Related Experiment Video
Updated: Jul 5, 2025

Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films
Published on: January 26, 2016
Gas Permeability through Polyimides: Unraveling the Influence of Free Volume, Intersegmental Distance and Glass
Alba Torres1,2, Cenit Soto1,2, Javier Carmona1,2
1Surface and Porous Materials (SMAP), Associated Research Unit to CSIC, Facultad de Ciencias, Universidad de Valladolid, Paseo Belén 7, E-47011 Valladolid, Spain.
Abstract:
The relationships between gas permeability and free volume fraction, intersegmental distance, and glass transition temperature, are investigated. They are analyzed for He, CO2, O2, CH4, and N2 gases and for five similar polyimides with a wide range of permeabilities, from very low to extremely high ones. It has been established here that there is an exponential relationship between permeability and the free volume fraction, and between permeability and the most probable intersegmental distance as measured by WAXS; in both cases, with an exponential coefficient that depends on the kinetic gas diameter as a quadratic polynomial and with a preexponential positive constant. Moreover, it has been proven that the intersegmental distance increases linearly with the free volume fraction. Finally, it has been established that the free volume fraction increases with the glass transition temperature for the polymers tested, and that they depend on each other in an approximate linear way.
More Related Videos
Related Concept Videos
pV-Diagrams
Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion
Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation
Polymer Classification: Crystallinity
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Molecular Weight of Step-Growth Polymers
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
Molecular Comparison of Gases, Liquids, and Solids

