Role of counter-substrate surface energy in macroscale friction of nanofiber arrays

The effect of counter-substrate surface energy on macroscale friction of nanofiber array is studied. Low-density polyethylene (LDPE) fibrillar array fabricated from silicon nanowire template is tested against glass substrates modified with various self-assembled monolayers, which exhibit a wide range of surface energy. A large drop in friction over a narrow range of surface energy is observed and explained in terms of drastically reduced number of fibers in actual contact, in addition to the reduced surface energy. The relationship between surface energy and fiber engagement is discussed with Johnson-Kendall-Roberts (JKR) and elastic beam models.     

Electrochemical Oxidation of Catechols (=Benzene‐1,2‐diols) in the Presence of Benzoylacetonitrile: Synthesis of New Derivatives of 5,6‐Dihydroxybenzofuran

The electrochemical oxidation of catechol (=benzene‐1,2‐diol; 1a ) and some of its derivatives in H₂O/MeCN 1 : 1 containing benzoylacetonitrile (=β‐oxobenzenepropanenitrile; 3 ) as a nucleophile was studied by cyclic voltammetry and controlled‐potential coulometry. The voltammetric data showed that electrochemically generated o‐benzoquinones (=cyclohexa‐3,5‐diene‐1,2‐diones) from catechol ( 1a ) and 3‐methylcatechol ( 1b ) participate in a Michael‐addition reaction with 3 to form the corresponding 5,6‐dihydroxybenzofuran‐3‐carbonitrile 8 (Scheme 1). In this work, we report an efficient one‐pot method with high atom economy for the synthesis of new substituted 5,6‐dihydroxybenzofuran‐3‐carbonitriles in an undivided cell under ambient conditions.