Topography and nanomechanical properties of tribochemical films derived from zinc dialkyl and diaryl dithiophosphates

In this paper we present recent results from an on‐going effort to characterize the nanomechanical properties of a variety of tribochemical, antiwear films through the use of modern scanning probe techniques. The two types of antiwear wear films studied, derived from zinc dialkyl dithiophosphate (alkyl ZDDP) and zinc diaryl dithiophosphate (aryl ZDDP), were chosen because they possess significantly different wear characteristics. High resolution AFM topographic images showed significant differences between the two types of films. More interestingly, high resolution imaging and quantitative mechanical properties testing using the interfacial force microscope (IFM), revealed different elastic and plastic properties between the two types of films; in addition each type of film possessed several distinct regions with respect to mechanical properties. The maximum values for elastic modulus and hardness were located on the highly loaded regions of the alkyl ZDDP films which exhibited the best tribological performance. In contrast, the aryl ZDDP films, which exhibited poorer antiwear behaviour, were devoid of such resilient regions. Our results correlate the macroscopic wear behavior of the tribochemical films to differences in the mechanical properties on a nanometer scale. This revised version was published online in July 2006 with corrections to the Cover Date.     

An Enantioconvergent Synthesis of (R)‐4‐Aryloxy‐1‐butyne‐3‐ols for Prostanoid Side Chains

The single enantiomer title alcohols, useful as ω‐side chain precursors for pharmaceutically important prostaglandin analogues were synthesised from the corresponding racemic alcohols by a convenient 4‐step sequence. After enzymatic acylation of the alcohol with a vinyl carboxylate, the residual (S)‐alcohol in the mixture was converted to the mesylate. Subsequent displacement with the corresponding carboxylate anion, followed by enzymatic deacylation gave the desired (R)‐alcohol. In this way, all of the starting alcohol was utilised without the need for separation of the starting material and product after the bioresolution.