Water-soluble copolymers,XXIII. Copolymers of acrylamide with N-(1,1-dimethyl-3-oxobutyl)-N-(n-propyl)acrylamide: Synthesis and characterization

The copolymerization of acrylamide (AM) with N-(1,1-dimethyl-3-oxobutyl)-N-(n-propyl)acrylamide (PDAAM) has been studied in the range from 5 to 20% PDAAM in the feed. The copolymer compositions have been determined from elemental analysis and ¹³C-NMR. Reactivity ratio studies have been performed and the value of r₁ r₂ determined to be 2.20. The molecular weights of the copolymers were found to decrease with increasing PDAAM content in the feed. The copolymer microstructures were predicted from the experimentally determined reactivity ratios. These model structures are utilized for assessment of structure/dilute solution property relationships reported in a subsequent paper in this series.     

Synthesis,characterization, and aqueous solution behavior of copolymers of acrylamide and sodium 10-acryloyloxydecanoate

A new water-soluble monomer of sodium 10-Acryloyloxydecanoate (NaAD), which possesses a hydrophobic group and an ionizable group, was synthesized from acryloyl chloride and 10-hydroxydecanoic acid, and the series of copolymers of NaAD with acrylamide (AM) were prepared by the free radical polymerization in aqueous solution using ammonium persulfate as the initiator. The feed ratio of NaAD:AM was varied from 5:95 to 70:30 mol%, with the total monomer concentration held constant at 0.5 M. The copolymer compositions were determined from elemental analysis. The molecular weights of the copolymers were determined by gel permeation chromatography ranged from 0.76 × 10⁶ to 1.37 × 10⁶ g/mol. All copolymers were soluble in deionized water and salt solutions at pH > 5. The dilute and semidilute solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes, and the results indicated that NaAD30 exhibited much higher viscosity values. At moderate pH values, the copolymers coils become slightly more expanded and intermolecular association interactions occur, which was indicated by fluorescence and apparent viscosity measurements. Upon the addition of NaCl and in low pH, viscosities tended to decrease because of the disruption of the intermolecular associations.     

Water soluble copolymers. 55: N-isopropylacrylamide-co-acrylamide copolymers in drag reduction: Effect of molecular structure,hydration, and flow geometry on drag reduction performance

Non-ionic, hydrophobically associating, water soluble N-isopropylacrylamide-co-acrylamide (IPAM) copolymers have been synthesized and characterized specifically for the study of drag reduction. The drag reduction (DR) performance has been measured with a rotating disk rheometer and a capillary flow apparatus. The DR studies were performed in deionized water, 0.514 M NaCl and 1 M urea. DR efficiency is dependent on copolymer structure, composition, and solvation. Copolymers showing intermediate values of hydrophobic character are found to be the most effective drag reducers. For this copolymer series, IPAM-70 (the copolymer synthesized with 70 mole% N-isopropylacrylamide in the feed) is the most efficient drag reducer. The DR properties of the IPAM copolymers are influenced by hydrophobic associations as well as hydrogen bonding. The effects of salts from the Hofmeister series, cosolvents such as dioxane, and temperature are also examined. Drag reduction performance of the various copolymers is correlated to empirical relationships involving degree of polymerization, second virial coefficient or other solvation parameters, and concentration.     

Water‐soluble acrylamide copolymers. X. Flocculation efficiencies of poly[acrylamide‐co‐N,N‐dimethylacrylamide], poly[acrylamide‐co‐methacrylamide], poly[acrylamide‐co‐N‐t‐butylacrylamide], and their cationic derivatives

A hydrated, 1% by weight Na‐kaolinite suspension in deionized water was prepared, completely characterized, and reproducible measures of flocculation efficiency were validated. Flocculation tests of copolymers of acrylamide (AM) with dimethylacrylamide (DMA), methacrylamide (MeAM), or N‐t‐butylacrylamide (NTBAM) with 1% Na‐kaolinite suspensions gave average settling rate rates which decreased as the proportion of DMA, MeAM, or NTBAM in the copolymer increased. However, for a similar weight‐average molecular weight and slightly lower 〈r_g〉, the copolymer from DMA‐co‐AM‐3 gave settling rates and supernatant turbidities comparable to similar types of commercial polymers. This new copolymer was also more resistant to changes in pH or the presence of an electrolyte than were the tested commercial polymers. Cationic derivatives of the new copolymers gave lower average settling rates and higher supernatant turbidities than those of Percol 721 (cationic PAM), probably because of their lower charge densities. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2090–2108, 2002; DOI 10.1002/app.10562     

Synthesis and characterization of novel twin‐tailed hydrophobically associated copolymers and their applications to Cr(III) removal from aqueous solutions

Water pollution is one of the most serious environmental problems facing society. The objective of this study was to provide an efficient and inexpensive way of removing Cr(III) from polluted water. Novel twin‐tailed hydrophobically associating copolymers (PAAD) were prepared by micellar copolymerization of acrylamide (AM) and sodium 2‐acrylamido‐2‐methylpropane sulfonate with N,N‐dibutylmethacrylamide in an aqueous solution. The PAAD series, comprising copolymers of different molecular weights (ranged from 1.42 to 1.78 × 10⁶ g/mol) and compositions was characterized by gel permeation chromatography–multiangle laser light scattering, ¹H NMR and FTIR spectroscopy, and elemental analysis. The surface activity, morphology, and aggregation properties of PAAD samples were measured by surface tension and dynamic light scattering. A schematic representation of the formation of Cr(OH)₃ and its precipitation using PAAD samples as coagulant aid is discussed in the article. In addition, the Cr(OH)₃–copolymer interaction, as investigated by precipitation experiments, demonstrated that these copolymers have good Cr(OH)₃ binding capacity and potential as coagulant aid for the removal of Cr(III) from polluted water. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41028.     

Water-soluble copolymers. VI. Dilute solution viscosity studies of random copolymers of acrylamide with sulfonated comonomers

Dilute solution viscosity of a series of random copolymers of acrylamide (AM) with sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS) and with sodium-2-sulfoethylmethacrylate (NaSEM) has been studied using a four-bulb shear dilution capillary viscometer. The hydrodynamic volume of the copolymers in aqueous media was determined as a function of salt concentration, temperature, shear rate, and time. A linear relationship was observed between the intrinsic viscosity [η]₀ and the reciprocal of the square root of ionic strength in sodium chloride solutions, with salt concentrations varying from 0.043M to 0.257M. Negative temperature coefficients for [η]₀ indicate a decrease in the hydrodynamic volume of the ionic polymer molecules with increasing temperature. The relative zero-shear-intrinsic-viscosity change in distilled water to 0.257M sodium chloride aqueous media is used to elucidate viscosity–structure relationships. A maximum value is reached for this parameter at a composition of about 30 mol % of ionic comonomers for AM–NaAMPS and AM–NaSEM copolymer series.     

Flocculation of clay suspensions with water-insoluble starch grafting acrylamide/sodium allylsulfonated copolymer powder

Use of water-soluble and -insoluble starch grafting acrylamide/sodium allylsulfonated copolymers as flocculants to flocculate the clay suspension was investigated. The composition of acrylamide (AM), sodium allylsulfonated (SAS), and starch (St) repeating units in the water-soluble and -insoluble starch-grafted copolymer is about 0.718, 0.022, and 0.260 and 0.439, 0.014, and 0.547, respectively. For the water-soluble starch-grafted copolymer, the fast initial A_r decreasing rate and the lowest final A_r value occur at pH 2, 80 mg/L water-soluble starch-grafted copolymer and 100 mg/L clay suspension. As the suspension contains 1000 mg/L Na⁺ ion, the flocculating capability would be increased. For the water-insoluble starch-grafted copolymer, the initial A_r decreasing rate and the final A_r value are 1.6 times and 0.4 times, respectively, that of the water-soluble starch-grafted copolymer at the same test suspension. © 1995 John Wiley & Sons, Inc.     

Synthesis,characterization, and reactivity ratios of copolymers derived from 4‐nitrophenyl acrylate and n‐butyl methacrylate

Free‐radical copolymerization of 4‐nitrophenyl acrylate (NPA) with n‐butyl methacrylate (BMA) was carried out using benzoyl peroxide as an initiator. Seven different mole ratios of NPA and BMA were chosen for this study. The copolymers were characterized by IR, ¹H‐NMR, and ¹³C‐NMR spectral studies. The molecular weights of the copolymers were determined by gel permeation chromatography and the weight‐average (M _w) and the number‐average (M _n) molecular weights of these systems lie in the range of 4.3–5.3 × 10⁴ and 2.6–3.0 × 10⁴, respectively. The reactivity ratios of the monomers in the copolymer were evaluated by Fineman–Ross, Kelen–Tudos, and extended Kelen–Tudos methods. The product of r₁, r₂ lies in the range of 0.734–0.800, which suggests a random arrangement of monomers in the copolymer chain. Thermal decomposition of the polymers occurred in two stages in the temperature range of 165–505°C and the glass transition temperature (T_g) of one of the systems was 97.2°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1817–1824, 2003     

Water‐soluble allyl and diallyl camphor sulfonamides‐based polyacrylamide copolymers for enhanced oil recovery

The monomers N‐allyl camphor sulfonamide (CSAP) and N,N‐diallyl camphor sulfonamide (CSDAP) were copolymerized with acrylamide (AM), acrylic acid (AA) for EOR, respectively. The effect of the synthesis conditions on apparent viscosity was investigated, and the copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance (¹H NMR), environmental scanning electron microscope (ESEM), and thermogravimetric analysis (TGA). Increasing mass ratio of diallyl CSDAP could lead to the water‐insoluble of copolymer, and competition of free radicals could make polymerization of AM/AA/CSDAP more difficult than AM/AA/CSAP. The thickening function and temperature resistance of two copolymers were remarkably improved in comparison with similar molecular weight partially hydrolyzed polyacrylamide (HPAM). In addition, the pronounced temperature resistance of the copolymers has been also demonstrated by temperature resistance test. It has also found that copolymers AM/AA/CSAP and AM/AA/CSDAP brine solutions could obtain significant enhanced oil recovery at 70°C suggesting their potential being applied in chemical enhanced oil recovery. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41238.     

Water‐soluble copolymers from functionalized monomers (sodium o‐ and p‐methacryloylaminophenylarsonate): Synthesis and characterization

Copolymers of sodium o‐methacryloylaminophenylarsonate (o‐MAPHA‐Na) 1 and p‐methacrylolylaminophenylarsonate (p‐MAPHA‐Na) 2 with sodium acrylate (AA‐Na) 3 , sodium methacrylate (AM‐Na) 4 and acrylamide (AAD) 5 were prepared by free radical polymerization in aqueous media at 70°C using potassium persulfate (K₂S₂O₈) as the initiator. The total monomer concentration was carried out at 0.5M and the feed ratio ( M₁ : M₂ ) was varied from 10 : 90 to 90 : 10 mol%. The kinetic study was carried out by dilatometric method. The copolymer compositions were calculated by arsenic content in the copolymers. The As content (ppm) was determined by atomic absorption spectrometry (AAS). The reactivity ratios (r₁, r₂) were estimated by the Kelen‐Tüdös linearization method as well as error‐in‐variables method using the computer program RREVM®. In all cases, r₁ < 1 and r₂ > 1, indicating a tendency to form random copolymers. The values suggest that the copolymers contain a larger proportion of comonomer (i.e., AA‐Na, AM‐Na, or AAD). Weight‐average molar masses (M _w) of copolymers were determined by multi‐angle light scattering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formation of thermosensitive water‐soluble copolymers with phosphinic acid groups and the thermosensitivity of the copolymers and copolymer/metal complexes

Thermosensitive and water‐soluble copolymers were prepared through the copolymerization of acryloyloxypropyl phosphinic acid (APPA) and N‐isopropyl acrylamide (NIPAAm). The thermosensitivity of the copolymers and copolymer/metal complexes was studied. The APPA–NIPAAm copolymers with less than 11 mol % APPA moiety had a lower critical solution temperature (LCST) of approximately 45°C, but the APPA–NIPAAm copolymers with greater than 21 mol % APPA moiety had no LCST from 25 to 55°C. The APPA–NIPAAm copolymers had a higher adsorption capacity for Sm³⁺, Nd³⁺, and La³⁺ than for Cu²⁺, Ni²⁺ and Co²⁺. The APPA–NIPAAm (10:90) copolymer/metal (Sm³⁺, Nd³⁺, or La³⁺) complexes became water‐insoluble above 45°C at pH 6–7, but the APPA–NIPAAm (10:90) copolymer/metal (Cu²⁺,Ni²⁺, or Co²⁺) complexes were water‐soluble from 25 to 55°C at pH 6–7. The temperature at which both the APPA–NIPAAm copolymers and the copolymer/metal complexes became water‐insoluble increased as the pH values of the solutions increased. The APPA–NIPAAm copolymers were able to separate metal ions from their mixed solutions when the temperature of the solutions was changed; this was followed by centrifugation of the copolymer/metal complexes after the copolymers were added to the metal solutions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 116–125, 2004     

Sequence determination of vinyl acetate–methyl acrylate copolymers by NMR spectroscopy

Vinyl acetate/methyl acrylate (V/M) copolymers were prepared by free-radical solution polymerization in benzene. Copolymer compositions were obtained from ¹H-NMR spectroscopy. Reactivity ratios for the copolymerization of V with M were calculated using the Kelen-Tudos (KT) and the nonlinear error in variables (EVM) methods. The reactivity ratios obtained from the KT and EV methods are r_V = 0.04 ± 0.03 and r_M = 7.28 ± 2.88 and r_v = 0.04 ± 0.01 and r_M = 7.28 ± 0.37, respectively. The microstructure was obtained in terms of the distribution of V- and M-centered triad sequences from ¹³C{¹H}-NMR spectra of copolymers. Homonuclear ¹H-2D-COSY and 2D-NOESY NMR were used to determine the most probable conformer for the V/M copolymer. The copolymerization behavior of the V/M copolymers as a function of conversion is also reported. © 1994 John Wiley & Sons, Inc.     

Investigation of microstructure of 4‐vinyl pyridine–methacylonitrile copolymers by NMR spectroscopy

4‐Vinyl pyridine–methacrylonitrile (V/M) copolymers of different composition were prepared by bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition was determined from quantitative ¹³C{¹H}‐NMR spectra. The reactivity ratios for V/M copolymer obtained from a linear Kelen‐Tudos method (KT) and nonlinear error‐in‐variables method (EVM) are r_V = 0.79 ± 0.12, r_M = 0.38 ± 0.09 and r_V = 0.79 ± 0.13, r_M = 0.38 ± 0.07, respectively. The complete spectral assignment in term of compositional and configurational sequences of these copolymers were done with the help of distortionless enhancement by polarization transfer (DEPT), two‐dimensional heteronuclear single quantum coherence spectroscopy (HSQC). Total correlated spectroscopy (TOCSY) experiment was used to assign the various three‐bond ¹H‐¹H couplings in the V/M copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3232–3238, 2003     

pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers

A comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via ¹³C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na⁺ and Cl^?. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 10⁶ g/mol, corresponding to DPs of 1.6–1.9 × 10⁴ repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (R_g–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The R_g–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004     

4‐Acetamidophenyl acrylate copolymers with acrylonitrile and N‐vinyl‐2‐pyrrolidone: Synthesis,characterization, and reactivity ratios

4‐Acetamidophenyl acrylate (APA) was synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopies. Homo‐ and copolymers of APA with acrylonitrile (AN) and N‐vinyl‐2‐pyrrolidone (NVP) were prepared by a free radical polymerization. All the copolymer compositions have been determined by ¹H NMR technique, and the reactivity ratios of the monomer pairs have been evaluated using the linearization methods Fineman–Ross, Kelen–Tudos, and extended Kelen–Tudos. Nonlinear error‐in‐variable model (EVM) method was used to compare the reactivity ratios. The reactivity ratios for copoly(APA–AN) system were APA(r₁) = 0.70 and AN(r₂) = 0.333, and for copoly(APA–NVP) system the values were APA(r₁) = 4.99 and NVP(r₂) = 0.019. Thermal stability and molecular weights of the copolymers are reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1919–1927, 2006     

Kinetics of water absorbency in AA/AMPS copolymers: applications of a diffusion-relaxation model

Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a divinyl crosslinker, N,N′-methylenebisacrylamide, have been synthesized by free radical solution and inverse emulsion polymerization. The copolymerization has been carried at different pH values of the monomer mix reaction medium.The copolymers were characterized by their dynamic swelling behavior in deionized water, i.e. the mass of water absorbed by a sample of copolymer was measured vs time. The results were analyzed in terms of the Berens-Hopfenberg non-Fickian equation, leading to a one-only-term relaxation. These kinetics were interpreted by the diffusion-relaxation model and offer quantitative information by diffusivity at 20°C of water in the copolymers. In this investigation, the results have been confirmed within experimental error as the sample of the copolymer is swollen.     

Adiabatic compressibility of polyelectrolytes: Effect of solvents on copolymers of vinyl pyrrolidone with acrylic acid and N-dimethylaminoethyl methacrylate

The results of adiabatic compressibility measurements for two copolymers, acrylic acid-vinyl pyrrolidone (AA—VP) and N-dimethylaminoethyl methacrylate-vinyl pyrrolidone (DAM—VP), in three different solvents, namely, water, methanol, and dioxane, have been described. The molecular weight of copolymers was determined by the light scattering method and the IR and NMR spectra of the polymers and copolymers were examined to establish that the alternating acrylic acid–vinyl pyrrolidone and N-dimethylaminoethyl methacrylate–vinyl pyrrolidone structure exists in the copolymers. The AA—VP copolymer behaves as a slightly weaker acid than the homopolymer of acrylic acid, while DAM—VP copolymer is very feebly basic and has the same strength as that of the homopolymer of N-dimethylaminoethyl methacrylate. The reduced viscosity for the two copolymers in aqueous solution is very low (～0.08 dL/g for AA—VP copolymer). In methanol solution AA—VP and DAM—VP copolymers show a decrease of øK^°₂ and øV^°₂ by 61.6 × 10^?4 cc/bar/mol and 8.0 cc/mol, and 191.0 × 10^?4 cc/bar/mol and 20.0 cc/mol, respectively, over that of the values of aqueous solution. The void space around the solute is smaller in methanol than in water, and accordingly this decrease has been attributed to geometric effect. Only one copolymer, DAM—VP is soluble in dioxane, and the values are seen to have increased in this solution by 71.0 × 10^?4 cc/bar/mol and 18.7 cc/mol, respectively, compared to the values obtained from aqueous solution. The experimentally determined øK^°₂ and øV^°₂ for AA—VP and DAM—VP copolymer are 0.6 × 10^?4 cc/bar/mol, and 102.4 cc/mol and ?61.0 × 10^?4 cc/bar/mol, 94.4 cc/mol, respectively, in aqueous solution, and ?12.0 × 10^?4 cc/bar/mol, 211.0 cc/mol and ?203.0 × 10^?4 cc/bar/mol, 191.0 cc/mol, respectively, in methanol solution. In dioxane solution the values for DAM—VP copolymer are 59.0 × 10^?4 cc/bar/mol and 229.7 cc/mol, respectively. These experimentally determined values for AA—VP copolymer show an increase by 0.04 × 10^?4 cc/bar/mol, 4.4 cc/mol and 28.3 × 10^?4 cc/bar/mol, 8.0 cc/mol in aqueous and methanol solution, respectively, compared to calculated values determined on the basis of no interaction between acid and the pyrrolidone group. In contrast, the DAM—VP copolymer shows a decrease of 27.6 × 10^?4 cc/bar/mol and 10.3 cc/mol, 149.3 × 10^?4 cc/bar/mol and 20.2 cc/mol, and 23.0 × 10^?4 cc/bar/mol and 4.1 cc/mol in aqueous, methanol, and dioxane solutions, respectively. In aqueous solution these differences between calculated and observed values have been attributed to a change of water structure around the copolymer chain. A similar effect is responsible for the difference of the values in the methanol solution also. In the dioxane solution the difference is rather small, and the solvent structure has probably not altered much due to the presence of the DAM unit in the chain.     

Modified polyacrylamide containing phenylsulfonamide and betaine sulfonate with excellent viscoelasticity for EOR

The monomers containing phenylsulfonamide N-allyl-4-methylbenzenesulfonamide (TCAP) and N,N-diallyl-4-methyl benzenesulfonamide (TCDAP) were copolymerized with acrylamide (AM), acrylic acid (AA), and 3-(3-methacrylamidopropyl-dimethylammonio)-propane-1-sulfonate (MDPS), respectively, through free-radical micellar copolymerization in deionized water for enhanced oil recovery (EOR). Then, the effect of the synthesis conditions was investigated simultaneously; the copolymers were characterized by Fourier transform infraredFTIR, nuclear magnetic resonance, scanning electron microscopy, and thermogravimetric analysis. It was found that the thickening function, high-temperature resistance (120 °C), and anti-shear ability were improved significantly. It was also found that the copolymers had excellent viscoelasticity at the lower shear frequencies. When the copolymers were dissolved in 10,000 mg L⁻¹ NaCl, 2000 mg L⁻¹ CaCl₂, and 2000 mg L⁻¹ MgCl₂ solutions, the viscosity retention rates of AM/AA/TCAP/MDPS and AM/AA/TCDAP/MDPS were 13.3, 11.1, 10.6% and 18.6, 15.2, 11.7%, respectively. In addition, the copolymers for EOR at 60 °C were 11.4 and 13.8%, respectively, which demonstrated that the copolymers possessed excellent performance for potential application in EOR. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47971.     

Microstructure determination and thermal studies of n‐acryloylcarbazole/vinyl acetate copolymers

Copolymers of N‐acryloylcarbazole (A) and vinyl acetate (V) were synthesized by bulk polymerization using benzoyl peroxide (BPO) as free‐radical initiator at 65°C in different in‐feed ratios. The composition of the copolymer was determined by ¹H‐NMR spectrum. The comonomer reactivity ratios, determined by Kelen–Tudos (KT) and nonlinear error‐in‐variables (EVM) methods, were r_A= 16.75 ± 1.38, r_V = 0.015 ± 0.002, and r_A = 16.36, r_V = 0.015, respectively. Complete spectral assignments of the ¹H and ¹³C{¹H} NMR spectra of the copolymers were done by the help of distortionless enhancement by polarization transfer (DEPT) and two‐dimensional NMR techniques such as heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY). The methine and methylene carbon resonances were found to be compositional as well as configurational sensitive. The signals obtained were broad pertaining to the restricted rotation of bulky carbazole group. The thermal stability and glass‐transition temperatures (T_g) of the copolymers were found to be dependant on polymer composition and characteristic of rotational rigidity of the polymer chain. Variation in the values of T_g with the copolymer composition was found to be in good agreement with theoretical values obtained from Johnston and Barton equations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2720–2733, 2007     

Stereochemical and compositional assignments of trans‐4‐methacryloyloxyazobenzene–methyl methacrylate copolymers by one‐ and two‐dimensional NMR spectroscopy

The microstructure of trans‐4‐methacryloyloxyazobenzene–methyl methacrylate copolymers prepared by solution polymerization process using AIBN as initiator is analyzed by one‐and two‐dimensional spectroscopy. Sequence distribution was calculated from the ¹³C(¹H)‐NMR spectra of the copolymers. Comonomer reactivity ratios were determined using the Kelen–Tudos and the nonlinear error‐in‐variables methods are r_A = 1.14 ± 0.08 and r_M = 0.51 ± 0.03; r_A = 1.13 ± 0.1 and r_M = 0.50 ± 0.04, respectively. The sequence distribution of A‐ and M‐centered triads determined from ¹³C(¹H)‐NMR spectra of copolymer is in good agreement with triad concentration calculated from a statistical model. The 2‐D heteronuclear single‐quantum correlation and correlated spectroscopy (TOCSY) was used to analyze the complex ¹H‐NMR spectrum. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3016–3025, 1999