by National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Program, For sale by the National Technical Information Service] in [Washington, DC], [Springfield, Va .
Written in English
|Statement||Jag J. Singh...[et al.].|
|Series||NASA technical memorandum -- 4326.|
|Contributions||Singh, Jag J., United States. National Aeronautics and Space Administration. Scientific and Technical Information Program.|
|The Physical Object|
The free-volume theory of diffusion was developed by Vrentas and Duda. 1 This theory is based on the assumption that movement of a small molecule (e.g., solvent) is accompanied by a movement in the solid matrix to fill the free volume (hole) left by a displaced solvent molecule. Several important conditions must be described to model the process. It is commonly invoked that the molecular mobilit,y and hence the barrier properties of biopolymer matrices are related to the local free volume [5, 7]. However, to date there is limited information about the nature of this free volume in gelatin oligomers and how it is a ected by factors such as temperature, matrix composition and wa-ter content. Positron annihilation lifetime measurements are reported for four monodisperse polystyrenes with molar mass M = 4,, 9,, 25,, and , The temperature dependences of orthopositronium (o‐Ps) lifetime (τ 3) and intensity (I 3) were measured from 5°C to T g + 30°C for each sample. From these data, the free volume hole size, 〈v f (τ 3)〉, and fractional free volume h ps =CI 3. dependence of the viscosity of polymer solutions on molecular weight at different temperatures and concentrations. It was shown that a variation in this dependence with certain “intermediate” molecular weights is due to the formation of typical structures in polymer solutions. Viscosity of.
C 1 and C 2 can be calculated from free volume theory or measured experimentally. Both depend on the definition of T 0. If ln is replaced with the base 10 log and T 0 = T g then C 1 = and C 2 = These values which are commonly used indicate that the free volume of a glassy polymer at T g is % of the total volume. Polymers: Molecular Weight and its Distribution 1. Introduction Synthetic polymers are polydisperse to varying degrees in a variety of ways. The chains in a sample may differ in, for example, molecular weight, degree of long or short-chain branching, stereostructure or composition (either grossly, as with copolymers, or slightly, as with end groupFile Size: 73KB. Physical properties of polymers include molecular weight, molar volume, density, degree of polymerization, crystallinity of material, and so on. Specific volume Crystalline solid Solid crystalline state Temperature Variation of tensile strength with molecular weight of the polymer. 3. Free volume methods. Free volume is the fraction of the volume not occupied by the polymer. This concept has found uses in discussing physical properties such as viscosity, diffusion in liquids, viscoelasticity, electrical conductivity, the glass transition and plastic yielding. EarlyFile Size: 13KB.
In , Benoit and co-workers found an excellent correlation between elution volume and a dynamically based molecular size, the hydrodynamic volume VH, for a wide range of species and large-scale. Essentials of Polymer Science and Engineering. Paul C. Painter, Professor, Penn State University Michael M. Coleman, Professor Emeritus, Penn State University. ISBN: , ©, pages, 7×10, Hardcover or Online Book. Student price available. Radical solvent-free suspension polymerization of styrene with 3-mercapto hexyl-methacrylate (MHM) as the branching monomer has been carried out using 2,2′-azobisisobutyronitrile (AIBN) as the initiator to prepare branched polymer beads of high purity. The molecular weight and branching structure of the polymers have been characterized by triple detection size exclusion chromatography (TD Cited by: 6. An investigation of free volume using positron annihilation lifetime spectroscopy (PALS), and gas permeation measurements was carried out for the thin film composite copolymer membranes and compared to PIM The average free volume hole size and the gas permeance of the copolymer membranes increased with decreasing TTSBI content in the by: