title: Mediation of a phase transition in hyaluronate films by the counterions Li, Cs, Mg and Ca as observed by infrared spectroscopy, optical microscopy and optical birefringence.
abstract: Infrared (IR) spectroscopy and optical microscopy have been performed as a function of relative humidity (rh) on wet-spun oriented films of hyaluronate (HA) prepared with various counterions. Complete swelling measurements have been obtained through optical microscopy for films of Cs-, Mg-, and CaHA. IR spectroscopy of Cs-, Mg-, Ca-, and LiHA films was performed for skeletal vibrations (800-1000 cm(-1)) and for vibrational modes (1150-1300 cm(-1)) attributed to C-C and C-O stretching modes and C-C-H and C-O-H bending modes. These techniques reveal evidence of a counterion-dependent phase transition occuring at high relative humidities. Optical birefringence measurements on the polycrystalline samples showed order before and disorder after the transition from lower to higher humidity.
authors.affiliation: Dept. of Physics, Geology and Astronomy, The University of Tennessee at Chattanooga, 37403, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Marlowe
authors.forename: A
authors.initials: A
authors.lastname: Hoppe
authors.forename: A
authors.initials: A
authors.lastname: Rupprecht
authors.forename: S A
authors.initials: SA
authors.lastname: Lee
mesh_terms: D001718:Birefringence; D002118:Calcium / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002412:Cations; D002586:Cesium / Q000737:chemistry*; D006820:Hyaluronic Acid / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D008853:Microscopy; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D002412:Cations; D002586:Cesium; D006820:Hyaluronic Acid; D008094:Lithium; D008274:Magnesium; D002118:Calcium