CO2 Permeation and Diffusion Properties of Semicrystalline Poly(4-methyl pentene-1) Membranes

Abstract

ABSTRACT:C02 permeation and diffusion behaviors ofpoly(4-methyl pentene-1) (PMP) with three different degrees of crystallinity were examined at -I 0 to 45°C. Permeation and diffusion coefficients in crystalline and amorphous parts of PMP were obtained by an extrapolation to 100 and 0% degrees of crystallinity, respectively. The inflection corresponding to the glass transition temperature of PMP was observed in Arrhenius plot of both the permeability and diffusion coefficients only for the amorphous part of PMP. The non zero values of permeation and diffusion coefficients of crystalline part of PMP indicated that the permeation and diffusion of C02 occurred even in the crystalline part of PMP. The permeation and diffusion of C02 for the crystalline part of PMP were Arrhenius type within experimental scatter.KEY WORDS Poly(4-methyl pentene-1) I Gas Permeation / Gas Diffusion I Degree of Crystallinity IThe sorption, diffusion, and permeation of small molecules such as gas and vapor do not occur in and through a crystalline part of the crystalline polymers, in contrast to the amorphous part and amorphous polymers. 1.2 Therefore, the sorption, diffusion, and permeation of crystalline polymers are, in general, corrected by the degree of crystallinity using their quantities of purely amorphous phase. 3 -5 We recently reported that change of C02 sorption for the polystyrenejpolycarbonate blend membranes prepared by casting can be mainly explained from the amount of crystallite of the polycarbonate component, assuming that the crystallite cannot sorb C0 2 • 6 Poly(4-methyl pentene-1) (PMP; Scheme 1) is used in chemical experiments, medical appliances, electronic microwave tableware, heat stable wire, etc. with good light, transparent, heat stable, and solvent resistant properties. It has higher density for an amorphous part and lower density for a crystalline part. 7 -9 This indicates a negative volume change of melting at melting point. This polymer is also known to demonstrate characteristic thermodynamic properties of the pressure dependence of the melting temperature. 10 These facts suggest that a crystalline part of PMP is in a coarse packing of the PMP regular chain molecule compared with a random coiled amorphous part. Kusanagi et at. reported the crystal lattice structure of PMP, and concluded that the low density is due to the loose packing of the crystal. 11 There is coarse packing between PMP chains, i.e., the molecular cavity or micro void of approximately 4A exists between the chain segments in this model. This is a probable merit for the gas separation membranes with both high permeability and high selectivity which are expected from the crystalline part of PMP.Paul et a!. confirmed gas sorption and transport of a crystalline part of PMP. 12 They used the PMP with crystallinity levels ranging from 20 to 75%, including the crosslinking PMP to obtain low crystallinity, and reported that the solubilities for C0 2 and CH 4 in the t To whom all correspondence should be addressed. crystalline part of PMP ar...

Diffusion of C1-C3 Alkanes in Semicrystalline Poly(4-Methyl-1- Pentene) as a Two-Phase Polymeric System

“…The obtained dependences are difficult to interpret as a linear with a flex-point in the T g region. These temperature diffusion data are in contrary with permeability data for CO 2 in PMP [45]. In whole, PMP can be considered as a two phase polymer with ρ a ~ ρ c at T ~T g .…”

Diffusion of oxygen and carbon dioxide in thermally crystallized syndiotactic polystyrene

“…Gaps of 4 Å between the chain segments were predicted in the crystalline structure of this polymer in agreement with low crystalline density 4. Gas‐transport measurements have revealed that small gas molecules such as carbon dioxide and methane can dissolve and permeate in this crystalline structure to an extent that is significant in comparison with the amorphous phase 5, 6. Recently, a different semicrystalline polymer, with potentially similar properties, attracted our attention.…”

Characterization of the Cavity in Poly(4-methyl-1-pentene) Crystal by Gas Permeation and 129Xe NMR Measurements

“…The PMP is commercial one, and contains more than 95% of isotactic triads determined by 13 C NMR spectroscopy. Six kinds of membranes with different crystallinities were prepared by appropriate treatments.…”

“…This finding is probably attributed to an increase in tortuous diffusion path. 10,13 In the cylindrical cavity formed in PMP crystal, a gas molecule diffuses restrict- edly along molecular chains of PMP. Because the PMP crystal in the membranes studied here should orientate randomly, tortuous diffusion path of a gas molecule increases with increasing crystallinity.…”

“…Some groups have experimentally confirmed the transport phenomena of small molecules in the crystal region of PMP. [10][11][12][13] In recent years, 129 Xe NMR spectroscopy has become a powerful technique to characterize microstructures of various materials. Since Xe atom has a very large polarizability, induced 129 Xe NMR signal of 129 Xe in a medium is sensitively affected by surrounding microenvironments that disturb the electron density of Xe.…”