Luisa Andruzzi

Coatings based on side-chain ether-linked poly(ethylene glycol) and fluorocarbon polymers for the control of marine biofouling.

The preparation of side group modified polystyrene-based surface-active block copolymers (SABC) for use as marine fouling resistance/release applications is described. Modifying moieties such as poly(ethylene glycol) (PEG) and semifluorinated segments were used. A novel bilayer methodology has been employed that provides both suitable mechanical properties through the use of an elastomeric primer layer of styrene-ethylene/butylene-styrene (SEBS) and control of surface-chemistry through use of the SABCs. This approach has potential as a cost-effective technology for environmentally benign coatings that resist and release marine biofouling. Initial testing of these materials included determination of captive bubble contact angles and protein adsorption. Testing against marine fouling organisms was performed using settlement and adhesion bioassays with zoospores of the green alga Enteromorpha . The results showed that all surfaces had markedly reduced levels of zoospore settlement compared with glass controls and that adhesion strength was strongly affected by the semifluorinated SABC. The results are discussed in terms of surface properties.

Engineering low surface energy polymers through molecular design: synthetic routes to fluorinated polystyrene-based block copolymers

New narrow polydisperse polystyrene-based block copolymers comprising fluorinated aromatic substituents in the side chains were synthesized following two different synthetic routes: (i) TEMPO-mediated controlled radical polymerization of fluorinated styrene monomers; (ii) A sequence of polymer modification reactions on anionically formed polystyrene-block-polyisoprene block copolymers. Using the former route, AB diblock and ABA triblock copolymers were obtained in which a block of polystyrene bearing a fluorocarbon chain substituent with a range of nCF2 groups (n = 4, 6, or 8) was incorporated as B block. Following the latter route, polystyrene-block-polyisoprene AB diblock copolymers were prepared by anionic polymerization and then modification by introduction of fluorinated tails with different numbers of CF2 groups (n = 6 or 8). The thermal behavior as well as the bulk microstructure of the fluorinated block copolymers were investigated and the effect of the chemical structure on the properties was evaluated. All the samples showed a tendency to form layered mesophases in the bulk, and increasing the length of the fluorocarbon tail of the side chain enhanced the degree of order of the mesophase from a disordered smectic (n = 4 or 6) to ordered pseudohexagonal smectic (n = 8). Contact angles of block copolymer films were measured using water as the wetting medium. Values of advanced contact angles up to 130° (120° receded angles) were found which were quite constant over prolonged immersion times in water.

Fluorinated mesogen-jacketed liquid-crystalline polymers as surface-modifying agents: Design, synthesis and characterization†

Monomers with semifluorinated tails on monomeric vinyl hydroquinone cores were synthesized and their polymerization behavior was examined. The resulting semifluorinated mesogen-jacketed liquid-crystalline polymers (MJLCPs) proved to form fairly hydrophobic surfaces with water contact angles of 110–118°. These polymers were studied for the role of the fluorinated groups on both liquid-crystalline (LC) behavior and surface properties. Initial surface stability studies showed that these fluorinated MJLCP surfaces are relatively more stable than comparable systems of side-chain fluorocarbon LC blocks. Our studies show that M(1), 2,5-bis[(10-perfluorohexyl-decanoyl)oxy]styrene, could not be homopolymerized, while M(2) incorporating benzoate groups, 2,5-bis[4-(10-perfluorohexyl-decanyloxy)benzyloxy]styrene, permitted facile homopolymerization and block copolymer preparation by stable free-radical polymerization. As determined by wide-angle X-ray diffraction, the SCN transition temperature of the block copolymer shifted to a higher temperature with an increase in the DP of M(2). NEXAFS studies showed no net orientation of the (CF2)n side chains towards the surface normal consistent with observed low order smectic phases, nevertheless pointed to the presence of fairly hydrophobic CF2-covered surfaces. The above evidence proved the materials are suitable for application as surface-modifying agents. Polarized optical micrograph of M(1) showing a mosaic texture due to a smectic mesophase obtained on slow cooling at 2 K min−1 from the isotropic phase.

Methacrylic polymers containing permanent dipole azobenzene chromophores spaced from the main chain: synthesis and characterization

Three photochromic monomers containing a permanent dipole photochromic azobenzene group separated from the methacryloyl moiety by a polymethylene spacer, namely 4-(4-oxy-4′-cyanoazobenzene)but-1-yl methacrylate, 6-(4-oxy-4′-cyanoazobenzene)hex-1-yl methacrylate, and 8-(4-oxy-4′-cyanoazobenzene)oct-1-yl methacrylate, were synthesized in three steps starting from 4-cyanoaniline. These monomers were homopolymerized and copolymerized with an optically active monomer, (−)-menthyl methacrylate, in the presence of AIBN as a radical initiator. The polymeric materials, having a molar content of photochromic units comprised between 5 and 100% and molecular weights of about 15000, were characterized by an almost random distribution of monomeric units and a glass transition temperature ranging from 35 to 131°C. Polymer samples having a content of aromatic units larger than 75% were characterized by a thermotropic liquid crystalline structure, as evidenced by optical microscopy, X-ray diffraction and DSC measurements. Two-dimensional correlations spectroscopy (COSY) allowed an appreciable contribution by intramolecular charge transfer mesomers to the electronic distribution of the azobenzene chromophore to be highlighted.

Structural organisations in polystyrene-based semifluorinated block copolymers for low surface energy coatings

SummariesNew narrow-polydispersity AB block copolymers were prepared by 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO)-mediated, controlled radical polymerisation. The A block was a poly(styrene) block, and the B block was a semifluorinated block, using either a poly(styrene) or a polyacrylate backbone. The semifluorinated side segments self-assembled into smectic mesophases. The bulk morphology and the interplay between microphase separation and liquid crystalline order were examined using transmission electron microscopy (TEM) and x-ray scattering. Near-edge x-ray absorption fine structure (NEXAFS) studies revealed that the semifluorinated side groups were ordered and titled at the outer surface of polymer films and allowed evaluation of the orientational order parameters. The orientational order parameter of the C-F bonds of the semifluorinated side groups at the surface was correlated with the critical surface tension of the polymer that had been extrapolated from Zisman plots with n-alkanes as the interrogating liquidsRésuméDe nouveaux copolymères à blocs AB et à polydispersité étroite ont été préparés par le moyen de la polymérisation radicale contrôlée 2,2,6,6-tetraméthylpiperidin-1-yloxy (TEMPO)-mediated. Le bloc A était un bloc poly(styrène) et le bloc B était un bloc semifluoré avec une épine dorsale de polystyrène ou de polyacrylate. Les segments latéraux semifluorés se sont rassemblés en mésophase smectique. On a examiné la morphologie de masse aussi bien que l’interaction entre la séparation de microphase et l’ordre cristal liquide, grâce à l’utilisation de la microscopie électronique en transmission (TEM) et la diffraction des rayons x. Des études des bords faites grâce à la spectroscopie d’absorption x à structure fine (NEXAFS) ont révélé que les groupes latéraux semifluorés étaient en ordre et inclinés à la surface extérieure des feuils polymériques et ont permis l’évaluation des paramètres d’ordre d’orientation. Le paramètre d’ordre d’orientation des liens C-F des groupes latéraux semifluorés qui se trouvaient à la surface était en rapport avec la tension superficielle critique du polymère qui avait été extrapolee des graphiques Zisman avec des n-alcanes comme liquides d’interrogation.ZusammenfassungNeue eng-polydisperse AB Block-Copolymere wurden hergestellt mittels 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO)-kontrollierter radikaler Polymerasation. Der A-Block war ein Polystyrenblock, der B-Block ein semifluorinierter Block auf einem Polystyren oder einem Polyacrylatgerüst. Die semifluorinierten Seitensegmente arrangierten sich spontan in smetische Mesphasen. Wir untersuchten die Morphologie und das Verhältnis zwischen Mikrophasenseparation und der Flüssigkristallordnung mittels Transmission Electron Mikroskopie (TEM) und Röntgenstrahl-Scattering. Eine Studie mit Nearedge x-ray absorption fine structure (NEXAFS) ergab, daß die semifluorinierten Seitenketten sich gedreht an der Außenoberfläche des Polymerfilms angeordnet hatten. Dies erlaubte uns, die Parameter der Orientierungsordnung zu bewerten. Die Parameter der Orientierungsordnung der C-F Bindungen der semifluorinierten Seitenketten auf der Oberfläche korellierte mit der kritischen Oberflächenspannung des Polymeres, die wir mittels Zisman-Grafiken (unter Verwendung von n-Alkenen) ermittelt hatten.