Synthesis of Poly(2-methyl-2-oxazoline) Star Polymers with a β-Cyclodextrin Core

Synthesis of star polymers with a β-cyclodextrin (CD) core was undertaken using the arm-first, then the core-first strategy. Cationic ring opening polymerisation (CROP) of 2-methyl-2-oxazoline (MeOx) was first initiated by allyl bromide, and then quenched with heptakis(6-deoxy-6-amino)β-CD in order to get a 7-arm star polymer. Then heptakis(6-deoxy-6-iodo-2,3-di-O-acetyl)β-CD was synthesised in order to get an initiator for the CROP of MeOx. Initiation and propagation kinetic measurements were undertaken and the ratio kp/ki was found to be too high to provide a controlled polymerisation. Using iodine as co-initiator allowed a decrease of the kp/ki ratio that gave better control of the polymerisation. DOSY NMR and viscosity characterisations were undertaken, and both techniques lead to the demonstration of a lower hydrodynamic volume of the star polymers versus the linear counterparts, for compounds of the same molecular weight.