Τίτλος:
Thermal analysis studies of doping effects on the conformational motions of polymer chains in solid solutions with lasing molecules
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
The advancement of the solid-state dye laser performance largely depends on the systematic study of the dye-matrix interactions at the nanoscopic scale. The current work deals with blends of a comparatively inert dye host, poly(methyl methacrylate) (PMMA), with nonionic/apolar (substituted perylenes) and ionic/polar (rhodamine 6G, pyrromethene 567) dyes at ≈ 10-4 mol L-1 loading. Differential scanning calorimetry (DSC) and thermally stimulated currents (TSC) were used to explore the relative strength of inter- and intramolecular guest-host interactions by monitoring blending-induced modifications of the high-temperature signals: the segmental relaxation, the space-charge relaxation, and the liquid-liquid transition. Both techniques revealed the antiplasticizing role of the oligomeric organics on the relaxation dynamics of polymer segments, evidenced by clear glass-transition temperature upshifts. It becomes apparent that this effect is independent of the size, polarity, and ionicity of the dopant, signifying a common mechanism underway. It is suggested that, at least for the dyes under investigation, the chromophores simply fill the voids within the matrix, imposing strong steric hindrances on the rearrangement of the long-range structure. A comparison between the present results and earlier low-temperature dielectric data reveals that the large-scale relaxation dynamics show stronger perturbations due to blending, in comparison to the localized rotational motion of the pendant groups. DSC provided estimates for the unconverted monomer percentages in the solid blends. These were also determined more accurately by nuclear magnetic resonance (NMR), which additionally confirmed that the tacticity of the chains is not affected by the presence of the dye. © 2007 American Institute of Physics.
Συγγραφείς:
Kalogeras, I.M.
Pallikari, F.
Vassilikou-Dova, A.
Neagu, E.R.
Περιοδικό:
Journal of applied physics
Εκδότης:
American Institute of Physics Inc.
Λέξεις-κλειδιά:
Differential scanning calorimetry; Doping (additives); Nuclear magnetic resonance; Polymethyl methacrylates; Solid solutions; Solid state lasers; Thermoanalysis, Lasing molecules; Oligomeric organics; Polymer chains; Thermally stimulated currents (TSC), Dye lasers
