Premium
Time‐Resolved Emission Anisotropy of Anthracene Fluorophore in the Backbone of Stereoregular Poly(methyl methacrylate)
Author(s) -
Pokorná Veronika,
Výprachtický Drahomír,
Pecka Jan,
Mikeš František
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20010101)202:1<155::aid-macp155>3.0.co;2-i
Subject(s) - anthracene , fluorophore , methyl methacrylate , poly(methyl methacrylate) , polymer chemistry , materials science , anisotropy , photochemistry , fluorescence , chemistry , polymer , copolymer , optics , physics , composite material
Syndiotactic fluorescent poly(methyl methacrylate) labeled with anthracene in the middle of the polymer chain was prepared by living anionic polymerization ( s ‐PMMA‐A). Absorption and emission transition moments of the label are oriented in the direction of the polymer backbone, therefore the fluorophore really reflects the mobility of polymer segments. Stereocomplex formation between isotactic poly(methyl methacrylate) ( i‐ PMMA) and s‐ PMMA‐A was studied by time‐resolved fluorescence depolarization method in solvents with different complexing ability and at different i‐ PMMA/ s‐ PMMA‐A ratios. The stoichiometry of the stereocomplex i‐ PMMA/ s‐ PMMA‐A was 1/2 and 1/1.5 in N , N ‐dimethylformamide and 1,4‐dioxane, respectively. The stereocomplex was not formed in chloroform. Determination of the rotational correlation times at different temperatures enabled us to evaluate the height of the potential barrier to rotational motion of the anthracene fluorophore ( ΔU r ) or activation enthalpy and entropy ( ΔH ≠ , ΔS ≠ ) of this process in the presence and absence of the stereocomplex. Time‐resolved emission anisotropy data, r (t) , were analyzed by intermediate zone formula of the torsion dynamics theory for stiff macromolecules. The torsional rigidity of the stereocomplex i‐ PMMA/ s‐ PMMA‐A, α = 1.9×10 –18 N·m in N , N ‐dimethylformamide at 30°C, is larger than that obtained for DNA ( α = 3.8×10 –19 N·m). Self‐aggregation of s ‐PMMA takes place probably in N , N ‐dimethylformamide.