Synthesis and characterization of photoluminescent hybrids of poly(ε-caprolactone)-grafted-polyhedral oligosilsesquioxane by using a combination of ring-opening polymerization and click chemistry

Abstract

Photoluminescent hybrids of poly(ε-caprolactone) (PCL), polyhedral oligosilsesquioxane (POSS) and terbium ions (Tb³⁺) were synthesized by using a combination of ring-opening polymerization (ROP), click chemistry and coordination chemistry. Initially, acetylene functionalized PCL (alkyne-PCL-COOH) was prepared by using ROP of ε-caprolactone with propargyl alcohol, and azide-substituted POSS (POSS-N₃) was prepared by using the reaction of chloropropyl-heptaisobutyl-substituted POSS with NaN³. The click reaction between alkyne-PCL-COOH and POSS-N₃ afforded POSS-g-PCL, which was subsequently coordinated with Tb³⁺ ions in the presence of 1,10-phenanthroline to produce POSS-g-PCL-Tb³⁺-Phen. The structures and compositions of the hybrids were investigated by using ¹H nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscopy (TEM), and Thermogravimetric analysis (TGA). The optical properties of POSS-g-PCL-Tb³⁺-Phen complexes were characterized by using photoluminescence spectroscopy, which showed four high emission bands centered at 489, 545, 584, and 620 nm with excitation at 330 nm. The emission spectra of the europium-ion-coordinated hybrids, POSS-g-PCL-Eu³⁺-Phen, had four high-intensity peaks, 594, 617, 652 and 686 nm, for an excitation wavelength of 352 nm.