Macromolecular dyes by chromophore-initiated ring opening polymerization of L-lactide
| Autor: | Francesca Cicogna 1, Guido Giachi 2, Luca Rosi 2, Elisa Passaglia 1, Serena Coiai 1, Marco Frediani 2 |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Conferenza di Dipartimento DSCTM, Bressanone, 28-30/10/2019 info:cnr-pdr/source/autori:Francesca Cicogna 1, Guido Giachi 2, Luca Rosi 2, Elisa Passaglia 1, Serena Coiai 1, Marco Frediani 2/congresso_nome:Conferenza di Dipartimento DSCTM/congresso_luogo:Bressanone/congresso_data:28-30%2F10%2F2019/anno:2019/pagina_da:/pagina_a:/intervallo_pagine |
| Popis: | A lot of research is focusing on improving physico-chemical and mechanical features of PLA, but less efforts are made to study and expand its optical activity in the UV-visible region. Since its general characteristics make PLA particularly useful for fibers, packaging and similar applications, UV-barrier capabilities and aesthetic appearance are topic issues with a strong influence on the performances of products and appeal. Considering the difficulties in dying PLA-fibers and the possible loss by evaporation or leaching of low molecular weight dyes mixed with the polymer matrix, the immobilization of the chromophores onto the polymer matrix can be a valuable alternative to produce a stable and homogeneously dyed PLA films or fibers. In this paper the use of chromophores as initiators in the ring opening polymerization (ROP) of L-lactide catalyzed by stannous octoate was proposed. The so obtained end-functionalized polylactides may be considered "macromolecular dyes" that can be used "as synthesized" or can be blended with other polymers. In this study, the ROP of L-lactide catalyzed by stannous octoate was carried out in bulk in the presence of three chromophores: 9-fluorenyl-methanol (FM), 9H-carbazol-ethanol (CA) and 2-[4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino]ethanol (Disperse Red 13, DR). FM and CA absorb in the UVa and UVb region and emit by fluorescence in the range between 300 and 400 nm, whereas DR is a commercially available dye with absorption maximum at about 480 nm in the visible portion of the electromagnetic spectrum. Different initiator/lactide ratios were used for each chromophore in order to keep low the MWs of the products, to facilitate their characterization and to emphasize the relation between initiator and polymer properties. The obtained materials were structurally characterized by FT-IR, 1H-NMR and SEC; their thermal properties were studied by DSC and their photophysical features were determined by UV-Vis spectroscopy and fluorescence emission and compared to those of the free chromophores. Some selected macromolecular dyes were mixed to high molecular weight PLA with the aim to obtain "dyed PLA" films. For comparison high molecular weight PLA was melt mixed also with the free chromophores. The films were analyzed by UV-Vis spectroscopy and florescence emission and it was demonstrated that the photophysical properties of the macromolecular dyes were transferred to the PLA films. Moreover, by migration tests carried out suspending the PLA films containing the macromolecular dyes or the free chromophores in aqueous/ethanol solution, it was observed that the low molecular weight chromophores are lost by migration whereas macromolecular dyes are not released. |
| Databáze: | OpenAIRE |
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