The effect of spacer length on the polymerization of diacetylenes in SAMs on gold surfaces

The influence of the molecular architecture of diacetylene disulfides on th e structure and polymerizability of self assembled monolayers on gold was i nvestigated. The position of the diacetylene group was varied systematicall y by adjusting the length of the tail and the spacer. For the strutures stu died, the longer the tail, the higher the akyl chain crystallinity as sense d by IR spectroscopy, and the higher the polymerization efficiency as probe d by resonance Raman spectroscopy. The influence of the spacer on the polym erizability is more complicated. It is conjectured that the spacer reduces the lattice strain due to the misfit of the arrangement of the anchor group s and the arrangement of the diacetylene units and the polydiacetylene back bone, respectively. Simple modeling reveals that the number of the methylen e units (odd or even) and the overall length both influence the arrangement . The highest polymerization efficiency is found for the longest, odd numbe red spacer.