The functional implementation of graphene as a solid boundary lubricant requires the ability to control its frictional response across a variety of interfaces. This is challenging, as being a single atomic layer thick, the nanotribological properties of graphene depend highly on the competing interaction strengths with the converse sides of the top and bottom contacts of the interfaces it is placed in between. One method to modulate these interactions is to tune the surface chemistry (of one or both counter-faces) with self-assembled monolayers (SAMs). To fully understand the effects on the graphene/SAM (G-SAM) composite interfaces formed, however, first necessitates a basic understanding of graphene–SAM interactions. To explore graphene–SAM adhesive and frictional interactions over a range of chemical functionalities, SAMs were used to functionalize atomic force microscopy (AFM) tips with varying terminal end-groups (−NH2, −CH3, and –phenyl, compared to unfunctionalized −OH terminated reference tips). AFM pull-off force measurements and thermal gravimetric analysis (TGA) were used to evaluate the work of adhesion (mJ/m2) and interaction energy (kcal/mol) of the functionalized tips with graphene. Friction force microscopy (FFM) measurements were performed with the same functionalized AFM tips to examine the graphene-molecule frictional response. Tip–graphene interaction strength was increased for hydrophobic and aromatic functional groups. The frictional response was found to depend on a balance of graphene-molecule adhesion and shear strain.

The effects of octadecylamine functionalised reduced graphene oxide (FRGO) on the frictional and wear properties of diglycidyl ether of bisphenol A epoxy are studied using pin on disc tribometry. The nanocomposites are prepared by adding 0?1, 0?2, 0?5 and 1?0 wt-% of FRGO to the epoxy. The addition of FRGO increases by more than an order of magnitude the sliding distance during which the dynamic friction is #0?1. After this distance, the friction sharply increases to the range of 0?4-0?5. We explain the increase in sliding distance during which the friction is low by formation of a transfer film from the nanocomposite to the pin. The wear rates in the low and high friction regimes are y1?5610 24 and 5?5610 24 mm 3 N 21 m 21 respectively. The nanocomposites exhibit a 79% increase in Young's modulus with 0?5 wt-% of FRGO, and an increase in glass transition and thermal degradation temperatures.

The effectiveness of reinforcement of a polymer is known to depend on the strength of the interfaces between the reinforcement and the matrix. We have used polystyrene and a styrene-butadiene-styrene (SBS) copolymer as matrixes and ceramic boehmite gamma-AlO(OH) as reinforcement. We have applied boehmite both untreated and treated with sulphonic acid based surfactants with different alkyl groups. As expected, the coupling agents improve the adhesion between the polymers and the ceramic filler. The presence of boehmite and treatments affect the glass transition temperatures determined by dynamic mechanical analysis, nanoindentation hardness h(nanoindent) as well as Vickers microhardness h(Vickers). For SBS and SBS containing composites, the h(nanoindent)/ h(Vickers) ratio is a constant

Although chronic arterial hypertension (CAH) represents the major comorbid factor in stroke, it is rarely integrated in preclinical studies of stroke. The majority of those investigations employ spontaneously hypertensive rats (SHR) which display a susceptibility to ischemic damage independent of hypertension. Here, we used a renovascular model of hypertension (RH) to examine, with magnetic resonance imaging (MRI), brain alterations during the development of hypertension and after brain ischemia. We also examined whether MRI-derived parameters predict the extent of ischemia-induced brain damage. RH was induced according to the two-kidney one-clip model and multiparametric MRI was performed at 3, 6, 9, and 12 weeks after hypertension and also at 10, 50, and 60 min following stroke. Blood pressure values increased progressively and reached a plateau at 6 weeks after RH induction. At 12 weeks, all hypertensive animals displayed spontaneous brain lesions (hemorrhages, deep and cortical lesions, ventricular dilatation), increased apparent diffusion coefficient (ADC) values in the corpus callosum and higher fractional anisotropy in the cortex. Following ischemia, these animals showed larger brain lesions (406 ± 82 vs. 179 ± 36 mm, p < 0.002) which correlated with ADC values at chronic stage of hypertension. This model of hypertension displays many characteristics of the neuropathology of human CAH. The use of this model in stroke studies is relevant and desirable.

Composites consisting of fluorescein (F) entrapped inside various zeolite structures (i.e. FAU, LTL, MFI, and LTA) were prepared by catalytic synthesis of the dye from its precursors (phthalic anhydride and resorcinol) adsorbed in the zeolites.