Polimerik Jellerin Floresans Tekniği İle İncelenmesi

Abstract

Bu çalýþmada, poli(metil metakrilat) (PMMA) jellerinde; jeleleþme þiþme ve küçük moleküllerin jelden yavaþça sýzmasý, metakrilik asitdimetilakrilamid jellerinde; süreksiz hacým faz geçiþi, N’ izopropil akrilamid jellerinde; hedef moleküllerin dönüþümlü absorpsiyonu konularý kararlý durum floresans ölçümlerine dayanan yeni bir metodla incelenmiþtir. Jel noltasýnda, jelleþme kesri ve ortalama küme büyüklüðü icin tanýmlanan  ve  kritik üsleri 0.42  0.03 ve 1.70  0.02 olarak bulunmuþtur. Bulunan bu deðerlerin, sýzma teorisi ile mükemmel bir uyum gösterdikleri gözlenmiþtir. Çözücü katmadan ve çözücü katýlarak hazýrlanan PMMA jellerinde kooperatif difüzyon katsayýlarý sýrasýyla 10-5 ve 10-6 cm2/s civarýnda bulunmuþtur. Ayrýca yavaþ salýverilme difüzyon katsayýsý ve hem PMMA jelleri hem de lineer polimerler icin aktivasyon enerjileri hesaplanmýþtýr. Elde edilen sonuçlar, floresans ölçümlerinin jellerin incelenmesi konusunda kullanýlabilecek oldukca hassas bir teknik olduðunu göstermektedir.In this study, a novel method based on steady state fluorescence measurements is introduced for studying gelation, swelling and slow release processes for poly (methyl methacrylate) (PMMA) gels, discontinuous volume phase transition for methacrylic acidcodimethylacrylamide gels, and reversible absorption of target molecules by N’ isoprophyl acrylamide gels. The gel fraction and average cluster size exponents defined at the gel point were found to be  = 0.42  0.03 and  = 1.70  0.02, in excellent agreement with percolation theory. The fractal dimension of the incipient infinite cluster at the gel point was found to be 2.50.2. Cooperative diffusion coefficients for PMMA gels formed in bulk and solution polymerization, were found to be around 10-5 cm2/sec and 10-6 cm2/sec, respectively. Slow release diffusion coefficient and activation energies for gelation and linear polymerization of PMMA were also measured. All results show that fluorescence measurements is a quite sensitive technique for the studies on gels.