title: Hydrogel networks based on ABA triblock copolymers.
abstract: BACKGROUND
  Triblock copolymers from hydrophilic oligo(ethylene glycol) segment A and oligo(propylene glycol) segment B, providing an ABA structure (OEG-OPG-OEG triblock), are known to be biocompatible and are used as self-solidifying gels in drug depots. A complete removal of these depots would be helpful in cases of undesired side effects of a drug, but this remains a challenge as they liquefy below their transition temperature. Therefore we describe the synthesis of covalently cross-linked hydrogel networks.
  
  
  METHODS
  Triblock copolymer-based hydrogels were created by irradiating aqueous solutions of the corresponding macro-dimethacrylates with UV light. The degree of swelling, swelling kinetics, mechanical properties and morphology of the networks were investigated.
  
  
  RESULTS
  Depending on precursor concentration, equilibrium degree of swelling of the films ranged between 500% and 880% and was reached in 1 hour. In addition, values for storage and loss moduli of the hydrogel networks were in the 100 Pa to 10 kPa range.
  
  
  CONCLUSIONS
  Although OEG-OPG-OEG triblocks are known for their micellization, which could hamper polymer network formation, reactive OEG-OPG-OEG triblock oligomers could be successfully polymerized into hydrogel networks. The degree of swelling of these hydrogels depends on their molecular weight and on the oligomer concentration used for hydrogel preparation. In combination with the temperature sensitivity of the ABA triblock copolymers, it is assumed that such hydrogels might be beneficial for future medical applications - e.g., removable drug release systems.
authors.affiliation: Center for Biomaterial Development and Berlin-Brandenburg Centre for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow, Germany.
authors.forename: Lucile
authors.initials: L
authors.lastname: Tartivel
authors.forename: Marc
authors.initials: M
authors.lastname: Behl
authors.forename: Michael
authors.initials: M
authors.lastname: Schroeter
authors.forename: Andreas
authors.initials: A
authors.lastname: Lendlein
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008823:Micelles; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000737:chemistry*; D011312:Pressure; D012212:Rheology; D044366:Transition Temperature; D014466:Ultraviolet Rays
chemical_list: D001672:Biocompatible Materials; D008823:Micelles; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols