Supramolecular Linear-g-Hyperbranched Graft Polymers: Topology and Binding Strength of Hyperbranched Side Chains

Complex, reversible hyperbranched graft polymer topologies have been obtained by spontaneous self-assembly. Well-defined adamantyl- and β-cyclodextrin-functionalized polymers were employed to generate linear- g -(linear–hyperbranched) supramolecular graft terpolymers. For this purpose the synthesis of monoadamantyl-functionalized linear polyglycerols (Ada- lin PG) and hyperbranched polyglycerols (Ada- hb PG) as well as poly(ethylene glycol)- block -linear polyglycerol (Ada-PEG- b - lin PG) and poly(ethylene glycol)- block -hyperbranched poly(glycerol) (Ada-PEG- b - hb PG) block copolymers was established. Isothermal titration calorimetry (ITC) with β-cyclodextrin revealed a shielding effect of hyperbranched polyglycerol for the adamantyl functionality, which was significantly less pronounced when using a linear spacer chain between the adamantyl residue and the hyperbranched polyglycerol block. Additionally, well-defined poly(2-hydroxypropylamide) (PHPMA) with pendant β-cyclodextrin moieties was synthesized via RAFT polymerization and sequential postpolymerization modification. Upon mixing of the β-cyclodextrin-functionalized PHPMA with Ada-PEG- b - hb PG, a supramolecular linear- g -(linear–hyperbranched) graft terpolymer was formed. The self-assembly was proven by ITC, diffusion-ordered NMR spectroscopy (DOSY), and fluorescence correlation spectroscopy (FCS).