Poly[1‐(trimethylgermyl)‐1‐propyne] and poly[1‐(trimethylsilyl)‐1‐propyne] with various geometries: Their synthesis and properties

The polymerization of 1,2‐disubstituted acetylenes [1‐(trimethylgermyl)‐1‐propyne and 1‐(trimethylsilyl)‐1‐propyne] initiated by Nb‐ and Ta‐based catalytic systems was studied within a wide temperature range (?10 to +80 °C) with solvents (cyclohexane, CCl₄, toluene, anisol, and n‐chlorobutane) with variable dielectric constants (2.023–7.390). Conditions ensuring the synthesis of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) containing 20–80% cis units and poly[1‐(trimethylgermyl)‐1‐propyne] (PTMGP) containing 3–65% cis units were determined. The PTMSP and PTMGP samples were amorphous, exhibited a two‐phase structure characterized by the presence of less ordered regions and regions with an enhanced level of ordering, and differed in solubility. A correlation was found between the cis/trans ratio and the morphology, the geometrical density of PTMSP and PTMGP films, and the gas permeability of the polymers. The gas permeability and solubility behavior of PTMSP and PTMGP were examined in terms of the molecular characteristics of the polymer samples (the thermodynamic Kuhn segment and the Kerr electrooptic effect). It was demonstrated that the gas permeability, as well as the solubility of the polymers, was defined by their supramolecular ordering, which depended on the lengths of continuous sequences composed of units of analogous microstructures and on the flexibility of macrochains. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2133–2155, 2003     

Sorption,diffusion, and permeation of ethylbenzene in poly(1‐trimethylsilyl‐1‐propyne)

The solubility, diffusivity, and permeability of ethylbenzene in poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) at 35, 45 and 55 °C were determined using kinetic gravimetric sorption and pure gas permeation methods. Ethylbenzene solubility in PTMSP was well described by the generalized dual‐mode model with χ = 0.39 ± 0.02, b = 15 ± 1, and C^′_H = 45 ± 4 cm³ (STP)/cm³ PTMSP at 35 °C. Ethylbenzene solubility increased with decreasing temperature; the enthalpy of sorption at infinite dilution was −40 ± 7 kJ/mol and was essentially equal to the enthalpy change upon condensation of pure ethylbenzene. The diffusion coefficient of ethylbenzene in PTMSP decreased with increasing concentration and decreasing temperature. Activation energies of diffusion were very low at infinite dilution and increased with increasing concentration to a maximum value of 50 ± 10 kJ/mol at the highest concentration explored. PTMSP permeability to ethylbenzene decreased with increasing concentration. The permeability estimated from solubility and diffusivity data obtained by kinetic gravimetric sorption was in good agreement with permeability determined from direct permeation experiments. Permeability after exposure to a high ethylbenzene partial pressure was significantly higher than that observed before the sample was exposed to a higher partial pressure of ethylbenzene. Nitrogen permeability coefficients were also determined from pure gas experiments. Nitrogen and ethylbenzene permeability coefficients increased with decreasing temperature, and infinite dilution activation energies of permeation for N₂ and ethylbenzene were −5.5 ± 0.5 kJ/mol and −74 ± 11 kJ/mol, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1078–1089, 2000     

Gas permeability and hydrocarbon solubility of poly[1‐phenyl‐2‐[p‐(triisopropylsilyl)phenyl]acetylene]

The effects of film thickness, physical aging, and methanol conditioning on the solubility and transport properties of glassy poly[1‐phenyl‐2‐[p‐(triisopropylsilyl) phenyl]acetylene] are reported at 35 °C. In general, the gas permeability coefficients are very high, and this polymer is more permeable to larger hydrocarbons (e.g., C₃H₈ and C₄H₁₀) than to light gases such as H₂. The gas permeability and solubility coefficients are higher in as‐cast, unaged films than in as‐cast films aged at ambient conditions and increase to a maximum in both unaged and aged as‐cast films after methanol conditioning. For example, the oxygen permeability of a 20‐μm‐thick as‐cast film is initially 100 barrer and decreases to 40 barrer after aging for 1 week at ambient conditions. After methanol treatment, the oxygen permeabilities of unaged and aged films increase to 430 and 460 barrer, respectively. Thicker as‐cast films have higher gas permeabilities than thinner as‐cast films. Propane and n‐butane sorption isotherms suggest significant changes in the nonequilibrium excess free volume in these glassy polymer films due to processing history. For example, the nonequilibrium excess free volume estimated from the sorption data is similar for as‐cast, unaged samples and methanol‐conditioned samples; it is 100% higher in methanol‐conditioned films than in aged, as‐cast films. The sensitivity of permeability to processing history may be due in large measure to the influence of processing history on nonequilibrium excess free volume and free volume distribution. The propane and n‐butane diffusion coefficients are also sensitive to film processing history, presumably because of the dependence of diffusivity on free volume and free volume distribution. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1474–1484, 2000     

Gas permeability and n‐butane solubility of poly(1‐trimethylgermyl‐1‐propyne)

The gas permeability and n‐butane solubility in glassy poly(1‐trimethylgermyl‐1‐propyne) (PTMGP) are reported. As synthesized, the PTMGP product contains two fractions: (1) one that is insoluble in toluene and soluble only in carbon disulfide (the toluene‐insoluble polymer) and (2) one that is soluble in both toluene and carbon disulfide (the toluene‐soluble polymer). In as‐cast films, the gas permeability and n‐butane solubility are higher in films prepared from the toluene‐soluble polymer (particularly in those films cast from toluene) than in films prepared from the toluene‐insoluble polymer and increase to a maximum in both fractions after methanol conditioning. For example, in as‐cast films prepared from carbon disulfide, the oxygen permeability at 35 °C is 330 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐soluble polymer and 73 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐insoluble polymer. After these films are conditioned in methanol, the oxygen permeability increases to 5200 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐soluble polymer and 6200 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐insoluble polymer. The rankings of the fractional free volume and nonequilibrium excess free volume in the various PTMGP films are consistent with the measured gas permeability and n‐butane solubility values. Methanol conditioning increases gas permeability and n‐butane solubility of as‐cast PTMGP films, regardless of the polymer fraction type and casting solvent used, and minimizes the permeability and solubility differences between the various films (i.e., the permeability and solubility values of all conditioned PTMGP films are similar). © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2228–2236, 2002     

Thermal stability of poly[1‐(trimethylsilyl)‐1‐propyne] and the gas chromatographic stationary phase based on it

The thermal stability of poly[1‐(trimethylsilyl)‐1‐propyne] is investigated by heating the capillary column with this polymer as the stationary phase with the subsequent separation of the test mixture of light hydrocarbons. It is shown that heating of the column up to 130°C does not cause a decrease in efficiency or in the retention time of solutes. A further increase in temperature results in both decrease in column efficiency and sorbate retention. However, a decrease in column retentivity goes in one way for all the tested hydrocarbons. At the same time, the efficiency of the column is changed to a lesser degree for methane and ethane up to the temperature of polymer degradation, while for propane, butane, and iso‐butane the difference is rather sharp. The most expressed decrease in efficiency was found for iso‐butane: the column efficiency for this sorbate versus temperature of heating had two stages. The diffusion coefficients for sorbates in the polymeric phase were also evaluated and the sharp decrease in their values was found after the column heating.     

Permeability and morphology of poly(cis‐butadiene)/ester‐ether liquid crystal composite membranes

Various amounts of diethylene glycol bis[4‐(4′‐ethoxybenzoyloxy)benzoate] (DEBEB) were added into a poly(cis‐butadiene) (PB) membrane to improve its gas permeation ability. This type of rubber/liquid crystal (LC) composite membranes showed two obvious characteristics that are different from the gas permeation behavior reported in previous literature: (1) The permeabilities to O₂, N₂, and CO₂ were enhanced at room temperature, for example, the permeabilities for the PB/DEBEB (90/10) membrane were higher above six times than those of PB membrane under the same conditions. It is suggested that the interface microvoids probably existed on pontes between polar crystal domains and nonpolar PB matrix. (2) All relationships between the permeability coefficient (P) and temperature (T) were characterized by N‐shape, that is, there were the peaks and valleys on the P‐T curves. Furthermore, morphology studies demonstrated that when DEBEB content in the membranes was above 10 wt %, it was spherically dispersed and embedded in the PB matrix in a crystal domain state. Gas permeation characteristics of the composite membranes were appropriately interpreted as together influence results of DEBEB phase transition behavior and the membrane morphology. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1833–1840, 2000     

Comparison of gas diffusion in poly[1‐(trimethylsilyl)‐1‐propyne] and poly(dimethylsiloxane) by atomistic modeling

Diffusion of light gases in poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) and poly(dimethylsiloxane) (PDMS) was investigated by a molecular dynamics technique. Diffusion coefficients of helium and neon in PTMSP were larger than those in PDMS due to the larger free volume fraction of PTMSP in spite of its higher chain rigidity. This indicates that the amount of the free volume fraction is a more important factor than the redistribution of the free volume for the diffusion of light gases in either polymer. Conformational relaxation was not observed during the simulations for either PTMSP or PDMS, and therefore only thermal fluctuations could redistribute the free volume in both polymers. The higher chain flexibility of PDMS seems to redistribute the free volume more effectively by thermal fluctuation.     

Synthesis,structure, and properties of poly[1‐(trimethylgermyl)‐1‐propyne]

Polymerization of 1‐(trimethylgermyl)‐1‐propyne (TMGP) with TaCl₅ and NbCl₅ produced a colorless polymer in high yields, whose molecular weight reached about 3 × 10⁵–14 × 10⁵. The molecular weight distribution of the poly(TMGP) with NbCl₅ in cyclohexane was somewhat narrow (M_w /M_n = ∼1.54). The TaCl₅‐based poly(TMGP) dissolved in toluene, chloroform, cyclohexane, carbon disulfide, carbon tetrachloride, tetrahydrofuran, hexane, and so forth; the NbCl₅‐based polymer was less soluble and did not dissolve in hexane, despite its lower molecular weight. The cis contents of the NbCl₅‐ and TaCl₅‐based poly(TMGP)s determined by ¹³C NMR were 67 ± 5 and 28 ± 3%, respectively. The onset temperature of the weight loss of poly(TMGP) in air was 350 °C, indicating fair thermal stability. The oxygen permeability coefficient (P) of poly(TMGP) at 25 °C was 7800 barrer after the methanol conditioning, and the permeability was fairly stable to aging. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2964–2969, 2000     

Polyurethane elastomers based on amphiphilic poly(caprolactone)‐b‐poly(butadiene)‐b‐poly(caprolactone) triblockcopolyols

Hydroxyl‐terminated poly(butadiene) (HTPB; M_n = 2100 g mol⁻¹) was capped with 30 and 60 wt % of ɛ‐caprolactone to reach amphiphilic triblock copolymers in form of capped poly(butadiene) CPB. The former (CPB30; M_n = 3300 g/mol) is amorphous with a glass temperature of −56 °C. CPB60 (M_n = 4000 g mol⁻¹) is semi‐crystalline with a melting point of 50 °C and a glass transition at −47 °C. The CPBs, HTPB and polycaprolactone diol (M_n = 2000 g mol⁻¹) were used as soft segment components in the preparation of polyurethane elastomers (PUE), using a 1/1 mixture of an MDI prepolymer and uretonimine modified MDI, and hard phase components in form of 1,3‐propane diol, 1,4‐butane diol, and 1,5‐pentane diol. CPB‐based elastomers with 1,4 butane diol (8 wt %) show hard domains as fringed aggregates with a better connection to the continuous phase than the HTPB‐based PUE. The soft segment glass transition temperature (T_g) is at −28 °C for HTPB‐based PUE and at −43 °C for those of CPB. The tensile strength of the CPB30&60‐based PUE is found between 20 and 30 MPa at an elongation at break of 400% and 550%, respectively. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1162–1172     

Effect of physical aging of poly(1‐trimethylsilyl‐1‐propyne) films synthesized with TaCl5 and NbCl5 on gas permeability,fractional free volume,and positron annihilation lifetime spectroscopy parameters

The effect of physical aging on the gas permeability, fractional free volume (FFV), and positron annihilation lifetime spectroscopy (PALS) parameters of dense, isotropic poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) films synthesized with TaCl₅ and NbCl₅ was characterized. As‐cast films were soaked in methanol until an equilibrium amount of methanol was absorbed by the polymer. When the films were removed from methanol, film thickness initially decreased rapidly and was almost constant after 70 h in air for both catalysts. This timescale was much longer than the timescale for complete methanol desorption (ca. 5 h). From the film‐thickness data, the reduction in FFV with time was estimated. For samples prepared with either catalyst, the kinetics of FFV reduction were well‐described by a simple model based on the notion either that free‐volume elements diffuse to the surface of the polymer film and are subsequently eliminated from the sample or that lattice contraction controls polymer densification. Methane permeability decreased rapidly during the first 70 h, which was the same timescale for the thickness change. The decrease in methane permeability was smaller in films prepared with NbCl₅ than with TaCl₅. The logarithm of methane permeability decreased linearly as reciprocal FFV increased, in accordance with free‐volume theory. The PALS results indicate that the concentration of larger free‐volume elements (as indicated by the intensity I₄) decreased with aging time and that the other PALS parameters were not strongly influenced by aging. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1222–1239, 2000     

Sorption and transport of hydrocarbon and perfluorocarbon gases in poly(1‐trimethylsilyl‐1‐propyne)

Pure gas solubility and permeability of H₂, O₂, N₂, CO₂, CH₄, C₂H₆, C₃H₈, CF₄, C₂F₆, and C₃F₈ in poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) were determined as a function of pressure at 35°C. Permeability coefficients of the perfluorinated penetrants are approximately an order of magnitude lower than those of their hydrocarbon analogs, and lower even than those of the permanent gases. In striking contrast to hydrocarbon penetrants, PTMSP permeability to fluorocarbon penetrants decreases with increasing penetrant size. This unusual size‐sieving behavior in PTMSP is attributed to low perfluorocarbon solubilities in PTMSP coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. In general, perfluorocarbon penetrants are less soluble than their hydrocarbon analogs in PTMSP. The difference in hydrocarbon and perfluorocarbon solubilities in high free volume, hydrocarbon‐rich PTMSP is much smaller than in hydrocarbon liquids and liquidlike polydimethylsiloxane. The low solubility of perfluorocarbon penetrants is ascribed to the large size of the fluorocarbons, which inhibits their dissolution into the densified regions of the polymer matrix and reduces the number of penetrant molecules that can be accommodated in Langmuir sites. From the permeability and sorption data, diffusion coefficients were calculated as a function of penetrant concentration. With the exception of H₂ and the C₃ analogs, all of the penetrants exhibit a maximum in their concentration‐dependent diffusion coefficients. Resolution of diffusion coefficients into a mobility factor and a thermodynamic factor reveals that it is the interplay between these two terms that causes the maxima. The mobility of the smaller penetrants (H₂, O₂, N₂, CH₄, and CO₂) decreases monotonically with increasing penetrant concentration, suggesting that the net free volume of the polymer–penetrant mixture decreases as additional penetrant is added to PTMSP. For larger penetrants mobility either: (1) remains constant at low concentrations and then decreases at higher penetrant concentrations (C₂H₆, CF₄, and C₂F₆); (2) remains constant for all concentrations examined (C₃H₈); or (3) increases monotonically with increasing penetrant concentration (C₃F₈). Presumably these results reflect the varying effects of these penetrants on the net free volume of the polymer–penetrant system. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 273–296, 2000     

Interactions of Molecules with cis and trans Double Bonds: A Theoretical Study of cis‐ and trans‐2‐Butene

Noncovalent interactions of cis‐ and trans‐2‐butene, as the smallest model systems of molecules with cis and trans double bonds, were studied to find potential differences in interactions of these molecules. The study was performed using quantum chemical methods including very accurate CCSD(T)/CBS method. We studied parallel and displaced parallel interactions in 2‐butene dimers, in butane dimers, and between 2‐butene and saturated butane. The results show the trend that interactions of 2‐butene with butane are the strongest, followed by interactions in butane dimers, whereas the interaction in 2‐butene dimers are the weakest. The strongest calculated interaction energy is between trans‐2‐butene and butane, with a CCSD(T)/CBS energy of ?2.80 kcal mol^?1. Interactions in cis‐2‐butene dimers are stronger than interactions in trans‐2‐butene dimers. Interestingly, some of the interactions involving 2‐butene are as strong as interactions in a benzene dimer. These insights into interactions of cis‐ and trans‐2‐butene can improve understanding of the properties and processes that involve molecules with cis and trans double bonds, such as fatty acids and polymers.     

Solubility of N2 in poly(α‐n‐hexyl‐β,L‐aspartate): Temperature and force‐field dependence

The solubility of N₂ in poly(α‐n‐hexyl‐β,L ‐aspartate), a stereoregular poly(β‐peptide), was investigated with atomistic Monte Carlo simulations. The structure of this material is intermediate between that of polymers able to form a three‐dimensional crystal lattice and that of liquid‐crystalline polymers with a biphasic distribution. The dependence of the calculated solubility coefficients on both the parameters of the force field and the temperature was examined. The results are compared with recently reported experimental data. Furthermore, the motion of the penetrant molecules within the polymer matrix was analyzed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2928–2936, 2003     

Temperature dependence of the phase separation in ethyl cyanoethyl cellulose/poly(acrylic acid)/4′‐n‐pentyl‐4‐cyano‐biphenyl composite films

A novel polymer‐dispersed liquid‐crystal film consisting of micrometer‐scale liquid‐crystal droplets in ultraviolet‐cured polymer composite matrices with cholesteric order was prepared and the influence of cure temperature on the phase separation was studied. The existence and pitch of the ethyl cyanoethyl cellulose cholesteric liquid‐crystalline phase were influenced by the existence of low molecular weight liquid crystals. The macromolecular cholesteric phase disappeared when the 4′‐n‐pentyl‐4‐cyano‐biphenyl concentration was over 40 wt %, and 4′‐n‐pentyl‐4‐cyano‐biphenyl domains were dispersed in the isotropic matrix of the polymer composite. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1334–1341, 2002     

Structure of molten stereoregular polyolefins with different side‐chain sizes: Linear polyethylene,polypropylene, poly(1‐butene), and poly(4‐methyl‐1‐pentene)

The melt structures of linear polyethylene and the isotactic vinyl polymers polypropylene, poly(1‐butene), and poly(4‐methyl‐1‐pentene), along with the corresponding methyl, ethyl, and isobutyl side chains, were studied with wide‐angle X‐ray diffraction. As the size of the side branch increases from zero (polyethylene) to methyl, ethyl, and isobutyl, a prepeak appears below the main diffraction peak in the total structure factor. The prepeaks become stronger and shift to lower scattering vectors with increasing bulkiness of the side chain. There is a strong correlation between the position of the prepeaks in the melt and the average nearest‐neighbor helix–helix packing distance in the crystals, implying similar helical conformations in the melts. © 2000 John Wiley & Sons, Inc.* J Polym Sci B: Polym Phys 38: 2480–2485, 2000     

Long-term permeation properties of poly(1-trimethylsilyl-1-propyne) membranes in hydrocarbon—Vapor environment

Poly(1-trimethylsilyl-1-propyne) (PTMSP), a high free-volume glassy di-substituted polyacetylene, has the highest gas permeabilities of all known polymers. The high gas permeabilities in PTMSP result from its very high excess free volume and connectivity of free volume elements. Permeability coefficients of permanent gases in PTMSP decrease dramatically over time due to loss of excess free volume. The effects of aging on gas permeability and selectivity of PTMSP membranes continuously exposed to a 2 mol % n-butane/98 mol % hydrogen mixture over a period of 47 days are reported. The permeation properties of PTMSP membranes are quite stable when the polymer is continuously exposed to a gas mixture containing a highly sorbing organic vapor such af n-butane. The n-butane/hydrogen selectivity was essentially constant for the 47-day test period at a value of 29, or 88% of the initial value of the as-cast film of 33. Condensable gases such as n-butane may serve as a “filler” in the nonequilibrium free volume of the polymer, thereby preserving the high level of excess free volume. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1483–1490, 1997     

Permeation measurements in ethylene‐1‐hexene,ethylene‐1‐octene,and ethylene‐1‐dodecene copolymers synthesized with metallocene catalysts

The permeation behavior of different ethylene‐1‐hexene, ethylene‐1‐octene, and ethylene‐1‐dodecene copolymers synthesized with metallocene catalysts has been analyzed. These copolymers cover a wide range of comonomer contents, so their crystallinities display rather considerable variations. The results for the permeability to oxygen of the different ethylene copolymers show that the main factor influencing the permeability is the noncrystalline fraction, although some influence of the kind of comonomer may also be present, which may be explained by the fact that when the alkyl branch of the α‐olefin is longer, there is an increase in the free volume in the amorphous and interfacial regions, causing slightly higher values of the permeability coefficient. From the results with different gases, it follows that, in general, an increase in the size of the penetrant (as expressed by its kinetic diameter or critical molar volume) leads to an increase in the solubility and a decrease in the diffusion coefficient. A wide range of permeability values is covered by these ethylene copolymers, depending basically on the crystallinity of the sample, but the permselectivity of CO₂ with respect to oxygen (and probably between other pairs of gases) does not differ very much among the different copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2174–2184, 2003     

Maleation of poly(3,4‐epoxy‐1‐butene) for accelerated crosslinking in the presence of a redox catalyst

Accelerated crosslinking of novel poly(3,4‐epoxy‐1‐butene) (3,4‐PEPB) oligomers in the presence of a cobalt‐based redox catalyst was investigated. Previous studies using model compounds, 3,4‐dimethoxy‐1‐butene and 1,4‐dimethoxy‐2‐butene, suggested that maleation of hydroxyl‐terminated 3,4‐PEPB oligomers would result in more rapid crosslinking in thin films. Novel maleated oligomers offered a unique combination of both electron‐rich and electron‐poor olefinic sites, and quantitative maleation significantly increased the crosslinking rate of 3,4‐PEPB. Efficient copolymerization between terminal maleate groups and olefinic groups in the repeating unit was proposed to account for accelerated crosslinking rates. Furthermore, the addition of novel reactive diluents, such as maleic acid mono‐ethyl ester, also effectively improved the 3,4‐PEPB crosslinking rate. Sol fraction measurements as a function of coating thickness revealed that the crosslinking rate versus oxygen diffusion was less significant for the maleated oligomers because of the presence of reactive electron‐poor olefins. Sol fractions were constant for catalyst concentrations greater than 0.25–0.50 wt % (as compared with oligomer feed). This observation suggested that a redox process was not a dominant factor in determining crosslinking rates at various experimental conditions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2789–2798, 2002     

An investigation of the high gas permeability of poly (1-Trimethylsilyl-1-Propyne)

The permeability of poly (1–trimethylsilyl–1−propyne), PMSP, to light gases is higher than that of any other nonporous synthetic polymer at ambient temperatures. PMSP is in the glassy polymer state at these temperatures. Permeability, diffusion, and solubility coefficients were determined for N₂, O₂, CH₄, and CO₂ in PMSP, and are compared with values reported for these gases in poly (dimethyl siloxane). The higher gas permeability of PMSP results primarily from a substantial gas solubility, which appears to be due, in turn, to a large “excess” free volume in the unrelaxed (Langmuir) domains of this glassy polymer. The structure of PMSP, which consists of relatively rigid backbone chains separated by bulky trimethylsilyl side groups, probably is responsible for this large free volume.     

Morphologies and miscibilities of polypropene with random poly(ethene‐co‐1‐butene)

We investigated the miscibilities and morphologies of isotactic and syndiotactic polypropenes (i‐PP/s‐PP) with random poly(ethene‐co‐1‐butene) (PEB) as a function of 1‐butene content in PEB. The blend samples were studied by means of phase imaging atomic force microscopy, transmission electron microscopy, differential scanning calorimetry, dynamic mechanical analysis and X‐ray scattering. It was found that i‐PP is melt miscible with PEB for 1‐butene contents of ≈ 88 wt.‐% (miscibility window). Partial miscibility was found for s‐PP/PEB blends for 1‐butene contents ranging from 50‐88 wt.‐%.