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Joints held by polymeric adhesives are commonplace in many engineered products, but normal service can require exposure to environmental conditions that present a significant challenge for maintaining the structural integrity of the interface. In particular, aqueous environments can wreak havoc on the joint strength. Here, a mechanistic approach is used to understand the difference in the debonding behavior of an epoxy/aluminum (oxide) interface when exposed to deionized (DI) water and aqueous sodium chloride by correlating macroscopic failure with the sorption of salt and water into the adhesive and its nanoscale distribution. For the epoxy-aluminum system examined here, the presence of sodium chloride increases the resistance to crack growth in comparison to DI water. The debonding appears to be controlled by water near the buried interface. Salt water decreases the solubility of water in the epoxy and decreases the concentration of water near the buried interface, but the concentration of salt that enters the epoxy is below the detection limit. Thus, even if ions cannot penetrate or sorb into the adhesive, the presence of salt can significantly alter the water distribution within the adhesive and ultimately the strength of the joint. POLYM. ENG. SCI., 2015. © 2015 Society of Plastics Engineers

In this manuscript a series of cubic silsequioxane monomers with their eight vertices functionalized by different organic tethers and terminated with triethoxysilane groups were acid hydrolyzed, spin cast, and vitrified into hard organosilicate films. Both the length of the organic ligands and the number of triethoxysilane groups were varied to change the degree of cross-linking and cubic silsequioxane content of the vitrified films. This resulted in a series of high-quality optical-grade coatings with excellent properties. In general, higher concentrations of the cubic silsequioxane moiety in the network and higher cross-link densities led to enhanced mechanical properties, lower porosity, higher density, lower thermal expansion, and a very hydrophilic surface. The manner by which these properties can be tuned via the cubic silsesquioxane content is discussed in comparison to the structure–property relations for other spin on silsequioxane type films. Copyright © 2013 John Wiley & Sons, Ltd.

The incorporation of carbon nanofiber (CNF) into glass fiber (GF) composites is a potential route to extend polymer composite service-life and enhance mechanical properties. Under nonstatic conditions, only limited information concerning water uptake and contaminant release properties of nanocomposite materials is currently available. Polyester composites containing GF and oxidized CNF were immersed in water for 30 days under nominal pressure at 23 °C, below the polymer's glass-transition temperature. Water was analyzed and changed every three days to simulate water chemistry regeneration similar to exposures in flowing systems. Composites with oxidized CNF had greater water sorption capacity and leaching rates than CNF-free composites. The total mass of organic contaminant released correlated with the amount of water sorbed by each composite (r2 = 0.91), although CNF dispersion was found to vary greatly within composites. The greatest and least contaminant release rates were found for the polyester-CNF and the polyester-GF composites, respectively. While volatile aromatic resin solvents and stabilizer compounds were detected, their concentrations declined over the 30 day exposure period. We hypothesize that the hydrophilic nature of the oxidized CNF increased the water sorption capacity of the polyester composites. Additional studies are warranted that examine the impact of this phenomenon on composite mechanical and long-term durability properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43724.

Normal and shear forces between opposing polystyrene (PS) brushes made from preferentially assembled PS–polyvinylpyridine diblock copolymers were measured in toluene and in near-theta cyclohexane at 32, 40, and 50 °C, using a modified surface forces apparatus. In cyclohexane, over the temperature window probed, the normal forces of interaction are repulsive and the range of those force profiles changes only slightly; however, for both of the PS brushes studied, the onset of shear forces in near-theta cyclohexane is strongly influenced by changes in temperature: As the temperature is increased, the onset of the frictional interactions between the brushes in cyclohexane shifts to smaller distances, approaching the distances where frictional forces are observed for brushes in the good solvent toluene. The pattern of behavior seen in the frictional response between the limits of good and theta condition is attributed to composition fluctuations, which increase near the theta condition because of the decrease in excluded volume interactions. These fluctuations may give rise to increased drag during shearing motion because of interfacial roughness or interchain coupling across the brush–brush interface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 649–655, 2006

Three complementary techniques that probe different characteristics of curing: FTIR microspectroscopy, confocal microscopy and axisymmetric adhesion testing ware used to study discrete epoxy samples cured at different temperatures and to follow curing across a continuous gradient combinatorial library. Together, these techniques provide a comprehensive picture of chemical and physical changes.

In this manuscript a series of cubic silsequioxane monomers with their eight vertices functionalized by different organic tethers and terminated with triethoxysilane groups were acid hydrolyzed, spin cast, and vitrified into hard organosilicate films. Both the length of the organic ligands and the number of triethoxysilane groups were varied to change the degree of cross-linking and cubic silsequioxane content of the vitrified films. This resulted in a series of high-quality optical-grade coatings with excellent properties. In general, higher concentrations of the cubic silsequioxane moiety in the network and higher cross-link densities led to enhanced mechanical properties, lower porosity, higher density, lower thermal expansion, and a very hydrophilic surface. The manner by which these properties can be tuned via the cubic silsesquioxane content is discussed in comparison to the structure–property relations for other spin on silsequioxane type films. Copyright © 2013 John Wiley & Sons, Ltd.