Structure and reactivity of water at biomaterial surfaces

Durability of glass-fiber/polymer composites is dictated by the durability of the components: glass fiber, matrix, and the interface. Environmental attack by moisture, for example, can degrade the strength of the glass fiber; plasticize, swell, or microcrack the resin; and degrade the fiber/ matrix interface by either chemical or mechanical attack. The relative rates of these degradation processes are a function of the chemistry of the resin, temperature, length of time of exposure, degree of stress (whether cyclic or static), chemistry and morphology of coating of coupling agent on the glass fiber, and type of glass fiber. Several examples illustrate how the chemistry and morphology of the coatings of coupling agents that are on the glass fiber influence the strength and durability of the interfacial region.

Environmental durability of glass-fiber composites

THERE is a considerable demand for materials that have surfaces to which other substances will not easily stick. Coatings with these properties might be used to make surfaces non-adhesive towards soil, ice, biological foulants, graffiti and other unwanted contaminants. Here we describe a class of water-based non-stick coatings prepared by self-assembly and immobilization of reactive polymeric surfactants1,2. These polymer surfactants contain pendant perfluoroalkyl groups which become oriented so as to yield surfaces with very low energy. Immobilization by crosslinking increases non-stick performance and film toughness. These hard, clear coatings release adhesives and cannot be wetted or attacked by solvents.

Water-based non-stick hydrophobic coatings

Fluorinated polyhedral oligomeric silsesquioxanes–poly(vinylidene fluoride-co-hexafluoro propylene) (fluoroPOSS–PVDF-HFP) nanocomposite mixtures are prepared by individually mixing two fluorinated POSS materials (FP8 and FPSi8) with PVDF-HFP solution and transparent superhydrophobic coatings on a glass substrate are produced by electrospinning. The fabricated superhydrophobic surface exhibits continuous, uniform and non-beaded nanofibers with a high water contact angle (157.3°) and a low sliding angle (SA < 5°). The superhydrophobic properties including surface energy, water contact angle, and contact angle hysteresis as well as the optical properties are studied by altering the wt% of fluoroPOSS in PVDF-HFP solution. It is observed that due to the increase in the viscosity of the solution, the diameter of the nanofibers increases with increase in the concentration of fluoroPOSS. It is also observed that as the concentration of fluoroPOSS in PVDF solution increases, the amount of fluorine content increases thereby the surface energy of the coating decreases (to around 10 mN m−1) leading to a superhydrophobic surface with low contact angle hysteresis (<5°). The optical properties of the coatings produced using FPSi8 fluoroPOSS–PVDF-HFP mixture are compared with those of FP8 fluoroPOSS, and the former is found to be more transparent due to its relatively high solubility in PVDF-HFP.

Superhydrophobic fluorinated POSS–PVDF-HFP nanocomposite coating on glass by electrospinning

Hybrid organic–inorganic polymer nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) nanoparticles are of increasing interest for high performance materials applications. Octaisobutyl POSS/polypropylene nanocomposites were prepared at varying POSS concentrations via melt blending. The interplay of POSS molecular geometry, composition, and concentration in relation to the tribological, nanomechanical, surface energy, and bulk properties of the nanocomposites were investigated. Ultra-low friction and enhanced hardness, modulus, and hydrophobicity were observed for the nanocomposite surfaces, with minimal changes in the bulk thermomechanical properties. Parallel AFM, SEM, TEM, and spectroscopic analyses demonstrated significant differences in POSS distribution and aggregation in the surface and the bulk, with preferential segregation of POSS to the surface. Additionally, contact angle studies reveal significant reduction in surface energy and increase in hysteresis with incorporation of POSS nanoparticles. The differences in bulk and surface properties are largely explained by the gradient concentration of POSS in the polymer matrix, driven by POSS/POSS and POSS/polymer interactions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2441–2455, 2007

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/polb.21261

Surface energetics, dispersion, and nanotribomechanical behavior of POSS/PP hybrid nanocomposites

Characterization of polymer surface sites with contact angles of test solutions. 1. Phenol and iodine adsorption from methylene iodide onto PMMA films

Quantitative correlations among surface chemical composition, acid-base thermodynamics, adhesion strength, and locus-of-failure are demonstrated. Four types of functional Teflon surfaces were prepared: two acidic (containing hydroxyl and carboxyl groups), and two basic (containing acetyl and dinitrobenzoate groups). X-Ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared (ATR-IR) spectroscopy were used to characterize the molecular structure of the surface region. Contact angle adsorption isotherms were determined using phenol as an acidic probe and tetrahydrofuran (THF) as a basic probe. The carboxylated surface had a higher molar ▵Hab with basic THF than the hydroxylated surface, and neither surface had any interaction with the acidic phenol probe. The acetylated surface behaved as a base, interacting with phenol but not with THF, while the dinitrobenzoyl surface had both acidic and basic character. Adhesion tests were carried out in the 180° peel mode using post-chlorinated poly...

Mary B. Kaczinski

Papers

Characterization of polymer surface sites with contact angles of test solutions. 1. Phenol and iodine adsorption from methylene iodide onto PMMA films

Enhancement of polymer film adhesion using acid-base interactions determined by contact angle measurements