Investigation of microstructure of the acrylonitrile‐styrene copolymers by 2‐D NMR spectroscopy

Acrylonitrile‐Styrene (A/S) copolymers were prepared by photopolymerization using uranyl nitrate ion as initiator. The copolymer compositions were determined by elemental analysis, and comonomer reactivity ratios were determined by nonlinear least squares error in variables method (EVM). The complete spectral assignment of the ¹³C and ¹H‐NMR spectra were done with the help of Distortionless Enhancement by Polarization Transfer (DEPT) and by the two dimensional ¹³C‐¹H Heteronuclear Single Quantum Correlation (HSQC) and TOCSY experiments. The methylene and methine carbon resonance show both stereochemical and compositional sensitivity. The 2‐D Total Correlated Spectroscopy (TOCSY) experiment was used to ascertain the various geminal coupling between the methylene protons. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 721–727, 1999     

Synthesis and mesomorphic behavior of a new series of side-chain liquid crystalline polymethacrylates bearing 2,6-naphthylene-based mesogen

A new homologous series of liquid crystalline (LC) polymethacrylates, the poly[ω-(2-phenoxycarbonyl-naphthalene-6-yloxy)alkyl methacrylate]s, in which the length of the alkyl spacer is varied between 3 and 12 methylene units, have been synthesized by free-radical polymerization. The prepared polymers were studied by IR and ¹H-NMR spectroscopy, viscosity measurements, differential scanning calorimetry (DSC), and polarized microscopy. Polymers with 3 or 4 methylene units spacer were glassy in nature, whereas those with 5–12 methylene units spacer exhibited smectic behavior. The glass transition temperatures decrease on increasing spacer length. The isotropization temperatures and the corresponding transition entropies showed an odd–even effect, with the odd members exhibiting the higher values. This effect attenuates on increasing spacer length. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2391–2399, 1999     

Spectral assignment of poly(vinyl acetate) by one and two dimensional NMR spectroscopy: Revisited

Poly(vinyl acetate) (PVA) prepared by photopolymerization was studied by a combination of one and two dimensional NMR spectroscopy. The ¹³C{¹H} and ¹H NMR spectra of the homopolymer (PVA) were assigned to the configurational pentads (CH region) and tetrads (CH₂ region). These assignments were substantiated by the use of two dimensional heteronuclear single quantum correlation (HSQC), heteronuclear single quantum correlation‐total correlation spectroscopy (HSQC‐TOCSY) and double quantum filtered correlation spectroscopy (DQFCOSY) experiments. The results obtained by the analysis of the area under the resonance signals confirmed that PVA obeys Bernoullian statistics. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 551–556, 1999     

Examination of selected synthesis parameters for typical wood adhesive‐type urea–formaldehyde resins by 13C NMR spectroscopy. I

Selected synthesis parameters of typical wood adhesive‐type urea–formaldehyde (UF) resins were examined using the ¹³C NMR spectroscopy. The monomeric hydroxymethylureas and methylene–ether derivatives formed in the initial alkaline reaction polymerize in the subsequent acidic reaction by forming methylene bonds and cleaving some hydroxymethyl groups as formaldehyde. For typical resin syntheses at F/U ratio of 2.10, the resulting UF polymer is found to be a number‐averaged pentamer having 3.25 polymer chain branches with about 80% of chain ends bonded to hydroxymethyl groups and the rest being free amide groups. When the second urea is added during the cooling period, about 67% of hydroxymethyl groups cleave from the UF polymeric components and the freed formaldehyde reacts with second urea to form monomeric hydroxymethylureas. This hydroxymethyl group move is suppressed when the second urea is added at low temperatures, suggesting that wood adhesive‐type UF resins are composed of monomeric and polymeric UF components having hydroxymethyl functional groups in varying proportions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 995–1007, 1999     

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     

Studies on the odd‐even effect of methylene spacers in poly(pyromellitimide‐ester)s

Three series of poly(pyromellitimide‐ester)s were synthesized from various N,N′‐bis(ω‐hydroxyalkyl)pyromellitimides (HAPMIs) by melt condensation with dicarboxylic acids, including terephthalic acid (TPA), 4,4′‐biphenyldicarboxylic acid (BPDA), and 4,4′‐azobenzenedicarboxylic acid (ABDA). Polymers were characterized by elemental analysis, solubility, inherent viscosity, spectra (IR, ¹H‐NMR, ¹³C‐NMR), and X‐ray diffraction (XRD). Thermal stability and phase transition behaviour were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and hot‐stage optical polarized microscopy (HOPM). The d‐spacings, calculated from XRD data, showed an odd‐even effect with varying numbers of methylene spacers. Crystallinity of polymers decreased in the following order: azobenzene > biphenyl > phenyl polymers. Similarly, DSC‐obtained melting temperatures (T_m's) showed an odd‐even effect, and glass transition temperatures (T_g's) decreased with increasing numbers of methylene spacers. Thermal stability decreased as methylene chain length increased. Thermal stability of polymers occurred in the following order: phenyl > biphenyl > azobenzene polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1755–1761, 1999     

Infrared spectroscopic characterization of oriented polyamide 66: Band assignment and crystallinity measurement

Having found much ambiguity in the infrared band assignments for polyamide 66 (PA66), we revisited some of these assignments before using infrared spectroscopy to assess microstructure changes resulting from multiple thermal treatments. We discovered that earlier assignments of the 1144 and 1180 cm⁻¹ bands to the amorphous (noncrystalline) phase were incorrect, whereas the bands at 924 and 1136 cm⁻¹ can be attributed unambiguously to the noncrystalline phase. We also confirmed that PA66 bands at 936 and 1200 cm⁻¹ are crystalline bands. The normalized absorbance of the 1224‐cm⁻¹ fold band increases in proportion to crystallinity, indicating that chain folding is the predominant mechanism of thermal crystallization in PA66. We demonstrated that infrared spectroscopy can be used to estimate the degree of crystallinity of PA66, and two methods were explored. One is a calibration method in which the band ratio of 1200 and 1630 cm⁻¹ is plotted against crystallinity measured by density. The other is an independent infrared method based on the assumption that PA66 satisfies a two‐phase structure model. The crystallinity determined by the independent infrared method showed good agreement with the crystallinity obtained from density measurements. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 516–524, 2000     

On the anionic homo‐ and copolymerization of ethyl‐ and butyl‐2‐cyanoacrylates

Ethyl‐(ECA) and butyl‐2‐cyanoacrylate (BCA) monomers of high purity and acidic stabilization were synthesized and anionically polymerized to homo‐ and copolymers in two different ways: by piperidine‐catalyzed bulk polymerization leading to transparent, brittle films (method A) and by polymerization in aqueous medium in the presence of sodium bicarbonate to obtain white powders (Method B). The molecular structure of the synthesized monomers, homopolymers and copolymers were corroborated by spectral methods. The polymers were studied further by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and proton nuclear magnetic resonance (¹H NMR). Controlling the composition of the monomer feed and the way the polymerization was performed, it was possible to obtain phase separated or homogeneous cyanoacrylate copolymers with glass transitions varying between the T_g of polyECA and that of polyBCA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5142–5156, 2008     

Novel poly(etheraroylhydrazides). An example of “conformationally disordered crystalline” polymers

Novel aromatic poly(etheraroylhydrazides), PEHZ, incorporating a methylenic sequence (with number of  CH₂ units m = 2, 4, 6, 8, 10, 12) in the main chain, have been obtained by solution polycondensation and characterized with several techniques. In particular, Differential Scanning Calorimetry (DSC) and Wide Angle X‐ray Scattering (WAXS) gave interesting results. The complex thermal behavior and the lattice parameters of these linear polyhydrazides are a function of the number of methylene units present in the flexible segment. The relationships we found suggest a model: a polymer with disorder in aliphatic segment layers while preserving chain periodicity, that is the classical model of “conformationally disordered crystalline” polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1687–1701, 1999     

Synthesis of ladder polymers containing polydiacetylene backbones connected with methylene chains and their optical properties

The polymers consisting of polydiacetylene (PDA) backbones were obtained from the novel monomer derivatives, R CC CC R′ CC CC R [where R =  (CH₂)₄OCONHCH₂COOC₄H₉, R′ =  (CH₂)_n ; n = 2, 4, 8] [4BCMU4A(n)], in which linear methylene chain is sandwiched between two diacetylene moieties by solid-state 1,4-addition reaction. The polymerization process was investigated in detail by using spectroscopic techniques such as solid-state ¹³C-NMR, visible absorption, and IR absorption spectra. It was estimated that the polymerization of 4BCMU4A(8) and 4BCMU4A(4) takes place by two consecutive 1,4-addition reactions to form two PDA backbones, which constitute the two poles of the respective ladders. The bridging methylene chain length in the monomer was found to play a vital role as far as the polymerization process is concerned. Thus, the monomers with eight or four methylene units could form the ladder–PDAs by a two-step process, whereas the monomer containing two methylene units could only undergo one-step of 1,4-addition reaction. Further, it was found that the crystallinity of the polymers depends on the methylene chain length in the monomers, 4BCMU4A(8) being the most crystalline of all. These structural features strongly affect their absorption spectra. The third-order nonlinear optical susceptibilities (χ⁽³⁾) for these polymers were measured using third-harmonic generation method. The largest χ⁽³⁾ value obtained was 3.4 × 10⁻¹¹ esu for the poly[4BCMU4A(8)] thin film in resonant region. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3537–3548, 1999     

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     

Model compounds and 13C NMR increments for the characterization of maleic anhydride-grafted polyolefins

A set of model compounds that mimic the graft sites of maleic anhydride (MA) functionalized polyolefins was synthesized and characterized with NMR spectroscopy. The acquired carbon nuclear magnetic resonance data were used to deduce chemical-shift increments for the prediction of ¹³C chemical shifts of MA functionalized polyolefins. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4368–4385, 1999     

The distribution of stereochemical configurations in polystyrene as observed with 13C NMR

¹³C NMR configurational assignments are made for an amorphous polystyrene sample examined at 25.2 MHz and 120°C. The assignments are based strictly on a one-parameter Bernoullian fit that was in satisfactory agreement with the nine observed methylene relative intensities. The methylene regions of the ¹³C NMR spectra of a polystyrene were examined before and after hydrogenation of the side-chain phenyl substituents. It was concluded that ring current effects have influenced the ¹³C methylene chemical shifts substantially and are limited largely to contributions from adjacent phenyl substituents. In addition, aromatic substituent parameters are reported that can be used in conjunction with the Grant and Paul parameters for calculating chemical shifts in aromatic hydrocarbons and polymers. Finally, it is concluded that free-radical and n-butyllithium-prepared polystyrenes have essentially atactic structures with meso additions favored over racemic additions by approximately 55/45.     

Chemistry of novolac resins. X. Polymerization studies of HMTA and strategically synthesized model compounds

The reactions between hexamethylenetetramine (HMTA) and compounds which model novolac resins have been studied by ¹³C‐ and ¹⁵N‐NMR techniques. The dimer and tetramer compounds vary in molecular size and structure and react with HMTA to yield benzylamines and benzoxazine as the major initial‐formed intermediates and convert to methylene linked compounds at increased temperatures. The reaction of the compounds with only ortho reactive sites paralleled the 2,4‐xylenol–HMTA case reported by us previously; however, increasing molecular weight favored the formation of benzylamines and not benzoxazines. Those compounds with only para reactive sites paralleled the 2,6‐xylenol–HMTA case. The reactivity of the systems containing both ortho and para reactive sites depends on the ratio of ortho/para sites and various aspects such as the chemical structure and molecular weight of the compound, the HMTA level, and the melting point and pH of the system. These results parallel those obtained from novolac/HMTA systems. The xylenol/HMTA reactions formed similar products but showed quite different relative reaction rates by varying the HMTA ratio and structures of the materials. The importance of careful selection of model systems is also discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1347–1355, 1999     

Microstructure determination of methyl methacrylate and n‐butyl acrylate copolymers synthesized by atom transfer radical polymerization with two‐dimensional NMR spectroscopy

Copolymers of methyl methacrylate (MMA) and n‐butyl acrylate (n‐BA) were synthesized under atom transfer radical polymerization (ATRP) conditions. The molar infeed ratio was varied to obtain copolymers with different compositions. Methyl 2‐bromo propionate was used as the initiator with CuBr/Cu(0)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst at 60 °C. Molecular weight distribution was determined by gel permeation chromatography (GPC). Copolymer compositions (F_M) were calculated from ¹H NMR spectra. Reactivity ratios calculated with the Mao–Huglin terminal model at a high conversion were found to be r_M = 2.17 and r_B = 0.47. The polymerization mechanism was studied with the α‐methyl region of MMA. The backbone methylene and carbonyl carbons of both MMA and n‐BA units were found to be compositionally as well as configurationally sensitive. Complete spectral assignments were performed with the help of heteronuclear single quantum coherence (HSQC) spectroscopy along with total correlated spectroscopy (TOCSY). Further, the assignments of the carbonyl region were made with the help of heteronuclear multiple quantum coherence (HMBC) spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1100–1118, 2005     

Determination of molecular weight distributions of novolac resins by gel permeation chromatography

The number- and weight-average molecular weights of several statistical and high ortho novolac resins were determined using gel permeation chromatography (GPC). The standards used were pure compounds having between 2 and 12 phenol units bridged via methylene linkages. Three series of compounds were studied: (i) those with methylene linkages substituted in only the ortho positions relative to the phenolic hydroxyl group; (ii) those in which all para positions, together with sufficient ortho positions, were used to synthesize the compounds; and (iii) those in which the methylene linkages were substituted at a mixture of ortho and para positions. Such compounds, having known molecular architecture and units similar to the segments of industrial novolac resins, provide for a more exact measurement of the molecular weight than do the commonly used poly(styrene) standards. Using these new standards the number average molecular weights of the resins determined by GPC were in good agreement with the average molecular weight obtained by ¹H-NMR spectra of the resins, particularly for low molecular weight resins. GPC analysis of higher molecular weight resins tends to underestimate the molecular weights because of complications introduced by hydrogen bonding. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1399–1407, 1997     

Photolysis of bisphenol‐based polyurethanes in solution

Photolysis of bisphenol‐based polyurethanes, using bisphenols A, S, and AF with methylene diphenyl diisocyanate (MDI), has been shown by the observed changes in fluorescence spectra, reduced viscosity, and UV absorbance. Analysis of the fluorescence spectra of model compounds and polymers showed that para‐photo‐Fries and cleavage‐type products were the major components formed during photolysis. The reduced viscosity and UV absorbance changes are consistent with a two‐step photodegradation process. The reduced viscosity changes indicate that oxygen inhibition on the cleavage process is more significant for bisphenol S‐based polyurethanes than for bisphenol A‐ and bisphenol AF‐based polyurethanes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1331–1339, 1999     

Stereochemical and compositional assignment of acrylonitrile/methyl methacrylate copolymers by DEPT and inverse HECTOR NMR spectroscopy

The acrylonitrile/methyl methacrylate copolymers of different monomer concentration were prepared by photo polymerization using uranyl ion as initiator. The carbon 13 and proton spectra of these copolymers are overlapping and complex. The complete spectral assignment of the ¹³C- and ¹H-NMR spectra were done with the help of Distortionless Enhancement by Polarization Transfer (DEPT) and two dimensional ¹³C–¹H Heteronuclear Single Quantum Correlation (HSQC) experiments. The methylene, methine and the methyl carbon resonances show both stereochemical (triad level) and compositional (dyad, triad, tetrad, pentad and hexad level) sensitivity. 2D Double Quantum Filtered Correlated Spectroscopy (DQFCOSY) experiment was used to ascertain the various geminal couplings between the methylene protons. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1081–1092, 1998     

Reversible addition–fragmentation chain transfer polymerization of alkyl‐2‐cyanoacrylates: An assessment of livingness

Alkyl 2‐cyanoacrylates (CAs) are primarily used as instant adhesives, including those sold under the Loctite brand. The adhesive action can be inhibited with acid stabilizers allowing radical polymerization to be employed. The following article details the first attempted controlled/living radical polymerization of alkyl CAs: Reversible addition fragmentation chain transfer (RAFT) polymerization mediated by a poly(methyl methacrylate) dithiobenzoate macroRAFT agent for three different CA monomers (ethyl 2‐cyanoacrylate, n‐butyl 2‐cyanoacrylate, and 2‐phenylethyl cyanoacrylate) allowed the preparation of the first block copolymers of this challenging but commercially important monomer class. Nevertheless, GPC with UV detection indicated significant loss of the RAFT end‐group for all three CAs limiting control/living character. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1397–1408     

Synthesis and fractionation of poly(phenylene methylene)

Poly(phenylene methylene) (PPM) was isolated in a broad range of molar masses by optimization of the catalytic polymerization of benzyl chloride with SnCl₄ or FeCl₃, followed by fractionation by Soxhlet extraction or phase separation in concentrated solutions in poor solvents. Low molar mass products were also obtained by quenching the reaction at moderate monomer conversions. Products with number average molar masses (M_n) ranging from 200 to 61,000 g mol⁻¹ were isolated, the latter being an order of magnitude above the previously reported values. DSC analysis of polymers of different molar masses revealed that the glass transition temperature follows the Flory‐Fox equation reaching a plateau value of 65 °C at a molar mass between 10,000 and 20,000 g mol⁻¹. The onset of decomposition temperature of higher molar mass products proceeds above 450 °C (maximum decomposition rate at 515 °C), according to TGA. Furthermore, the substitution pattern of PPM was discussed by study of chemical shifts of the methylene group by extensive NMR spectroscopy (¹H, ¹³C, DEPT, and HSQC) and by comparison with two mono‐substituted derivatives of PPM—poly(2,4,6‐trimethylphenylene methylene) and poly(2,3,5,6‐tetramethylphenylene methylene)—which were synthesized analogous to PPM. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 309–318