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Relations Between Hole Volume and Macroscopic Volume in Various Polymers

100%

Dlubek G., Alam M., Saarinen K., Stejny J., Fretwell H.

Acta Physica Polonica A

1999

vol. 95

issue 4

521-526

Different definitions of the free volumes are discussed and related to the total specific volume and to the local free (hole) volume. Positron lifetime measurements are reported for polyethylene, polytetrafluoroethylene, and CR39-copolymers. Two long-lived components appear in polyethylene and polytetrafluoroethylene, which were attributed to o-Ps annihilations in crystalline regions and in holes of the amorphous phase. From a relation between the coefficients of the thermal expansion of macroscopic and hole volume, the fractional hole volume h and from this the number of holes, N, is estimated. Values of T_{g}=195 K, h_{g}=4.5% (polyethylene) and 5.7% (polytetrafluoroethylene) and N_{g}=0.73 nm^{-3} (polyethylene) and 0.36 nm^{-3} (polytetrafluoroethylene) were obtained. In semicrystalline polymers these values agree with estimates obtained from the densities of the crystalline and amorphous phases. The effect of cross-linking on the free-volume properties of CR39-copolymer networks was studied. The comparison of the hole volume with the specific volume allowed us to estimate the number density of holes to ≈1 nm^{-3}.

Free Volume, Molecular Mobility and Polymer Structure: Towards the Rational Design of Multi-Functional Materials

73%

Roussenova M., Hughes D., Enrione J., Diaz-Calderon P., Sivaniah E., Song Q., Ubbink J., Beavis P., Swain A., Alam M.

Acta Physica Polonica A

2014

vol. 125

issue 3

801-805

In this short paper we illustrate the versatility of positron annihilation lifetime spectrometry when used for material characterisation by presenting a selection of recent lifetime studies carried out on novel polymeric materials with a wide range of potential industrial applications. We highlight the importance of local free volume in governing the macroscopic properties (e.g. permeation properties, mechanical strength) of these materials and how lifetime measurements can be used in conjunction with a number of complementary techniques in order to establish composition-structure-property relationships for these systems.

The Temperature and Pressure Dependence of the Free Volume in Fluoroelastomers from PALS and PVT Experiments

73%

Dlubek G., Sen Gupta A., Wawryszczuk J., Kilburn D., Pionteck J., Krause-Rehberg R., Goworek T., Alam M., Kaspar H., Lochhaas K.

Acta Physica Polonica A

2005

vol. 107

issue 4

685-689

Positron lifetime and pressure-volume-temperature experiments were performed as function of T (100-485 K) and P (10^{-5} Pa-500 MPa) on a fluoroelastomer. From positron annihilation lifetime spectroscopy, analyzed with LT9.0 assuming a dispersion in the e^+ (τ_2) and o-Ps (τ_3) lifetime, the mean, 〈v_h〉, and the width (standard deviation), σ_h, of the hole size distribution were calculated. The pressure-volume-temperature data were analyzed using the Simha-Somcynsky hole-lattice theory to estimate the specific hole free volume V_f. From a comparison of V_f with 〈v_h〉 the specific hole number, N'_h, is estimated. The data from thermal expansion and pressure experiments show complete agreement when taking into account the compressibility of the occupied volume.

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3 Acta Physica Polonica A

1 2014

1 2005

1 1999

3 Alam M.

2 Dlubek G.

1 Beavis P.

1 Diaz-Calderon P.

1 Enrione J.

1 Fretwell H.

1 Goworek T.

1 Hughes D.

1 Kaspar H.

1 Kilburn D.

1 Krause-Rehberg R.

1 Lochhaas K.

1 Pionteck J.

1 Roussenova M.

1 Saarinen K.

1 Sen Gupta A.

1 Sivaniah E.

1 Song Q.

1 Stejny J.

1 Swain A.

1 Ubbink J.

1 Wawryszczuk J.

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Relations Between Hole Volume and Macroscopic Volume in Various Polymers

Free Volume, Molecular Mobility and Polymer Structure: Towards the Rational Design of Multi-Functional Materials

The Temperature and Pressure Dependence of the Free Volume in Fluoroelastomers from PALS and PVT Experiments