Quantitative analysis for reaction between epoxidized natural rubber and poly (L‐lactide) through 1H‐NMR spectroscopy

Reaction between epoxidized natural rubber and poly(L ‐lactide) (PLLA) was investigated quantitatively in terms of conversion of the epoxidized natural rubber. The epoxidized natural rubber was prepared by epoxidation of high ammonia natural rubber (HA‐NR) or deproteinized natural rubber (DPNR) with peracetic acid followed by depolymerization with ammonium persulfate. The resulting liquid HA‐NR having epoxy group (LENR) or liquid DPNR having epoxy group (LEDPNR) were subjected to heating at 473 K for 20 min, after blending with PLLA. The products were characterized through morphology observation, DSC measurement, and ¹H‐NMR spectroscopy. The conversions of the rubbers were estimated from intensity ratio of signals in ¹H‐NMR spectrum for the products after removing unreacted rubber with toluene. Difference in the estimated conversion between the LENR/PLLA and LEDPNR/PLLA blends was interpreted in relation to proteins present in the rubber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of poly(1‐methyl‐1,4‐butanediol‐1,4‐diyl/2,3,4‐trihydro‐5‐methylfuran‐2,5‐diyl) prepared from natural rubber through 2D NMR spectroscopy

Poly(1‐methyl‐1,4‐butanediol‐1,4‐diyl/2,3,4‐trihydro‐5‐methylfuran‐2,5‐diyl) was prepared by epoxidation of deproteinized natural rubber with m‐chloroperbenzoic acid followed by hydrolysis with sulfuric acid. Characterization of the resulting product was performed through FT‐IR, ¹H NMR, and ¹³C NMR spectroscopies. All signals appearing in the ¹H and ¹³C NMR spectra were assigned by distortionless enhancement by polarization transfer (DEPT), quaternary carbon observation (QUAT), correlation spectroscopy (COSY), and heteronuclear multiple quantum correlation (HMQC) measurements. After proving the primary structure of the product, one pot synthesis of poly(1‐methyl‐1,4‐butanediol‐1,4‐diyl/2,3,4‐trihydro‐5‐methylfuran‐2,5‐diyl) from deproteinized natural rubber latex was carried out with peracetic acid and 2‐propanol. The resulting product was characterized by ¹H NMR spectroscopy on the basis of the assignments established in this study, and its gas permeability was measured for a practical application as a film. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Crosslinking junctions of vulcanized natural rubber analyzed by solid-state NMR spectroscopy equipped with field-gradient-magic angle spinning probe

Crosslinking junctions of vulcanized natural rubber were analyzed by solid-state NMR spectroscopy equipped with a field-gradient high speed magic angle spinning probe. Resolution of ¹H and ¹³C NMR spectra and correlations between ¹H and ¹³C of the vulcanized natural rubber were investigated by one- and two-dimensional measurements, including inverse correlation measurements. The number of substitution of the carbon atom at the crosslinking junctions was determined by solid-state NMR spectroscopy.     

A 13C NMR study of hydroxylated natural rubber

Two methods have been used to introduce hydroxyl groups into natural rubber. In the first method, epoxidized natural rubber was reduced with lithium aluminium hydride or aluminium hydride with the production of a tertiary alcohol. The ¹³C NMR spectrum of this product was assigned in terms of shift factors from model compounds and quantitative analysis of the spectra confirmed that the hydroxylation process of partially epoxidized rubber was a random process. At higher levels of epoxidation, evidence was obtained for the formation of larger rings from adjacent epoxy groups. The second method involved hydroboration of natural rubber followed by oxidation, which was expected to produce secondary alcohol groups, but gave a mixture of secondary and tertiary alcohol groups as shown by the ¹³C NMR spectrum. A reaction scheme was proposed to explain this result.     

Epoxidation of natural rubber studied by nmr spectroscopy

Epoxidation of natural rubber with peroxyacids in homogeneous solution (CHCl₃, benzene) and in latex occurs without main chain fission or isomerization of the cis configuration. There are two possible modes of addition of oxygen to the double bond, which gives rise to diastereoisomers in dyad structures, as shown by the occurrence of splitting of ¹³C NMR resonances in 100% epoxidized rubber. In partially epoxidized rubber the ¹³C NMR resonances of the methylene carbon atoms have been fully assigned using pulse sequences and lanthanide shift reagents, in terms of triad sequences. Resonances in the olefinic region of the spectrum require assignment in terms of pentad sequences whereas those from the oxirane region are much more closely spaced and are assigned using triads. Intensity measurements on the methylene carbon NMR resonances show that the epoxidation reaction is a random process in both homogeneous solution and in latex particles.     

Microstructure analysis of poly(styrene‐co‐vinylidene chloride) copolymers by NMR spectroscopy

Poly(styrene‐co‐vinylidene chloride) (S/V) copolymers were prepared by free‐radical photopolymerization using uranyl nitrate as an initiator. The microstructure of the copolymer S/V was investigated by ¹H‐ and ¹³C{¹H}‐NMR, ¹H–¹³C‐heteronuclear shift quantum correlation (HSQC) NMR, and homonuclear total correlated spectroscopy (TOCSY). The ¹H‐NMR spectra of the copolymers is complex due to overlapping resonance signals of the various triad configurations. Assignments were made up to the triad and tetrad levels for the methylene and methine regions using two‐dimensional HSQC experiments. A ¹³C‐distortionless enhancement by polarization transfer (DEPT) spectrum was used to differentiate between the carbon resonance signals of methine and the methylene units. The geminal couplings in the methylene protons and vicinal coupling between the methine and methylene protons were detected from the TOCSY spectra. Monte Carlo simulations were used to investigate the effect of the degree of polymerization on the triad fractions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 544–554, 2001     

<Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR characterization and stereochemical assignments of bile acids in aqueous media

The unconjugated bile acids cholic acid, deoxycholic acid, and chenodeoxycholic acid; their glycine and taurine conjugated glycocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, taurocholic acid, taurodeoxycholic acid, and taurochenodeoxycholic acid; and a taurine conjugated ursodeoxycholic acid, tauroursodeoxycholic acid, were characterized through ¹H and ¹³C NMR in aqueous media under the physiological pH region (7.4±0.1). Assignments of ¹H and ¹³C signals of all the bile acids were made using a combination of several one- and two-dimensional, homonuclear (¹H−¹H) and heteronuclear (¹H−¹³C) correlations as well as spectral editing NMR methods. Stereochemical assignment of the five-membered ring of the bile acids is reported here for the first time. The complete characterization of various bile acids in aqueous media presented here may have implications in the study of the pathophysiology of biliary diseases through human biliary fluids using NMR spectroscopy.     

Compatibility of liquid deproteinized natural rubber having epoxy group (LEDPNR)/poly (L‐lactide) blend

Reaction after mixing of liquid epoxidized natural rubber/poly(L ‐lactide) blend was performed to enhance the compatibility of the blend. The liquid epoxidized natural rubber was prepared by epoxidation of deproteinized natural rubber with peracetic acid in latex stage followed by depolymerization with peroxide and propanal. The resulting liquid deproteinized natural rubber having epoxy group (LEDPNR) was mixed with poly(L ‐lactide) (PLLA) to investigate the compatibility of the blend through differential scanning calorimetry, optical light microscopy, and NMR spectroscopy. After heating the blend at 473 K for 20 min, glass transition temperature (T_g) of LEDPNR in LEDPNR/PLLA blend increased from 251 to 259 K, while T_g and melting temperature (T_m) of PLLA decreased from 337 to 332 K and 450 to 445 K, respectively, suggesting that the compatibility of LEDPNR/ PLLA blend was enhanced by a reaction between the epoxy group of LEDPNR and the ester group of PLLA. The reaction was proved by high‐resolution solid‐state ¹³C NMR spectroscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

One- and two-dimensional nuclear magnetic resonance studies on the compositional sequence and the microstructure of acrylonitrile–pentyl methacrylate copolymers

The chemical microstructure of acrylonitrile–pentyl methacrylate (A–P) copolymers prepared by photopolymerization using uranyl ion as the photo sensitizer is analyzed by ¹³C{¹H} nuclear magnetic resonance spectroscopy. The composition of the copolymers were determined by elemental analysis, and comonomer reactivity ratios were determined by the Kelen–Tudos (KT) and the error in variable (EVM) methods. The terminal model reactivity ratios obtained from the EVM method are r_A = 0.20 and r_P = 2.62. The complete spectral assignment of the overlapping proton and carbon spectra of these copolymers were done with the help of distortionless enhancement by polarization transfer and two-dimensional ¹H–¹³C heteronuclear shift correlation (inverse HETCOR) spectroscopy. The assignment of the various conformational and configurational sequences in the proton spectrum were made possible by two-dimensional correlated spectroscopy and total correlation spectroscopy experiments. Monte Carlo simulation was used to study the effect of the degree of polymerization on the triad fractions. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 2507–2516, 1998     

1H and 13C n.m.r. spectroscopic methods for the analysis of fossil fuel materials: Some novel approaches

A number of¹H and¹³C n.m.r. methods, apart from conventional procedures which rely on chemical shift classifications alone, can be used to identify chemical or structural characteristics of fossil fuel materials. The information available via multiplet selection in ¹³C n.m.r., two-dimensional J spectroscopy, homonuclear ¹H-¹H correlation spectroscopy, and heteronuclear ¹³C-¹H correlation procedures, is discussed and illustrated.     

Synthesis and Characterization of Polyethylene Glycol Diesters from Estolides Containing Epoxides and Diols

Estolides from oleic acid, 12-hydroxystearic acid, and methyl ricinoleate were synthesized and converted to polyethylene glycol (PEG) diesters. Oleic estolide was synthesized from oleic acid as a homo-oligomeric material using perchloric acid in 68.8% yield and an estolide number (EN) value of 1.29. Estolides from 12-hydroxystearic acid were homo-oligomers made by heating under vacuum at 150 °C for 24 hours to give a quantitative yield of estolide with an EN value of 2.55. Oleic acid-based estolides and 12-hydroxystearic acid-based estolide were esterified with PEG-200 diol to form PEG 200 diesters. Ricinoleate estolides was capped with lauric acid or 12-hydroxystearic estolide by reacting methyl ricinoleate with the corresponding fatty acids at 150 °C using tin(II) octoate as a catalyst. The corresponding estolides were transesterified with PEG-200 diol to form the diesters. The residual olefin of ricinoleate was then epoxidized and underwent ring opening hydrolysis to form the corresponding diol. NMR spectroscopy (¹H, ¹³C, distortionless enhancement by polarization transfer, heteronuclear single quantum correlation, heteronuclear multiple bond correlation, and correlated spectroscopy) was used to characterize the products.     

Surface modification of natural rubber laces

Epoxidation has been applied to modify the surface of natural rubber laces. When very thin laces of fractionated bleached rubber are used, about 6% of the double bonds could be modified. Using ¹H nuclear magnetic resonance (NMR) and infrared (IR) analysis the best condition for the reaction was worked out. Both ¹³C NMR and differential scanning calorimetry (DSC) results indicate that the 6% epoxide groups are placed in a predominantly block manner. Modification in yellow fraction rubber however gives lower epoxy contents. Increase in glass transition tempreature by epoxidation results in more damping and better abrasion resistance. The resultant polymer acts very similar to a 90/10 natural rubber/50% epoxidized natural rubber (NR/ENR-50) blend.     

Investigation of microstructure of the N‐vinyl‐2‐pyrrolidone/methyl methacrylate copolymers by NMR spectroscopy

The copolymers containing N‐vinyl‐2‐pyrrolidone (V) and methyl methacrylate (M) units of different compositions were synthesized by free radical bulk polymerization. The copolymer composition of these copolymers was determined by CHN analysis. The distortionless enhancement by polarization transfer (DEPT) technique was used to resolve the methine, methylene, and methyl resonance signals in the V/M copolymer. Comonomer reactivity ratios were determined by the Kelen–Tudos (KT) and nonlinear least‐square error‐in‐variable (EVM) methods. ¹H–¹³C Heteronuclear shift quantum correlation spectroscopy (HSQC) and ¹H–¹H homonuclear total correlation spectroscopy (TOCSY) spectra were used for the resolution of the proton nuclear magnetic resonance (¹H NMR) spectrum of the V/M copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1328–1336, 2002     

<Superscript>1</Superscript>H NMR characterization of milk lipids: A comparison between cow and buffalo milk

Characterization of the lipid fraction of raw cow and buffalo milk samples, collected in different breeding areas in Apulia, a region of southern Italy, were performed by means of ¹H NMR. The aim of this work was to establish whether FA composition data obtained by ¹H NMR can be used in the differentiation of buffalo and cow milk samples according to species. A complete assignment of the signals present in the spectrum was attempted by COSY, heteronuclear coherence spectra. Quantification of FA was carried out by inserting the integrals of particular peaks in suitable calculations. Multivariate statistical analysis, conducted on the results of the quantification, permitted buffalo and cow milks to be distinguished.     

Segmental mobility in poly(isoprene) rubber studied by deuterium-carbon NMR correlation spectroscopy

Summary A HMQC based deuterium-carbon correlation method is used for the first time to study the segmental mobility in a fully deuterated poly(isoprene) (PI) rubber network. The isotropic J _CD couplings can be utilized for polarization transfer between ²H and ¹³C spins in a mobile solid polymer. This makes it possible to correlate the ²H resonances with the ¹³C chemical shifts of the attached carbon in a two-dimensional (2D) experiment, and thus allow the extraction of the individual ²H signals. The experimental data obtained from the 2D correlation spectrum indicates differences in the segmental mobility of the C-D vectors in perdeuterated PI. The conclusions are fully consistent with ²H and ¹³C T ₁ relaxation data. The results shown in this paper demonstrate the potential of ²H-¹³C NMR correlation spectroscopy in solid systems which produce overlapped 1D ²H spectra. Received: 11 December 2000/Revised version: 1 March 2001/Accepted: 1 March 2001     

Stereochemical elucidation of complex α‐methyl and β‐methylene carbon resonances in poly(2‐hydroxy ethyl methacrylate‐co‐methacrylonitrile) by 2D NMR

Copolymers of 2‐hydroxy ethyl methacrylate and methacrylonitrile (H/M) of different composition were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The copolymers composition were calculated from ¹H and quantitative ¹³C{¹H}NMR spectra. The complete spectral assignment of complex and overlapped α‐methyl and β‐methylene carbon regions in ¹³C{¹H} NMR spectrum in term of compositional and configurational sequences of H/M copolymers were done with the help of two‐dimensional heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Two-dimensional nuclear magnetic resonance of resins

A group of resins was synthesised from a series of phenols and aldehydes, and their structures comprehensively deduced from two-dimensional nuclear magnetic resonance spectroscopy (2-D NMR). Correlation spectroscopy, in particular carbon-proton heteronuclear chemical shift correlation spectroscopy, was shown to be especially incisive in assigning structural features to the NMR signals. The method has permitted fuller structural characterisation of these materials than was heretofore possible, and has identified, inter alia, methylene and methyleneoxy bridges unequivocally: complex substitution patterns in the phenol-derived aromatic rings have also been elucidated. It is demonstrably possible to apply the same techniques to similar complex resin structures, and to utilise these structural insights to determine the mechanistic processes involved in their syntheses.     

Two‐dimensional NMR studies of styrene/n‐butyl acrylate copolymers synthesized by atom transfer radical polymerization

Copolymers of styrene and n‐butyl acrylate were prepared by atom transfer radical polymerization (ATRP) using CuBr/N,N,N′,N′,N″‐pentamethyl‐diethylenetriamine as catalyst and Methyl 2‐bromopropionate as initiator. The polydispersity of the copolymers is quite low (1.1–1.3). ¹³C {¹H} NMR spectra of these copolymers show that the methylene and methine signals of the main chain are compositional sensitive and highly overlapped. Even the distortionless enhancement by polarization transfer (DEPT) was not able to assign the complex and overlapping signals. Assignments of the various resonance signals were done with the help of heteronuclear single quantum coherence (HSQC), total correlation spectroscopy (TOCSY), and heteronuclear multiple bond correlation (HMBC) experiments. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Structural characterization of oligomers from the polycondensation of citric acid with ethylene glycol and long‐chain aliphatic alcohols

The structural characterization of polyesters of citric acid (CA) with ethylene glycol and long‐chain aliphatic alcohols (ROH), prepared by the composition of the reaction mixture being adjusted slightly away from stoichiometric equivalence, was performed with ¹H‐ and ¹³C‐NMR spectroscopy. The aliphatic alcohols employed were 1‐decanol, 1‐dodecanol, and 1‐octadecanol. The ¹³C‐NMR carbonyl region presented four groups of signals, two corresponding to the ester groups and two corresponding to the acid groups. However, symmetric and asymmetric groups of CA moieties were identified in the ¹³C‐NMR spectra. The ester yield from ROH decreased as the number of carbon atoms in the alcohols increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 302–306, 2003     

Poly(vinylidene chloride-co-vinyl acetate): comprehensive microstructure analysis by NMR spectroscopy

The microstructure analysis of poly(vinylidene chloride-co-vinyl acetate) was done using chemical shift modeling and 2D NMR spectroscopy. Chemical shift modeling was applied to analyze the compositional sensitive resonances of quaternary carbon of vinylidene chloride unit. Reactivity ratios determination was done from the diad and triad fractions. To resolve the complex ¹H and ¹³C{¹H} NMR spectra of copolymers, 2D ¹H/¹³C hetero-nuclear single quantum coherence (HSQC), ¹H/¹H total correlation spectroscopy (TOCSY) and hetero-nuclear multiple bond correlation (HMBC) experiments were conducted. The combination of 2D NMR experiments supported by chemical shift modeling enabled to assign the complex and overlapping proton and carbon-13 resonances unambiguously.