Semifluorinated Aromatic Side-Group Polystyrene-Based Block Copolymers:  Bulk Structure and Surface Orientation Studies

Abstract

Two families of narrow polydispersity poly(styrene)-based block copolymers bearing side groups containing both a phenyl ring and a para-linked semifluorinated side group were designed to produce stable low energy surfaces. The effects of the phenyl ring on the surface and bulk structure of the materials were investigated. The semifluorinated side chains were found to self-assemble into liquidcrystalline smectic layers within the microphase domains. An unexpected enhancement of surface organization by the aromatic group was observed. The bulk morphology and the interplay between microphase separation and liquid crystalline self-assembly were examined using transmission electron microscopy and X-ray scattering. Near-edge X-ray absorption fine structure (NEXAFS) studies were used to probe the surface coverage of the fluorinated segments. NEXAFS also allowed the determination of the orientation parameters (S C-F and Sπ*) of the C-F bond and phenyl ring of the semifluorinated side groups at the surface. On the basis of these data, the orientational coupling between the -CF2-helix and the aromatic ring was found to depend on the length of the fluorocarbon substituent.

Analysis of the surface density and reactivity of perfluorophenylazide and the impact on ligand immobilization

“…This resonance is commonly related to the p* resonance from C¼C bonds. [32][33][34][35][36][37][38] However, upon fluorination, the p* C¼C resonance is shifted by as much as 5 eV, 21,37 and therefore, the peak at 289.2 eV (labeled 4) is also related with the F-C*¼C-F p* resonance. In addition, the two PFPA-MUTEG/MDEG mixed films present a shoulder at 288.2 eV (labeled 3) and a peak at 289.8 (labeled 5).…”

“…The slides were then coated with a 2 nm thick Ti adhesion layer followed by a 45 nm thick gold film in an electron beam evaporator (SEC-600, CHA) at the Washington Nanofabrication Facility (University of Washington). Immediately before they were chemically functionalized, these substrates were cleaned by soaking them in the piranha solution for 30-45 s at 35 C followed by washing in boiling water three times for 20 min each. The substrates were then washed with milli-Q water followed by ethanol before soaking in the thiol solution for monolayer formation.…”

Síntese de copolímeros em bloco com propriedades líquido cristalinas

“…Desde então, uma série de trabalhos que envolvem rotas para produção dos mesmos foram sendo apresentados [5][6][7][8][9][10][11][12] . Pesquisadores italianos da Università di Piza e da Università di Bologna foram os que mais contribuíram para o desenvolvimento dessa área de pesquisa.…”

Low threshold voltage asymmetric antiferroelectric liquid crystal cells

“…It consists in replacing the thermally evaporated inorganic oxide by a spin coated fluorinated block copolymer (FBC). FBC provides low surface energy layers because the mutual incompatibility of the chemically different polymer blocks enhances surface segregation of the fluorinated polymer block [6]. Fluorinated polymers in fact exhibit very low values of sur-face tension (g s < 15-20 mN/m) [6][7][8] and might be exploited for new alignment layers of liquid crystals cells with slippery surfaces.…”

“…FBC provides low surface energy layers because the mutual incompatibility of the chemically different polymer blocks enhances surface segregation of the fluorinated polymer block [6]. Fluorinated polymers in fact exhibit very low values of sur-face tension (g s < 15-20 mN/m) [6][7][8] and might be exploited for new alignment layers of liquid crystals cells with slippery surfaces. A long term multistable grey level tuning of voltage shift when using the FBC as a low energy surface has been obtained as well [9].…”