Dual hydrophilic polymers based on (meth)acrylic acid and poly(ethylene glycol) – synthesis and water uptake behavior

Synthesis and characterization of dual hydrophilic random and block copolymers of acrylic acid (AA) or methacrylic acid (MAA) with poly(ethylene glycol) (PEG) via different controlled radical polymerization techniques are discussed. Initially, reversible addition fragmentation chain transfer (RAFT) polymerization was employed to synthesize homo, random and block copolymers of AA and MAA in ethanol. The polymers were characterized in detail by means of size exclusion chromatography (SEC), 1H NMR spectroscopy, matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry as well as MALDI-TOF MS coupled with collision induced dissociation (CID) to identify the end groups and the repeating units. Following that, atom transfer radical polymerization (ATRP) and RAFT polymerization were employed for the preparation of block copolymers using a PEG macroinitiator and a PEG macro chain transfer agent. Moreover, graft copolymers that contain oligo(ethyleneglycol) pendant groups and AA or MAA have been prepared using the RAFT polymerization process. Additionally, selected homo or block copolymers were tested for their water-uptake properties using a thermal gravimetrical analyzer with a controlled humidity chamber. An advantageous behavior of the copolymers compared to the related homopolymers was reached with the obtained ability to absorb moisture over the complete humidity range as well as to a very high absolute water uptake.