Effects of solvents on electrospun polymeric fibers: preliminary study on polystyrene

Six solvents [acetic acid, acetonitrile, m‐cresol, toluene, tetrahydrofuran (THF) and dimethylformamide (DMF)] with different properties (eg density, boiling point, solubility parameter, dipole moment and dielectric constant) were used to prepare electrospun polystyrene (PS) fibers. Fiber diameters were found to decrease with increasing density and boiling point of the solvents. A large difference between the solubility parameters of PS and the solvent was responsible for the bead‐on‐string morphology observed. Productivity of the fibers (the numbers of fiber webs per unit area per unit time) increased with increasing dielectric constant and dipole moment of the solvents. Among the solvents studied, DMF was the best solvent that provided PS fibers with highest productivity and optimal morphological characteristics. The beadless, well‐aligned PS fibers with a diameter of ca 0.7 µm were produced from the solution of 10 % (w/v) of PS in DMF at an applied electrostatic field of 15 kV/10 cm, a nitrogen flow rate of 101 ml min^?1 and a rotational speed of the collector of 1500 rev min^?1. Copyright © 2004 Society of Chemical Industry     

Dielectric investigation of isotropic and anisotropic solutions of cellulose acetate in dioxane

The dielectric and optical characteristics of a sample of cellulose acetate (DS = 2.45) in dioxane solutions were studied at 10–50°C of concentration 10–50 wt% to include both isotropic and anisotropic phases. The study showed that the loss maximum, ε_max″, magnitude of polarization, (ε₀ ? ε_∞), static dielectric constant, ε₀, time of relation, (2πf_m)^?1, and refractive index, n_D, steadily increase with concentration up to the critical concentration (41 wt%) and then decrease. The mean-square dipole moment, 〈gμ²〉, decreases steadily up to the critical concentration then remains nearly constant, indicating that the isotropic solution changes to anisotropic, with smaller mean-square dipole moment. Comparison between the results of cellulose acetate (CA) and those of hydroxypropyl cellulose (HPC) reveals that, at the critical concentration in dioxane, the cholesteric structure of HPC possesses a greater mean-square dipole moment with higher temperature coefficient than does CA. The activation energy of the relaxation process for hydroxypropyl cellulose is higher, indicating a greater intrachain interaction compared with cellulose acetate.     

The Influence of Solvent Properties and Functionality on the Electrospinnability of Polystyrene Nanofibers

Summary: In order to produce nanometer‐sized fibers at an industrial scale, not only the morphology but also the production rate of fibers is important. The effect of solvent properties and functionality on the production rate of electrospun PS nanofibers was investigated using eighteen different solvents. The solution concentration was varied between 10 and 30% w/v. Electrospinning of PS solutions was carried out at various applied voltages and tip‐to‐collector distances The production rate of the obtained PS nanofibers was quantified in terms of electrospinnability. We found that the chance for the resulting PS solution to be spinnable is greater for solvents with high dipole moment and low viscosity. The solvent that provided the highest electrospinnability for polystyrene was DMF and the functionalities that promoted high dipole moment and thus high spinnability were the carbonyl group and the nitrogen group with free electrons. General guidelines for choosing suitable solvents for successful production of electrospun nanofibers have also been proposed.

SEM image of PS 685D at 200× magnification and the %‐coverage of the fibers obtained by using DMF, chloroform, and 1,4‐dioxane.     

Fluoroacidity evaluation in molten salts

The fluoroacidity of several alkaline fluoride media was studied by monitoring the concentration of electroactive species which is decreasing vs. time due to a gas species release, such as silicon fluorides, as indicated by the reaction: SiF_{4 + x}^x− = SiF_4(g) + xF⁻. This article relates the Si(IV) reaction study to define a relative fluoroacidity scale by studying the silicon ions stability in different melts. Electrochemical techniques allow the measurement of SiF_{4 + x}^x− concentration evolution and thus the reaction rate constant to be calculated at different temperatures and for several fluoride media. The article shows that the free F⁻ content depends on the fluoride mixture and that the rate values are correlated with the fluoroacidity allowing a qualitative estimation. Then a fluoride solvents fluoroacidity scale was proposed, scaling the different eutectic melts from basic melt to acidic one: NaF–KF < LiF–KF < NaF–MgF₂ < NaF–CaF₂ < LiF–NaF < LiF < LiF–CaF₂.     

Studies of linear polymer dimensions of poly(4-chlorostyrene) in various solvents around the θ temperatures by intrinsic viscosity

Intrinsic viscosities of poly(4-chlorostyrene) solutions in isopropyl-benzene and n-propylbenzene at temperatures above and below the theta (θ) temperatures of these solvents were measured using a capillary viscometer. The viscosity measurements were performed on three poly(4-chlorostyrene) samples having molecular weights (M?;_v) 1.75 × 10⁶, 6.5 × 10⁵ and 2.7 × 10⁵. A smooth and continuous contraction below the θ temperatures was observed for both solvents. The temperature dependence of [/eta] can be represented by a master curve in a plot of α³/eta|/tau|M^1/2 (g^1/2 mol^?1/2) versus |/tau|M^1/2 (g^1/2 mol^?1/2), where α/eta = [/eta(T)]/[/eta(θ)]^1/3 is the expansion factor and /tau = (T - θ)/T is the reduced temperature. A universal plot of reduced viscosity size (α/eta) versus reduced blob parameter (N/N_c) shows the achievement of collapsed state for T<θ. The prediction of thermal blob theory is also verified for T > θ. The temperature dependence of intrinsic viscosity, both below and above the θ temperature, exhibits similar behaviour to the temperature dependence of dipole moments for both of these solvents.     

Synthesis of novel amphiphilic pH‐sensitive polyurethane networks through W/O soap‐free emulsion polymerization process. II. Mechanical property and biphasic swelling behaviors

Amphiphilic urethane acrylate anionomer (UAA) chains exhibited very different solution properties in various solvents, such as water, dioxane, and dimethyl sulfoxide (DMSO). UAA chains showed a polyelectrolyte effect in a highly polar solvent, DMSO, but gave constant viscosity at various concentrations in aqueous solution, because of the microstructural difference of the UAA chain formed in solvents. In polar solvents (water and DMSO), the swelling of UAA networks prepared with water and dioxane strongly depended on the properties of the hydrophilic domains. In low and nonpolar solvents (dioxane and methylene chloride), the swelling of UAA networks was only dependent on the property of the hydrophobic segments. In the polar solvent medium, UAAG networks prepared with water exhibited greater swelling than UADG networks prepared with dioxane. Concerning swelling in a nonpolar solvent, however, UADG networks showed greater swelling than UAAG networks. This is because of the microstructural difference between these networks, which was confirmed by the mechanical property measurement. UAAG networks, having highly microphase‐separated structures, had higher modulus and transition temperatures than the UADG networks, because of the microstructural difference between UADG and UAAG networks. Both the UAAG and UADG networks take up two immiscible solvents simultaneously within their hydrophobic and hydrophilic domains. Equilibrium swelling ratio of these networks in two immiscible solvents strongly depends on their hydrophilic/hydrophobic balance that is controlled by the type of solvent used in the network synthesis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 621–630, 2001     

Processable heat-resistant polymers. XIII. Structure–property relationship in polyamideimides

Novel isomeric polyamideimides were synthesized by reacting the diacid chloride of 2-(4-carboxy phenyl)-1,3-dioxoisoindoline-5-carboxylic acid and o-, m-, and p-phenylenediamine at 30–70°C using polar solvents. The reactivity of the isomeric amines in the polycondensation reaction was studied. The isomeric effects on the physical, chemical, thermal, and electrical properties of the polymers were also studied. The polymers were found to be soluble in highly polar solvents such as DMF, DMAC, NMP, DMSO, m-cresol, etc. Thermal analysis indicated that polymers were thermostable and that their thermal stability follows the order para > meta > ortho. X-ray diffraction data revealed that para polymer is crystalline in nature. Dielectric properties with the variation of frequency at room temperature indicated that the dielectric constant and dielectric loss of the polymers follow the order ortho > meta > para.     

Phosphorus‐containing poly(ester‐imide)–polydimethylsiloxane copolymers

New phosphorus‐containing poly(ester‐imide)‐polydimethylsiloxane copolymers were prepared by solution polycondensation of 1,4‐[2‐(6‐oxido‐6H‐dibenz < c,e > < 1, 2 > oxaphosphorin‐6‐yl)]naphthalene‐bis(trimellitate) dianhydride with a mixture of an aromatic diamine (1,3‐bis(4‐aminophenoxy)benzene) and α,ω‐bis(3‐aminopropyl)oligodimethylsiloxane of controlled molecular weight, in various ratios. Poly(amic acid) intermediates were converted quantitatively to the corresponding polyimide structures using a solution imidization procedure. The polymers are easily soluble in polar organic solvents, such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylformamide, as well as in less polar solvents such as tetrahydrofuran. They show good thermal stability, the decomposition temperature being above 370 °C. The glass transition temperatures are in the range 165–216 °C. Solutions of the polymers in N‐methyl‐2‐pyrrolidone exhibit photoluminescence in the blue region. Copyright © 2010 Society of Chemical Industry     

An experimental and computational study of intramolecular charge transfer: Diarylamino derivatives of 7H-benzimidazo(2,1-a)benz(d,e)isoquinolin-7-ones

A novel intramolecular donor–acceptor system of four isomers consisting of 7H-benzimidazo(2,1-a)benz(d,e)isoquinolin-7-ones and diarylamine units was synthesized and characterized; the absorption and fluorescence spectra of the system in a variety of solvents were investigated. Intramolecular charge transfer was confirmed within the system by virtue of shifts in emission maximum with increasing solvent polarity; a high dipole moment for the intramolecular excited state was calculated using the Lippert equation. Shorter lifetimes were observed in polar solvents compared with those in non-polar solvents, indicating strong dipole–dipole interactions occurred. The ground-state geometry, lowest energy transition and the UV–vis spectrum of the system were studied using density functional theory and time-dependent density functional theory at B3LYP/6-31G^* level, which showed that the calculated outcomes were in good agreement with experimental data.     

Solvent Effects on the Selectivity of Palladium-Catalyzed Suzuki-Miyaura Couplings

The use of polar solvents MeCN or dimethylformamide (DMF) was previously shown to induce a selectivity switch in the Pd/P^tBu₃-catalyzed Suzuki-Miyaura coupling of chloroaryl triflates. This phenomenon was attributed to the ability of polar solvents to stabilize anionic transition states for oxidative addition. However, we demonstrate that selectivity in this reaction does not trend with solvent dielectic constant. Unlike MeCN and DMF, water, alcohols, and several polar aprotic solvents such as MeNO₂, acetone, and propylene carbonate provide the same selectivity as nonpolar solvents. These results indicate that the role of solvent on the selectivity of Suzuki-Miyaura couplings may be more complex than previously envisioned. Furthermore, this observation has the potential for synthetic value as it greatly broadens the scope of solvents that can be used for chloride-selective cross coupling of chloroaryl triflates.     

Preparation,characterization, and some properties of ionomers from a sulfonated styrene–butadiene–styrene triblock copolymer without gelation

The conditions for the sulfonation of a highly unsaturated styrene–butadiene–styrene triblock copolymer (SBS) in cyclohexane containing a small amount of acetone with acetyl sulfate made by sulfuric acid and acetic anhydride without gelation were studied. After neutralization with metallic ions, the ionomers were characterized with IR spectrophotometry, dynamic mechanical analysis, and transmission electron microscopy. The melt flow, solution properties, and mechanical properties of the ionomers were studied. The results showed that gelation occurred during the sulfonation of SBS in cyclohexane at a 5–10% concentration without acetone, whereas in the presence of 5–10 vol % acetone, sulfonation proceeded smoothly without gelation. Transmission electron microphotographs of the lead ionomer indicated the presence of ionic domains. A dynamic mechanical spectrum showed the presence of three transition temperatures: ?82.9, 68, and 96.5°C. The melt viscosity of the ionomer increased with the sulfonate content. The melt viscosity of the different ionomers neutralized with different cations seemed to decrease with decreasing ionic potential for both monovalent cations and divalent cations The solution viscosity of the sodium‐sulfonated ionomer increased with increasing sulfonate content. The ionomer still behaved as a thermoplastic elastomer and showed better mechanical properties than the original SBS. The tensile strength of the different ionomers decreased as follows. For the monovalent cations, it decreased with decreasing ionic potentials: Li⁺ > Na⁺ > K⁺. For the divalent cations, it decreased with increasing ionic potentials: Pb²⁺ > Zn²⁺ > Mg²⁺. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1398–1404, 2005     

Pebax membrane for CO2/CH4 separation: Effects of various solvents on morphology and performance

In this study, the effects of different solvents on the morphology and permeation of poly(ether‐block‐amide) (Pebax‐1657) membranes were investigated. Pebax membranes were fabricated via a solution casting method with five different solvents, that is, N,N‐dimethyl formamide (DMF), N,N‐dimethyl acetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), formic acid, and a mixture of ethanol (EtOH) with water (H₂O). Cross‐sectional scanning electron microscopy analysis of the membranes was performed to investigate the morphology of the prepared membranes. X‐ray diffraction and Fourier transform infrared analysis were also carried out to characterize the membranes. The interactions of the polymer and various solvents were evaluated with Hansen solubility parameters. Permeation experiments for CO₂ and CH₄ gases were performed to study the effects of the solvents on the permeation properties of the membranes. The solvent properties, such as the molar volume, boiling point, and solubility parameters, were investigated as were the membranes characteristics, such as the crystallinity, d‐spacing, and fractional free volume. The results obtained from the experiments show that the CO₂ permeability for the membranes prepared with different solvents followed this order: NMP > DMF > Formic acid > DMAc > H₂O/EtOH mixture. With increasing molar volume, the gas permeability increased for all of the membranes, except for DMAc, which showed a lower permeability because of its highly crystalline structure. DMF showed a higher CO₂/CH₄ ideal selectivity compared to the other membranes and, consequently, could be introduced as the best solvent from all aspects for the Pebax‐1657 membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44531.     

Permeation of xylene isomers through nitrile gloves

The physical parameters of the xylene isomers (the positional isomers o-, m-, and p-xylenes and the skeletal isomer ethyl benzene) responsible for the differing permeation behavior of the isomers through lined unsupported 0.41 mm thick nitrile glove material were investigated. An ASTM type permeation cell at 30°C, constant mixing conditions, hexane liquid collection, and capillary column gas chromatography/mass spectrometry of samples taken from the collection side every ten minutes allowed break through times t_b and steady-state sections to be defined. While pure isomers had distinct break through times t_b(m-xylene = p-xylene < ethyl benzene = o-xylene), steady-state permeation rates P_s(p-xylene > m-xylene > ethyl benzene = o-xylene), lag times t_l(m-xylene < p-xylene = ethyl benzene < o-xylene), and diffusion coefficients D_p(m-xylene < p-xylene = ethyl benzene < o-xylene), such behavior was lost in a equal volume mixture (t_b, t_l, P_s, and D_p were equivalent). The average P_s of the mixture isomers of equal volumes did not differ from that expected from the individual pure isomer P_s values. The results for the pure isomers were attributed to o-xylene and ethyl benzene being similarly sterically hindered, the p-xylene being the flattest and most symmetrical molecule and having no dipole moment, and m-xylene being intermediate in steric structure. The pure isomer t_l were directly related to viscosity divided by the log octanol-water coefficient, while their log P_s was inversely related to dipole moment times the logarithm of the capacity factor for water for a reversed-phase high-performance liquid chromatography column. In an equivolume mixture of the isomers, isomer interactions caused equivalence for all permeation kinetic parameters, indicating that the kinetics of mixture constituents is not predictable from the behavior of the pure constituents, although mass transfer appears additive. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1713–1721, 1997     

Complexation studies of some newly synthesized precursors for substituted dibenzo and dibenzodiaza crown ethers

This study represents the synthesis of dibenzo and dibenzodiaza crown ether precursors with various functional groups in good yield by employing four different methods using polar protic and aprotic solvents with high boiling points. Also the complexation abilities of all synthesized ligands with Cu²⁺, Zn²⁺, and Ag⁺ were studied by conductometry; thus the conductometric behavior of Cu(NO₃)₂, ZnCI₂, and AgNO₃ in 80% dioxane–water mixture was investigated in the presence of these ligands. The order of formation constant for complexes of the ligands with Cu²⁺, Zn²⁺, and Ag⁺ ions was found to be: Cu²⁺ > Zn²⁺ > Ag⁺ for the ligands of VI , VII , XI , and XII ; Cu²⁺ > Ag⁺ > Zn²⁺ for the ligands of III and VIII ; and Zn²⁺ > Cu²⁺ > Ag⁺ for the ligands of I , II , IV , V , IX , and X . © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2497–2501, 2004     

Novel polyaryletherketones containing various pendant groups. I. Synthesis and characterization

Novel high glass transition temperature polyaryletherketones, containing pendant amido, alkyl, and carboxyl groups with reduced viscosity above 0.54 dL/g, were synthesized via solution nucleophilic polycondensation reaction of phenolphthalin, 2′,2′-diisopropyl-5′,5′-dimethylphenolphthalin, and 3,3′-bis (4-hydroxyphenyl) isobenzopyrrolidone with bis(4-nitrophenyl)ketone in the presence of potassium carbonate. By ion exchange with Na⁺ and K⁺, four ionomers were also prepared. A new monomer simultaneously containing carboxyl and alkyl substituents was synthesized by reduction reaction of 2′,2′-diisopropyl-5′,5′-dimethyl-phenolphthalein. The resulting polymers were soluble in a few polar aprotic solvents; transparent, colorless, and tough films could easily be cast from DMF or DMSO solution. The mechanical properties of the films were excellent; and their tensile strength, elongation at break, and tensile moduli were in the range of 67.1–97.1 MPa, 7.8–165%, and 1.47–2.27 GPa, respectively. The prepared polymers showed fairly good thermal stability and resonably high glass transition temperatures above 210°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1127–1135, 1997     

Effect of solvent proton affinity on the kinetics of michael addition polymerization of n,n′‐bismaleimide‐4,4′‐diphenylmethane with barbituric acid

The effect of solvent proton affinity on the kinetics of the Michael addition polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) and barbituric acid (BTA) in different solvents [N‐methyl‐2‐pyrrolidone (NMP), N,N′‐dimethylacetamide (DMAC), and N,N′‐dimethylformamide (DMF)] were investigated. This was achieved by the complete suppression of the competitive free radical polymerization via the addition of a sufficient amount of hydroquinone (HQ). A mechanistic model was developed to adequately predict the polymerization kinetics before a critical conversion, at which point the diffusion‐controlled polymerization become the predominant factor during the latter stage of polymerization, was achieved. The activation energy (E_a) of the Michael addition polymerization of BMI with BTA in the presence of HQ in increasing order was: NMP < DMAC < DMF, which was correlated quite well with the solvent proton affinity (NMP > DMAC > DMF). By contrast, the frequency factor (A) in increasing order is: NMP < DMAC < DMF. As a result of the compensation effect between E_a and A, at constant temperature, the Michael addition rate constant decreased with increasing solvent proton affinity. POLYM. ENG. SCI., 54:559–568, 2014. © 2013 Society of Plastics Engineers     

Grafting of dichlorodimethylsilane onto cellulose acetate as a model system in homogeneous media

Homogeneous graft copolymerization of dichlorodimethylsilane (DCDMS) onto cellulose acetate (CA) was carried out in acetone. The weight conversion, grafting percentage and grafting efficiency were determined as functions of the polymerization temperature and the concentrations of monomer and cellulose acetate. The IR and NMR data of the graft copolymers showed peaks characteristic of grafted chains. The order of the solvents used for increasing the grafting yield values was found as follows: cyclohexanone > ethyl acetate > dioxane, which is in accordance with their dielectric constants. Cellulose acetate previously oxidized by treatment with a mixture of oxalic acid and potassium dichromate when grafted with DCDMS gave low grafting yield values. The rate of copolymerization grafting of DCDMS onto CA was determined (R_p = 1.1 %min⁻¹). The activation energy of the reaction between DCDMS and CA was calculated (1.32 kJ mol⁻¹, 0.32 kcal mol⁻¹). The mechanism of graft copolymerization of DCDMS onto CA is discussed.     

Solubility parameter-based analysis of polyacrylonitrile solutions in N,N-dimethyl formamide and dimethyl sulfoxide

The physical properties of the solutions of polyacrylonitrile (PAN) in N,N-dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) were characterized in terms of solubility parameter. The physical properties were largely determined by individual solubility parameters, particularly the polar term, rather than overall solubility parameter. With increasing temperature, the intrinsic viscosity and hydrodynamic diameter of dilute solutions were decreased but the dynamic viscosity (η′) of concentrated solutions was increased. Of the two solvents, these phenomena were more pronounced with DMF; DMF gave greater η′ and yield stress than DMSO. When the polymer solutions were dried at 25 °C DMSO generated a cocontinuous structure whereas DMF produced a dispersed morphology. In addition, DMF dissolved PAN faster than DMSO, and the dissolution process followed a mechanism analogous to S_N2 reaction.     

Flow birefringence studies of polymer conformation: cellulose tricarbanilate in two characteristic solvents

Flow birefringence measurements are reported on ten samples of cellulose tricarbanilate (14.1 × 10³ < M < 2180 × 10³). Phenyl benzoate, dioxane and mixtures of both were used as solvents. The ratio of Maxwell constant to intrinsic viscosity $\text{[n]}\text{[η]}$ strongly depends on temperature and kind of solvent. In ether solvents this polymer has a stiffer conformation than in an ester or a ketone. With the aid of the theory of Gotlib and Svetlov quantitative conclusions about chain stiffness can be drawn from the observed molecular weight dependence of $\text{[n]}\text{[η]}$. A number of 50 monomer units per random link were obtained in dioxane at 25°C. This agrees quite well with light scattering and intrinsic viscosity data. According to Burchard an interpretation of the great chain stiffness of this polymer in ether solvents can be given in terms of the formation of intramolecular hydrogen bonds. The tremendous influence of a change in stiffness on $\text{[n]}\text{[η]}$ must be ascribed to the varying sterical hindrance of rotation of the phenyl rings in the side groups of the chain. Unfortunately, no valuable information with respect to chain stiffening can be deduced from extinction angle data. Relatively small effects, as expected from theory, are almost completely masked by the influence of the polydispersity of the samples.     

Effect of reaction medium on radical copolymerization of acrylonitrile with vinyl acids

Radical polymerization of acrylonitrile (AN) with methacrylic acid (MAA) and itaconic acid (IA) was carried out in a mixture of dimethylformamide (DMF) and water at 70°C using α, α′‐azobisisobutyronitrile (AIBN) as an initiator. Monomer feed in the polymerization vessel was 98:2 (AN:MAA/IA) in the molar ratio, and the DMF:H₂O ratio was varied between 20:80 and 80:20 (w/w). Copolymers were characterized by FTIR, carbon, hydrogen, nitrogen elemental CHN analysis, ¹H‐ and ¹³C‐NMR, and viscometry. The rate of polymerization (R_p) was found to decrease with an increase in DMF concentration in the reaction medium, that is, in 20% DMF for AN–MAA system, the R_p is 1.23% min⁻¹ in 1 h of polymerization, while in 80% DMF, R_p is reduced to 0.37% min⁻¹. The nature of the vinyl acid also affects the R_p. It has been shown that the rate of polymerization is higher for an AN–MAA system as compared to an AN–IA system (R_p = 1.0% min⁻¹) and the methacrylic or itaconic acid content in the copolymer increases with an increase in the DMF concentration. The MAA content in the poly(AN–MAA) polymer produced in 20% DMF is 3.2 mol %, which increases to 6.1 mol % (calculated through FTIR spectra) when DMF is increased to 80% in the reaction medium. The intrinsic viscosity [η] of the poly(AN–IA) and poly(AN–MAA) copolymers in DMF was found to be in the range of 0.67–2.90 dLg⁻¹ depending on the reaction medium. In determining the intrinsic viscosity, a definite deviation from rectilinearity of the concentration dependence in the high‐dilution region is observed, thereby demonstrating the polyelectrolyte behavior of these polymers. Through FTIR and NMR spectral studies, PAN homopolymer and other copolymers have shown the formation of a small quantity of acrylamide units. In addition copolymer P₁₀, which contains 10.1 mol % IA, has shown anhydride formation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1640–1652, 2001