title: Characterization of anisotropic poly(vinyl alcohol) hydrogel by small- and ultra-small-angle neutron scattering.
abstract: Poly(vinyl alcohol) (PVA) hydrogels are formed from PVA solution when physical cross-links form during freeze/thaw cycling. By applying a stress during the freeze/thaw process, PVA hydrogels with anisotropic mechanical properties are produced. We have used small- and ultra-small-angle neutron scattering to study the structure at length scales of 2 nm to 10 mum. By supplementing the neutron data with data from atomic force microscopy, we have probed a large range of length scales within which structural changes responsible for bulk anisotropy occur. We model the gel as interconnected PVA blobs of size 20-50 nm arranged in fractal aggregates extending to micrometers or tens of micrometers. Bulk mechanical anisotropy appears to be due to the alignment of blobs and connections between blobs. This information is essential for tailoring mechanical properties for applications where anisotropy is desirable such as to match the properties of natural tissue in coronary grafts and to control diffusive properties in active wound dressings.
authors.affiliation: Department of Physics and Astronomy, The University of Western Ontario, London, Ontario N6A 3K7, Canada.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Hudson
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Hutter
authors.forename: Mu-Ping
authors.initials: MP
authors.lastname: Nieh
authors.forename: Jeremy
authors.initials: J
authors.lastname: Pencer
authors.forename: Leonardo E
authors.initials: LE
authors.lastname: Millon
authors.forename: Wankei
authors.initials: W
authors.lastname: Wan
mesh_terms: D000535:Aluminum / Q000737:chemistry; D016880:Anisotropy; D001672:Biocompatible Materials / Q000737:chemistry; D001026:Coronary Artery Bypass; D004058:Diffusion; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D020100:Hydrogels; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D009502:Neutrons; D011142:Polyvinyl Alcohol / Q000737:chemistry*; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D014945:Wound Healing
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011142:Polyvinyl Alcohol; D000535:Aluminum