Functional PMMA nanogels by cross-linking with cyclodextrin methacrylate

Poly(methyl methacrylate) (PMMA) nanogels cross-linked with cyclodextrin-methacrylate (CD-MA) are synthesized by surfactant-free precipitation polymerization. α-, β- and γ-cyclodextrins (CD) are functionalized with methacrylic groups (CD-MAs) with an average amount of vinyl bonds per CD molecule of 2, 4, or 6, and they are used as cross-linker and as complexation unit. The formation and the particle growth correlate with increase of the CD-MA concentration in the reaction mixture. This leads to reduction of the final hydrodynamic radii of the nanoparticles from 363 nm to 36 nm and an improved colloidal stability in the aqueous phase. The number of vinyl groups per CD molecule influences the size of the nanogels, too, and induces the formation of smaller particles with higher cross-linking degree. The PMMA nanogels with CD-MA are swellable in water mixable and water immiscible solvents, their size increases with increase of the portion of organic media. Controlled complexation of guest molecules was achieved by the nanogels in dependence on their CD-MA content and their degree of cross-linking, as shown by studies with phenolphthalein.