Dissolution of percolation cluster on UV-cured polymeric films; a fluorescence study

UV-cured polimerik filmlerde perkolasyon kümelerinin çözünmesi; floresans çalışması

Abstract

Steady state fluorescence (SSF) technique was used for studying dissolution of UV-induced polymer films. These films are formed from polvfmethvl methacrylate) {PMMA) chains labeled with pyrene (P) which was introduced as a fluorescence probe to monitor the dissolution processes. PMMA films in various ethylene glycol dimethaaylate (EGDM) content, cured by UV radiation for 3 and 25 hours, were dissolved in chloroform-heptane (80%-20%) mixtures. Dissolution of the films were monitored in real-time by the pyrene fluorescence intensity. Ip change in the solvent mixture. It was observed that maximum P intensity, $Ip_{infty}$ increased and decreased above a critical EGDM content for 3h and 25h irradiated films, respectively. It was atributed to the formation of a percolation cluster. The percolation treshold (Pc=0.35) found for 3h irradiated films obeys site percolation model, however the measured percolation threshold (pc=0.25) for 25h irradiated films obeys the bond percolation model. Desorption rates, $D_d$ were measured for films prepared with various EGDM content was observed that $D_d$ values are much lower above Pc, than below Pc for both films. These UV cured films dissolve much faster below the percolation threshold (Pc) where dissolution coefficients were found to be around $10^{-9}$ $cm^2 s^{-1}$. However above Pc highly crosslinked films dissolve at least 4 times slower than low crosslinked films i. e. UV cured films hardly dissolve above critical EGDM content (Pc) in the film.

Özet

UV-cured polimerik filmlerin çözünmesini çalışmak için kararlı durum floresans teknik (SSF)kullanıldı. Bu filmler piren(P) ile etiketli poli(metil metakrilat) (PMMA) zincirlerinden elde edildi. Burada P çözünme işlemini takip etmek için floresans madde olarak tanımlandı. Çeşitli oranlarda etilen-glikol dimetakrilat (EGDM) çapraz bağlayıcı içeren, 3 ve 25 saat UV radyasyonu ile ışınlanmış PMMA filmler %(80-20) klorofrom-heptan karışımında çözdürüldüler. 3 saat ışınlanmış filmler için bulunan perkolasyon eşiği (pc-0.35) nokta perkolasyon modeline uyarken, 25 saat ışınlanmış film için ölçülen perkolasyon eşiği (pc=0.25) bağ perkolasyon modeline uyar.