Functionalization of multihydroxyl branched poly(3-ethyl-3-hydroxy- methyloxetane). Synthesis of star poly(ethylene oxide)

The synthesis of star polymers containing polyethylene oxide) (PEOX) arms connected to poly(3-ethyl-3-hydroxymethyloxetane) (PEHMOX) core is described. The medium molecular weight (Mn ∼2 · 103) branched multihydroxyl polyether -PEHMOX - was functionalized by acrylate groups. Polyethers with different functionalization degree were obtained using different molar excess of (meth)acryloyl chloride as esterification agent. Functionality of polymers was analyzed by 1H NMR and MALDI TOP MS methods. PEHMOX samples with different number of acrylate groups (PEHMOX-Acrylate functionalized in 55% and 80%) were further applied to the synthesis of star polymers using grafting onto method. Thus, star copolyethers with hydrophobic PEHMOX core and hydrophilic arms PEOX were obtained by Michael addition of α-amino-ω-methoxy-poly(ethylene oxide) (PEOX-NH2). Complete conversion of acrylate groups was confirmed on the basis of 1H NMR analysis. From the overall composition of star polymers it was concluded that PEOX arms were attached to the PEHMOX core either through one or two acrylate groups, which means that Michael addition proceeded with involvement of one or two protons of primary end-amine groups of the PEOX-NH2 chain. Star PEOX polymers with PEHMOX core not fully functionalized, i.e. still containing reactive hydroxyl groups, are potential precursors for miktoarm star polymers.