Easy orientation of diblock copolymers on self-assembled monolayers using UV irradiation

A simple method based on UV/ozone treatment is proposed to control the surface energy of dense grafted silane layers for orientating block copolymer mesophases. Our method allows one to tune the surface energy down to a fraction of a mN/m. We show that related to the surface, perpendicular orientation of a lamellar phase of a PS-PMMA diblock copolymer (neutral surface) is obtained for a critical surface energy of 23.9-25.7 mN/m. Perpendicular cylinders are obtained for 24.6 mN/m and parallel cylinders for 26.8 mN/m.Comment: 3 figures, 1 tabl

Organization of Block Copolymers using NanoImprint Lithography: Comparison of Theory and Experiments

We present NanoImprint lithography experiments and modeling of thin films of block copolymers (BCP). The NanoImprint lithography is used to align perpendicularly lamellar phases, over distances much larger than the natural lamellar periodicity. The modeling relies on self-consistent field calculations done in two- and three-dimensions. We get a good agreement with the NanoImprint lithography setups. We find that, at thermodynamical equilibrium, the ordered BCP lamellae are much better aligned than when the films are deposited on uniform planar surfaces

Two Methods for One-Point Anchoring of a Linear Polysaccharide on a Gold Surface

Two strategies to achieve a one-point anchoring of a hydrolyzed pullulan (P9000) on a gold surface are compared. The first strategy consists of forming a self-assembled monolayer of a 6-amino-1-hexanethiol (AHT) and then achieving reductive amination on the surface between the aminated surface and the aldehyde of the polysaccharide reductive end sugar. The second consists of incorporating a thiol function at the extremity of the pullulan (via the same reductive amination), leading to P9000-AHT and then immobilizing it on gold by a spontaneous reaction between solid gold and thiol. The modified pullulan was characterized by NMR and size-exclusion chromatography coupled to a light-scattering detector. P9000-AHT appears to be in a disulfide dimer form in solution but recovers its unimer form with dithiothreitol (DTT) treatment. The comparison of the two strategies by contact angle and XPS revealed that the second strategy is more efficient for the pullulan one-point anchoring. P9000-AHT even in its dimer form is easily grafted onto the surface. The grafted polymer seems to be more in a coil conformation than in a rigid brush. Furthermore, QCM measurements highlighted that the second strategy leads to a grafting density of around 3.5 × 10¹³ molecules·cm^–2 corresponding to a high surface coverage. The elaboration of a dense and oriented layer of polysaccharides covalently linked to a gold surface might enhance the use of such modified polysaccharides in various fields

Carboxymethylpullulan Grafted with Aminoguaiacol: Synthesis, Characterization, and Assessment of Antibacterial and Antioxidant Properties

Aminoguaiacol, the aminated derivative of guaiacol, a natural phenolic compound, was chemically grafted onto a polysaccharide (carboxymethylpullulan, CMP) in the presence of the activator agent 1-ethyl-3-(3-(dimethylamino)­propyl)­carbodiimide hydrochloride (EDCI). The grafted polysaccharides were characterized by FTIR and ¹H NMR spectroscopy to confirm and quantify the grafting. All polysaccharide derivatives (grafting rates of aminoguaiacol between 16% and 58%) were soluble in water. Their physicochemical properties were studied in a dilute regime and a semidilute regime by light scattering, fluorescence, and rheology, showing associative properties with peculiar polysoap behavior. The antibacterial activities of the synthesized products against Staphyloccocus aureus were assessed using a counting method. The antioxidant activities of the derivatives were also highlighted using the α,α-diphenyl-β-picrylhydrazyl (DPPH) method. Finally, the cytotoxicity of the derivatives was studied with fibroblast cells and they showed a very good cytocompatibility. Such polymers could be used to replace chemical preservatives in food and cosmetic aqueous formulations