New hyaluronic acid based brush copolymers synthesized by atom transfer radical polymerization

In this work, an efficient method for the synthesis of hyaluronic acid based brush copolymers using atom transfer radical polymerization (ATRP) has been reported. At first, two different hyaluronic acid (HA) based macroinitiators have been prepared and then they have been used for the polymerization via ATRP of hydrophilic or hydrophobic molecules carrying vinyl portions. In particular, by linking 2-bromo-2-methylpropionic acid (BMP) to the primary hydroxyl groups of tetrabutyl ammonium salt of HA (HA-TBA) or to amino groups of the ethylenediamino derivative of HA-TBA (HA-TBA-EDA), two macroinitiators (HA-TBA-BMP and HA-TBA-EDA-BMP) have been obtained. Then they have been used for the ATRP of poly(ethylene glycol) methacrylate (PEGMA), butyl methacrylate (BUTMA) or N-isopropylacrylamide (NIPAM) using a complex of Cu(I) and 2,2'-Bipyridyl (Bpy), as a catalyst. Both macroinitiators and final copolymers, named as HA-BMP-pPEGMA, HA-BMP-pBUTMA, HA-BMP-pNIPAM, HA-EDA-BMP-pPEGMA, HA-EDA-BMP-pBUTMA and HA-EDA-BMP-pNIPAM, have been characterized by spectroscopic analysis and size exclusion chromatography to confirm the success of the polymerization process.