Hyperbranched fluoropolymer-polydimethylsiloxane-poly(ethylene glycol) cross-linked terpolymer networks designed for marine and biomedical applications: heterogeneous nontoxic antibiofouling surfaces.

Synthesis of terpolymer coatings composed of hyperbranched fluoropolymers cross-linked with bisamino-propyl poly(ethylene glycol) and bisamino-propyl polydimethylsiloxane (PDMS) was performed to generate antibiofouling surfaces. Nanoscale imaging and surface spectroscopy confirmed that this system possessed complex surface topographies and chemical compositions. Surface complexity was determined to be due to molecular interactions, phase segregation, and compositional gradients arising between the three components. A clear difference in surface behavior was observable before and after exposure to water. Antibiofouling characteristics were investigated by bovine serum albumin (BSA) adsorption studies; the terpolymer coating displayed a 60% greater resistance to protein adsorption in comparison to the fouling of a commercial antibiofouling silicone coating. The unique surface topography, topology, and chemical heterogeneity expressed at a variety of scales provide a robust regime for the generation of hardy, complex surfaces known to incorporate characteristics appropriate for antibiofouling applications. Thorough assessment of thermal responses and mechanical properties in relevant environments demonstrated a formulation platform immediately appropriate for consideration in marine and in vivo applications.

Model Diels-Alder Studies for the Creation of Amphiphilic Cross-Linked Networks as Healable, Antibiofouling Coatings.

Diels-Alder (DA) chemistry was used in the construction of amphiphilic cross-linked polymer networks comprised of furan-functionalized hyperbranched fluoropolymers and maleimide-functionalized linear poly(ethylene glycol)s, which were designed as antibiofouling coatings capable of repair. Discrete molecules and a linear polymer analog were studied as model systems to understand the nature of the thermally reversible [4 + 2] cycloaddition reaction involving a tetrafluorobenzylfuranyl ether unit, which was part of the structure for the incorporation of the DA functionalities into the composite network materials. Atomic force microscopy confirmed the complex, nanoscopically resolved topography needed for antibiofouling. Bright field and fluorescence imaging monitored healing at damage sites as well as the ability of the coatings to resist protein adsorption.

Noradrenaline-functionalized hyperbranched fluoropolymer-poly(ethylene glycol) cross-linked networks as dual-mode, anti-biofouling coatings.

The strategy of decorating antibiofouling hyperbranched fluoropolymer-poly(ethylene glycol) (HBFP-PEG) networks with a settlement sensory deterrent, noradrenaline (NA), and the results of biofouling assays are presented. This example of a dual-mode surface, which combines both passive and active modes of antibiofouling, works in synergy to improve the overall antibiofouling efficiency against barnacle cyprids. The HBFP-PEG polymer surface, prior to modification with NA, was analyzed by atomic force microscopy, and a significant distribution of topographical features was observed, with a nanoscopic roughness measurement of 110 ± 8 nm. NA attachment to the surface was probed by secondary ion mass spectrometry to quantify the extent of polymer chain-end substitution with NA, where a 3- to 4-fold increase in intensity for a fragment ion associated with NA was observed and 39% of the available sites for attachment were substituted. Cytoskeletal assays confirmed the activity of tethered NA on adhering oyster hemocytes. Settlement assays showed deterrence toward barnacle cyprid settlement, while not compromising the passive biofouling resistance of the surface. This robust strategy demonstrates a methodology for the incorporation of actively antibiofouling moieties onto a passively antibiofouling network.

Antibiofouling hybrid dendritic Boltorn/star PEG thiol-ene cross-linked networks.

A series of thiol-ene generated amphiphilic cross-linked networks was prepared by reaction of alkene-modified Boltorn polyesters (Boltorn-ene) with varying weight percent of 4-armed poly(ethylene glycol) (PEG) tetrathiol (0-25 wt%) and varying equivalents of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) (0-64 wt%). These materials were designed to present complex surface topographies and morphologies, with heterogeneity of surface composition and properties and robust mechanical properties, to serve as nontoxic antibiofouling coatings that are amenable to large-scale production for application in the marine environment. Therefore, a two-dimensional matrix of materials compositions was prepared to study the physical and mechanical properties, over which the compositions spanned from 0 to 25 wt% PEG tetrathiol and 0-64 wt% PETMP (the overall thiol/alkene (SH/ene) ratios ranged from 0.00 to 1.00 equiv), with both cross-linker weight percentages calculated with respect to the weight of Boltorn-ene. The Boltorn-ene components were prepared through the esterification of commercially available Boltorn H30 with 3-butenoic acid. The subsequent cross-linking of the Boltorn-PEG-PETMP films was monitored using IR spectroscopy, where it was found that near-complete consumption of both thiol and alkene groups occurred when the stoichiometry was ca. 48 wt% PETMP (0.75 equiv SH/ene, independent of PEG amount). The thermal properties of the films showed an increase in T(g) with an increase in 4-armed PEG-tetrathiol wt%, regardless of the PETMP concentration. Investigation of the bulk mechanical properties in dry and wet states found that the Young's modulus was the greatest at 48 wt% PETMP (0.75 equiv of SH/ene). The ultimate tensile strength increased when PETMP was constant and the PEG concentration was increased. The Young's modulus was slightly lower for wet films at constant PEG or constant PETMP amounts, than for the dry samples. The nanoscopic surface features were probed using atomic force microscopy (AFM), where it was observed that the surface of the amphiphilic films became increasingly rough with increasing PEG wt%. On the basis of the physicochemical data from the diverse sample matrix, a focused compositional profile was then investigated further to determine the antifouling performance of the cross-linked Boltorn-PEG-PETMP networks. For these studies, a low, constant PETMP concentration of 16 wt% was maintained with variation in the PEG wt% (0-35 wt%). Antifouling and fouling-release activities were tested against the marine alga Ulva. Spore settlement densities were low on these films, compared to that on standards of polydimethylsiloxane and glass.

Synthesis and structural studies of NCN diimine palladium pincer complexes bearing m-terphenyl scaffolds.

The reaction of 2,6-[2-{RN=C(H)}C(6)H(4)](2)C(6)H(3)I [R = Ph (4), Cy (5), 2,6-Me(2)C(6)H(3) (6), 2,4,6-Me(3)C(6)H(2) (7), (S)-alpha-methylbenzyl (8)] with Pd(2)(dba)(3) afforded the NCN diimine pincer palladium complexes [2,6-[2-{RN=C(H)}C(6)H(4)](2)C(6)H(3)PdI] (9-13) by oxidative addition of the C-I bonds of the ligand precursors. Single-crystal X-ray diffraction analyses of complexes 9-13 reveal formal C(2)-symmetric environments. Variable-temperature NMR studies of complexes 11 and 12 show hindered rotation about the N-Ar bonds and also suggest that atropisomers of complexes 9-13 do not interconvert on the NMR time scale. Consistent with this proposal, isolation of the two possible isomers of 13 (13a and 13b) was possible, and their structures and NMR properties have been examined in detail.