THE EFFECT OF ACIDS ON THE INFRARED SPECTRA OF SCHIFF BASES—II. IMINES CONTAINING THE C=C-C=N AND C=C-C=C-C=N UNITS

Abstract— The Fourier-transform infrared spectra of chloroform-d solutions of conjugated imines CH₃CH=CHCH=NCH(CH₃)₂ and CH₃CH₂CH=CHCH=CHCH=NCH(CH₃)₂ and the related protonated species with HCl, HBr, HI, trichloro, dichloro, monobromo and monochloroacetic acids or propionic acid are presented. The effects of conjugation and protonation are examined. The results show that conjugation slightly increases the basicity of the Schiff bases. HCl, HBr and HI protonate the Schiff bases completely. The carboxylic acids protonate partially depending on their p K _a, values. When the Schiff base contains two (or more) C=C bonds conjugated with C=N, the main C=C stretching band undergoes a strong intensification showing that sizeable dipole moment variations occur along the conjugated chain.     

Evidence of meniscus interface transport in dip-pen nanolithography: An annular diffusion model

Ring shaped dots were patterned with mercaptohexadecanoic acid ink by dip-pen nanolithography. These dots have an ink-free inner core surrounded by an inked annular region, making them different from the filled dots usually obtained. This suggests a different transport mechanism than the current hypothesis of bulk water meniscus transport. A meniscus interface ink transport model is proposed, and its general applicability is demonstrated by predicting the patterned dot radii of chemically diverse inks.     

Relative humidity effects in dip-pen nanolithography of alkanethiol mixtures

In the dip-pen nanolithography of a binary alkanethiol mixture of mercaptohexadecanoic acid (MHA) and 1-octadecanethiol (ODT) at a relative humidity (RH) of less than 80%, two distinct phases of MHA and ODT were patterned. However, on ramping up the RH to greater than 80%, only MHA was observed to pattern. This effect was reversible, as shown by the fact that two distinct thiol regions were again patterned on lowering the RH. This segregation could be exploited for generating exclusive MHA (hydrophilic) templates for subsequent architectures from a mixture of alkanethiols driven solely by the RH.