Origin of the methylene bonds in poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene] prepared according to Gilch's method: novel applications

Impurities containing methylene bridges between 2‐((2′‐ethylhexyl)oxy)‐5‐methoxy‐benzene molecules are inevitably formed during the synthesis of 1,4‐bis(chloromethyl)‐2‐((2′‐ethylhexyl)oxy)‐5‐methoxy‐benzene, the monomer used in the preparation of poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV), but they can be removed by double recrystallization of the monomer prior to polymerization. When impurities containing methylene bridges participate in a Gilch polymerization, the methylene bonds formed in the main chains are prone to break at 200 °C, that is, at least 150 °C below the major degradation temperature of defect‐free MEH‐PPV. Interestingly, the thermal treatment used to break the methylene bonds present reduces the chain aggregation of MEH‐PPV during film formation and induces its blends with poly(2,3‐diphenyl‐5‐octyl‐p‐phenylene‐vinylene) (DPO‐PPV) to form a morphology similar to that of block copolymers. Both significantly enhance the luminescence properties. Copyright © 2006 Society of Chemical Industry     

Morphology and properties of poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene]/silica nanoparticle hybrid films

Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry     

导电聚合物有序超薄膜合成工艺的优化

采用Langmuir-Blodgett(LB)诱导沉积方法制备了不同层数的聚(3,4-乙烯二氧噻吩)/聚苯乙烯磺酸(PEDOT-PSS)导电复合膜。首次研究了十八胺(ODA)和十八胺/硬脂酸(SA)离子化单分子膜在PEDOT-PSS纳米粒子亚相及ODA/PEDOT-PSS组装体在纯水亚相上的成膜行为。实验表明:PEDOT-PSS纳米粒子对单分子层具有包裹作用,形成了稳定的复合单分子膜;不同膜压下制备的膜表面形貌不同,较高膜压下得到颗粒紧密排列的薄膜,亚相温度23℃,PEDOT-PSS浓度1×10-4mol/L,压缩速率5 mm/min,拉膜速率为1 mm/min的条件下薄膜具有较好的成膜性能。     

Thermal degradation kinetics and lifetime prediction of poly(aryl ether ketone)s containing 2,6‐naphthalene moieties

The kinetics of thermal degradation and lifetime of poly(aryl ether ketone) containing 2,6‐naphthalene moieties (PANEK) in nitrogen and in air were studied with dynamic thermogravimetry. The results showed that the thermal stability of PANEK in air was substantially less than that in nitrogen. The kinetic parameters for PANEK, including the activation energy, the reaction order; and the frequency factor of the degradation reaction, were analyzed with the Ozawa method. The lifetime of PANEK decreased gradually from 1.09 × 10⁷ to 0.65 × 10² min as the temperature increased from 200 to 400°C in air and from 2.12 × 10⁸ to 3.30 × 10² min in nitrogen. These lifetime parameters indicated that the service/process temperature had a strong influence on PANEK. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chemical synthesis and characterization of some conducting polyaniline derivatives: Investigation of the effect of protonation medium

Poly(o‐toluidine) (POT) and poly(2‐chloroaniline) (P2ClAn) emeraldine salts were synthesized chemically by using formic (HCOOH), acetic (CH₃COOH), propionic (C₂H₅COOH), and boric (H₃BO₃) acids. Ultraviolet‐visible absorption spectra (UV–Vis) analysis results indicated that POT has the better protonation effects than P2ClAn. Among the POTs synthesized using the four different acids, POT(H₃BO₃) showed the least protonation effect. The conductivities of prepared polymers were measured by a four‐probe technique. The highest conductivities were obtained in POTs synthesized by using formic, acetic, and propionic acids. Magnetic susceptibility measurements of the polymer salts were analyzed by using Gouy scale and it was found that POT(CH₃COOH) and POT(C₂H₅COOH) salts are of bipolaron structure; other polymer salts are of polaron structure. The characterization of the polymers were investigated by Fourier infrared spectroscopy (FTIR), UV–Vis, thermogravimetric analysis, and scanning electron microscopy. It was observed from UV–Vis spectra of the emeraldine salt of POT that wavelengths belonging to π → π* transitions shifted to shorter wavelengths with increasing pKa values of acids. POT and P2ClAn synthesized in four different protonation media decomposed with three‐step and three‐ or two‐step weight loss, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1993–2000, 2002; DOI 10.1002/app.10487     

Processing and characterization of a biaxially oriented conducting polymer

Two methods have been developed for the preparation of biaxially oriented poly(phenylene vinylene) from its poly(sulfonium salt) precursor. A two-stage stretching process permits non-equibiaxial stretching over a wide range of deformation ratios and a bubble expansion technique allows equibiaxial planar extension. The resulting films were examined using X-ray diffraction prior to chemical doping with SbF₅ vapor. Biaxial orientation was shown to exert considerable influence over the attainable electrical conductivity.     

Effect of zeolite filler on the thermal degradation kinetics of polypropylene

In this study, the thermal degradation behavior of polypropylene (PP) and PP–zeolite composites was investigated. Clinoptilolite, a natural zeolitic tuff, was used as the filler material in composites. The effects of both pure clinoptilolite and silver‐ion‐exchanged clinoptilolite on the thermal degradation kinetics of the PP composites was studied with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Polymer degradation was evaluated with DSC at heating rates of 5, 10, and 20°C/min from room temperature to 500°C. The silver concentration (4.36, 27.85, and 183.8 mg of Ag/g of zeolite) was the selected parameter under consideration. From the DSC curves, we observed that the heat of degradation values of the composites containing 2–6% silver‐exchanged zeolite (321–390 kJ/kg) were larger than that of the pure PP (258 kJ/kg). From the DSC results, we confirmed that the PP–zeolite composites can be used at higher temperatures than the pure PP polymer because of its higher thermal stability. The thermal decomposition activation energies of the composites were calculated with both the Kissinger and Ozawa models. The values predicted from these two equations were in close agreement. From the TGA curves, we found that zeolite addition into the PP matrix slowed the decomposition reaction; however, silver‐exchanged zeolite addition into the matrix accelerated the reaction. The higher the silver concentration was, the lower were the thermal decomposition activation energies we obtained. As a result, PP was much more susceptible to thermal decomposition in the presence of silver‐exchanged zeolite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 143–148, 2006     

Synthesis and properties of novel deep red‐emitting copolymers based on a poly(p‐phenylenevinylene) derivative

A series of novel copolymers based on a poly(p‐phenylenevinylene) (PPV) derivative with different content of narrow band‐gap unit 2,1,3‐benzoselenadiazolevinylene (BSeV) was prepared via Stille coupling reaction. The copolymers emit light from deep red to near‐infrared (NIR) depending on BSeV content in the copolymers. The electroluminescence (EL) emission peaked at 752 nm for the copolymer with the content of 30 mol % BSeV is among the longest reported so far for the PPV polymers. The best device performance is observed for the copolymer with 1 mol % BSeV content with external quantum efficiency (QE_ext) of 0.26% and CIE coordinate 0.65, 0.34 (x,y). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4321–4327, 2006     

Photocrosslinking kinetics of polymer blends undergoing spinodal decomposition process

Photocrosslinking reaction kinetics of poly(2-chlorostyrene) performed inside the spinodal region of poly(2-chlorostyrene)/poly(vinyl methyl ether) (P2CS/PVME) blends was investigated by means of ultraviolet (UV)-visible absorption spectroscopy. The reaction was performed via photodimerization of anthracene moieties chemically labeled on the P2CS chains. The crosslinking kinetics of (P2CS/PVME) blends submitted to a temperature jump from the one-phase into the spinodal regions was observed by monitoring the irradiation time dependence of the absorbances of anthracene as well as of the blend in two regions of wavelengths. One is inside and the other is outside the absorption range of anthracene. The contribution of the sample cloudiness to the absorbance of anthracene was subtracted from the absorption data by using an empirical power law experimentally established between the incident wavelengths and the absorption of the blends. It was found that the reaction kinetics approximately follows the mean-field kinetics inside the spinodal region, resembling the behavior of the crosslinking reaction performed in the miscible region at relatively low crosslinking densities. On the other hand, the method described here fails to estimate the crosslinking densities when the phase separation proceeds rapidly, overcoming the reaction. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:885–893, 1998     

Thermal decomposition kinetics of thermotropic poly(oxybenzoate‐co‐trimethylene terephthalate)

A new kind of thermotropic liquid crystalline, poly(oxybenzoate‐co‐trimethylene terephthalate), was prepared from p‐hydroxybenzoic acid (B) and poly(trimethylene terephthalate) (PTT or T) by melting polycondensation. The monomer ratio of B to T is 60:40. The dynamic thermogravimetric kinetics of the copolymer B/T (60:40) and PTT in nitrogen were analyzed by four single heating rate techniques and two multiple heating rate techniques. The effects of the heating rate and the calculating technique on the thermostable and degradation kinetic parameters of the B/T copolymer and PTT are systematically discussed. The four single heating rate techniques used in this work include Friedman, Freeman‐Carroll, Chang, and the second Kissinger techniques, whereas the two multiple heating rate techniques are the first Kissinger and Flynn‐Wall techniques. Additionally, the isothermal thermogravimetric kinetics of B/T (60:40) in nitrogen were investigated by the Flynn technique. The activation energy, the order, and the frequency factor of the degradation reaction for B/T (60:40) copolymer are determined to be 185 kJ/mol, 1.8, and 7.14 × 10¹³ min⁻¹, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2025–2036, 2000     

Crystallization kinetics of thermosetting polymer blends of poly(ε‐caprolactone) and unsaturated polyester resin

A study has been made of the isothermal crystallization kinetics of poly(ε‐caprolactone) (PCL) in partially miscible crosslinked polyester resin (PER)/PCL blends by using differential scanning calorimetry (DSC). For comparison, miscible blends of PCL with uncured polyester resin, i.e., oligoester resin (OER), were also investigated. The overall crystallization rate of PCL remarkably decreased with the addition of amorphous component, OER or PER. The kinetic rate constant K_n decreased sharply for both the OER/PCL blends and the crosslinked PER/PCL blends with decreasing PCL concentration. The mechanism of nucleation and geometry of the growing PCL crystals was not remarkably affected by the incorporation of OER, but changed considerably with the addition of PER. However, the overall crystallization rate of PCL in the crosslinked PER/PCL blends was much higher compared with the corresponding uncured OER/PCL blends, which is attributable to the phase‐separated structure and the reduced miscibility in the crosslinked blends. According to the nucleation and growth theories, the nucleation process was considered to be the rate controlling step in the crystallization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 322–327, 1999     

New chitin-based polymer hybrids, 4: soil burial degradation behavior of poly(vinyl alcohol)/chitin derivative miscible blends

Soil burial degradation behavior of miscible blend systems of poly(vinyl alcohol) (PVA)/partially deacetylated chitin (1), PVA/chitin-graft-poly(2-methyl-2-oxazoline) (2), and PVA/chitin-graft-poly(2-ethyl-2-oxazoline) (3) was investigated in comparison with the case of a pure PVA film. The degradation of the blend films was followed by the weight changes, scanning electron microscopic observation, Fourier transform infrared spectroscopy, ¹H-NMR, and size exclusion chromatography analyses. The rate of weight decrease in these PVA/chitin derivative hybrids was higher than that of control PVA in the soil burial test. Fourier transform infrared spectra of the recovered samples of the blends showed an apparent increase of the absorption intensity due to β-diketone structure in PVA, which reflects the progress of biodegradation of PVA by PVA-oxidizing enzymes. Scanning electron microscopic observation revealed that these blend films were degraded by bacteria and actinomycetes. The triad tacticity and number-average molecular weight of PVA in the hybrids after soil burial determined by ¹H-NMR and size exclusion chromatography, respectively, were almost the same as those before soil burial. These results suggested that enzymatic degradation of the hybrid films occurred mainly on the surface and that degradation of the PVA-based samples in the soil was accelerated by blending the chitin derivatives. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1171–1179, 1999     

Effect of organomodified clay on the reaction kinetics,properties and thermal degradation of nanocomposites based on poly(styrene‐co‐ethyl methacrylate)

In this research, synthesis of novel nanocomposites based on a poly(styrene‐co‐ethyl methacrylate) copolymer matrix was investigated with different types and amounts of organomodified montmorillonite (MMT) clays. The in situ polymerization technique was selected with dispersion of the MMT nanoparticles into the comonomer mixture and subsequent bulk radical polymerization. Reaction kinetics was measured gravimetrically and it was found that the existence of rigid phenyl rings in the organomodifier may result in a hindered reaction rate especially at high clay loadings. Structural characteristics of the nanocomposites formed were verified with XRD and Fourier transform infrared analysis and mainly intercalated/partially exfoliated structures were verified; their glass transition temperature was measured with DSC, and their molecular weight distribution and average molecular weights were measured with gel permeation chromatography. The latter was also used to measure the variation of the copolymer average molecular weight with conversion. Slightly higher average molecular weight and T_g values for the copolymer in the nanocomposites were measured, compared with neat copolymer. The thermal stability of the nanocomposites was measured with TGA and found to be significantly improved. One‐step degradation revealed the existence of macromolecular chains without defective structures. Finally, pyrolysis of the nanocomposite copolymers resulted in the production of both comonomers in high amounts, followed by some dimers or trimers. © 2013 Society of Chemical Industry     

The effect of substitution levels on the luminescent and degradation properties of fluorescent poly(ester‐anhydride)s

In this work, two kinds of diacid monomers were synthesized by a convenient scheme, where 4‐hydroxy‐3‐methoxybenzoic acid (vanillic acid) or 4‐hydroxy‐3,5‐dimethoxybenzoic acid (syringic acid) directly condensated with succinic chloride. Corresponding polyanhydrides were obtained by melt polycondensation. Copolyanhydrides composed of the new monomers and sebacic acid (SA) were further prepared and characterized by NMR, DSC, and fluorometer. The two new kinds of polyanhydride emit strong fluorescence and have similar fluorescent spectra to poly(di(p‐carboxyphenyl) succinate anhydride) (P(dCPS)). The emission wavelength (λ_em) of the copolymers could be tuned by the excitation wavelength (λ_ex). Degradation rate of the copolyanhydrides decreased as dMOCPS or ddMOCPS fraction increased, and the degradation duration could be modulated from several days to more than 3 months. It addition, the copolyanhydrides displayed typical surface‐degradation characteristics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1214–1221, 2006     

Thermal degradation kinetics of thermotropic poly(p‐oxybenzoate‐co‐p,p′‐biphenylene terephthalate) fiber

An advanced heat‐resistant fiber (trade name Ekonol) spun from a nematic liquid crystalline melt of thermotropic wholly aromatic poly(p‐oxybenzoate‐p,p′‐biphenylene terephthalate) has been subjected to a dynamic thermogravimetry in nitrogen and air. The thermostability of the Ekonol fiber has been studied in detail. The thermal degradation kinetics have been analyzed using six calculating methods including five single heating rate methods and one multiple heating rate method. The multiple heating‐rate method gives activation energy (E), order (n), frequency factor (Z) for the thermal degradation of 314 kJ mol⁻¹, 4.1, 7.02 × 10²⁰ min⁻¹ in nitrogen, and 290 kJ mol⁻¹, 3.0, 1.29 × 10¹⁹ min⁻¹ in air, respectively. According to the five single heating rate methods, the average E, n, and Z values for the degradation were 178 kJ mol⁻¹, 2.1, and 1.25 × 10¹⁰ min⁻¹ in nitrogen and 138 kJ mol⁻¹, 1.0, and 6.04 × 10⁷ min⁻¹ in air, respectively. The three kinetic parameters are higher in nitrogen than in air from any of the calculating techniques used. The thermostability of the Ekonol fiber is substantially higher in nitrogen than in air, and the decomposition rate in air is higher because oxidation process is occurring and accelerates thermal degradation. The isothermal weight‐loss results predicted based on the nonisothermal kinetic data are in good agreement with those observed experimentally in the literature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1923–1931, 1999     

Synthesis and characterization of electrically conducting copolymers based on benzene and biphenyl

Poly(p‐phenylene) (H‐PPP), which is one of the firstly investigated conducting polymer, has the disadvantage of difficult processability because it is infusible and insoluble. The use of biphenyl instead of benzene leads to ortho‐, meta‐, para‐polyphenylenes (H‐PP) which are more soluble and easier to be processed, however their electrical conductivity is lower. Copolymers of polyphenylenes (C₁ and C₂) and corresponding homopolymers (H‐PPP and H‐PP) were produced by the oxidative cationic polymerization of benzene and/or biphenyl. The soluble (‐S) and the insoluble (‐I) in chlorobenzene polyphenylenes were separated (H‐PP‐I, H‐PP‐S, C₁‐I, C₁‐S, C₂‐I, and C₂‐S) and they were doped with a solution of FeCl₃. All polyphenylenes were studied by FTIR, XRD, TGA, and their electrical conductivity with constant current was determined. Pronounced differences between the copolymers and the homopolymers were observed, indicating the different structure of the former. The values of the electrical conductivity of doped insoluble copolymers (10^?4 and 10^?5 S/cm) are between that of H‐PPP (10^?3 S/cm) and H‐PP‐I (10^?6 S/cm). The values of the electrical conductivity of doped soluble copolymers (10^?5 S/cm) are considerably higher than that of H‐PP‐S (10^?9 S/cm). The new electrically conductive polyphenylenes that were produced differ significantly from the corresponding homopolymers and combine good electrical conductivity and solubility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photocatalytic degradation of organic dyes by a donor–acceptor type conjugated polymer: poly(thiophene‐1,3,4‐oxadiazole) and its photocatalytic mechanism

A donor–acceptor conjugated‐type polymer, poly(thiophene‐1,3,4‐oxadiazole) (PThOD), was synthesized by one‐step polycondensation in polyphosphoric acid. PThOD was confirmed and characterized using Fourier transform infrared spectra, thermogravimetric analysis, X‐ray diffraction and UV‐visible spectra. The UV‐visible spectra showed that PThOD could absorb not only in the whole ultraviolet range from 200 to 400 nm but also in the visible light range up to 500 nm. Considering the conjugated structure of PThOD, studies were carried out of its performance for the photocatalytic degradation of various dyes, such as methyl orange, methylene blue, rhodamine B and reactive brilliant blue (RBB), under medium‐pressure Hg light source irradiation. The results showed that PThOD was an effective photocatalyst, which could degrade the four types of dye solution. Besides, visible light was also used to investigate the degradation of RBB, and the results showed that RBB could be degraded as well, though the efficiency was not as high as using the Hg lamp. The superoxide anion radical (O₂^??), which is one of the reactive oxide species, was detected using the nitrotetrazolium blue chloride method and considered to play a key role in photodegradation of dyes. Moreover, various scavengers were also used to further prove the function of ^?. Furthermore, it was found that degradation rate could be changed by adding H⁺, which might be attributed to a change of adsorption capacity of PThOD. Finally, the reusability of PThOD as photocatalyst was investigated. The results indicated that the reusability efficiency of PThOD was excellent even after ten continuous rounds of use. © 2018 Society of Chemical Industry     

Crystallization kinetics and melting behaviour of microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

Isothermal and non‐isothermal crystallization kinetics of microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(3HB‐3HHx)] was investigated by differential scanning calorimetry (DSC) and ¹³C solid‐state nuclear magnetic resonance (NMR). Avrami analysis was performed to obtain the kinetic parameters of primary crystallization. The results showed that the Avrami equation was suitable for describing the isothermal and non‐isothermal crystallization processes of P(3HB‐3HHx). The equilibrium melting temperature of P(3HB‐3HHx) and its nucleation constant of crystal growth kinetics, which were obtained by using the Hoffman–Weeks equation and the Lauritzen–Hoffmann model, were, respectively, 121.8 °C and 2.87 × 10⁵ K² when using the empirical ‘universal’ values of U* = 1500 cal mol^?1. During the heating process, the melting behaviour of P(3HB‐3HHx) for both isothermal and non‐isothermal crystallization showed multiple melting peaks, which was the result of melting recrystallization. The lower melting peak resulted from the melting of crystals formed during the corresponding crystallization process, while the higher melting peak resulted from the recrystallization that took place during the heating process. Copyright © 2005 Society of Chemical Industry     

Thermally induced crystallization and enzymatic degradation studies of poly (L‐lactic acid) films

Poly(L ‐lactic acid) (PLLA) films with different crystallinities were prepared by solvent casting and subsequently annealed at various temperatures (T_a) (80–110°C). The effects of crystallinity on enzymatic degradation of PLLA films were examined in the presence of proteinase K at 37°C by means of weight loss, DSC, FTIR spectroscopy, and optical microscopy. DSC and the absorbance ratio of 921 and 956 cm^?1 (A₉₂₁/A₉₅₆) were used to evaluate crystallinity changes during thermally induced crystallization and enzymatic hydrolysis. The highest percentage of weight loss was observed for the film with the lowest initial crystallinity and the lowest percentage of weight loss was observed for the film with highest crystallinity. FTIR investigation of degraded films showed a band at 922 cm^?1 and no band at 908 cm^?1 suggested that all degraded samples form α crystals. The rate of degradation was found to depend on the initial crystallinity of PLLA film and shown that enzymatic degradation kinetics followed first‐order kinetics for a given enzyme concentration. DSC crystallinity and IR absorbance ratio, A₉₂₁/A₉₅₆ ratio, showed no significant changes with degradation time for annealed PLLA films whereas as‐cast PLLA film showed an increase in crystallinity with degradation; this revealed that degradation takes place predominantly in the free amorphous region of annealed PLLA films without changing long range and short range order © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Positron annihilation lifetime studies of gas sorption and desorption in polyethylene and poly[1‐(trimethylsilyl)‐1‐propyne]

The variation of free‐volume parameters (lifetime, intensity, and distribution) after sorption and desorption of CO₂ and CH₄ gases in the glassy polymer poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) and in the rubbery high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) were determined by the PAL technique. Size distributions deduced from PAL measurements reveal the presence of large free‐volume holes in PTMSP with an average size of 0.725 nm³ and intensity of 22% in addition to a free‐volume hole size of 0.197 nm³ with an intensity of 11%. In polyethylene free‐volume hole sizes of 0.107 and 0.153 nm³ with intensities of 21% and 25% could be deduced for HDPE and LDPE, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 970–974, 2001