Temperature-sensitive nanogels: poly(N-vinylcaprolactam) versus poly(N-isopropylacrylamide)

Poly(N-isopropylacrylamide) (PNIPAM) and poly(N-vinylcaprolactam) (PVCL) are temperature-responsive polymers which show a lower critical solution temperature (LCST) around 32 degrees C in aqueous solutions. Nanogels based on these temperature sensitive polymers swell at low temperatures and collapse at high ones, showing a volume phase transition temperature (VPTT) near physiological temperature. This unique behavior makes these nanogels attractive for biotechnological applications. PNIPAM is the building block of a huge amount of nanogels reported in the literature. However, PVCL is especially interesting due to the fact that it is very stable against hydrolysis and biocompatible. In this mini-review, various synthesis procedures together with the functionalization of different PNIPAM-and PVCL-based nanogels are revised and compared.