Fleury (3, 2) , Eric Cloutet (3, 2) , Georges Hadziioannou (3, 2) , Cyril Brochon (3, 2)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Team 4 LCPO : Polymer Materials for Electronic, Energy, Information and Communication Technologies
3 LCPO - Laboratoire de Chimie des Polymères Organiques

Cyan Ni1-xAl2+2x/3O4 single phase pigments with various Ni:Al atomic ratios (from 1:2 down to 1:4) have been prepared by sol gel route (Pechini) followed by post-annealing treatments. Nickel aluminates crystallize in the well-known spinel structure (Fd-3m space group) where metals are located at two different Wyckoff positions: 16d (octahedron) and 8a (tetrahedron). Based on XRD Rietveld refinements, Ni 2+ cations are shown to be partially located in both tetrahedral and octahedral sites and, in addition, cationic vacancies occupy Oh environment. In the pure phase series, Ni/Al = 0.35, 0.40, 0.45, as the Al content increases, the Ni 2+ rate in Td site decreases for Ni/Al=0.45, thus altering the cyan color ; within this series, the most saturated cyan coloration is reached for the highest Al concentration. Inorganic pigment drawbacks are their high density and hydrophilic surface, which induced sedimentation and aggregation in non-polar media used in electrophoretic inks. Hybrid core shell particles pigments have been synthesized from cyan pigments by using nitroxide mediated radical polymerization (NMRP) with methyl methacrylate monomer in isopar G leading to a dispersion of electrically charged hybrids in apolar media. Surface functionalization of the pigments by OTS and DTS modifiers have been compared. The 2 inorganic pigments are successfully encapsulated by organic shells to allow a strong decrease of their density. Cyan inks, adequate for their use in e-book readers or other electrophoretic displays, taking further advantage of the high contrast ratio and reflectivity of inorganic pigments as regards to organic dyes, have been stabilized.

Mots clés: Electrophoretic inks; cyan pigment; spinel; hybrids particles; Pechini; dispersion polymerization

Domaines: Polymères; Chimie inorganique; Science des matériaux [cond-mat.mtrl-sci]; Matériaux

Béatrice Serment, Manuel Gaudon, Alain Demourgues, Amélie Noël, Guillaume Fleury, et al.. Cyan Ni1-xAl2+2x/3□x/3O4 single phase pigments synthesis and modification for electrophoretic inks formulation. ACS Omega, 2020, ⟨10.1021/acsomega.0c01289⟩. ⟨hal-02908162⟩