Synthesis and self-assembly behavior of thermo-responsive star-shaped POSS–(PCL–P(MEO2MA-co-PEGMA))16 inorganic/organic hybrid block copolymers with tunable lower critical solution temperature

Abstract

In this work, we report that well-defined amphiphilic star-shaped polyhedral oligomeric silsesquioxane (POSS)-based inorganic/organic hybrid block copolymers of poly(ε-caprolactone)–poly(2-(2-methoxyethoxy)ethyl methacrylate)-co-poly(ethylene glycol) methacrylate (POSS–(PCL–P(MEO₂MA-co-PEGMA))₁₆) were synthesized via click chemistry, ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP), and their synthesis was confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC) and X-ray photoelectron spectroscopy (XPS). The obtained polymers could self-assemble into ellipsoidal aggregates with a moderately uniform size, owing to the amphiphilic properties of the hydrophobic inorganic POSS and PCL cores and the hydrophilic P(MEO₂MA-co-PEGMA) segments. These thermo-responsive organic/inorganic hybrid polymeric micelles exhibited critical phase transition temperatures in water, which could be finely tuned by changing the feed ratios of PEGMA and MEO₂MA. The lower critical solution temperature (LCST) of star-shaped POSS–(PCL–P(MEO₂MA-co-PEGMA))₁₆ increased from 34 to 57 °C with the increase of PEGMA content. The results were investigated by ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). When the temperature was higher than the corresponding LCSTs, the micelles started to associate and form spherical nanoparticles. Therefore, POSS–(PCL–P(MEO₂MA-co-PEGMA))₁₆ block copolymers, a class of novel organic/inorganic hybrid materials with advantageous properties, are amphiphilic hybrid polymers with potential applications as nano-carriers, nano-reactors, and smart materials and in the biomedical field.