Luminesence study of polymer-copolymer blends using a carbazole/iodine probe/quencher system

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Title: Luminesence study of polymer-copolymer blends using a carbazole/iodine probe/quencher system
Author: Davis, Tammy
Abstract: The miscibility behavior of binary blends of polystyrene (PS), poly(methyl methacrylate) (PMMA) and their copolymers was re-evaluated using the luminescence of carbazole (Cz) and its quenching by 4-iodoaniline (I). The chromophore and quencher probes were polymerized into the polymers and copolymers to be blended. These experiments were conducted at room temperature, on thin films, and were compared to the published results of Braun, et. al.13Homopolymer/copolymer blend compositions were selected from regions of miscible, partially miscible, and immiscible phase behavior. The quencher molecule, 4-iodoaniline, was derivatized to form the vinylfunctionalized monomer, N-(4-iodophenyl)maleimide (NIPMI). The synthesis of NIPMI was carried out in two steps: (1) nucleophilic attack and (2) dehydration. ' The vinylfunctionalized chromophore, N-vinylcarbazole (VCz), was purchased through Aldrich. The polymers and copolymers used in this study were synthesized by free-radical polymerization using 2,2'-azobisisobutyronitrile (AIBN) to initiate the reaction. The polymers were characterized by proton nuclear magnetic resonance ('H-NMR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and size exclusion chromatography (SEC). Although there are several identifiable variations between the experimental luminescence results and what was expected based on the values published by Braun,et. al,13 the results for the miscibility of the homopolymers, PS and PMMA, were as expected. The results for the phase behavior of the homopolymer-copolymer blend systems exhibit a larger deviation away from the results of Braun, et. al. The blends of poly[(methyl methacrylate)i6-co-(styrene)82-co-(vinylcarbazole)2] (P(MMAi6S82VCz2)) and poly [(methyl methacrylate)5i-co-(styrene)47-co-(vinylcarbazole)2] (P(MMA5iS47VCz2)) with the quencher tagged PS homopolymer, PSi, both gave 20-30% relative luminescence intensities rather than the predicted 100%. The blends of poly[(methyl methacrylate)77-co- (styrene)22-co-(vinylcarbazole)i] (P(MMA77S22VCzi)) and poly[(methyl methacrylate)5ico-( styrene)47-co-(vinylcarbazole)2] (P(MMA5iS47VCz2)) with the quencher tagged PMMA homopolymer, PMMAi, gave nearly 100% relative luminescence intensities rather than the predicted 0% results. Many of these discrepancies may be explained by the polydispersity and the properties of the polymers used in the study. We found, the preparation conditions, specifically regarding oxygen contamination, also play an important role in determining the luminescence characteristics. Taking these factors into account, this luminescence method was found to be a valuable tool in probing the phase behavior of blends on the molecular level, which is a limitation of many methods currently in use. *See document for correct formulas
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Date: 2000-01

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