Introducing Photo-Cross-Linkable Functionalities on P(VDF-co-TrFE) Ferroelectric Copolymer.

Ferroelectric polymers have emerged as crucial materials for the development of advanced organic electronic devices. Their recent high-end commercial applications as fingerprint sensors have only increased the amount of scientific interest around them. Despite an ever-larger body of studies focusing on optimizing the properties of ferroelectric polymers by physical means (e. g., annealing, stretching, blending or nano-structuring), post-polymerization chemical modification of such polymers has only recently become a field of active study with great promise in expanding the scope of those polymers. In this work, a solution-based post-polymerization modification method was developed for the safe and facile grafting of a plethora of functional groups to the backbone of commercially available Poly(vinylidene fluoride-co-trifluoroethylene P(VDF-co-TrFE) ferroelectric polymers. To showcase the versatility of this approach, photosensitive groups were grafted onto the polymeric backbone, enabling them to undergo photo-cross-linking. Finally, these modified polymers were used as functional negative photoresists in a photolithographic process, highlighting the potential of this method to integrate ferroelectric fluorinated electroactive polymers into standard electronic microfabrication production lines.

The versatile Co2+/Co3+ oxidation states in cobalt alumina spinel: how to design strong blue nanometric pigments for color electrophoretic display.

Blue cobalt inorganic pigments with spinel-type structure have been revisited in order to understand the origin of blackening at low temperatures and to design strong blue nanosized materials. Starting from a sol-gel process, the so-called Pechini route, the correlation between the structural features (inversion rate, Co over-stoichiometry, Co valence states) of the spinel network and its thermal history under air up to high temperatures (T = 1400 °C) allows concluding that the stabilization of CoIII in octahedral sites is at the origin of the blackening of the pigment annealed at low and medium temperatures. EELS coupled with TEM analyses (occurrence of multiple phases with various Al/Co atomic ratios) lead to us to conclude definitively about the variation of Co valence states. A top-down (mechanical grinding) and a bottom-up approach lead to the definition of a synthesis route (co-precipitation in basic medium followed by annealing at medium temperatures under Ar) allowing the design of strong blue pure nano-sized pigments to be incorporated in inks. Hybrid blue positively charged particles were mixed with white negatively charged particles to formulate dual-colour inks. A dual-colour display was filled with the as-prepared inks and tested under ±150 V.

Design of colored multilayered electrophoretic particles for electronic inks.

The preparation of multilayered latex particles with surface functional groups suitable for use as electrophoretic particles in electronic inks has been studied. The particles are formed by dispersion polymerization and have a polystyrene core, slightly cross-linked with divinylbenzene (DVB), and a poly(methyl methacrylate) (PMMA) or a poly(acrylic acid) (PAA) shell. After grafting alkyl chains on their surface, the particles are negatively or positively charged and sterically stabilized against aggregation in nonpolar solvent. The particles were dyed by incorporation of Nigrosin during polymerization or by swelling in supercritical CO(2) in the presence of a dye. Particle size, morphology, incorporated dye content and zeta potential were determined. A dual-particle electronic ink based on a mixture of the colored multilayered particles and white hybrid TiO(2)-polymer particles was prepared and electro-optically tested.

Self-assembly of rod-coil block copolymers from weakly to moderately segregated regimes.

We report on the self-assembly behaviour of two homologue series of rod-coil block copolymers in which, the rod, a pi -conjugated polymer, is maintained fixed in size and chemical structure, while the coil is allowed to vary both in molecular weight and chemical nature. This allows maintaining constant the liquid crystalline interactions, expressed by Maier-Saupe interactions, omega , while varying the tendency towards microphase separation, expressed by the product between the Flory-Huggins parameter and the total polymerization degree, chi N . Therefore, the systems presented here allow testing directly some of the theoretical predictions for the self-assembly of rod-coil block copolymers in a weakly segregated regime. The two rod-coil block copolymer systems investigated were poly(DEH-p-phenylenevinylene-b-styrene), whose self-assembly takes place in the very weakly segregated regime, and poly(DEH-p-phenylenevinylene-b-4vinylpyridine), for which the self-assembly behaviour occurs under increased tendency towards microphase separation, hereby referred to as moderately segregated regime. Experimental results for both systems are compared with predictions based on Landau expansion theories.