An acyl chain modified diacetylenic phospholipid containing a sulfur beta to the diacetylene, 1,2-bis(15-thia-pentacosa-10,12-diynoyl)-sn-3-phosphocholine, was synthesized. Comparisons of the UV spectra of the lipid, the diacetylenic carboxylic acid precursor, and the unmodified diacetylenic lipid 1,2-bis(tricosa-10,12-diynoyl)-sn-3-phosphocholine reveal that the sulfur acts as an auxochrome resulting in bathochromic shifts and higher intensities for the absorption peaks. Differential scanning calorimetry was used to determine the acyl chain melting transition temperatures of 1,2-bis(15-thia-pentacosa-10,12-diynoyl)-sn-3-phosphocholine in water (31.2°C) and 70:30 ethanol:water mixture (28.7°C) and revealed that the lipid packed more homogeneously in the ethanol:water mixture. Subsequent dispersal of the lipid in water produced ribbons with diameters ranging from 0.01-0.1 μm while dispersal in 70:30 ethanol:water leads to formation of tubules with diameters ranging from 0.6-0.8 μm. A gel comprised of interwoven ribbons was formed from an equimolar mixture of the lipid and 1,2-bis(nonoyl)-sn-glycero-3-phosphocholine (DNPC) in 0.1 M aqueous NaCl.