Complex Macromolecular Architectures by Atom Transfer Radical Polymerization

Controlled radical polymerization has proven to be a viable route to obtain polymers with narrow polydispersities (PDI’s) and controlled molecular weights under simple reaction conditions. It also offers control over the chain‐ends of the synthesized polymer. Atom transfer radical polymerization (ATRP) is the most studied and utilized of these techniques. In this study ATRP has been utilized as a tool to obtain different complex macromolecular structures. In order to elaborate a system for which a multitude of chains can polymerize in a controlled manner and in close proximity to one another, a multifunctional initiator based on poly(3‐ethyl‐3‐(hydroxymethyl)oxetane was synthesized. The macroinitiator was used to initiate ATRP of methyl acrylate (MA). The resulting dendritic‐linear copolymer hybrids had controlled molecular weights and low PDI’s. Essentially the same system was used for the grafting of MA from a solid substrate, cellulose. A filter paper was used as cellulose substrate and the hydroxyl groups on the cellulose were modified into bromo‐ester groups, known to initiate ATRP. Subsequent grafting of MA by ATRP on the cellulose made the surface hydrophobic. The amount of polymer that was attached to the cellulose could be tailored. In order to control that the surface polymerization was ‘living’ and hence that the chain‐end functionality was intact, a second layer of a hydrophilic monomer, 2‐hydroxyethyl methacrylate, was grafted onto the PMA‐ grafted cellulose. This dramatically changed the hydrophilicity of the cellulose. Dendronized polymers of generation one, two and three were synthesized by ATRP of acrylic macromonomers based on 2,2‐bis(hydroxymethyl)propionic acid. In the macromonomer route, macromonomers of each generation were polymerized by ATRP. The polymerizations resulted in polymers with low PDI’s. The kinetics of the reactions were investigated, and the polymerizations followed first‐order kinetics when ethyl 2‐bromopropionate was used as the initiator. In the ‘graft‐onto’ route dendrons were divergently attached to a dendronized polymer of generation one, that had been obtained by ATRP.