Amphiphilic polydiacetylenes

Table 2. Raman frequencies and absorption maxima of amphiphilic polydiacetylenes...

A sensor is a system that displays a readily detectable response in the presence of a specific analyte. Indeed, stimulus-responsive vesicles have been tailor-made to function as highly specific sensors. The overwhelming majority of vesicle-based sensors are based on a very simple type of amphiphile polydiacetylenes. These polymeric amphiphiles are easily formed from simple diacelylene amphiphiles by in situ photopolymerization of vesicles. If the vesicles are additionally equipped with ligand or receptor groups, the absorbance and fluorescence of the conjugated polymer backbone is highly sensitive to the presence of metal ions, anions, and small as well as large... 

Polydiacetylenes with appropriate amphiphilic structures can be used to fabricate thin films in this way, e.g., heptadeca-4,6-diyne-l-ol and the corresponding add. It is often found that the stability of the monolayers is a function of the stmcture of the molecules. It has also been found advantageous to use the neutralized form of acid derivatives, and diacetylene monocarboxylic acids generally form much more stable films if the cadmium salt is used initially, where the Cd + ion is then present in the aqueous phase as a counterion. 

During the late 1960s, Wegner reported that single-crystalline diacetylenes could be topochemically polymerized to ene-yne polydiacetylenes [78], and several groups subsequently applied this chemistry to crosslinking polymerizations in 2-D confinement. For example, Leblanc synthesized the dendrimer-based amphiphile 34 in which sixteen 10,12-pentacosadiynoic acid chains were coimected to the periphery of a third-generation poly(amidoamine) (PAMAM) dendrimer [79]. A monolayer of this dendritic amphiphile was prepared at the air/water interface, in which the... 

Fluorescence of polydiacetylenes was first reported qualitatively by Baughman and Chance, and has also been abserved in multilayers of polymerized 5a While the blue form of polymerized amphiphiles is non-fluorescent, the red form exhibits a strong fluorescence with emission maxima at 570 and 640 nm. The luminescence is likely due to a polymer degradation product formed in disordered areas of the sample In multilayers of 2 the fluorescence quantum yield has been determined to be (2.0 0.5)xl0- >. 

The polymer is expected to be at least occasionally cross-linked Since the polymer chains are very flexible, the amphiphilic polybutadienes represent a better approach to biological membranes than the corresponding polydiacetylenes In particular of interest are partially polymerized membranes, which consist of polymerizable butadiene lecithines and saturated lecithines (e.g. dimyristoyl-lecithin, DMPC). While vesicles of DMPC exhibit a typical ripple structure, the surface of the polymerized vesicles appears homogeneous. Electron micrographs of mixed vesicles show a phase separation, indicated by the simultaneous presence of regions with a smooth surface due to the polymer, and rippled regions due to DMPC Instead of... 

Molecules of amphiphilic nature which contain the diacetylene moiety and which give rise to stable solid-analogue films at the air-water interphase can generally be polymerized by UV-irradia-tion. The polymerization proceeds according to the topochemical rules. A solid monomolecular film of the corresponding polydiacetylene is thus formed (12). 

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