Structural transformations of diacetylenes during solid-state polymerization and chromatic transitions of poly(diacetylenes) as measured by a modified diffuse reflection-absorption ftir-technique

Summary form only given. A modified Diffuse Reflection-Absorption (DRA) FTIR technique is reported. This based on use of a metallic diffusely reflecting sample holder in standard DRIFT accessories and allows different sample preparation procedures to be used. The samples of monomer diacetylenes after being applied onto the metal plate from solution, and thus prepared for the DRA experiment, may be made structurally identical to those samples which are usually used in other measurements (e.g., polymerization kinetics by DSC). It is often not the case in conventional transmission IR experiments due to grinding and pressing of samples with KBr. It is shown that the DRA spectra so obtained in several aspects are favourably compared with those acqiured either in transmission or by the conventional DRIFT. The effects of sampling methods or the quality of the DRA spectra are discussed in terms of possible optical distortion effects. It is shown that this optical geometry is highly convenient for the subsequent photo- or thermally-induced polymerization kinetics studies by the FTIR-DRA spectroscopy. The same is true as well for IR-spectroscopic investigation of thermo- or solvatochromic transitions in various poly(diacetylenes) with the aid of a temperaure controlled environment chamber. It is argued that the suggested DRA technique permits safe safe semi-quantitative data to be obtained. Dynamics of structural transformations of 4-BCMU during photo-polymerization and that of poly-(4-BCMU) during thermochromic transitions is discussed using the obtained FTIR-DRA results in comparison with the relevant literature data. The potential of the modified technique is illustrated by a number of examples.