Abstract
PMMA based polymer blends have been infused with luminescent phospholes and have been structured via nanoimprint. While symmetrically substituted phospholes are prone to crystallization and phase separation, structural modification of the phosphole backbone in the α‐ and β‐positions has been explored, which prevents these issues; a structural explanation for this is suggested. Best phase integrity has been obtained for β‐silyl‐substituted phospholes, which were implemented in thin films and beads. The emission wavelengths of the phospholes are shifted bathochromically in the polymer matrix as compared to the neat compounds featuring emission bands near 500 nm. This enables tracking of the fluorescent beads using standard fluorescence microscopy.
Highlights
Phospholes are fundamental and relatively simple functional molecules with fascinating properties useful in designing molecular electronic devices.[1]
The literature known triphenylphosphole 1 was used as a first example owing to its high fluorescence quantum yield at an emission wavelength of 459 nm and its chemical robustness.[7]
During the spin coating process phase separation was observed for typical imprint mixtures of 4 % PMMA in ethyl lactate with phosphole 1 at a concentration of 20 g/L leading to crystalline 1
Summary
Phospholes are fundamental and relatively simple functional molecules with fascinating properties useful in designing molecular electronic devices.[1]. Since its early demonstration in 1996, NIL has been continuously developed and its use has been implemented within a wide variety of fields and applications.[4] As a proof of concept fluorescent NIL beads have been prepared using fluorescein as a simple molecular fluorophore.[4d,5] Fluorescent metal ions such as lanthanides are difficult to incorporate into polymer blends owing to their polar properties. NIL patterned fluorescent beads containing europium(III)oxide nanoparticles have been developed recently where phase separation could be avoided at low particle loadings.[6] Given the proven flexibility of the phosphole scaffold in tuning the luminescence properties of molecules we set out to explore the possibility to infuse the nanoimprinted polymer with phospholes as fluorescent molecules (Scheme 1). We report our results in preparing the first imprinted 3D structures and beads containing phospholes along with variation of the molecular structure to avoid phase separation between fluorophore and polymer blend during the NIL process
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