3 research outputs found
Effects of surface-active block copolymers with oxyethylene and fluoroalkyl side chains on the antifouling performance of silicone-based films
Block copolymers made from a poly(dimethyl siloxane) (Si) and a poly(meth)acrylate carrying oxyethylene (EG) or fluoroalkyl (AF) side chains were synthesized and incorporated as surface-active components into a silicone matrix to produce cross-linked films with different surface hydrophilicity/phobicity. Near-edge X-ray absorption fine structure (NEXAFS) studies showed that film surfaces containing Si-EG were largely populated by the siloxane, with the oxyethylene chains present only to a minor extent. In contrast, the fluorinated block was selectively segregated to the polymer–air interface in films containing Si-AF as probed by NEXAFS and X-ray photoelectron spectroscopy (XPS) analyses. Such differences in surface composition were reflected in the biological performance of the coatings. While the films with Si-EG showed a higher removal of both Ulva linza sporelings and Balanus amphitrite juveniles than the silicone control, those with Si-AF exhibited excellent antifouling properties, preventing the settlement of cyprids of B. amphitrite
Interactions, Structure, and Dynamics of Polymer-Tethered Nanoparticle Blends
We report on the
structure, jamming, and dynamics of blends of
self-suspended hairy silica nanoparticles grafted with poly(ethylene
glycol) (PEG) and poly(methyl methacrylate) (PMMA). We find that favorable
enthalpic attraction between tethered PEG and PMMA chains augment
previously reported entropic attractions between tethered polymer
chains in self-suspended suspensions to enhance particle-particle
correlations, increase jamming, and slow down chain dynamics. As with
their single-component counterparts, the hairy SiO<sub>2</sub>-PEG/SiO<sub>2</sub>-PMMA nanoparticle blends exhibit soft glassy rheological
behavior and both the energy dissipated at yielding and the plateau
elastic modulus display strong maxima in the symmetric case. A comparison
of the small angle X-ray scattering (SAXS) measurements with theoretical
analysis from density functional theory (DFT) reveals that the addition
of SiO<sub>2</sub>-PMMA to a self-suspended SiO<sub>2</sub>-PEG suspension
initially leads to a higher degree of stretching of the corona chains,
which produces stronger interdigitation of the tethered chains, enhanced
jamming, and slower polymer relaxation than observed in the single-component
materials. By means of an analysis of the heat of mixing released
upon blending tethered and untethered PEG and PMMA chains, we find
that the strong enthalpic attraction between the grafted polymer chains
enhances entropic attractive forces produced by the space-filling
constraint on tethered ligands in self-suspended suspensions to produce
entangled-polymer-like physical properties in polymers with molecular
weights below the thresholds normally associated with the transition
to an entangled state
Model Amphiphilic Block Copolymers with Tailored Molecular Weight and Composition in PDMS-Based Films to Limit Soft Biofouling
A set of controlled surface composition films was produced utilizing amphiphilic block copolymers dispersed in a cross-linked poly(dimethylsiloxane) network. These block copolymers contained oligo(ethylene glycol) (PEGMA) and fluoroalkyl (AF6) side chains in selected ratios and molecular weights to control surface chemistry including antifouling and fouling-release performance. Such properties were assessed by carrying out assays using two algae, the green macroalga Ulva linza (favors attachment to polar surfaces) and the unicellular diatom Navicula incerta (favors attachment to nonpolar surfaces). All films performed well against U. linza and exhibited high removal of attached sporelings (young plants) under an applied shear stress, with the lower molecular weight block copolymers being the best performing in the set. The composition ratios from 50:50 to 60:40 of the AF6/PEGMA side groups were shown to be more effective, with several films exhibiting spontaneous removal of the sporelings. The cells of N. incerta were also removed from several coating compositions. All films were characterized by surface techniques including captive bubble contact angle, atomic force microscopy, and near edge X-ray absorption fine structure spectroscopy to correlate surface chemistry and morphology with biological performance