384051 Morphology and Mesoscale Characterization of Self-Assembled Poly (ethylene glycol)-Poly(MTC-benzyl ester) Triblock Copolymer Hydrogels

Wednesday, November 19, 2014: 5:25 PM
International 9 (Marriott Marquis Atlanta)
Courtney Fox1, Amanda C. Engler2, James Hedrick3 and Curtis W. Frank1, (1)Chemical Engineering, Stanford University, Stanford, CA, (2)Nanomedicine, IBM, San Jose, CA, (3)IBM Almaden Research Center, San Jose, CA

A novel class of supramolecular hydrogels was produced by synthesizing a triblock polycarbonate material using organocatalytic ring-opening polymerization (ROP) of a poly(ethylene glycol) PEG macroinitiator with a cyclic monomer (MTC-OBn), then subsequently physically cross-linking triblock copolymers by hydrophobic collapse to form hydrogels in water. Controlling the molecular properties of triblock copolymer materials, primarily poly(carbonate) and poly(ethylene glycol) segment lengths, resulted in a viable platform for probing mesoscale material properties using small angle X-ray scattering (SAXS). Furthermore, the macroscale mechanical properties of these supramolecular networks were characterized using oscillatory shear rheology. SAXS spectra show a strong scattering peak, indicating a molecular domain size of 20 - 25 nm. At higher concentrations of the triblock hydrogelator a structural transition from isolated hydrophobic clusters to a lamellar assembly was observed. Modeling of poly(carbonate) and poly(ethylene glycol) backbone size demonstrated that the polymers in this structure behaved as a 2D SAW.  SAXS and rheological characterization indicates that the molecular weight of the polycarbonate segment affects the gel structure on both the mesoscale and macroscale.

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See more of this Session: Mechanics and Structure in Polymers
See more of this Group/Topical: Materials Engineering and Sciences Division