Pox groups which can be used post
Pox are synthesized by CROP and this provides access to block copolymers by the sequential addition of 2-oxazoline monomers. This concept was applied to the synthesis of amphiphilic systems with tailored composition of the blocks to tune their properties and self-assembly. the vast variety of initiators, terminating agents and 2-oxazoline monomers for the CROP allows to specifically introduce functional groups which can be used post polymerization for the attachment and polymerization of functional groups and polymers, respectively.
Typically, MeOx, EtOx and iPrOx are employed as hydrophilic block forming monomers while long aliphatic chain or aromatic monomers such as 2-nonyl-2-oxazoline (NonOx) and 2-phenyl-2-oxazoline (PhOx) are prominent 2-oxazolines which are used for the formation of the hydrophobic block. Block coPOx consisting of MeOx and 2-butyl-2-oxazoline (ButOx), 2-octyl-2-oxazoline (OctOx) and PhOx blocks were studied and, observed different morphologies depending on the composition and type of block coPOx. Interaction tests with human serum albumin (HSA) revealed that the protein mainly adsorbs at the hydrophilic shell of the assemblies. Tiller and coworkers prepared PMeOx-b-PPhOx-b-PMeOx which formed three different morphologies upon dissolution in aqueous media; unimolecular micelles, micellar aggregates and stable polymersomes. Acidic hydrolysis of PMeOx-b-PPhOx was found to cleave methyl side chains more selectively than in PMeOx-grad-PPhOx. The hydrolyzed block copolymer PEI-b-PPhOx were found to be thermo- and pH-responsive forming spherical micelles in acidic conditions at room and elevated temperature whereas micelles were only observed in water at elevated temperatures. In a recent study Hiller, Weberskirch and coworkers revealed new insights in the temperature dependent stability (between 20 and 80 C) of amphiphilic diblock coPOx composed of a hydrophilic PMeOx block and either 2-pentyl, 2-heptyl or 2-nonyl-2oxazoline as the hydrophobic block.