Ring‐opening polymerization of ϵ‐caprolactam and ϵ‐caprolactone via microwave irradiation

A novel process for synthesizing nylon‐6 and poly(?‐caprolactone) by microwave irradiation of the respective monomers, ?‐caprolactam and ?‐caprolactone, is described. The ring opening of ?‐caprolactam to produce nylon‐6 was performed in a microwave oven by the forward power being controlled to about 90–135 W in the presence of an ω‐aminocaproic acid catalyst (10 mol %) and for periods of 1–3 h at temperatures varying from 250 to 280 °C. The ring opening of ?‐caprolactone to produce poly(?‐caprolactone) was performed in a microwave oven by the forward power being controlled to about 70–100 W for a period of 2 h in the presence of stannous octoate with and without 1,4‐butanediol over a temperature range of 150–200 °C. The yields, conditions of the reactions, and properties of the products generated relative to the thermal processes are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2264–2275, 2002     

Crystallization behavior of isotactic propylene‐1‐hexene random copolymer revealed by time‐resolved SAXS/WAXD techniques

The crystallization behavior of isotactic propylene‐1‐hexene (PH) random copolymer having 5.7% mole fraction of hexene content was investigated using simultaneous time‐resolved small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray diffraction (WAXD) techniques. For this copolymer, the hexene component cannot be incorporated into the unit cell structure of isotactic polypropylene (iPP). Only α‐phase crystal form of iPP was observed when samples were melt crystallized at temperatures of 40 °C, 60 °C, 80 °C, and 100 °C. Comprehensive analysis of SAXS and WAXD profiles indicated that the crystalline morphology is correlated with crystallization temperature. At high temperatures (e.g., 100 °C) the dominant morphology is the lamellar structure; while at low temperatures (e.g., 40 °C) only highly disordered small crystal blocks can be formed. These morphologies are kinetically controlled. Under a small degree of supercooling (the corresponding iPP crystallization rate is slow), a segmental segregation between iPP and hexene components probably takes place, leading to the formation of iPP lamellar crystals with a higher degree of order. In contrast, under a large degree of supercooling (the corresponding iPP crystallization rate is fast), defective small crystal blocks are favored due to the large thermodynamic driving force and low chain mobility. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 26–32, 2010     

One‐pot,Three‐component Synthesis of a New Series of 2‐Amino‐4‐aroyl‐5‐oxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carbonitrile in the Presence of SBA‐15 as a Nanocatalyst

One‐pot, three‐component reaction of arylglyoxals, malononitrile and 4‐hydroxyquinolin‐2(1H)‐one in the presence of SBA‐15 as a nanocatalyst and using green solvent systems under various temperatures afforded the 2‐amino‐4‐aroyl‐5‐oxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carbonitrile derivatives. The best yield (70‐96%) were obtained using 20% mol of SBA‐15 as a nanocatalyst in H2O/EtOH (1:1) at 80 °C. The simplicity of work up procedure, using green solvent system, and good to excellent yields of products are the main advantages of this synthetic strategy.     

Shaped Ceria Nanocrystals Catalyze Efficient and Selective Para‐Hydrogen‐Enhanced Polarization

Intense para‐hydrogen‐enhanced NMR signals are observed in the hydrogenation of propene and propyne over ceria nanocubes, nano‐octahedra, and nanorods. The well‐defined ceria shapes, synthesized by a hydrothermal method, expose different crystalline facets with various oxygen vacancy densities, which are known to play a role in hydrogenation and oxidation catalysis. While the catalytic activity of the hydrogenation of propene over ceria is strongly facet‐dependent, the pairwise selectivity is low (2.4 % at 375 °C), which is consistent with stepwise H atom transfer, and it is the same for all three nanocrystal shapes. Selective semi‐hydrogenation of propyne over ceria nanocubes yields hyperpolarized propene with a similar pairwise selectivity of (2.7 % at 300 °C), indicating product formation predominantly by a non‐pairwise addition. Ceria is also shown to be an efficient pairwise replacement catalyst for propene.     

Synthesis and characterization of self‐catalyzed imide‐containing pthalonitrile resins

Some new amino‐ and imide‐containing phthalonitrile compounds with 1:1 molar ratio of amino group to pthalonitrile unit were successfully synthesized. The molecular structures were characterized by spectroscopic techniques. They were thermally polymerized under nitrogen/air, even in the absence of curing additives. The thermal properties of the cured products were characterized by thermogravimetric analysis and differential scanning calorimetry. The 5% weight loss temperatures ranged from 525 to 528 °C and 513 to 520 °C under nitrogen and air, respectively. Char yields (900 °C) were in the range of 62–70%. Rheometric measurements showed that the rate of the cure reaction differs for all the three monomers. The glass transition temperature advances with increasing extent of cure and disappears on postcure at 375 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Microwave‐enhanced rapid synthesis of organosoluble polyamides based on 5‐(3‐acetoxynaphthoylamino)‐isophthalic acid

A series of photoactive polyamides (PAs) containing acetoxynaphthalamide side chain with inherent viscosities of 0.27–0.56 dl g^?1 were prepared by the direct polycondensation reaction of the 5‐(3‐acetoxynaphthoylamino)isophthalic acid with various commercially available diamines by means of triphenyl phosphite (TPP) and pyridine (Py) in the presence of calcium chloride and N‐methyl‐2‐pyrrolidone (NMP) under microwave irradiation and conventional heating conditions. Most of the resulting PAs are soluble in strong polar solvents such as N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide, and NMP. Thermo‐gravimetric analysis (TGA) showed that polymers are thermally stable, 10% weight loss temperatures in excess of 320 and 378°C, and char yields at 600°C in nitrogen higher than 60%. These macromolecules exhibited maximum UV‐Vis absorption at 265 and 300 nm in a DMF solution. Their photoluminescence in the DMF solution demonstrated fluorescence emission maxima around 361 and 427 nm for all of the PAs. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and properties of soluble aromatic polyamides derived from 2,2′‐bis(4‐carboxyphenoxy)‐9,9′‐spirobifluorene

The synthesis of a new bis(ether carboxylic acid), 2,2′‐bis(4‐carboxyphenoxy)‐9,9′‐spirobifluorene, in which two orthogonally arranged carboxyphenoxyfluorene entities are connected through an sp³ carbon atom (the spiro center), is reported. The direct phosphorylation polycondensation of this diacid monomer with various aromatic diamines yields aromatic polyamides containing 9,9′‐spirobifluorene moieties in the main chain. The presence of the spiro segment restricts the close packing of the polymer chains and decreases interchain interactions, resulting in amorphous polyamides with enhanced solubility, and high glass‐transition temperatures and good thermal stability are maintained through controlled segmental mobility. The glass‐transition temperatures of these polyamides are in the range of 234–306 °C, with 10% weight losses occurring at temperatures above 530 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1160–1166, 2003     

Synthesis and optical and electrochemical properties of new π‐conjugated 1,3,5‐triazine‐containing polymers

Two new π‐conjugated polymers containing 1,3,5‐triazine units in the main chain, Pa and Pb , are reported. Pa and Pb (R = H and ? OCH₃, respectively) showed blue photoluminescence emissions with quantum yields of more than 50% in toluene. In the solid state, Pa and Pb showed photoluminescence maximum emission peaks at 479 and 475 nm, respectively. Electrochemically, Pa and Pb showed good stability and reversibility under repeated electrochemical reduction. The polymers had glass‐transition temperatures higher than 90 °C and had 5 wt % loss temperatures higher than 400 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6554–6561, 2005     

Laboratory studies of the ·OH‐initiated photooxidation of ethyl‐n‐butyl ether and di‐n‐butyl ether

Oxygenated compounds such as ethers and alcohols are used as gasoline additives and industrial solvents. However, despite their widespread use, the atmospheric reaction mechanisms of some of these compounds are unknown. This study examines the ^·OH‐initiated gas‐phase removal mechanisms of ethyl‐n‐butyl ether (ENBE) and di‐n‐butyl ether (DNBE) utilizing gas chromatography–mass spectrometry techniques. The primary products and molar yields from the hydroxyl‐radical–initiated photooxidation of ENBE in the presence of nitric oxide were acetaldehyde (0.173 ± 0.012), ethyl formate (0.219 ± 0.033), butyraldehyde (0.076 ± 0.004), butyl formate (0.241 ± 0.009), butyl acetate (0.032 ± 0.001), and ethyl butyrate (0.0044 ± 0.0006). From the calculated molar yields, approximately 45.5% of the reacted carbon were recovered. The primary products and molar yields from the DNBE and hydroxyl radical reaction in the presence of nitric oxide were propionaldehyde (0.379 ± 0.022), butyraldehyde (0.119 ± 0.003), butyl formate (0.410 ± 0.009), and butyl butyrate (0.019 ± 0.001). Approximately 47.7% of the reacted DNBE were recovered. The chemical mechanisms are presented to explain the formation of these products. In addition, the importance of the isomerization and nitrate/nitrite formation pathways in the reactions of large ethers are discussed. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 328–341, 2001     

Synthesis and properties of new aromatic polyamides with redox‐active 2,4‐dimethoxytriphenylamine moieties

A new triphenylamine‐based diamine monomer, 4,4′‐diamino‐2″,4″‐dimethoxytriphenylamine ( 2 ), was synthesized from readily available reagents and was reacted with various aromatic dicarboxylic acids to produce a series of aromatic polyamides ( 4a–h ) containing the redox‐active 2,4‐dimethoxy‐substituted triphenylamine (dimethoxyTPA) unit. All the resulting polyamides were readily soluble in polar organic solvents and could be solution cast into tough and flexible films. These polymers exhibited good thermal stability with glass transition temperatures of 243–289 °C and softening temperatures of 238–280 °C, 10% weight loss temperatures in excess of 470 °C in nitrogen, and char yields higher than 60% at 800 °C in nitrogen. The redox behaviors of the polymers were examined using cyclic voltammetry (CV). All these polyamides showed two reversible oxidation processes in the first CV scan. The polymers also displayed low ionization potentials as a result of their dimethoxyTPA moieties. In addition, the polymers displayed excellent stability of electrochromic characteristics with coloration change from a colorless neutral state to green and blue‐purple oxidized states. These anodically coloring polyamides showed high green coloration efficiency (CE = 329 cm²/C), high contrast of optical transmittance change (ΔT% = 84% at 829 nm), and long‐term redox reversibility. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3392–3401, 2010     

Improved Dehydrogenation Properties of LiBH4 Using Catalytic Nickel‐ and Cobalt‐based Mesoporous Oxide Nanorods

Lithium borohydride (LiBH₄) with a theoretical hydrogen storage capacity of 18.5 wt % has attracted intense interest as a high‐density hydrogen storage material. However, high dehydrogenation temperatures and limited kinetics restrict its practical applications. In this study, mesoporous nickel‐ and cobalt‐based oxide nanorods (NiCo₂O₄, Co₃O₄ and NiO) were synthesized in a controlled manner by using a hydrothermal method and then mixed with LiBH₄ by ball milling. It is found that the dehydrogenation properties of LiBH₄ are remarkably enhanced by doping the as‐synthesized metal oxide nanorods. When the mass ratio of LiBH₄ and oxides is 1:1, the NiCo₂O₄ nanorods display the best catalytic performance owing to the mesoporous rod‐like structure and synergistic effect of nickel and cobalt active species. The initial hydrogen desorption temperature of the LiBH₄‐NiCo₂O₄ composite decreases to 80 °C, which is 220 °C lower than that of pure LiBH₄, and 16.1 wt % H₂ is released at 500 °C for the LiBH₄‐NiCo₂O₄ composite. Meanwhile, the composite also exhibits superior dehydrogenation kinetics, which liberates 5.7 wt % H₂ within 60 s and a total of 12 wt % H₂ after 5 h at 400 °C. In comparison, pure LiBH₄ releases only 5.3 wt % H₂ under the same conditions.     

Gold Nanorods with Phase‐Changing Polymer Corona for Remotely Near‐Infrared‐Triggered Drug Release

Herein, we report a new drug‐delivery system (DDS) that is comprised of a near‐infrared (NIR)‐light‐sensitive gold‐nanorod (GNR) core and a phase‐changing poly(ε‐caprolactone)‐b‐poly(ethylene glycol) polymer corona (GNR@PCL‐b‐PEG). The underlying mechanism of the drug‐loading and triggered‐release behaviors involves the entrapment of drug payloads among the PCL crystallites and a heat‐induced phase change, respectively. A low premature release of the pre‐loaded doxorubicin was observed in PBS buffer (pH 7.4) at 37 °C (<10 % of the entire payload after 48 h). However, release could be activated within 30 min by conventional heating at 50 °C, above the T_m of the crystalline PCL domain (43.5 °C), with about 60 % release over the subsequent 42 h at 37 °C. The NIR‐induced heating of an aqueous suspension of GNR@PCL‐b‐PEG under NIR irradiation (802 nm) was investigated in terms of the irradiation period, power, and concentration‐dependent heating behavior, as well as the NIR‐induced shape‐transformation of the GNR cores. Remotely NIR‐triggered release was also explored upon NIR irradiation for 30 min and about 70 % release was achieved in the following 42 h at 37 °C, with a mild warming (<4 °C) of the surroundings. The cytotoxicity of GNR@PCL‐b‐PEG against the mouse fibroblastic‐like L929 cell‐line was assessed by MTS assay and good compatibility was confirmed with a cell viability of over 90 % after incubation for 72 h. The cellular uptake of GNR@PCL‐b‐PEG by melanoma MEL‐5 cells was also confirmed, with an averaged uptake of 1250(±110) particles cell^?1 after incubation for 12 h (50 μg mL^?1). This GNR@PCL‐b‐PEG DDS is aimed at addressing the different requirements for therapeutic treatments and is envisaged to provide new insights into DDS targeting for remotely triggered release by NIR activation.     

Ring‐opening copolymerization of ethylene carbonate and ε‐caprolactone catalyzed by neodymium tris(2,6‐di‐tert‐butyl‐4‐methylphenolate): Synthesis,characterization, and dynamic mechanic analysis

The ring‐opening copolymerization of ethylene carbonate (EC) with ε‐caprolactone (CL) was carried out using neodymium tris(2,6‐di‐tert‐butyl‐4‐methylphenolate) as a single‐component catalyst. Copolymers containing up to 22.0% EC contents with high molecular weights (up to 23.97 × 10⁴) and moderate molecular weight distributions (between 1.66 and 2.03) were synthesized at room temperature. Compared with homopoly(ε‐caprolactone), the copolymers with EC units exhibited increased glass transition temperatures (?35.6 °C), reduced melting temperatures (44.5 °C), and greatly enhanced elongation percentage at break (2383%) based on dynamic mechanic analysis. The crystallinities of the copolymers decreased with the increasing EC molar percentage in the products. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4050–4055, 2008     

Blue‐light‐emitting and anodically electrochromic materials of new wholly aromatic polyamides derived from the high‐efficiency chromophore 4,4′‐dicarboxy‐4″‐methyltriphenylamine

A series of organosoluble, aromatic polyamides were synthesized from a 4‐methyl‐substituted, triphenylamine‐containing, aromatic diacid monomer, 4,4′‐dicarboxy‐4″‐methyltriphenylamine, which is a blue‐light (454‐nm) emitter with a fluorescence quantum efficiency of 46%. These triphenylamine‐based, high‐performance polymers had strong fluorescence emissions in the blue region with high quantum yields up to 64% and one reversible oxidation redox couple around 1.20 V versus Ag/AgCl in acetonitrile solutions. They exhibited good thermal stability, with 10% weight loss temperatures above 480 °C under a nitrogen atmosphere and with relatively high glass‐transition temperatures (252–309 °C). All the polyamides revealed excellent stability of electrochromic characteristics, changing color from the original pale yellow to blue. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4095–4107, 2006     

Thermally stable,light‐emitting,triphenylamine‐containing poly(amine hydrazide)s and poly(amine‐1,3,4‐oxadiazole)s bearing pendent carbazolyl groups

A series of new organosoluble poly(amine hydrazide)s were synthesized via the Yamazaki phosphorylation reaction and were solution‐cast into transparent films. Differential scanning calorimetry indicated that the hydrazide polymers could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the range of 300–400 °C. The resulting poly(amine‐1,3,4‐oxadiazole)s exhibited glass‐transition temperatures in the range of 276–297 °C, 10% weight loss temperatures in excess of 520 °C, and char yields at 800 °C in nitrogen higher than 67%. The hole‐transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of these polymers prepared by the casting of polymer solutions onto an indium tin oxide coated glass substrate exhibited two reversible oxidative redox couples at 1.10–1.19 and 1.35–1.60 V versus Ag/AgCl in an acetonitrile solution, respectively. The poly(amine hydrazide)s revealed excellent stability of the electrochromic characteristics, changing color from the original pale yellow to green and then to blue. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 48–58, 2007     

Synthesis and properties of new soluble triphenylamine‐based aromatic poly(amine amide)s derived from N,N′‐bis(4‐carboxyphenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine

A new triphenylamine‐containing aromatic dicarboxylic acid, N,N′‐bis(4‐carboxyphenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was synthesized by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 4‐fluorobenzonitrile, followed by the alkaline hydrolysis of the intermediate dinitrile compound. A series of novel triphenylamine‐based aromatic poly(amine amide)s with inherent viscosities of 0.50–1.02 dL/g were prepared from the diacid and various aromatic diamines by direct phosphorylation polycondensation. All the poly(amine amide)s were amorphous in nature, as evidenced by X‐ray diffractograms. Most of the poly(amine amide)s were quite soluble in a variety of organic solvents and could be solution‐cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with glass‐transition temperatures up to 280 °C, 10% weight‐loss temperatures in excess of 575 °C, and char yields at 800 °C in nitrogen higher than 60%. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 94–105, 2003     

Synthesis and characterization of novel soluble triphenylamine‐containing aromatic polyamides based on N,N′‐bis(4‐aminophenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine

A new triphenylamine‐containing aromatic diamine, N, N′‐bis(4‐aminophenyl)‐N, N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 4‐fluoronitrobenzene, followed by catalytic reduction. A series of novel aromatic polyamides with triphenylamine units were prepared from the diamine and various aromatic dicarboxylic acids or their diacid chlorides via the direct phosphorylation polycondensation or low‐temperature solution polycondensation. All the polyamides were amorphous and readily soluble in many organic solvents such as N, N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass‐transition temperatures (257–287 °C), 10% weight‐loss temperatures in excess of 550 °C, and char yields at 800 °C in nitrogen higher than 72%. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2810–2818, 2002     

Nucleophilic Substitution on Porphyrin Ring： Synthesis of 2-（2-Hydroxynaphthyl）-5,10,15,20-tetraphenylporphyrin

The reactions of 2-nitro-5,10,15,20-tetraphenylporphyrin （1） and its Ni （Ⅱ） （2）, Cu （Ⅱ） （3）, Zn （Ⅱ） （4） complexes with sodium 2-naphthoxide have been investigated in different solvents for preparing 2-substituted porphyrins. 2-（2-Hydroxynaphthyl）-5,10,15,20-tetraphenyl porphyrin （5） and its Ni （Ⅱ） （6）, Cu （Ⅱ） （7）, Zn （Ⅱ） （8） complexes were obtained in 72%, 78%, 81% and 65% yields in 2-naphthol at 150 ℃ respectively. The same products were also obtained in other protic solvents such as diglycol and diglycol monomethyl ether. When the reactions proceeded in aprotic solvent DMF at 150 ℃, besides 5 （70%）, 6 （34%）, 7 （54%） and 8 （50%）, the corresponding 2-（2-naphythoxy）-5, 10,15,20-tetraphenylporphyrin （9）, and its Ni （Ⅱ） （10）, Cu （Ⅱ） （11）, Zn （Ⅱ） （12） complexes were also obtained in minor, 40%, 18% and 2% yields respectively, but only 5, 6, 7, 8 were found at room temperature in DMF or DMSO. These reactions axe much faster than those of 1-4 with sodium phenoxide. The formation of C-coupling products 5-8 was proposed via SRN 1 mechanism.     

Flame‐retardant epoxy resins from o‐cresol novolac epoxy cured with a phosphorus‐containing aralkyl novolac

A novel phosphorus‐containing aralkyl novolac (Ar‐DOPO‐N) was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) first with terephthaldicarboxaldehyde and subsequently with phenol. The chemical structures of the synthesized compounds were characterized with Fourier transform infrared, ¹H and ³¹P NMR, and elemental analysis. Ar‐DOPO‐N blended with phenol formaldehyde novolac was used as a curing agent for o‐cresol formaldehyde novolac epoxy, resulting in cured epoxy resins with various phosphorus contents. The epoxy resins exhibited high glass‐transition temperatures (159–177 °C), good thermal stability (>320 °C), and retardation on thermal degradation rates. High char yields and high limited oxygen indices (26–32.5) were observed, indicating the resins' good flame retardance. Using a melamine‐modified phenol formaldehyde novolac to replace phenol formaldehyde novolac in the curing composition further enhanced the cured epoxy resins' glass‐transition temperatures (160–186 °C) and limited oxygen index values (28–33.5). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2329–2339, 2002     

A steady‐state mass balance model of the polycarbonate–CO2 system reveals a self‐regulating cell growth mechanism in the solid‐state microcellular process

A simple mechanism regulating polymer mobility is demonstrated to determine initial and final growth states of solid‐state microcellular foams. This mechanism, governed by the extent of plasticization of the polymer by the dissolved gases, is examined with a mass balance model and results from foam growth experiments. Polycarbonate was exposed to CO₂, which acted as both a plasticizing gas and a physical blowing agent driving foam growth. The polycarbonate specimens were saturated to the equilibrium gas concentration at 25 °C for CO₂ pressures of 1–6 MPa in 1‐MPa increments. Equilibrated specimens were heated in a glycerin bath until thermal equilibrium was reached, and a steady foam structure was attained. Glycerin bath temperatures of 30–150 °C in 10 °C increments were examined. Using knowledge of gas solubility, the equation of state for CO₂, the effective glass‐transition temperature as a function of gas concentration, and a model for mass balance within a solid‐state foam, we demonstrate that foam growth terminates when sufficient gas is driven from the polycarbonate matrix into the foam cells. The foam cell walls freeze at the elevated bath temperature because of gas transport from the polycarbonate matrix and the associated rise in the polymer glass‐transition temperature to that of the heated bath. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 868–880, 2001