Abstract
Hybrid polymers containing pyrene (Py) units bound to linear poly(silsesquioxane) (LPSQ) chains through flexible linkers containing heteroatoms (S, N, O) (LPSQ-triazole-Py and LPSQ-amide-Py) exhibit intense fluorescence emission, both in very diluted solutions (c = 10−8 mol/L) and in the solid state. The materials are thermally stable and exhibit good thin film forming abilities. Their optical and physicochemical properties were found to be strongly dependent on the structure of the side chains. Comparative studies with octahedral silsesquioxane (POSS) analogues (POSS-triazole-Py and POSS-amide-Py) emphasized the role of the specific double-strand architecture of the LPSQ backbone and distribution of side Py groups for their photo-luminescent properties. The new hybrid materials were tested as fluorescence energy donors to red-emitting dyes (Nile Red and Coumarine 6). All the silsesquioxanes studied were found to be able to transfer FL emission energy to Coumarin 6, irrespectively of their spatial structure. However, due to the differences in the wavelength range of FL emission, only LPSQ-triazole-Py were able to act as energy donors to Nile Red. The Py-grafted LPSQ may be also applied for development of soluble and highly emissive chemosensors. Their fluorescent nature was explored for the detection of Cu(II), Fe(III), Co(II), Ag(I), Hg(II), Mg(II), Ca(II), Pb(II) and Zn(II). The morphology of the side chains and hydrogen-bonding interactions influenced the sensing capacity of all the studied materials.
Highlights
With fast growing awareness of environmental issues, an increasing level of pollution in the natural environment and the search for new reproducible energy sources, the demand for technologies has been shifted to novel intelligent materials
LPSQoligomeric silsesquioxanes (POSS), are linear counterparts of Properties the well-known polyhedral but due to are their polymeric nature andwell-known highly ordered double-chain structures, they exhibit linear counterparts of the polyhedral oligomeric silsesquioxanes (POSS), completely different physicochemical properties but due to their polymeric nature and highly ordered double-chain structures, they exhibit completely with a physicochemical highly regular backbone can be prepared by polycondensation of different properties [32,38,39,40]
linear poly(silsesquioxane) (LPSQ) with a highly cyclotetrasiloxane-2,4,6,8-tetraols or step-wise coupling polycondensation. The latter regular backbone can be prepared by polycondensation of cyclotetrasiloxane-2,4,6,8-tetraols [31] or method was used forpolycondensation the preparation of polymeric precursors—poly(3-chloropropylsilsesquioxanes) step-wise coupling. The latter method was used for the preparation of polymeric
Summary
With fast growing awareness of environmental issues, an increasing level of pollution in the natural environment and the search for new reproducible energy sources, the demand for technologies has been shifted to novel intelligent materials. Derivatives of pyrene (Py) are organic π-conjugated molecules that exhibit strong absorbance, high quantum yield and good photochemical stability [4,5]. Those optoelectronic properties may be of advantage in light harvesting systems based on nonradiative excited state energy transfer (EnT). Green light emitting Py excimers are formed when geometrical overlap of aromatic rings is provided. Organized systems, such as crystals of Py-containing molecules emit almost exclusively excimer fluorescence in the solid state [9]. Luminescence decrease or quenching is Materials 2020, 13, 4491; doi:10.3390/ma13204491 www.mdpi.com/journal/materials
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