Crystallization-promoted emission enhancement of poly( l -lactide) containing a fluorescent salicylideneazine center with aggregation-enhanced emission properties

Fluorescent 1,2-bis(2,4-dihydroxybenzylidene)hydrazine (CN 4 OH) with aggregation-enhanced emission (AEE) properties was used as the initiator to induce the ring-opening polymerization (ROP) of l -lactide, resulting in polymer CN-PLLA( n )s containing an AEE-active CN center. With both pairs of p -...

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Bibliographic Details
Published in:Polymer chemistry 2015-01, Vol.6 (12), p.2264-2273
Main Authors: Hsiao, Tai-Shen, Huang, Po-Chiao, Lin, Li-Yang, Yang, Deng-Jie, Hong, Jin-Long
Format: Article
Language:English
Subjects:
Constrictions
Crystal structure
Crystallization
Emission
Emission analysis
Neighbouring
Polylactides
Rotational
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Summary:Fluorescent 1,2-bis(2,4-dihydroxybenzylidene)hydrazine (CN 4 OH) with aggregation-enhanced emission (AEE) properties was used as the initiator to induce the ring-opening polymerization (ROP) of l -lactide, resulting in polymer CN-PLLA( n )s containing an AEE-active CN center. With both pairs of p - and o -hydroxyl (OH) groups, CN 4 OH initiates an ROP of l -lactide solely with the p -OH groups and the resulting CN-PLLA( n )s are highly-emissive due to the rotational restriction imposed by the remaining p -OHs of the central CN unit. A study on the solid emission of CN-PLLA( n )s reveals that crystallization of the neighbouring PLLA chains, instead of the fluorescent CN center itself, determines the AEE activity, e.g. the emission of crystalline CN-PLLA( n )s is much higher in emission intensity than amorphous CN-PLLA( n )s. As restricted molecular rotation is the main mechanism leading to AEE activity, effective rotational restriction imposed by crystalline polylactide chains is responsible for the high emission of crystalline CN-PLLA( n )s, in contrast to the weak emission of amorphous CN-PLLAs. The emission promotion of the fluorescent CN center by the neighbouring polylactide chains is designated as crystallization-promoted emission enhancement (CPEE) and is the focus of the study.
ISSN:1759-9954
1759-9962
DOI:10.1039/C4PY01774A