Double Hydrophilic Poly(ethylene oxide)-block-Poly(dehydroalanine) Block Copolymers: Comparison of Two Different Synthetic Routes

Abstract

Two different synthetic pathways give access to the amphiphilic block copolymer poly(ethylene oxide)-block-poly(tert-butoxycarbonylaminomethylacrylate). In the first approach, two end-functionalized segments are linked via click chemistry; and in the second approach, a poly(ethylene oxide) (PEO) based macroinitiator is chain extended via atom transfer radical polymerization (ATRP). In both cases the linking unit consists of an amide group, which is necessary to effectively deprotect the corresponding polymer precursor without cleavage of both segments. For this, amide-containing ATRP initiators are employed and successful synthesis by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC) analyses before comparing both pathways is demonstrated. After deprotection, a novel double hydrophilic block copolymer, poly(ethylene oxide)-block-poly(dehydroalanine), is obtained, which is investigated using SEC (aqueous and DMSO) and 1H-NMR spectroscopy. Containing a potentially zwitterionic PDha segment and a high density of both amino and carboxylic groups, pH-dependent aggregation of the block copolymer is expected and is studied using dynamic light scattering, revealing interesting solution properties. The corresponding polymers are applied in various areas including drug delivery systems or in biomineralization.