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
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.