300 Mendeleev Commun. 2006 Polymer films with an amphiphilic crown-ether styryl dye as a prototype of chemosensing materials Sergei Yu. Zaitsev,* a,b Elena A. Varlamova, a Marina S. Tsarkova, a Irina N. Staroverova, a Kirill A. Gogasov, b Sergei P. Gromov, c Mikhail V. Alfimov, c Andrei A. Turshatov d and Dietmar Möbius d a Department of Organic and Biological Chemistry, K. I. Skryabin Moscow State Academy of Veterinary Medicine and Biotechnology, 109472 Moscow, Russian Federation. Fax: +7 495 377 4939; e-mail: szaitsev@mail.ru b M. M. Shemyakin–Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russian Federation c Photochemistry Center, Russian Academy of Sciences, 119421 Moscow, Russian Federation d Max Planck Institute for Biophysical Chemistry, D-37071 Göttingen, Germany DOI: 10.1070/MC2006v016n06ABEH002398 A combination of the photosensitive and ion-selective properties of thin polymer films with immobilised amphiphilic crown-ether styryl dye (in particular dye interaction with alkaline earth metal ions) gives evidence that such films can serve as a prototype of chemosensors with optical signal detection. The synthesis and structure-functional study of the multifunc- tional polymeric composites are of growing interest for scientists working with supramolecular systems and nanoscale mate- rials. 1–3 Special attention is devoted to the composites with ion-selective, photosensitive and self-assembly properties, such as amphiphilic crown ether dyes. 4–7 Our recent studies 8–10 on the monolayers and LB films of amphiphilic crown-ether dyes with variable size of the polyether ring and substitutions in the chromophoric part demonstrated the possibility of preparing photosensitive monolayer films with the ability to selectively bind particular alkali and heavy metal ions. A further important step towards the application of these systems is the preparation of polymeric thin films (thickness of 10–50 µm) with immo- bilised crown-ether dyes. These systems are promising sensitive components for ion detection in optical and electrochemical devices; photocontrolled extraction of metal ions; and materials for recording, storing and processing of optical information. 1–3 The aim of this work was to prepare and characterise polymer thin films with an immobilised amphiphilic crown-ether styryl dye, in particular, to investigate its ion-selective and photo- sensitive properties. The amphiphilic benzo-15-crown-5 styryl dye (E12) was synthesised as described earlier. 9 The dye was characterised by elemental analysis, NMR and IR spectroscopy. 9 Polystyrene (PSt) high purity standard with M n 200000 was purchased from Aldrich. Polyvinylcaprolactam (PVC) with M n 300000 and a copolymer (PVCSt) with M n 900000 (PVC:PSt ratio of 10:1) were prepared and purified as described earlier. 2 The salts KClO 4 (99%), Ca(ClO 4 ) 2 (98%) and Mg(ClO 4 ) 2 (98%) were purchased from Merck. Water was purified with a Milli-Q filtration unit from Millipore Corp. The polymer films with and without the dye (total thickness of 40±5 µm) were prepared by classical spreading techniques on the medical glass substrate (5.0×1.5 cm 2 ) from 10% polymer solutions in chloroform. The concentration of the dye in chloro- form was 1 mM, whereas in the obtained films the average dye amount was 1.09±0.05 µg cm –2 . Numerous experiments showed that this dye did not dissolve in the aqueous solutions and was not extracted from the polymer films by interaction with studied salts. The spectra of the polymer-dye films were recorded in the range 300–600 nm using a DU-90 spectrophotometer (Beckman, USA) under the following conditions: (i) 24 h dark relaxation; (ii) intense 10 min illumination at a 15 cm distance. The absorbance of the polymer films without dye was below 300 nm (maximum was about 255 nm). The experimental errors were ±1 nm for l measurements and ±0.001 units for absorbance intensity measure- ments. The average data of three to four measured samples in each case are presented in Tables 1 and 2. The influence of various cations on these films was studied using 1.0 mM KClO 4 , Ca(ClO 4 ) 2 or Mg(ClO 4 ) 2 aqueous solutions. Each film was stored in the salt solution for 60 min, washed with distilled water and placed in distilled water for 20 min. This procedure allowed the cation interaction with the dye in the film, as well as the removal of the excess of the salt from the film afterwards (especially in the case of PVCSt). After such a washing procedure, the film was dried at 40 °C during 30 min and stored in the dark. The procedure was the same for all the films at various salt concentrations (from 3 to 9 mM). The most important information on the dye photosensitive properties, as well as on dye–cation complexation, was gained by measuring the absorption spectra of obtained dye–polymer films under various conditions. The spectra of the dye–poly- mer films in all cases showed a strong band with an absorption maximum at 400–450 nm, which was assigned to the dye trans form according to published data 8–10 on the pure dye in some organic solvents. The pronounced shoulder at 320–350 nm was assigned to the dye cis form according to our preliminary studies. 9 From the original spectra, it was possible to obtain directly only the parameters of the dye trans form, even if its maximum was shifted. In order to obtain the parameters of the dye cis form, the original spectra were recalculated. 2 This allows us to estimate a relative amount of the dye trans and cis forms in the freshly prepared polymer films under various conditions (Table 1). Note that, for all polymer and copolymer films after dark relaxation, the cis–trans ratios of the dye (from 31.6 to 36.7%) were significantly higher than those of the dye in a chloroform solution (24.1%) due to the particular polymeric environment. The cis–trans ratios of the dye in the studied films increased significantly after intense 10 min illumination, as compared to the initial values or values after dark relaxation of these films (Table 1). Such effects clearly indicate the reversible photo- O N C 17 H 35 H N S Et O O O O O ClO 4 – trans-isomer O N C 17 H 35 H N S Et O O O O O ClO 4 – cis-isomer