Morpholine and thiomorpholine derived polymers: Multifunctional platforms for biological applications

Polymers containing morpholine or thiomorpholine (oxide) functions showed an increased interest for biological applications in the recent years. Morpholine containing polymers provide high hydrophilicity and comparable biocompatibility with polyethylene glycol (PEG) which is the gold standard in biology. In particular, poly(N-acryloyl) morpholine is one of the most cited polymers containing morpholine, with applications in drug delivery, protein detection or the design of anticoagulant materials. However, there are very few examples of polymers derived from thiomorpholine and thiomorpholine oxide. Compared to morpholine polymers, thiomorpholine containing polymers are less hydrophilic, while thiomorpholine oxide derived polymers are more hydrophilic. Thiomorpholine and thiomorpholine oxide polymers are biocompatible and were recently studied as oxidation sensitive materials and as hemocompatible materials. This review highlights the correlation between the structural characteristics of morpholine and thiomorpholine (oxide) based polymers and their use in various biological applications.