One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002     

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002     

Microstructural characterization of acrylonitrile/pentyl acrylate copolymers by one and 2‐D NMR spectroscopy

Acrylonitrile/pentyl acrylate (A/P) copolymers of different monomer composition were prepared by solution polymerization using benzoyl peroxide as initiator. Copolymer compositions were determined by elemental analysis and quantitative ¹³C¹H‐NMR spectroscopy. The comonomer reactivity ratios, determined by both Kelen Tudos (KT) and nonlinear error in variables (EVM) methods are r_A = 0.75 and r_p = 0.45. 2‐D heteronuclear correlation spectroscopy (HSQC) was used to simplify the complex ¹H spectra of A/P copolymers in terms of configurational and compositional sequences. The microstructure was obtained in terms of the distribution of A‐ and P‐ centered triad sequences from ¹³C¹H‐NMR spectra of the copolymers. The copolymerization mechanism was found to follow a first order Markov Model. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 533–543, 1999     

Poly(isobornyl methacrylate‐co‐methyl acrylate): Synthesis and stereosequence distribution analysis by NMR spectroscopy

Copolymerization of isobornyl methacrylate and methyl acrylate ( I/M ) is performed by atom transfer radical polymerization using methyl‐2‐bromopropionate as an initiator and PMDETA/CuBr as catalyst under nitrogen atmosphere at 70 °C. The copolymer compositions determined from ¹H NMR spectra are used to determine reactivity ratios of the monomers. The reactivity ratio determined from linear Kelen–Tudos method and non‐linear error‐in‐variable method, are r_I = 1.25 ± 0.10, r_M = 0.84 ± 0.08 and r_I = 1.20, r_M = 0.82, respectively. 1D, distortion less enhancement by polarization transfer and 2D, heteronuclear single quantum coherence, and total correlation spectroscopy NMR experiments are employed to resolve highly overlapped and complex ¹H and ¹³C{¹H} NMR spectra of the copolymers. The carbonyl carbon of I and M units and methyl carbon of I unit are assigned up to triad compositional and configurational sequences, whereas β‐methylene carbons are assigned up to tetrad compositional and configurational sequences. Similarly, methine carbon of I unit is assigned up to triad level. The couplings of carbonyl carbon and quaternary carbon resonances are studied in detail using 2D hetero nuclear multiple bond correlation spectra. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Atom transfer radical copolymerizationof acrylonitrile/n‐butyl acrylate: Microstructure determination by two‐dimensional nuclearmagnetic resonance spectroscopy

Atom transfer radical polymerization conditions were optimized and standardized with different initiator and catalyst systems. Acrylonitrile/n‐butyl acrylate copolymers were synthesized with 2‐bromopropionitrile as the initiator and CuCl/Cu(0)/2,2′‐bipyridine as the catalyst system. Variations of the feed composition led to copolymers with different compositions. The number‐average molecular weight and the polydispersity index were determined by gel permeation chromatography. Quantitative ¹³C{¹H} NMR was employed to determine the copolymer composition. The reactivity ratios calculated with a methodology based on the Mao–Huglin terminal model were r_A = 1.30 and r_B = 0.68 for acrylonitrile and n‐butyl acrylate, respectively. The reactivity ratios determined by the modified Kelen–Tudos method were r_A = 1.29 ± 0.01 and r_B = 0.67 ± 0.01. ¹³C{¹H} NMR and distortionless enhancement by polarization transfer (DEPT‐45, 90, and 135) were used to distinguish methyl, methylene, methine, and quaternary carbon resonance signals. The overlapping and broad signals of the copolymers were assigned completely to various compositional and configurational sequences by the correlation of one‐dimensional (¹H, ¹³C{¹H}, and DEPT) and two‐dimensional (heteronuclear single quantum coherence, total correlation spectroscopy, and heteronuclear multibond correlation) NMR spectral data. The complete spectral assignments of carbonyl and nitrile carbons were performed with the help of heteronuclear multibond correlation spectra. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2810–2825, 2005     

Chain microstructure of homogeneous ethylene‐1‐alkene copolymers and characteristics of single site catalysts using a direct 13C NMR peak method. Part III. Application to ethylene–propylene copolymers showing no inversion

All relevant ¹³C NMR signals of two series of seven homogeneous ethylene–propylene copolymers were used to fit the second‐order Markov reactivity ratios of the catalysts and the theoretical feeds. The copolymers cover a very broad range of comonomer incorporations, from about 10 to 93%, and show only primary (1,2) insertions. For both series, solutions are found with reliabilities >>99.5%. The reactivity ratios, r₁₁₂ = 2.54, r₁₂₁ = 0.12, r₂₁₂ = 2.05, and r₂₂₁ = 0.29 for the used Zirconocone and r₁₁₂ = 1.69, r₁₂₁ = 0.32, r₂₁₂ = 1.56, and r₂₂₁ = 0.51 for the hafnocene, provide direct information about the metallocenes, the kinetics, and the chain microstructure. With these results, the direct peak method demonstrates that the use of all relevant ¹³C NMR peaks enables accurate second‐order Markov modeling, revealing subtle differences between copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 747–755, 2006     

Microstructure of glycidylmethacrylate/vinyl acetate copolymers by two‐dimensional nuclear magnetic resonance spectroscopy

Glycidylmethacrylate/vinyl acetate copolymers were prepared by solution polymerization with benzene as a solvent and benzoyl peroxide as an initiator. Copolymer compositions were determined from ¹H NMR spectra, and comonomer reactivity ratios were determined by the Kelen–Tudos (KT) method and the nonlinear least‐squares error‐in‐variable method (EVM). The reactivity ratios obtained from KT and EVM were r_G = 37.4 ± 12.0 and r_V = 0.036 ± 0.019 and r_G = 35.2 and r_V = 0.03, respectively. Complete spectral assignments of ¹³C and ¹H NMR spectra were done with the help of distortionless enhancement by polarization transfer and two‐dimensional ¹³C–¹H heteronuclear single quantum coherence and total correlation spectroscopy. The methyl, methine, and methylene carbon resonance showed both stereochemical and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4051–4060, 2001     

Microstructure analysis and thermal property of copolymers made of glycolide and ϵ‐caprolactone by stannous octoate

Glycolide (GL) and ?‐caprolactone (CL) were copolymerized in bulk at relatively high temperatures using stannous octoate as a catalyst. To investigate the relationship among microstructure, thermal properties, and crystallinity, three series of copolymers prepared at various reaction temperatures, times, and comonomer feed ratios were prepared and characterized by ¹H and ¹³C NMR, DSC, and wide‐angle X‐ray diffraction (WAXD). The 600‐MHz ¹H NMR spectra provided information about not only the copolymer compositions but also about the chain microstructure. The reactivity ratios (r_G and r_C) were calculated from the monomer sequences and were 6.84 and 0.13, respectively. In terms of overall feed compositions, the sequence lengths of the glycolyl units calculated from the reactivity ratios exceeded those measured from the polymeric products. Mechanistic considerations based on reactivity ratios, monomer consumption data, and average sequence lengths are discussed. The unusual phase diagram of GL/CL copolymers implies that the copolymer melting temperature does not depend on its composition alone but rather on the nature of the sequence distribution. The DSC and WAXD measurements show a close relationship between polymer crystallinity and the nature of the polymer sequence. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 544–554, 2002; DOI 10.1002/pola.10123     

Compositional and configurational sequence determination of methyl methacrylate/ethyl acrylate copolymers by one‐ and two‐dimensional nuclear magnetic resonance spectroscopy

Ethyl acrylate (E)/methyl methacrylate (M) copolymers of different compositions were prepared, and their compositions were determined with ¹H NMR spectra. The complete spectral assignments, in terms of the compositional and configurational sequences of these copolymers, were made with the help of distortionless enhancement by polarization transfer and two‐dimensional heteronuclear single quantum coherence spectroscopy. The α‐(CH₃)_M, ? CH (E), ? CH₂, and 〉C?O carbons of both M and E units were found to be sensitive to various compositional and configurational sequences. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 313–326, 2003     

Synthesis and enzymatic degradation of 2‐methylene‐1,3‐dioxepane and methyl acrylate copolymers

Copolymers of 2‐methylene‐1,3‐dioxepane (MDO) and methyl acrylate (MA) containing ester units both in the backbone and as pendant groups were synthesized by free‐radical copolymerization. The influence of reaction conditions such as the polymerization time, temperature, initiator concentration, and comonomer feed ratio on the yield, molecular weight, and copolymer composition was investigated. The structure of the copolymers was confirmed by ¹H NMR, ¹³C NMR, and IR spectroscopy. Differential scanning calorimetry indicated that the copolymers had a random structure. An NMR study showed that hydrogen transfer occurred during the copolymerization. The reactivity ratios of the comonomers were r_MDO = 0.0235 and r_MA = 26.535. The enzymatic degradation of the copolymers obtained was carried out in the presence of proteinase K or a crude enzyme extracted from earthworms. The experimental results showed that the higher ester molar percentage in the backbone caused a faster degradation rate. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2898–2904, 2003     

Comprehensive 2D NMR analysis: Acrylonitrile/ethyl methacrylate copolymers synthesized by ATRP at ambient temperature

Copolymerization of acrylonitrile and ethyl methacrylate using atom transfer radical polymerization (ATRP) at ambient temperature was carried out under optimized reaction conditions using 2‐bromopropionitrile as initiator and CuBr/2,2′‐bipyridine as the catalyst system. The copolymer composition, obtained from ¹H NMR spectra, were used to determine the monomer reactivity ratios (r_A = 0.68 and r_E = 1.75) involved in ATRP. Two‐dimensional NMR (heteronuclear single quantum correlation and total correlated spectroscopy) experiments were employed to resolve the highly overlapping and complex ¹H and ¹³C{¹H} NMR spectra of copolymers. The complete spectral assignments of the quaternary carbons viz. carbonyl and nitrile carbons were done with the help of heteronuclear multiple bond correlation spectra. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2955–2971, 2006     

Copolymerization of ethylene with styrene catalyzed by a linked bis(phenolato) titanium catalyst

Copolymerization of ethylene with styrene, catalyzed by 1,4‐dithiabutanediyl‐linked bis(phenolato) titanium complex and methylaluminoxane, produced exclusively ethylene–styrene copolymers with high activity. Copolymerization parameters were calculated to be r_E = 1.2 for ethylene and r_S = 0.031 for styrene, with r_E r_S = 0.037 indicating preference for alternating copolymerization. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with styrene content up to 68%. The copolymer microstructure was fully elucidated by ¹³C NMR spectroscopy revealing, in the copolymers with styrene content higher than 50%, the presence of long styrene–styrene homosequences, occasionally interrupted by isolated ethylene units. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1908–1913, 2006     

Chain microstructure of homogeneous ethylene‐1‐alkene copolymers and characteristics of single site catalysts using a direct 13C NMR peak method. Part II. Application to ethylene–propylene copolymers showing inversion

All relevant ¹³C NMR signals of a series of 19 homogeneous ethylene–propylene copolymers were used to fit the first‐order Markov reactivity ratios of the catalyst and the theoretical feeds. The copolymers cover a broad range of comonomer incorporations, from 17.0 to 56.5%, and show both primary (1,2) and secondary (2,1) insertions. As expected, two solutions are found, the normal solution showing a better fit and reliability > 99.5%. The reactivity ratios, r₁₂ = 20.0, r₁₃ = 162.0, r₂₁ = 0.015, r₂₃ = 1.3, and r₃₁ = 0.060, provide direct information about the vanadium‐based catalyst, the kinetics, and the chain microstructure. The values also explain the comonomer content‐dependent inversion and even predict a 100% secondary insertion PP homopolymer. With these results, the direct peak method shows that the use of all relevant ¹³C NMR peaks improves the accuracy of first‐order Markov modeling. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 738–746, 2006     

Synthesis of styrene/methyl methacrylate copolymers by atom transfer radical polymerization: 2D NMR investigations

Copolymers of styrene and methyl methacrylate were synthesized by atom transfer radical polymerization using methyl 2‐bromopropionate as initiator and CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as catalyst. Molecular weight distributions were determined by gel permeation chromatography. The composition of the copolymer was determined by ¹H NMR. The comonomer reactivity ratios, determined by both Kelen–Tudos and nonlinear error‐in‐variables methods, were r_S = 0.64 ± 0.08, r_M = 0.63 ± 0.08 and r_S = 0.66, r_M = 0.65, respectively. The α‐methyl and carbonyl carbon resonances were found to be compositionally and configurationally sensitive. Complete spectral assignments of the ¹H and ¹³C NMR spectra of the copolymers were done by distortionless enhancement by polarization transfer and two‐dimensional NMR techniques such as heteronuclear single quantum coherence and heteronuclear multiple quantum coherence. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2076–2085, 2006     

Sequencing of trans-4-methacryloyloxyazobenzene/vinylidene chloride copolymers by one- and two-dimensional NMR spectroscopy

Trans-4-methacryloyloxyazobenzene/Vinylidene Chloride (M/V) copolymers of different monomer concentrations were prepared by solution polymerization using benzoyl peroxide as an initiator. The copolymer composition was determined from the ¹³C{¹H}-NMR spectrum. The quaternary carbon of M- and V-centered resonances were used for determining the sequences in terms of the distribution of M- and V-centered triads. The sequence distribution of M- and V-centered triads determined from ¹³C{¹H}-NMR spectra of the copolymer is in good agreement with the triad concentration calculated from the statistical model. The comonomer reactivity ratios, determined by both the Kelen Tudos (KT) and the nonlinear error in variables (EVM) methods are r_M = 3.59 ± 0.19, r_V = 0.89 ± 0.07; r_M = 3.76, and r_V = 0.93, respectively. ¹³C Distortionless Enhancement by Polarization Transfer (DEPT) spectrum was used to differentiate between the resonance signals of M- and V-methylene and methyl carbon units. Assignments to the methylene resonance signals have been assigned up to the tetrad levels using 2D HSQC experiments. The geminal couplings in the methylene proton region is shown in the 2D DQF-COSY spectrum. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3179–3185, 1999     

Cationic copolymerization of ε‐caprolactone and L,L‐lactide by an activated monomer mechanism

The cationic homopolymerization and copolymerization of L,L ‐lactide and ε‐caprolactone in the presence of alcohol have been studied. The rate of homopolymerization of ε‐caprolactone is slightly higher than that of L,L ‐lactide. In the copolymerization, the reverse order of reactivities has been observed, and L,L ‐lactide is preferentially incorporated into the copolymer. Both the homopolymerization and copolymerization proceed by an activated monomer mechanism, and the molecular weights and dispersities are controlled {number‐average degree of polymerization = ([M]₀ ? [M]_t)/[I]₀, where [M]₀ is the initial monomer concentration, [M]_t is the monomer concentration at time t, and [I]₀ is the initial initiator concentration; weight‐average molecular weight/number‐average molecular weight ～1.1–1.3}. An analysis of ¹³C NMR spectra of the copolymers indicates that transesterification is slow in comparison with propagation, and the microstructure of the copolymers is governed by the relative reactivity of the comonomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7071–7081, 2006     

Radical polymerization of new functional monomer: Methacryloyl isocyanate containing 4‐chloro‐1‐phenol

New functional monomer methacryloyl isocyanate containing 4‐chloro‐1‐phenol (CPHMAI) was prepared on reaction of methacryloyl isocyanate (MAI) with 4‐chloro‐1‐phenol (CPH) at low temperature and was characterized with IR, ¹H, and ¹³C‐NMR spectra. Radical polymerization of CPHMAI was studied in terms of the rate of polymerization, solvent effect, copolymerization, and thermal properties. The rate of polymerization of CPHMAI has been found to be smaller than that of styrene under the same conditions. Polar solvents such as dimethylsulfoxide (DMSO) and N,N‐dimethyl formamide (DMF) were found to slow the polymerization. Copolymerization of CPHMAI (M₁) with styrene (M₂) in tetrahydrofuran (THF) was studied at 60°C. The monomer reactivity ratio was calculated to be r₁ = 0.49 and r₂ = 0.66 according to the method of Fineman—Ross. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 469–473, 2000     

Synthesis and properties of polyethylene with side‐chain triphenylamines as hole‐transporting materials

The copolymerization of ethylene with triphenylamine (TPA)‐containing α‐olefin monomer 1 using a rac‐Et(Ind)₂ZrCl₂ ( EBIZr )/MAO catalytic system was investigated to prepare polyethylene with pendent TPA groups. Despite the presence of a large excess of TPA moieties, the polymerization reactions efficiently produce copolymers of high‐molecular‐weight with the comonomer incorporation up to 6.1 mol % upon varying the comonomer concentration in the feed. Inspection of the aliphatic region of the ¹³C‐NMR spectrum and the estimated copolymerization parameters (r ₁ ≈ 0 for 1 and r_E ≈ 43 for ethylene) reveal the presence of isolated comonomer units in the polymer chain. While UV–vis absorption measurements of the copolymers show an invariant absorption feature, PL spectra exhibit a slightly red‐shifted emission with increasing content of 1 in the polymer chain. All the copolymers show high thermal stability (T_d5 > 436 °C), and the electrochemical stability toward oxidation is also observed. Particularly, the copolymer displays hole‐transporting ability for the stable green emission of Alq₃ when incorporated into the hole‐transporting layer of an electroluminescence device. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5816–5825, 2008     

Catalytic systems Me2SiCp*NtBuMX2/(CPh3)(B(C6F5)4) (MTi,XCH3, MZr,XiBu) in copolymerization of ethylene with styrene

Catalytic activity of Me₂SiCp*N^tBuMX₂/(CPh₃)(B(C₆F₅)₄) [MTi, XCH₃ (1); MZr, X=ⁱBu (2)] systems in the ethylene/styrene (E/S) feed was examined. Experimental data revealed high activity for the catalytic system (1) for copolymerization ethylene with styrene, whereas the system with enhanced catalytic activity for ethylene homopolymerization (2) was temporarily blocked in the styrene presence yielding, even at high styrene content, homopolyethylene as the final product. Properties of thus obtained polymers were analyzed. Catalytic system (1) occurred very sensitive to S/E ratio in the comonomers feed. The 10‐fold acceleration for ethylene consumption was shown in two experimental sets conducted at S/E = 1.3 ratio, 1 bar, and 7.5 bar ethylene pressure, respectively. The consequent enhancement in S/E ratio resulted in slowing down both ethylene consumption and catalyst deactivation rates. Atactic polystyrene was formed at high styrene content with the catalyst (1). Catalytic system (1) allowed design of products with the highest styrene content (20 mol %) at low ethylene pressure, moderate temperature, and high S/E ratio. The apparent activation energy estimated from the initial rates of ethylene consumption was 54.6 kJ/mol. Analysis of apparent reactivity factors (r_E = 9 and r_S = 0.04; r_E × r_S = 0.4) and ¹³C‐NMR copolymer spectra revealed an alternating tendency of the comonomers for active center incorporation. DSC measurements showed considerable decrease of melting points and crystallinity even for copolymers with low styrene content. The catalyst produced relatively high–molecular weight copolymers (140–150 kg/mol) even at 80°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1083–1093, 1999     

Influence of the reaction medium on the composition and the microstructure of styrene–acrylic acid copolymers

Two series of acrylic acid-styrene copolymers of various composition have been prepared in benzene and dimethylformamide in order to study their sequence distribution by using ¹³C NMR spectroscopy. The reactivity ratios in benzene were r_A = 0.13, r_A = 0.30 and in dimethylformamide r_A = 0.05, r_S = 1.60. Copolymers with the same overall composition but prepared in different media display marked differences in sequence distribution, the copolymers obtained in dimethylformamide always having longer sequences. For the series of copolymers prepared in dimethylformamide, the experimental percentages of acrylic acid-centered triads (SAS, SAA, AAA) disagree with the values calculated from the monomer reactivity ratios.