A study of the polymerization properties and the morphology of a new type of ultrathin diacetylene multilayers is presented. The multilayers were built-up on charged surfaces by alternating self-assembly of dipolar amphiphilic diacetylenes (2,4-hexadiyne 1,6-disulfate (HDDS), 5,7-dodecadiyne 1,12-disulfate (DDDS), 10,12-docosadiyne 1,22-disulfate (DCDS)) and a cationic polyelectrolyte (polyallylamine hydrochloride) from aqueous solution. Upon UV- and gamma-irradiation, the multilayers containing DCDS dianions polymerized. X-ray studies indicate a layered structure with a layer thickness of 2.7 +/- 0.1 nm. The DCDS dianions are tilted by 38 +/- 4 degrees with regard to the layer plane. The morphological study by scanning force microscopy indicates that the multilayers do not represent a homogeneous film but consist of a multitude of small, separate domains of up to 300 nm in diameter covering the substrate in a way that the macroscopic appearance is fairly regular and homogeneous.