It is important that solid state PVA’s structure is conserved at PVA-iodine complex deiodination. Such deiodination can be carried out by soaking of solid PVA-iodine complex in ethanol, for example. Blue color disappears at such a treatment and restores reversible at following soaking in iodine ethanolic solution. Control solid PVA sample does not become blue at similar treatment. Such behavior can be used as the mean for HICs identification. The HIC’s structure can be proven if some hybrid complex of PVA become blue in iodine ethanolic solution.
In our research solid films (50-200 mcm thickness) of PVA complexes were soaked in 5% I2 (and 2% KJ) ethanolic solution for several hours at room temperature. PVA complexes preparation was described earlier [1,5]. Pristine transparent colorless PVA film was produced by drying at room condition of 2% water PVA solution poured on fluoroplastic plate. Reference film of blue PVA-iodine complex was produced by the similar way from water solution with 3% PVA, 0.05% J2 and 0.15% KJ.
Complex of PVA with boric acid is well known [6] but its structure remains discussing issue. In particular, interpolymeric structure has been suggested [5]. Our measurements indicate that it becomes blue (from colorless) after treatment in iodine ethanolic solution. Its absorption spectrum is similar to that of PVA-iodine complex (figure). It means that boric acid is substituted by iodine in HIC’s structure with their general conservation. Inheriting of a structure in solid state reactions is known effect in solid state chemistry (predecessor technique). Polymeric structure of the product (blue colored polyiodine chains) confirms polymeric structure of reagent (boric acid chains (-BOOH-)n as component of HIC). The similar results (blue coloring) were obtained for complexes of PVA with borax and chlorides of manganese(II), zinc and cadmium. Polymeric structure of latter was discussed earlier [7-9]. On the other hand, this effect was not observed for PVA compounds with Sn(IV) and Sn(II) chlorides.
Figure. Transmittance spectra of iodine treated pristine PVA film (a), reference PVA-iodine complex’ film (b) and iodine treated PVA-boric acid complex’ film (c).
In our opinion, described above “iodine test” allows to verify existence of HICs as a new class of chemical compounds. It fits for HICs containing alcohol solved inorganic compounds. They can be transformed through solid state synthesis [1] in HICs with insoluble inorganic compounds which are prospective for various applications.