The Use of Monodisperse Poly(propylene glycol)‑8 as a Polymeric Additive: Effect on the Gelation Temperature and Rheological Properties of Pluronic Hydrogels.

Pluronic F127 is widely used for hydrogel preparation, but its low gelation temperature (21 °C at a concentration of 25 wt %) and limited ability to deliver hydrophobic drugs hinder medical applications. A standard approach to address these limitations involves combining Pluronic F127 with other polydisperse polymers, further increasing the system complexity. This study demonstrates the use of monodisperse and high-purity poly-(propylene glycol)-8 (PPG-8), obtained via cost-effective chromatographic purification, as a polymeric modifier. The effect of PPG-8 addition to Pluronic F127, varying from 5 to 20 parts (w/w), was assessed via the vial tilt method and oscillatory rheology. The incorporation of PPG-8 increased the gelation temperature from 21 to 31 °C. The impact of PPG-8 addition on the release of small hydrophilic and hydrophobic molecules was also studied. In the presence of PPG-8, the cumulative release of a hydrophobic small molecule increased from 20% to 60%. Contrastingly, the initial burst release of a small hydrophilic molecule was reduced from 81% to 56% in the first 10 min. These findings showcase the use of high-purity modifiers such as PPG-8 to fine-tune the properties of Pluronic hydrogels, enabling more reproducible formulations for potential clinical use.