The distribution of the unoccupied volume in glassy polymers

Schmidtke, E.; Günther-Schade, K.; Hofmann, Dieter; Faupel, Franz

doi:10.1016/j.jmgm.2003.11.001

Cited by 28 publications

(30 citation statements)

References 36 publications

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“…Excepting the recent publications (Srithawatpong et al 1999;Olson et al 2002;Olson 2004;Schmidtke et al 2004;Consolati et al 2005), it has been assumed that the free volume cells, V 3 , are spherical. The quantum mechanical calculations (Tao 1972;Eldrup et al 1981) gave a semiempirical equation, relating the free volume cell radius, R, to the measured o-Ps lifetime, t 3 :…”

Section: Application Of S-s Theory To Palsmentioning

confidence: 99%

“…The quantum mechanical computations (Srithawatpong et al 1999;Olson et al 2002;Schmidtke et al 2004;Olson 2004) showed that better description of the PALS data is obtained assuming nonspherical shapes (Consolati et al 2005). It is reasonable to postulate that under pressure, the anisometric structures will coalesce easier than the spherical ones, thus increasing the availability of large-enough voids and facilitating the flow.…”

Section: Structures and Relaxations In Molten Polymersmentioning

confidence: 99%

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Free volume dependence of polymer viscosity

Utracki

Sedláček

2006

Rheol Acta

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Section: Application Of S-s Theory To Palsmentioning

confidence: 99%

Section: Structures and Relaxations In Molten Polymersmentioning

confidence: 99%

Free volume dependence of polymer viscosity

Utracki

Sedláček

2006

Rheol Acta

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“…[6,7] The free volume and its fluctuation are important parameters in controlling the dynamical behavior of a polymer. [8][9][10][11][12][13][14] It is realized that for a segmental motion larger local free volumes (holes) are required. [11][12][13] The Summary: The microstructure of the free volume and its temperature and pressure dependence in PIB were studied by PVT experiments and PALS.…”

Section: Introductionmentioning

confidence: 99%

Temperature and Pressure Dependence of the Free Volume in Polyisobutylene from Positron Lifetime and Pressure‐Volume‐Temperature Experiments

Kilburn

Wawryszczuk

Dlubek

et al. 2006

Macro Chemistry & Physics

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Summary: The microstructure of the free volume and its temperature and pressure dependence in PIB were studied by PVT experiments and PALS. Employing the Simha–Somcynsky equation of state, the hole‐free volume fraction h and the specific free and occupied volumes, Vf = hV and Vocc = (1 − h)V, respectively, and their expansivity and compressibility were calculated. From the PALS spectra analyzed using the LT9.0 software, the hole size distribution, the mean hole size 〈vh〉 and mean dispersion σh were calculated. From a comparison of 〈vh〉 with Vf, the hole density $N'_{\rm h}$ was obtained. It was found that PIB shows an unusual thermal expansion with glass‐like transitions at 210 K and 290 K (at 0 MPa). A similar behavior is observed for tan δ. It was found that at 296 K, 〈vh〉 decreases exponentially from 80 Å3 at 0.1 MPa to the extremely low value of 10 Å3 at 1 300 MPa. Starting from a fluctuation approach, the free‐volume fluctuations and the characteristic length scale (ξ) of dynamic heterogeneity of structural relaxation were estimated from σh. It was found that ξ increases from ≈1.5 nm to ≈1.9 nm when the temperature decreases from 293 K to the glass transition temperature Tg = 207 K (at 0 MPa) or the pressure increases from 0.1 MPa to 200 MPa (at 296 K).Fractional free volume and its mean fluctuation in PIB as determined from positron lifetime spectroscopy and PVT experiments analyzed with the Simha‐Somcynsky equation of state.imageFractional free volume and its mean fluctuation in PIB as determined from positron lifetime spectroscopy and PVT experiments analyzed with the Simha‐Somcynsky equation of state.

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“…This fractional free volume consists of many isolated spaces of variable volume and size, which can be determined experimentally by Positron annihilation lifetime spectroscopy (PALS). Detailed information on the particulars of the free volume can be provided by applying computational modeling and molecular dynamics simulations [15][16][17]. By manipulating the polymeric chains and the size, shape and distribution of the nano-channels, the free volume in the polymeric matrix can be tuned to provide variations in the membrane permeability and selectivity [2,4,5,[18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Investigation into the High Permeability and High Selectivity of Nano-Porous Polyimide Membranes for the “Green” Separation of Natural Gas

Madkour

2012

e-J. Surf. Sci. Nanotechnol.

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Molecular modeling techniques were used to investigate the permeability and selectivity of various natural gas components through nano-porous polyimide membranes for the environmentally-friendly "green" separation of natural gas. The polyimide membranes showed the ability of creating nano-scale channels within the polymeric matrix during the molecular mobility of the polymeric chains through which specific gas molecules can penetrate the membrane surface. The four natural gas components investigated in this study were methane, ethane, propane and butane, all hydrocarbon materials of similar basic chemical structures. The self-diffusion coefficients of the gas molecules were thus used to express the permeability of the various gases through the membranes since the solubility of the gas molecules in the polymeric substances were assumed to be constant. Methane showed a noticeably high self-diffusion coefficient calculated from the application of Einstein relation to the generated molecular dynamics trajectories. All other gases had similar values for the self-diffusion coefficients, which indicate the ability of the methane molecules to penetrate the polymeric membrane in a much larger speed due to a possible matching between the methane molecular size and the size of the interconnected nano-channels within the membranes. The results also showed that the polymer molecules had lower self-diffusion coefficients than the gas ones due to the large size of the polymeric segments. Other structural parameters such as the radial distribution function in direct relationship to the local packing of the polymeric segments and penetrant molecules are also illustrated.

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The distribution of the unoccupied volume in glassy polymers

Cited by 28 publications

References 36 publications

Free volume dependence of polymer viscosity

Free volume dependence of polymer viscosity

Temperature and Pressure Dependence of the Free Volume in Polyisobutylene from Positron Lifetime and Pressure‐Volume‐Temperature Experiments

Molecular Dynamics Investigation into the High Permeability and High Selectivity of Nano-Porous Polyimide Membranes for the “Green” Separation of Natural Gas

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