Preparation and structure/property relationships of novel polyesters containing conjugated diacetylene groups

Abstract

A series of diacetylene diols were synthesised and characterised by FTIR, Raman spectroscopy and WAXD. The most useful Raman bands are those around 2250, 2100 and 1510 cm"1, which are respectively assigned to O C stretch of unreacted diacetylene, C=C and C=C stretch in polydiacetylene backbone. The results of Raman spectroscopic studies of ODD2 and HDD may suggest a different topochemical polymerisation mechanism. For the partially polymerised ODD2, ODD2 is likely to follow the biradical scheme and hence a butatriene form of PDA chains is constructed due to the presence of a very strong peak at 1970 cm'1. On the other hand, the acetylenic forms were apparently observed in both partially polymerised HDD and poly(HDD), as well as in poly(ODD2). Structural analysis enables the determination of the lattice parameters of these diacetylene diols and shows that intermolecular distance rises with increasing the numbers of substituted methyl groups and this results in a decrease in the reactivity of these diacetylene. The findings are also supported by the DSC and TGA analysis. The high steric hindrance and hence large lattice distance of tertiary diol ODD2M, i.e., diffusion limited and improper molecular alignments, make it difficult to undergo thermal and x-ray induced topochemical polymerisation below its melting point. It was only observed to crosspolymerise in a melt or vapour state.