Anomalous Stability of “colored” Form of Spiroxazine Photochroms Trapped in Polycarbonate Matrix after Supercritical Fluid Impregnation

Various thermoplastic polymers (polyethylene, polypropylene, PMMA, polycarbonate) were impregnated with spiroxazine photochrom (-1,3,3-threemethylspyro (indoline-2,3-3Нantrazeno[2,1-b] [1,4] oxazin) (SAO) dissolved in supercritical CO2 SAO molecules have usually stable unexcited form (A) that transfers to unstable “colored” form (B) under the action of UV light. It was found that, unlike other polymers under study, the supercritical fluid (SCF) impregnation of polycarbonate (PC) with SAO causes the anomalous stabilization of its colored form B. The bleaching time of SAO in PC after its photoexcitation (900 с) is two orders of magnitude higher than that in polypropylene. Moreover, after supercritical fluid impregnation of PC up to 20% of SAO is originally formed in colored form, which is not bleachable for 250days (the whole period of observation), i.e. is extremely stable. The temperature and pressure effects on SAO concentration in different polymer matrixes were measured. At least some part of SAO incorporated into the polymeric matrix forms nanocrystals of ~10-20 nm size. Possible mechanisms of the observed effect of the anomalous stability of colored SAO form trapped in the polycarbonate matrix after its SCF are discussed.