Calculation of reactivity ratios of methacrylic acid-ethyl acrylate copolymer by on-line quantitative 1H NMR spectroscopy

The solution copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was studied by online proton nuclear magnetic resonance spectroscopy (¹H NMR) using 2,2′–azobisisobutyronitrile as an initiator in deuterated dimethyl sulfoxide at 60 °C. The chemical compositions of the copolymer and the comonomer concentrations were determined from the conversion of comonomers to copolymer by quantitative in situ NMR monitoring to estimate the reactivity ratios of the comonomers at low conversion. This is a new and easy methodology to analyze radical copolymerization. In this research, it is shown that monomer reactivity ratios can be calculated by data collected only from one initial comonomer mixture composition via online monitoring progress of the copolymerization reaction. The reactivity ratios of MAA and EA are equal to 2.360 and 0.414, respectively. This approach is used to compute the monomer reactivity ratios in a nonlinear integrated form of the copolymerization equation which is described by Mayo and Lewis terminal model. The fairly good agreement between the results and the literature data reported for the emulsion system represent the accuracy of the reactivity ratios calculated by this new approach. The calculated reactivity ratios for emulsion copolymerization are r _MAA = 2.040 and r _EA = 0.470, and the previous literature data are r _MAA = 2.580 and r _EA = 0.157.     

Synthesis,characterization and thermal properties of homo and copolymers of 3,5-dimethoxyphenyl methacrylate with glycidyl methacrylate: Determination of monomer reactivity ratios

The new methacrylic monomer, 3,5-dimethoxyphenyl methacrylate (DMOPM) was synthesized by reacting 3,5-dimethoxyphenol dissolved in ethyl methyl ketone (EMK) with methacryloyl chloride in presence of triethylamine as a catalyst. The homopolymer and copolymers of DMOPM with glycidyl methacrylate (GMA) were synthesized by free radical polymerization in EMK solution at 70 ± 1 °C using benzoyl peroxide as a free radical initiator. The copolymerization behaviour was studied in a wide composition interval with the mole fractions of DMOPM ranging from 0.15 to 0.9 in the feed. The homopolymer and the copolymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility was tested in various polar and non-polar solvents. The molecular weight and polydispersity indices of the polymers were determined using gel permeation chromatography. The glass transition temperature of the copolymers increases with increase in DMOPM content. The thermogravimetric analysis of the polymers showed that the thermal stability of the copolymer increases with DMOPM content. The copolymer composition was determined using ¹H NMR spectra. The monomer reactivity ratios were determined by the application of conventional linearization methods such as Fineman–Ross (r₁ = 0.520, r₂ = 2.521), Kelen–Tudos (r₁ = 0.629, r₂ = 2.554) and extended Kelen–Tudos methods (r₁ = 0.600, r₂ = 2.502).     

Kinetic study of atom transfer radical homo- and copolymerization of styrene and methyl methacrylate initiated with trichloromethyl-terminated poly(vinyl acetate) macroinitiator

Atom transfer radical bulk copolymerization of styrene (St) and methyl methacrylate (MMA) was performed in the presence of CuCl/PMDETA as a catalyst system and trichloromethyl-terminated poly(vinyl acetate) telomer as a macroinitiator at 90 °C. The overall monomer conversion was followed gravimetrically and the cumulative average copolymer composition at moderate to high conversion was determined by ¹H NMR spectroscopy. Reactivity ratios of St and MMA were calculated by the extended Kelen–Tudos (KT) and Mao–Huglin (MH) methods to be r_St = 0.605 ± 0.058, r_MMA = 0.429 ± 0.042 and r_St = 0.602 ± 0.043, r_MMA = 0.430 ± 0.032, respectively, which are in good agreement with those reported for the conventional free-radical copolymerization of St and MMA. The 95% joint confidence limit was used to evaluate accuracy of the estimated reactivity ratios. Results showed that in the controlled/living radical polymerization systems such as ATRP, more reliable reactivity ratios are obtained when copolymer composition at moderate to high conversion is used. Good agreement between the theoretical and experimental composition drifts in the comonomer mixture and copolymer as a function of the overall monomer conversion was observed, indicating the accuracy of reactivity ratios calculated by copolymer composition at the moderate to high conversion. Instantaneous copolymer composition curve and number-average sequence length of comonomers in the copolymer indicated that the copolymerization system tends to produce a random copolymer.     

A comprehensive study on the kinetics of aqueous free-radical homo- and copolymerization of acrylamide and diallyldimethylammonium chloride by online 1H-NMR spectroscopy

Free-radical homo- and copolymerization of acrylamide (AAm) and diallyldimethylammonium chloride (DADMAC) initiated with potassium persulfate (KPS) were performed in the presence of 0.1 M NaCl solution in D₂O at 50 °C. Online ¹H-NMR kinetic experiments were used to study polymerization kinetics via determination of the individual and overall conversion of the comonomers and compositions of the comonomer mixture and produced copolymer as a function of the reaction time. Reactivity ratios of the AAm and DADMAC were calculated by Mao-Huglin (MH) and extended Kelen-Tudos (KT) methods to be 7.0855?±?1.3963, 0.1216?±?0.0301 and 6.9458?±?2.0113, 0.1201?±?0.0437 respectively. “Lumped” kinetic parameter (k _p k _t ^??0.5 ) was estimated from experimental data. Results showed that k _p k _t ^??0.5 value increases by increasing mole fraction of the AAm in the initial reaction mixture. Drift in the comonomer mixture and copolymer compositions with reaction progress was evaluated experimentally and theoretically. Theoretical values were calculated from Meyer-Lowry equation by using reactivity ratios obtained from MH method. A good fitting between the experimental and theoretical values was observed, indicating accuracy of the reactivity ratios estimated in the present work. It was found from following changes in the copolymer composition with the comonomer conversion that produced copolymer has a statistical structure.     

Study on monomer reactivity ratios of acrylonitrile/itaconic acid in aqueous deposited copolymerization system initiated by ammonium persulfate

A single water-soluble initiator-ammonium persulfate (APS), not containing alkali metal ions, was first utilized to initiate copolymerization of acrylonitrile (AN)/itaconic acid (IA) in aqueous deposited copolymerization system. Monomer reactivity ratios of this polymerization system were investigated using element analysis method and Q–e schemes. It was found that the monomer reactivity ratios of AN/IA calculated from Q–e schemes are 0.505 (r _AN) and 1.928 (r _IA), while the monomer reactivity ratios of AN/IA in aqueous deposited copolymerization system at 60 °C are 0.64 (r _AN) and 1.37 (r _IA) calculated from Kelen–Tüdõs method, 0.61 (r _AN) and 1.47 (r _IA) from Fineman–Ross method. The three pairs of monomer reactivity ratios are in good agreement. With the increase of the polymerization temperature, the monomer reactivity ratios of AN and IA approach to unity, indicating that the aqueous deposited copolymerization of AN/IA has a tendency to ideal copolymerization. At lower polymerization conversion, the monomer reactivity ratios of AN and IA have hardly any changes. When the polymerization conversion is more than 5%, the monomer reactivity ratio of AN increases, while that of IA decreases.     

Determination of monomer reactivity ratios for copolymerizations of methacrylic acid with poly (ethylene glycol) monomethacrylate

Self-associating copolymers of methacrylic acid (MAA) with poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by free radical copolymerization of MAA with PEGMA using dispersion polymerization in D₂O, or solution polymerization in a 50/50 ethanol–D₂O mixture. These copolymers have been studied as components of reversible hydrogels¹ and in medical applications.² In order to understand the relationship between the copolymer structure and its performance, it is important to determine the sequence distribution of the copolymer. The copolymer architecture is determined by the reactivity ratios and integrated instantaneous feed compositions. The reactivity ratios were determined using the first-order Markov method³ by running a series of reactions at various initial monomer ratios and determining the monomer incorporation into the copolymer as a function of time, via ¹H nuclear magnetic resonance. The reactivity ratios for dispersion copolymerizations of MAA with PEGMA in water were determined to be r₁ = 1.03 and r₂ = 1.02, whereas solution copolymerization in 50/50 EtOH–H₂O gave reactivity ratios of r₁ = 2.0 and r₂ = 3.6. These results show that the reactivity ratios and copolymer architecture are influenced by the solvent system. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1019–1025, 1998     

The effect of various catalysts on the monomer reactivity ratios in oxidative copolymerization of styrene and α‐methylstyrene

Oxidative copolymerizations of styrene (St) with α‐methylstyrene (AMS) have been studied under 100 psi (690 kPa) oxygen pressure at 50 °C in the presence of various catalysts, namely 2,2′‐azobisisobutyronitrile, cobalt(II) phthalocyanine pyridine complex and cobalt(II) tetraphenylporphyrin pyridine complex. The rates of copolymerization reactions (R_p) are obtained from oxygen consumption versus time plots. The reactivity ratios are computed with the Fineman–Ross and Kelen–Tüdös methods, using copolyperoxide compositions obtained from ¹H NMR analysis. The effects of these catalysts on R_p, molecular weight and monomer reactivity ratios have been examined. Using all three catalysts, the comonomer incorporation in the copolyperoxide chain is controllable over a wide range by adjusting the comonomer feed ratios. The reactivity ratio results indicate that incorporation of St or AMS in the copolyperoxides is independent of initiating system. © 2014 Society of Chemical Industry     

Use of n.m.r. data to calculate copolymer reactivity ratios

Reactivity ratios can be determined from n.m.r. analyses of binary copolymers. Measurement of the diad or triad sequence distribution provides an estimate of the number average sequence length of each copolymer. Each average sequence length is directly related to the corresponding reactivity ratio in the terminal copolymerization model. Extension to more complicated reaction models is straightforward. A single copolymerization experiment yields values for both reactivity ratios with this procedure. When pentads or triads, centred on one monomer only, are measured the two reactivity ratios cannot normally be estimated unless the copolymer is highly alternating. It is possible, however, to combine such data with an n.m.r. or other analysis of the chemical composition of the copolymer to obtain r₁ and r₂. When the sequence distribution of runs, centred on only one of the monomers, can be analysed and the chemical composition of the copolymer is not available the procedure can yield a good value for the reactivity ratio of that monomer and a poor estimate for that of the comonomer.     

Atom transfer radical homo‐ and copolymerization of styrene and methyl acrylate initiated with trichloromethyl‐ terminated poly(vinyl acetate) macroinitiator: A kinetic study

Atom transfer radical bulk copolymerization of styrene (St) and methyl acrylate (MA) initiated with trichloromethyl‐terminated poly(vinyl acetate) macroinitiator was performed in the presence of CuCl/PMDETA as a catalyst system at 90°C. Linear dependence of ln[M]₀/[M] versus time data along with narrow polydispersity of molecular weight distribution revealed that all the homo‐ and copolymerization reactions proceed according to the controlled/living characteristic. To obtain more reliable monomer reactivity ratios, the cumulative average copolymer composition at moderate to high conversion was determined by ¹H‐NMR spectroscopy. Reactivity ratios of St and MA were calculated by the extended Kelen‐Tudos (KT) and Mao‐Huglin (MH) methods to be r_St = 1.018 ± 0.060, r_MA = 0.177 ± 0.025 and r_St = 1.016 ± 0.053, r_MA = 0.179 ± 0.023, respectively, which are in a good agreement with those reported for the conventional free‐radical copolymerization of St and MA. Good agreement between the theoretical and experimental composition drifts in the comonomer mixture and copolymer as a function of the overall monomer conversion were observed, indicating that the reactivity ratios calculated by copolymer composition at the moderate to high conversion are accurate. Instantaneous copolymer composition curve and number‐average sequence length of comonomers in the copolymer indicated that the copolymerization system tends to produce a random copolymer. However, MA‐centered triad distribution results indicate that the spontaneous gradient copolymers can also be obtained when the mole fraction of MA in the initial comonomer mixture is high enough. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A method of calculating copolymerization reactivity ratios

An improved linearization method is proposed for determining the monomer reactivity ratios of free-radical copolymerizations by fitting the data of cumulative copolymer compositions and overall weight fractional conversions, or cumulative copolymer compositions and residual monomer compositions of the reaction mixture. The reactivity ratios of monomers for four different copolymerization reactions are determined. The results are very close to those of literature reports and account well for the experimental results.     

Copolymerizations of ethylene with α-olefin-ω-ols by highly active vanadium(III) catalysts bearing [N,O] bidentate chelated ligands

The copolymerizations of ethylene with polar hydroxyl monomers such as 10-undecen-1-ol, 5-hexen-1-ol and 3-buten-1-ol were investigated by the vanadium(III) catalysts bearing bidentate [N,O] ligands (1, [PhNC(CH₃)CHC(Ph)O]VCl₂(THF)₂; 2, [PhNCHC₆H₄O]VCl₂(THF)₂; 3, [PhNCHC(Ph)CHO]VCl₂(THF)₂). The polar monomers were pretreated by alkylaluminum before the polymerization. High catalytic activities and efficient comonomer incorporations can be easily obtained by changing monomer masking reagents and polymerization conditions in the presence of diethylaluminium chloride as a cocatalyst. The longer the spacer group, the higher the incorporation of the monomer. Under the mild conditions, the incorporation level of 10-undecen-1-ol reached 13.9 mol% in the resultant copolymers was obtained. The reactivity ratios of copolymerization (r₁ = 41.4, r₂ = 0.02, r₁r₂ = 0.83) were evaluated by Fineman–Ross method. According to ¹³C NMR spectra, polar units were located both on the main chain and at the chain end. The end-hydroxylated polymers were probably obtained due to the formation of dormant species after the insertion of the comonomer followed by the chain transfer to alkylaluminum. In addition, the signals derived from polar monomer inverse insertion were detected for the first time.     

Cross-linking photocopolymerization of dodecyl methacrylate with oxyethylene glycol dimethacrylates: Kinetics and reactivity ratios

The photo-induced copolymerization of dodecyl methacrylate (DDM) with five oxyethylene glycol dimethacrylates (OEGDM) was investigated. Effects of the monomer ratio and of the length of dimethacrylate spacer group on the polymerization kinetics, the extent of the after-effect and pendant double bond content in the polymerization product were studied and the reactivity ratios estimated. For systems containing OEGDM with short spacers between the methacrylate groups, R_p^max reached the highest value at certain monovinyl/divinyl monomer ratio. This phenomenon was discussed in terms of the behavior of the reaction diffusion parameter (as a function of monomer ratio and conversion). Determination of the reactivity ratios by five calculation methods showed that r₁ (DDM) values were lower than 1 and the r₂ (OEGDM) values were higher than 1 indicating that the polymer formed at the beginning of the reaction is more densely cross-linked than that formed in the final reaction stages.     

Gasification reactivity of char from dried sewage sludge in a fluidized bed

The gasification reactivity of char from dried sewage sludge (DSS) applicable to fluidized bed gasification (FBG) was determined. The char was generated by devolatilizing the DSS with nitrogen at the selected bed temperature and was subsequently gasified by switching the fluidization agent to mixtures of CO₂ and N₂ (CO₂ reactivity tests) and steam and N₂ (H₂O reactivity tests)._. The tests were conducted in the temperature range of 800–900 °C at atmospheric pressure, using partial pressure of the main reactant in the mixture (CO₂ or H₂O) in the range of 0.10–0.30 bar. Expressions for the intrinsic reactivity (free of diffusion effects) as a function of temperature, partial pressure of gas reactant (CO₂ or H₂O) and degree of conversion were obtained for each reaction. For the whole range of conversion it was found that the char reactivity in an H₂O–N₂ mixture was roughly three times higher than that in a mixture with the corresponding partial pressure of CO₂. The reactivity was only influenced by particle size greater than 1.2 mm in the tests with steam at 900 °C. It was demonstrated that the method of char preparation greatly influences the reactivity, highlighting the importance of generating the char in conditions similar to that in FBG.     

Gelation-free synthesis of poly(allyl methacrylate-co-butyl acrylate) copolymers by atom transfer radical polymerization

The preparation of functional copolymers based on allyl methacrylate (AMA) and butyl acrylate (BA) without gel formation via atom transfer radical polymerization is described. The gelation-free controlled radical copolymerizations were carried out in benzonitrile solution at 70 °C using ethyl 2-bromoisobutyrate as initiator and mixed halogen technique, copper chloride along with N,N,N′,N″,N″-pentamethyldiethylenetriamine as the catalyst system. Kinetic analyses have demonstrated that all the copolymerizations showed a general behaviour characterized by two clearly differentiated stages. Thus, in an initial stage, the polymerizations presented first order kinetic with respect to the monomer concentration. In the subsequent stage, at low-intermediate conversions, a deceleration in the rate copolymerization leads to limit conversions, which decrease as the initial concentration of BA in the feed increases. The reactivity ratios values were calculated from the copolymer composition determined by ¹H NMR, and using the extended Kelen–Tüdös method. Values of 2.70 ± 0.21 and 0.49 ± 0.04 were obtained for AMA and BA, respectively. The cumulative copolymer compositions as a function of conversion degree for the different monomer molar fractions in the feed showed gradient character of the copolymers obtained.     

Kinetic study of radical polymerization. VII. Investigation into the solution copolymerization of acrylonitrile and itaconic acid by real‐time 1H NMR spectroscopy

Free radical solution copolymerization of acrylonitrile (AN) and itaconic acid (IA) was performed with DMSO‐d₆ as the solvent and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. Weight ratio of the monomers to solvent and molar ratio of initiator to monomers were constant in all experiments. The initial comonomer composition was the only variable in this study. On‐line ¹H NMR spectroscopy was applied to follow individual monomer conversion. Mole fraction of AN and IA in the reaction mixture (f) and in the copolymer chain (F) were measured with progress of the copolymerization reaction. Overall monomer conversion versus time and also compositions of monomer mixture and copolymer as a function of overall monomer conversion were calculated from the data of individual monomer conversion versus time. Total rate constant for the copolymerization reaction was calculated by using the overall monomer conversion versus time data and then k_p/k_t^0.5 was estimated. The dependency of k_p/k_t^0.5 on IA concentration was studied and it was found that this ratio decreases by increasing the mole fraction of IA in the initial feed. The variation of comonomer and copolymer compositions as a function of overall monomer conversion was calculated theoretically by the terminal model equations and compared with the experimental data. Instantaneous copolymer composition curve showed the formation of alternating copolymer chain during copolymerization reaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3253–3260, 2007     

Monomer apparent reactivity ratios for acrylonitrile/ammonium itaconate radical copolymerization systems

Ammonium itaconate was first used to copolymerize with acrylonitrile. This was achieved by using azobisisobutyronitrile as the initiator and dimethyl sulfoxide as the solvent. Effects of copolymerization systems on monomer apparent reactivity ratios for acrylonitrile/ammonium itaconate copolymers were studied. The values of monomer apparent reactivity ratios were calculated by Kelen‐Tudos method. The apparent reactivity ratios in the aqueous suspension polymerization system are similar to those in the solution polymerization system at polymerization conversions of less than 18% [reactivity ratio of acrylonitrile (r_AN) = 0.47 ± 0.01, reactivity ratio of ammonium itaconate (r_AIA) = 3.08 ± 0.01]. At conversions of more than 50%, the changes of monomer apparent reactivity ratios become less prominent (r_AN = 0.68 ± 0.01, r_AIA = 2.47 ± 0.01). In water‐rich reaction medium [(H₂O/dimethylsulfoxide (DMSO) > 80/20)], the monomer apparent reactivity ratios are approximately equivalent to those in the aqueous suspension polymerization system. In DMSO‐rich reaction medium (DMSO/H₂O > 80/20), the apparent reactivity ratios are similar to those in the solution polymerization system. With an increase in the polarity of the solvent, the values of apparent reaction ratios both decrease. The values of apparent reaction ratios gradually tend to 1 with increasing the copolymerization temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3920–3923, 2007     

Determination of monomer reactivity ratios in styrene/2‐ethylhexylacrylate copolymer

The monomer reactivity ratios for styrene/2‐ethylhexylacrylate in bulk at 80°C were investigated by studying the resulting copolymer composition via ¹H‐NMR. Composition results were summarized and various methods were employed to estimate the reactivity ratios including the use of the Error‐in‐Variables‐Model (EVM) approach by using the Mayo–Lewis model. The estimates of the reactivity ratios from the EVM method are found to be r_s = 0.979 and r_EHA = 0.292. The resulting copolymer has a tendency toward alternation with an azeotrope of f(styrene) = 0.972. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3368–3370, 2004     

Synthesis,reactivity, and X-ray structural characterization of a vanadium(III) oxidation pre-catalyst, (CpPOEtCo)VCl2(DMF)

Vanadium complexes are extensively used in the chemical industry as oxidation catalysts. During the course of our investigations into vanadium oxidation catalysis, the rich reactivity of a vanadium(III) scorpionate analogue complex, (CpP^OEtCo)VCl₂(DMF) (1), was investigated. The octahedrally coordinated 1 was prepared by mixing vanadium(III) chloride with Na(CpP^OEtCo) in DMF. The crystal structure of 1 has been determined through X-ray diffraction. Complex 1, C₂₀H₄₂Cl₂CoNO₁₀P₃V, crystallizes in the monoclinic space group P2₁/c with a = 38.566(9) Å, b = 9.499(2) Å, c = 18.149(4) Å, and β = 100.485(4)° with Z = 8. Complex 1 was found to be an effective pre-catalyst for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone. The reactivity studies, oxidative catalytic ability, as well as X-ray structural characterization of (CpP^OEtCo)VCl₂(DMF) will be discussed. ((CpP^OEtCo) = [η⁵-cyclopentadienyltris(diethylphosphito-κ¹P) cobaltate(III)⁻; DMF = N,N-dimethylformamide).     

Conventional and RAFT miniemulsion copolymerizations of butyl methacrylate with fluoromethacrylate and monomer reactivity ratios

Reversible addition fragmentation chain transfer (RAFT) mediated and conventional miniemulsion copolymerizations of butyl methacrylate (BMA) with fluoromethacrylate (FMA) were carried out at 70°C with potassium persulphate as initiator. The kinetics of the copolymerizations was investigated comparatively. Copolymer compositions at low conversion levels were determined by ¹H NMR and FTIR spectra techniques. In the presence of RAFT agent 2‐cyanoprop‐2‐yl dithiobenzoate, the copolymerization of BMA with FMA in miniemulsion was obviously retarded. The copolymerization exhibited typical features of controlled molecular weights and narrow polydispersities. The reactivity ratios were evaluated by Kellen‐Tudos (K‐T) method, which yields the apparent reactivity ratios: r_BMA = 0.73 and r_FMA = 0.75 in conventional copolymerizations, and r_BMA = 0.65 and r_FMA = 0.70 in CPDB‐mediated system. The results show that the monomer FMA with a perfluoroalkyl side chain is slightly more reactive than BMA, and the copolymerizations process have a tendency to crosspropagate and to produce a higher FMA content in the copolymers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Hetero-trinuclear near-infrared (NIR) luminescent ZnLn2 (Ln = Nd,Yb or Er) complexes based on monomer ZnL Schiff-base precursor and o-vanillin

With the monomer [Zn(L¹)(H₂O)] (1) complex in situ formed by the deprotonated hexadentate Salen-type Schiff-base ligand H₂L¹ (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) and Zn(NO₃)₂ as the precursor, series of the hetero-trinuclear ZnLn₂ complexes [ZnLn₂(L¹)₂(L²)(NO₃)₂Cl] (Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained from the further reaction with LnCl₃ (Ln = Nd, Yb Er or Gd) and the second o-vanillin (HL²) ligand, respectively. The photophysical properties of complexes 2–4 showed that the characteristic near-infrared (NIR) luminescence of Ln^3 + ions with two emission centers and emissive lifetimes in microsecond ranges, was sensitized from the excited state (both ¹LC and ³LC) of mixed H₂L¹–HL² ligands.