title: PEO-PPO-PEO-based poly(ether ester urethane)s as degradable reverse thermo-responsive multiblock copolymers.
abstract: Aiming at developing biodegradable thermo-responsive polymers that display enhanced rheological properties, a family of PEO-PPO-PEO based poly(ether ester urethane)s, was developed. The materials were produced following a two-step synthetic pathway. The PEO-PPO-PEO triblocks were first end-capped with LA or CL oligo(ester)s whereby pentablocks were produced. Then, the different precursors were chain extended using hexamethylene diisocyanate to create the respective polymers. The length and type of the ester block influenced the behavior of the molecules in water, especially their viscosity versus temperature response. The gelation temperature increased from 23 degrees C for a 20wt% F127 solution to 26 and 31 degrees C for pentablocks with 4.4 and 7.5 lactoyl units, respectively. Materials containing longer LA units failed to show any reverse thermo-responsiveness. The presence of the oligo(ester) blocks also reduced the viscosity of the gel at 37 degrees C. While F127 displayed a viscosity of around 28,000Pas, pentablocks containing 4.4 and 7.5 LA units showed values of 15,400 and 12,600Pas. Also, the viscosity at 37 degrees C as well as the gelation temperature decreased as the molecular weight of the oligo(ester)s increased. Finally, the degradation process of the gels was studied by monitoring their viscosity at body temperature and determining the molecular weight of the polymers, over time. Polymers were tailored so to combine high initial viscosity values with diverse degradation rates, as a function of the length and type of the oligo(ester) present along the polymeric backbone.
authors.affiliation: The Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel. danielc@@vms.huji.ac.il
authors.forename: Daniel
authors.initials: D
authors.lastname: Cohn
authors.forename: Gilad
authors.initials: G
authors.lastname: Lando
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sosnik
authors.forename: Shai
authors.initials: S
authors.lastname: Garty
authors.forename: Avraham
authors.initials: A
authors.lastname: Levi
mesh_terms: D020341:Absorbable Implants; D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry*; D001673:Biodegradation, Environmental; D004952:Esters / Q000737:chemistry; D004987:Ethers / Q000737:chemistry; D005782:Gels; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity
chemical_list: D001672:Biocompatible Materials; D004952:Esters; D004987:Ethers; D005782:Gels; C116176:PEO-PPO-PEO; D011108:Polymers; D011140:Polyurethanes; D011409:Propylene Glycols; D011092:Polyethylene Glycols