Evaluation of the interaction parameter for poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends

In this article, the miscibility of poly(ε‐caprolactone) (PCL) with poly(styrene‐co‐acrylonitrile) (SAN) containing 25 wt % of acrylonitrile is studied from both a qualitative and a quantitative point of view. The evidences coming from thermal analysis (differential scanning calorimetry) demonstrate that PCL and SAN are miscible in the whole range of composition. The Flory interaction parameter χ_1,2 was calculated by the Patterson approximation and the melting point depression of the crystalline phase in the blends; in both cases, negative values of χ_1,2 were found, confirming that the system is miscible. The interaction parameter evaluated within the framework of the mean field theory demonstrates that the miscibility of PCL/SAN blends is due to the repulsive interaction between the styrene and acrylonitrile segments in SAN. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Miscibility of poly(styrene‐co‐butyl acrylate) with poly(ethyl methacrylate): Existence of both UCST and LCST

A miscible homopolymer–copolymer pair viz., poly(ethyl methacrylate) (PEMA)–poly(styrene‐co‐butyl acrylate) (SBA) is reported. The miscibility has been studied using differential scanning calorimetry. While 1 : 1 (w/w) blends with SBA containing 23 and 34 wt % styrene (ST) become miscible only above 225 and 185 °C respectively indicating existence of UCST, those with SBA containing 63 wt % ST is miscible at the lowest mixing temperature (i.e., T_g's) but become immiscible when heated at ca 250 °C indicating the existence of LCST. Miscibility for blends with SBA of still higher ST content could not be determined by this method because of the closeness of the T_g's of the components. The miscibility window at 230 °C refers to the two copolymer compositions of which one with the lower ST content is near the UCST, while the other with the higher ST content is near the LCST. Using these compositions and the mean field theory binary interaction parameters between the monomer residues have been calculated. The values are χ_ST‐BA = 0.087 and χ_EMA‐BA = 0.013 at 230 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 369–375, 2000     

A thermodynamic analysis of specific interactions in homoblends of poly(styrene‐co‐4‐vinylpyridine) and poly(styrene‐co‐methacrylic acid)

Miscibility and strong specific interactions that occurred within homoblends of poly(styrene‐co‐4‐vinylpyridine) containing 15 mol % of 4‐vinylpyridine (PS4VP15) and poly(styrene‐co‐methacrylic acid) containing 15 mol % of methacrylic acid (PSMA15) have been examined by Fourier Transform infrared spectroscopy and DSC. The observed positive deviation of the glass transition temperature of the blends from the linear average line, was analyzed by the frequently used theoretical conventional approaches including the one very recently proposed by Brostow. A better fit was obtained when this latter is used. A reasonable agreement with experimental values was also obtained when the theoretical fitting parameter free method developed by Coleman, is applied to predict the composition dependence of the T_g of this system. A thermodynamic analysis of hydrogen bonding in this system was carried using the Painter‐Coleman association model and the variation of the Gibbs function of mixing and its different contributions and corresponding phase diagrams as a function of temperature and composition were estimated. This analysis predicted PSMA15 to be miscible with PS4VP15 in the whole composition range up to 150 °C. Above this temperature, a partial miscibility is predicted when the PS4VP15 is in excess. The DSC results are in agreement with these predictions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 923–931, 2009     

A thermodynamic analysis of specific interactions in blends of poly(styrene‐co‐N,N‐dimethylacrylamide) and poly(styrene‐co‐acrylic acid). Screening and self‐association effects

In a first step of this contribution, the observed glass transition temperature‐composition behavior of miscible blends of poly(styrene‐co‐N,N‐dimethylacrylamide) (SAD17) containing 17 mol % of N,N‐dimethylacrylamide and poly(styrene‐co‐acrylic acid) (SAA18, SAA27, and SAA32) containing increasing acrylic acid content, are analyzed according to theoretical approaches. Both Kwei and Brostow equations describe well the experimental data though better fits were obtained with the Brostow's approach. The specific interactions involved in these systems are a combination of intra and interassociation hydrogen bonding. The positive deviation from the linear mixing rule of T_g‐composition observed within the SAA18+SAD17 blend system, indicates that interassociation interactions are prevailing. More pronounced intra‐association interactions within the SAA32+SAD17 blend system led to a large negative deviation while a fine balance is established between these two types of interactions within the SAA27+SAD17 blend. A thermodynamic analysis was carried out according to the Painter‐Coleman association model. The miscibility and phase behavior of SAD17+SAA18 and SAD17+SAA27 blends are well predicted. However, this model predicts a partial miscibility of SAD17+SAA32 system. Finally, the fitting parameter free method developed by Coleman to predict the T_g‐composition behavior is applied. This method predicts fairly well the evolution trend of experimental T_gs of the SAA18+SAD17 and SAA27+SAD17 blend systems. However, the compositional dependence of SAA32+SAD17 blend T_g was not predictable by this method. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47:2074–2082, 2009     

Specific interaction governing the melt intercalation of clay with poly(styrene‐co‐acrylonitrile) copolymers

In the melt intercalation of cation‐exchange clay, mixtures of montmorillonite and poly(styrene‐co‐acrylonitrile) (SAN) with various acrylonitrile contents were studied to examine the effect of specific interaction. When organic molecules with hydroxyl groups were used as intercalants for the clay, the amount of SAN penetrating the gallery of the layered structure of the clay and the corresponding increase in the gallery height occurred at a much higher rate because of the attractive specific interaction between acrylonitrile groups and polar groups on the clay surface. However, there was a limit to the increase in the gallery height, and the tendency for the gallery height to increase with the acrylonitrile group content disappeared when the acrylonitrile content was greater than 30 wt %, implying that excessive attractive interaction on the clay surfaces and polymer molecules glued the two adjacent silicate layers together; consequently, the increase in the gallery height could not be accomplished. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2430–2435, 2001     

Miscibility of polysulfone blends with poly(1‐vinylpyrrolidone‐co‐styrene) copolymers and their interaction energies

The miscibility of polysulfone (PSf) with various hydrophilic copolymers was explored. Among these blends, PSf gave homogeneous mixtures with poly(1‐vinylpyrrolidone‐co‐styrene) [P(VP–S)] copolymers when these copolymers contained 68–88 wt % 1‐vinylpyrrolidone (VP). Miscible PSf blends with P(VP–S) copolymers underwent phase separation on heating caused by lower critical solution temperature (LCST)‐type phase behavior. The phase behavior depended on the copolymer composition. Changes in the VP content of P(VP–S) copolymers from 65 to 68 wt % shifted the phase behavior from immiscibility to miscibility and the LCST behavior. The phase‐separation temperatures of the miscible blends first increased gradually with the VP content, then went through a broad maximum centered at about 80 wt % VP, and finally decreased just before the limiting content of VP for miscibility with PSf. The interaction energies of binary pairs involved in PSf/P(VP–S) blends were evaluated from the phase‐separation temperatures of PSf/P(VP–S) blends with lattice‐fluid theory combined with a binary interaction model. The decrease in the contact angle between water and the membrane surface with increasing VP content in P(VP–S) copolymers indicated that the hydrophobic properties of PSf could be improved via blending with hydrophilic P(VP–S) copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1401–1411, 2003     

Two‐dimensional Fourier transform infrared spectroscopy study of biosynthesized poly(hydroxybutyrate‐co‐hydroxyhexanoate) and poly(hydroxybutyrate‐ co‐hydroxyvalerate)

Generalized two‐dimensional (2D) Fourier transform infrared correlation spectroscopy was used to investigate the effect of the comonomer compositions on the crystallization behavior of two types of biosynthesized random copolymers, poly(hydroxybutyrate‐co‐hydroxyhexanoate) and poly(hydroxybutyrate‐co‐hydroxyvalerate). The carbonyl absorption band around 1730 cm^?1 was sensitive to the degree of crystallinity. 2D correlation analysis demonstrated that the 3‐hydroxyhexanoate units preferred to remain in the amorphous phase of the semicrystalline poly(hydroxybutyrate‐co‐hydroxyhexanoate) copolymer, resulting in decreases in the degree of crystallinity and the rate of the crystallization process. The poly(hydroxybutyrate‐co‐hydroxyvalerate) copolymer maintained a high degree of crystallinity when the 3‐hydroxyvalerate fraction was increased from 0 to 25 mol % because of isodimorphism. The crystalline and amorphous absorption bands for the carbonyl bond for this copolymer, therefore, changed simultaneously. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 649–656, 2002; DOI 10.1002/polb.10126     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

Structures and photoactive properties of poly(styrene‐co‐vinylbenzophenone)

Poly(styrene‐co‐vinylbenzophenone) prepared by a graft reaction on polystyrene revealed photoactive properties under irradiation of UVA. The photoactive structural features of the polymer were examined via electron paramagnetic resonance (EPR) under irradiation of UVA and fluorescent light. The photoactive functions of the polymer such as antimicrobial performance and dye decolorization ability were investigated. The results revealed that the poly(styrene‐co‐vinylbenzophenone) could generate radicals under fluorescent and UVA irradiation, and some radicals could stay alive for about 30 min in a dark chamber. The photoexcited polymer showed excellent antibacterial ability and decolorization effect on methylene blue and methyl orange dye under both daylight and UVA light. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2423–2430, 2008     

Characterization of poly(styrene‐co‐methacrylonitrile)s obtained by low‐temperature radiation polymerization and thermal degradation behavior measured by Py‐GC and CRTG

Poly(styrene‐co‐methacrylonitrile)s were polymerized in solutions with different polarities (n‐hexane and THF) by low‐temperature γ‐ray irradiation polymerization in a temperature range of −83.6–30 °C. It was found by IR measurement that the composition of the copolymers changed remarkably due to the effects of the polarity of solvents and the polymerization temperature. The thermal degradation behavior in the flash pyrolysis and in the continuous heating pyrolysis of these copolymers was measured by Py‐GC and controlled rate thermogravimetry (CRTG). The effects of the copolymer composition and sequence distribution on the thermal degradation behavior were investigated. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3569–3577, 2000     

Fast reversed‐phase liquid chromatographic separation of proteins by flow‐through poly(styrene‐co‐divinylbenzene) microspheres

With the explosive growth of the bioscience and biopharmaceuticals, the demand for high efficient analysis and separation of proteins is urgent. High‐performance liquid chromatography is an appropriate technology for this purpose, and the stationary phase is the kernel to the separation efficiency. In this study, flow‐through poly(styrene‐co‐divinylbenzene) microspheres characteristic of the binary pores, i.e. flow‐through pores and mesopores, were synthesized; this special porous structure would benefit the convective mass transfer while guarantee the high specific surface area. Owing to the hydrophobic nature, poly(styrene‐co‐divinylbenzene) microspheres were suitable as the reversed‐phase stationary phase for separation of proteins. For the high permeability of the poly(styrene‐co‐divinylbenzene) microspheres packed column, fast separation of the studied six proteins in ～2 min was achieved. The recoveries of studied proteins were acceptable in the range of 79.0–99.4%. The proposed column had good pH stability of 1–13 and repeatability. Moreover, the column was applied for egg white fast separation, further demonstrating its applicability for complex bio‐sample separation. The flow‐through poly(styrene‐co‐divinylbenzene) microspheres were promising for fast separation of large molecules.     

Analysis of blends of poly(styrene‐co‐acrylonitrile) with an epoxy/aromatic amine resin using scanning thermal microscopy

Using a microthermal analyzer TA Instruments 2990 μTA, we have analyzed the morphologies developed for the resin tetraglycidyl‐4,4′‐diaminodiphenylmethane cured with an aromatic amine 4,4′‐diaminodiphenylsulphone modified with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic. The phase‐separation phenomenon induced by polymerization was also followed by scanning electron microscopy. Using the modulated local thermal‐analysis mode of μTA, the glass‐transition temperatures of different domains for each sample were evaluated. Dynamic mechanical analyzer experiments were made to evaluate the macroscopic thermal properties of the blends. A morphology was well established for all blends examined with these techniques showing a nodular structure, the epoxy‐rich phase, and a continuous phase, the SAN‐rich phase, that forms the matrix. From both microscopic and macroscopic thermal analyses, it is concluded that a phase separation exists for the blends investigated. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 284–289, 2002     

Phase behavior study of poly(N‐tertbutylacrylamide‐co‐acrylamide) in the mixture of water–methanol: The role of polymer–nonsolvent second‐order interactions

The phase behavior of poly(N‐tertbutylacrylamide‐co‐acrylamide) (PNTBAM) in pure water and mixture of water–methanol is studied at different temperatures. The different compositions of PNTBAM are prepared by free‐radical polymerization technique and their phase behavior is studied by turbidimetry. The effects of copolymer and solvent composition on the phase behavior of the copolymers are discussed. It has been suggested that the inhomogenities in polymer chains are responsible for lowering the rate of phase transition by increasing the N‐tertbutylacrylamide (NTBAM) and methanol contents in copolymer and mixture, respectively. For the first time we have revealed that there are second‐order binary interactions in the water–methanol which are dominant in the special range of copolymer composition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 455–462, 2009     

Synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] by incorporation of carbon dioxide into epoxide polymer and the miscibility behavior of its blends with poly(methyl methacrylate) or poly(vinyl chloride)

This study was related to the investigation of the chemical fixation of carbon dioxide to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer‐to‐polymer blends. In the synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] [poly(DOMA‐co‐EA)] from poly(glycidyl methacrylate‐co‐ethyl acrylate) [poly(GMA‐co‐EA)] and CO₂, quaternary ammonium salts showed good catalytic activity. The films of poly(DOMA‐co‐EA) with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) blends were cast from N,N′‐dimethylformamide solution. The miscibility of the blends of poly(DOMA‐co‐EA) with PMMA or PVC have been investigated both by DSC and visual inspection of the blends. The optical clarity test and DSC analysis showed that poly(DOMA‐co‐EA) containing blends were miscible over the whole composition range. The miscibility behaviors were discussed in terms of Fourier transform infrared spectra and interaction parameters based on the binary interaction model. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1472–1480, 2001     

Phase behavior of tetramethylpolycarbonate blends with styrene‐based methacrylate copolymers and their interaction energies

The miscibility of tetramethylpolycarbonate (TMPC) blends with styrenic copolymers containing various methacrylates was examined, and the interaction energies between TMPC and methacrylate were evaluated from the phase‐separation temperatures of TMPC/copolymer blends with lattice‐fluid theory combined with a binary interaction model. TMPC formed miscible blends with styrenic copolymers containing less than a certain amount of methacrylate, and these miscible blends always exhibited lower critical solution temperature (LCST)‐type phase behavior. The phase‐separation temperatures of TMPC blends with copolymers such as poly(styrene‐co‐methyl methacrylate), poly(styrene‐co‐ethyl methacrylate), poly(styrene‐co‐n‐propyl methacrylate), and poly(styrene‐co‐phenyl methacrylate) increase with methacrylate content, go through a maximum, and decrease, whereas those of TMPC blends with poly(styrene‐co‐n‐butyl methacrylate) and poly(styrene‐co‐cyclohexyl methacrylate) always decrease. The calculated interaction energy for a copolymer–TMPC pair is negative and increases with the methacrylate content in the copolymer. This would seem to contradict the prediction of the binary interaction model, that systems with more favorable energetic interactions have higher LCSTs. A detailed inspection of lattice‐fluid theory was performed to explain such phase behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1288–1297, 2002     

XPS studies of Ni deposition on polymethyl methacrylate and poly(styrene‐co‐acrylonitrile)

Thin Ni layers were deposited onto clean polymethyl methacrylate (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) surfaces by a high vacuum thermal evaporation process. The resulting interfaces were studied by X‐ray photoelectron spectroscopy. The Ni deposition on PMMA changes the relative intensity of the C1s spectra associated with the O CO and C O carbon species, and modifies the shape of the O1s peak, while the Ni evaporation on SAN alters the C1s band intensity assigned to the CN moiety and gives a second N1s band at low binding energies. These observations suggest the formation of new chemical species at the interface between Ni and the PMMA ester group, and between Ni and the SAN nitrile group, which are the most reactive sites on these two polymers. Copyright © 2000 John Wiley & Sons, Ltd.     

Water‐disintegrative and biodegradable blends containing poly(L‐lactic acid) and poly(butylene adipate‐co‐terephthalate)

In this study, novel biodegradable materials were successfully generated, which have excellent mechanical properties in air during usage and storage, but whose structure easily disintegrates when immersed in water. The materials were prepared by melt blending poly(L ‐lactic acid) (PLLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) with a small amount of oligomeric poly(aspartic acid‐co‐lactide) (PAL) as a degradation accelerator. The degradation behavior of the blends was investigated by immersing the blend films in phosphate‐buffered saline (pH = 7.3) at 40 °C. It was shown that the PAL content and composition significantly affected morphology, mechanical properties, and hydrolysis rate of the blends. It was observed that the blends containing PAL with higher molar ratios of L ‐lactyl [LA]/[Asp] had smaller PBAT domain size, showing better mechanical properties when compared with those containing PAL with lower molar ratios of [LA]/[Asp]. The degradation rates of both PLLA and PBAT components in the ternary blends simultaneously became higher for the blends containing PAL with higher molar ratios of [LA]/[Asp]. It was confirmed that the PLLA component and its decomposed materials efficiently catalyze the hydrolytic degradation of the PBAT component, but by contrast that the PBAT component and its decomposed materials do not catalyze the hydrolytic degradation of the PLLA component in the blends. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

A polymer of bisphenol A and bisphenol A diglycidyl ether and its blends with poly(styrene‐co‐acrylonitrile): In situ polymerization preparation,morphology, and mechanical properties

The poly(hydroxy ether of bisphenol A)‐based blends containing poly(acrylontrile‐co‐styrene) (SAN) were prepared through in situ polymerization, i.e., the melt polymerization between the diglycidy ether of bisphenol A (DGEBA) and bisphenol A in the presence of poly(acrylontrile‐co‐styrene) (SAN). The polymerization reaction started from the initial homogeneous ternary mixture of SAN/DGEBA/bisphenol A, and the phenoxy/SAN blends with SAN content up to 20 wt % were obtained. Both the solubility behavior and Fourier transform infrared (FTIR) spectroscopy studies demonstrate that no intercomponent reaction occurred in the reactive blend system. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electronic microscopy (SEM) were employed to characterize the phase structure of the as‐polymerized blends. All the blends display the separate glass transition temperatures (T_g's); i.e., the blends were phase‐separated. The morphological observation showed that all the blends exhibited well‐distributed phase‐separated morphology. For the blends with SAN content less than 15 wt %, very fine SAN spherical particles (1–3 μmm in diameter) were uniformly dispersed in a continuous matrix of phenoxy and the fine morphology was formed through phase separation induced by polymerization. Mechanical tests show that the blends containing 5–15 wt % SAN displayed a substantial improvement of tensile properties and Izod impact strength, which were in marked contrast to those of the materials prepared via conventional methods. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 525–532, 1999     

Synthesis of new amphiphilic diblock copolymers containing poly(ethylene oxide) and poly(α‐olefin)

This article discusses an effective route to prepare amphiphilic diblock copolymers containing a poly(ethylene oxide) block and a polyolefin block that includes semicrystalline thermoplastics, such as polyethylene and syndiotactic polystyrene (s‐PS), and elastomers, such as poly(ethylene‐co‐1‐octene) and poly(ethylene‐co‐styrene) random copolymers. The broad choice of polyolefin blocks provides the amphiphilic copolymers with a wide range of thermal properties from high melting temperature ～270 °C to low glass‐transition temperature ～?60 °C. The chemistry involves two reaction steps, including the preparation of a borane group‐terminated polyolefin by the combination of a metallocene catalyst and a borane chain‐transfer agent as well as the interconversion of a borane terminal group to an anionic (? O^?K⁺) terminal group for the subsequent ring‐opening polymerization of ethylene oxide. The overall reaction process resembles a transformation from the metallocene polymerization of α‐olefins to the ring‐opening polymerization of ethylene oxide. The well‐defined reaction mechanisms in both steps provide the diblock copolymer with controlled molecular structure in terms of composition, molecular weight, moderate molecular weight distribution (M_w/M_n < 2.5), and absence of homopolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3416–3425, 2002     

Effect of inert diluent segment on the miscibility behavior of poly(vinylphenol) with poly(acetoxystyrene) blends

Polymer blends of poly(vinylphenol) (PVPh) and poly(styrene‐co‐vinylphenol) with poly(p‐acetoxystyrene) (PAS) were prepared by solution casting from tetrahydrofuran solution. The thermal properties and hydrogen bonding of the blends were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. Although hydrogen bonding existed between the PVPh and PAS segments, the experimental results indicated that PVPh is immiscible with PAS as shown by the existence of two glass‐transition temperatures over the entire composition range by DSC. This phenomenon is attributed to the strong self‐association of PVPh, intramolecular screening, and functional group accessibility effects of the PVPh/PAS blend system. However, the incorporation of an inert diluent moiety such as styrene into the PVPh chain renders the modified polymer to be miscible with PAS. Copolymers containing between 16 and 51 mol % vinylphenol were fully miscible with PAS according to DSC studies. These observed results were caused by the reduction of the strong self‐association of PVPh and the increase of the interassociation between PVPh and PAS segments with the incorporation of styrene on the PVPh chain. According to the Painter‐Coleman association model, the interassociation equilibrium constant of PVPh/PAS blends was determined by a model compound and polymer blend. Good correlation between these two methods was obtained after considering the intramolecular screening and functional group accessibility effect in the polymer blend. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1661–1672, 2002