Self-association behavior of amphiphilic molecules based on incompletely condensed cage silsesquioxanes and poly(ethylene glycol)s

Abstract

Polyhedral oligomeric silsesquioxane (POSS) is an important building block for constructing organic-inorganic hybrid molecules or polymers. In this work, we report amphiphilic, incompletely condensed POSSs (IC-POSSs) possessing various substituents on the seven silicon atoms and two kinds of poly(ethylene glycol)s (PEGs) with different chain lengths. The IC-POSS cores possessed comparable thermal stability to that of the completely condensed POSS (CC-POSS) analogs, despite their open cage structure. The amphiphilic IC-POSSs formed micelles of different sizes and had polydispersity indices (PDIs) that were dependent on the substituents and the PEG chain length. Additionally, the lower critical solution temperatures (LCSTs) were observed for amphiphilic IC-POSSs possessing shorter PEG chains, while aqueous solutions of those with longer PEG chains showed high transmittance even at 80 °C. Amphiphilic incompletely condensed polyhedral oligomeric silsesquioxanes possessing various substituents and poly(ethylene glycol)s of different chain lengths have been developed. It has been elucidated that their self-association behaviors in water are dependent on the substituents and chain lengths of poly(ethylene glycol)s. Precise molecular design, excellent thermal stability, and good dispersibility have been realized at once.