scholarly journals Temperature dependence of free volume distributions in polymers studied by positron lifetime spectroscopy

1993 ◽  
Vol 03 (C4) ◽  
pp. 265-270 ◽  
Author(s):  
J. KRIŠTIAK ◽  
K. KRIŠTIAKOVÁ ◽  
O. ŠAUŠA ◽  
P. BANDŽUCH ◽  
J. BARTOŠ
Keyword(s):  
Temperature Dependence ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Lifetime Spectroscopy

STUDY OF MOLECULAR MOTIONS IN TWO LIQUID CRYSTAL FORMING COMPOUNDS EMPLOYING PLS

2006 ◽  
Vol 20 (14) ◽  
pp. 2019-2034 ◽  
Author(s):  
K. CHANDRAMANI SINGH ◽  
M. SHARMA ◽  
P. C. JAIN
Keyword(s):  
Liquid Crystal ◽  
Temperature Dependence ◽  
Liquid Crystalline ◽  
Positron Lifetime ◽  
Strong Temperature Dependence ◽  
Molecular Motions ◽  
Temperature Dependent ◽  
Slow Cooling ◽  
Positron Lifetime Spectroscopy ◽  
Motion Studies

Results of molecular motion studies carried out in two liquid crystal forming compounds n-p-cyano-p-hexyloxybiphenyl (M18) and n-p-ethoxybenzylidene-p-butylaniline (EBBA) using positron lifetime spectroscopy (PLS) are presented. Temperature dependent positron lifetime measurements have been performed in each compound during the heating cycle of samples prepared by either quenching or slow cooling from the respective liquid crystalline phase of the compounds. In both the compounds, behaviors of the quenched and slow cooled samples are found to be different. The material in the quenched sample, unlike the slow-cooled sample, exhibits strong temperature dependence before it undergoes a glass transition. In each case, the temperature dependence of o-Ps pick-off lifetime in the quenched sample shows broad peaks at various characteristic temperatures. These peaks have been attributed to various intra- and inter-molecular motions associated with these compounds. The characteristic frequencies of some of the modes observed in the present work agree well with the literature reported values obtained from FIR and Raman studies. The present study demonstrates the usefulness of PLS in the study of molecular motions.

Temperature and time dependence of free volume in bisphenol A polycarbonate studied by positron lifetime spectroscopy

1992 ◽  
Vol 25 (19) ◽  
pp. 5089-5093 ◽  
Author(s):  
J. E. Kluin ◽  
Z. Yu ◽  
S. Vleeshouwers ◽  
J. D. McGervey ◽  
A. M. Jamieson ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Time Dependence ◽  
Free Volume ◽  
Positron Lifetime ◽  
Bisphenol A Polycarbonate ◽  
Positron Lifetime Spectroscopy

Effect of Water on the Size Distribution of Free-Volume Holes in Nafion Membrane

2012 ◽  
Vol 733 ◽  
pp. 49-52 ◽  
Author(s):  
Jakub Čížek ◽  
Zuzana Barnovská ◽  
Michal Šourek ◽  
Ivan Procházka
Keyword(s):  
Size Distribution ◽  
Free Volume ◽  
Water Uptake ◽  
Positron Lifetime ◽  
Ionic Clusters ◽  
Mean Size ◽  
Positron Lifetime Spectroscopy ◽  
The Mean ◽  
Kinetics Of

Positron lifetime spectroscopy was employed for investigation of the size distribution of free volume holes in Nafion N-1110 membrane. Size distribution of free volume holes was determined in the as-received and dried membrane and in the membrane immersed in water at various temperatures. It was found that absorbed water causes reduction of the mean size of free volume holes and increase of their dispersion and concentration. This indicates that free volumes are split by swollen ionic clusters absorbing water. The kinetics of water uptake and the amount of absorbed solvent was determined by in-situ measurement of the weight increase.

scholarly journals Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy

2008 ◽  
Vol 113 (5) ◽  
pp. 1359-1364 ◽  
Author(s):  
M.F. Ferreira Marques ◽  
P.M. Gordo ◽  
A.P. de Lima ◽  
D.P. Queiroz ◽  
M. Norberta de Pinho ◽  
...  
Keyword(s):  
Free Volume ◽  
Propylene Oxide ◽  
Positron Lifetime ◽  
Positron Lifetime Spectroscopy ◽  
Poly Propylene

Temperature Dependence of the Free Volume in Fluoroelastomers from Positron Lifetime and PVT Experiments

2004 ◽  
Vol 37 (17) ◽  
pp. 6606-6618 ◽  
Author(s):  
Günter Dlubek ◽  
Asmita Sen Gupta ◽  
Jürgen Pionteck ◽  
Reinhard Krause-Rehberg ◽  
Harald Kaspar ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Free Volume ◽  
Positron Lifetime

Monitoring the Crystallization Stages of Silicalite by Positron Lifetime Spectroscopy

2008 ◽  
Vol 607 ◽  
pp. 173-176 ◽  
Author(s):  
Z. Kajcsos ◽  
C. Kosanovic ◽  
S. Bosnar ◽  
B. Subotic ◽  
P. Major ◽  
...  
Keyword(s):  
Porous Media ◽  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Large Change ◽  
Zeolite Framework ◽  
Positron Lifetime Spectroscopy

In porous media, positron annihilation techniques (PAT) revealed the existence of annihilation modi with long lifetimes connected to structural and extrastructural free volumes acting as trapping centres for o-Ps. Our aim in this work was to study the influence of the synthesis applied for the production of the zeolite framework and the correlation between the trapping pattern and crystallization progress. PAT lifetime (LT) measurements were performed in silicalite-1 samples in various stages of crystallization and a large change was observed in the long components. The results are discussed in connection to the crystallization and the availability of free volume.

Free volume and phase transitions of 1-butyl-3-methylimidazolium based ionic liquids from positron lifetime spectroscopy

2012 ◽  
Vol 14 (19) ◽  
pp. 6856 ◽  
Author(s):  
Yang Yu ◽  
Witali Beichel ◽  
Günter Dlubek ◽  
Reinhard Krause-Rehberg ◽  
Marian Paluch ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Phase Transitions ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Lifetime Spectroscopy
Sign in / Sign up

Export Citation Format

Share Document