High-resolution 13C NMR Studies Research Articles

Structures of crystalline and amorphous phases of the poly(ethylene oxide)/lithium trifluoromethanesulfonate complexes as studied by solid-state high-resolution 13C nuclear magnetic resonance

Solid-state high-resolution 13C NMR studies are carried out on a series of PEO/LiCF3SO3 complexes with different EO/Li molar ratios at room temperature. The obtained spectra clearly show that there are four phases, namely the crystalline PEO, the amorphous PEO, the PEO3:LiCF3SO3 crystalline complex and the PEO3:LiCF3SO3 amorphous complex, coexisting in the samples with EO/Li molar ratios larger than 3. The solid-state 13C NMR spectrum of the PEO3:LiCF3SO3 crystalline complex exhibits six peaks with high resolution at room temperature, while the previously reported 13C NMR spectra showed only one peak. These six peaks are assigned with the combination of the 13C dipolar-INADEQUATE and the two-dimensional exchange spectra. Moreover, remarkable helical jumps of PEO segments are demonstrated to exist in the crystalline complex. Our study paves the way towards a better understanding of the phase structures and subsequently the conduction mechanism of PEO-based solid polymer electrolytes.

High-resolution 13C NMR studies of cellulose and cellulose oligomers in ionic liquid solutions

High-resolution 13C NMR studies of cellulose and cellulose oligomers dissolved in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) show that the beta-(1-->4)-linked glucose oligomers are disordered in this medium and have a conformational behavior which parallels the one observed in water, and thus, reveal that the polymer is disordered in IL solution as well.

Solid-state high-resolution 13C NMR study on the interphase in lamellar semi-crystalline polymers

The 13C spin-lattice relaxation time T 1c, the spin–spin relaxation time T 2c, the chemical shift values as well as mass fractions of the interphase of PE samples crystallized under various conditions were reported mainly in this work. The existence of the interphase is identified by the method of solid-state high-resolution 13C NMR and the thickness of interfacial region has been obtained. Also, a model of chain folding in the interphase region is proposed and compared with Flory's calculations; consequently, the applicable extent of the theory is examined.

High-resolution 13C NMR studies of the tetragonal two-dimensional polymerized C 60 phase

We present NMR data of tetragonal (tet-2D) two-dimensional polymerized C 60 obtained under high pressure. By using 13C MAS NMR, we were able to identify two resonances, a broad and intense resonance around 146 ppm and a small one at 73.5 ppm. The former line has several components due to inequivalent sp 2 carbons on the C 60 molecules which were distorted by the transformation under high pressure. We attribute the latter line to the sp 3 carbons of the interball bondings. The 13C MAS NMR line-shape simulation of the obtained spectrum is compatible with the suggested polymeric structure where the C 60 molecules are connected by [2+2] cycloadditions. We also report on 13C MAS NMR measurements of tet-2D at ambient pressure and at temperature ranging from 298 to 500 K. We verified that the FCC structure of the pristine C 60 is recovered by annealing the sample above 200°C.

High-Resolution13C NMR Study of an Antiferroelectric Liquid Crystal: Verification of the Bent Chain Structure

A high-resolution 13C NMR study is reported on the antiferroelectric liquid crystal MHPOBC, 4-[(1-methylheptyloxy)carbonyl]phenyl 4-[4-(octyloxy)biphenyl]carboxylate. The structures of the two alkyl chains, the chiral and achiral chains, are analyzed using isotropic shielding constants, cross polarization efficiency, and the field alignment-induced shifts. A comprehensive theoretical treatment for the alignment-induced shift is given. It is shown that the average direction of the chiral chain deviates from the molecular long axis by as much as 43° (bent chain structure), while that of the achiral chain extends along the molecular long axis. The relationships of this particular shape of the molecule with the emergence of the molecular biaxiality and with the onset of antiferroelectricity are discussed.

High resolution 13C NMR studies for crystalline and liquid crystalline phases of PB-18 polyester composed of 4,4'-dihydroxybiphenyl and octadecanedioic acid

Main-chain liquid crystalline PB-18 polyester composed of 4,4'-dihydroxybiphenyl and octadecanedioic acid forms two distinct crystalline phases, K 1 and K 2, and smectic H ( S H) phase in the order of increasing temperature. The detailed structures of the three phases were studied by 13C solid-state NMR spectroscopy with variable temperature accessories. With a comparison of the observed 13C chemical shifts to the calculated 13C NMR shieldings by FPT-INDO method, the conformations of the mesogenic moiety and alkylene spacer are discussed among these three phases.

High resolution 13C NMR studies of one- and two-dimensional polymerized C 60 under high pressure

We report on 13C NMR measurements of orthorhombic one-dimensional and rhombohedral two-dimensional polymers of C 60 obtained under high pressure. The obtained 13C MAS NMR spectrum of the orthorhombic polymer shows two resonances at 146 ppm and 73.5 ppm, and the one of the rhombohedral polymer presents six isotropic lines at 149.1, 147.9, 145.2, 139.6, 134.8 and 73.5 ppm. The static distortion of the C 60 molecules induced by the transformation under pressure must be at the origin of the observed inequivalent carbons in both systems. The 13C NMR lineshape simulation of the obtained spectra are compatible with the suggested polymeric structures where the C 60 molecules are connected by [2 + 2] cycloadditions.

High-resolution 13C NMR study of oxygen intercalation in C60.

Solid state high resolution $^{13}C$ NMR has been used to investigate the physical properties of pristine $C_{60}$ after intercalation with molecular oxygen. By studying the dipolar and hyperfine interactions between Curie type paramagnetic oxygen molecules and $^{13}C$ nuclei we have shown that neither chemical bonding nor charge transfer results from the intercalation. The $O_2$ molecules diffuse inside the solid $C_{60}$ and occupy the octahedral sites of the fcc crystal lattice. The presence of oxygen does not affect the fast thermal reorientation of the nearest $C_{60}$ molecules. Using Magic Angle Spinning we were able to separate the dipolar and hyperfine contributions to $^{13}C$ NMR spectra, corresponding to buckyballs adjacent to various numbers of oxygen molecules.

Artificial granule suspensions of long side chain poly(3-hydroxyalkanoate)

In vitro preparation of long side chain poly(3-hydroxyalkanoate) artificial granule suspensions that mimic the "as biosynthesized" inclusions in vivo is reported. Elastomeric poly(3-hydroxyalkanoate) can be made into an aqueous suspension of noncrystalline, submicron-sized particles. Light-scattering measurements on these suspensions showed polymer particles in the range of 90–200 nm in diameter. High-resolution 13C-NMR studies demonstrated the noncrystalline character of the in vitro artificial granules. Upon drying at room temperature, the suspensions yielded a continuous film resulting from the coalescence of these polymers with a low glass transition temperature and low Young's modulus. Aqueous suspensions of poly(3-hydroxyoctanoate) are ideal substrates for enzymatic degradation studies because of their stability and purity, since they are self-stabilized. The range of poly(3-hydroxyalkanoates) that can be converted to artificial granules and the methods of preparation are described.Key words: poly(3-hydroxyalkanoate), artificial granules, in vitro bacterial inclusions, enzyme model substrates, poly(3-hydroxyoctanoate).

13C High Resolution NMR Study of Methyl-Diethyl Sulfonium TCNQ 1:2 Complex

Solid state high resolution 13C NMR studies of a 1 : 2 charge transfer complex of TCNQ with diethyl-methyl sulfonium S + Et2Me(TCNQ)2 are presented. The metallic shifts of TCNQ resonances are interpreted as due to the Pauli paramagnetism of conducting electrons and quantitatively connected with inhomogeneous spin density distribution over (TCNQ2)— dimer. A singularity of NMR parameters at T = 330 K is observed and described as a structural phase transition occurring in the S + Et2Me cation sublattice.

Solid-state high-resolution 13C NMR study of the intermolecular interaction in organic semiconductors TTCn-TTF

Solid-state high-resolution 13C NMR study of the intermolecular interaction in organic semiconductors TTCn-TTF

High-Resolution 13C NMR Study of Liquid 2-Ethylhexyl Benzoate Confined to Porous Silica Glasses

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-Resolution 13C NMR Study of Liquid 2-Ethylhexyl Benzoate Confined to Porous Silica GlassesJing Zhang and Jiri JonasCite this: J. Phys. Chem. 1994, 98, 27, 6835–6839Publication Date (Print):July 1, 1994Publication History Published online1 May 2002Published inissue 1 July 1994https://doi.org/10.1021/j100078a028RIGHTS & PERMISSIONSArticle Views72Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (554 KB) Get e-Alerts

Rigid-Rod Polyesters with Flexible Side Chains Based on 1,4-Dialkyl Esters of Pyromellitic Acid and 4,4'-Biphenol. 5. High-Resolution 13C NMR Studies for Crystalline and Liquid Crystalline Layered Phases

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRigid-Rod Polyesters with Flexible Side Chains Based on 1,4-Dialkyl Esters of Pyromellitic Acid and 4,4'-Biphenol. 5. High-Resolution 13C NMR Studies for Crystalline and Liquid Crystalline Layered PhasesMasato Sone, Brian R. Harkness, Hiromichi Kurosu, Isao Ando, and Junji WatanabeCite this: Macromolecules 1994, 27, 10, 2769–2777Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/ma00088a018RIGHTS & PERMISSIONSArticle Views165Altmetric-Citations33LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (877 KB) Get e-Alerts Get e-Alerts

High resolution 13C NMR study of synthetic branched-chain acids and of wool wax acids and isostearic acid

The 13C NMR spectra of 28 branched-chain acids (including two from the literature) have been recorded and assigned. These range from C 6 to C 18 in chain length. They are mainly methyl-branched but include also C 2, C 3, C 4, C 5, C 6, and C 16 branches. On the basis of these results the branched-chain acids in wool grease and the industrially produced isostearic acid have been examined.

Solution and Solid State High Resolution 13C NMR Studies on Tetraphenylchlorins

Abstract High-resolution 13C NMR spectra in solid and solution states were observed for tetraphenylchlorin (TPC), tetraphenylbacteriochlorin (TPBC), and tetraphenylisobacteriochlorin (TPIBC). Chemical-shift assignments of the 13C NMR signals for TPBC were completed by a comparison of the 1H decoupled solution 13C NMR spectra with non-decoupled and solid state ones. The absence of signal number changes by temperature in the solution 13C NMR spectra and their comparison with those of the solid state ones suggested the absence of an NH tautomerism in the chlorin ring for TPC and TPBC, indicating the predominant stability of one tautomer over the other. On the other hand, for TPIBC the presence of temperature-dependent signal number changes in the solution 13C NMR spectra were observed. The rate constants of cross polarization (CP) (TCH) and the 1H spin-lattice relaxation time in the rotating frame (T1ρH) were determined based on the dependence of the NMR magnitude on the contact time.

High resolution 13C NMR studies of organic conductor TTF[Ni (dmit) 2] 2

High resolution 13C NMR studies of organic conductor TTF[Ni (dmit) 2] 2

Solid-state high-resolution 13C-NMR study of crosslinks in heavily gamma-irradiated polyethylene

Chemical species produced by heavy γ-irradiation to high-density polyethylene were identified by solid-state high-resolution 13C-NMR, that is, by the CP-MAS method. The majority of chemical species responsible for crosslinks are tertiary carbons, even after such a heavy dosage as 995 Mrad of γ-irradiation. The MAS method, without CP, was used to detect selectively the NMR signal from 13C in amorphous regions. By using a Torchia pulse sequence, spectra from either crystalline or amorphous regions are observed selectively. The results indicate that short branches are produced preferentially in amorphous regions. More crosslinks are produced (by nearly 3.6 times) in amorphous regions than in crystalline regions.

High-Resolution 13C NMR Study of (1→3)-β-d-Glucans in the Solid State: DMSO-Induced Conformational Change and Conformational Characterization by Spin-Relaxation Measurements

Abstract High-resolution 13C NMR spectra of a variety of (1→3)-β-d-glucans were recorded in the solid state after lyophilization from DMSO solution in order to study resulting conformations free from the triple-helix conformation. Lyophilization from DMSO solution caused conformational change of laminaran from Laminaria species (‾Dp=38) from the triple helix to the oligomer-type form (form I). On the contrary, single-chain conformation (form II) of high molecular-weight curdlan was unchanged before and after lyophilization from DMSO solution. Further, DMSO induced conformational change of both single-chain (form II) and triplehelical (form III) conformations of acid-degraded curdlan (‾Dp=14) to the form I. These findings support our view that the single-chain conformation is a major form in curdlan powder. We found that these three forms are distinguished by either the 13C spin-lattice relaxation times (T1C’s) of the laboratory frame or proton spin-lattice relaxation times in the rotating frame (T1ρH). In particular, the form I was distinguishable from others by its prolonged T1C values (3.5–12 s) of C-6 carbon. In addition, the T1ρH of the triple helix of annealed curdlan was one order of magnitude longer than that of the single chain, reflecting their difference in the manner of molecular packing.

High-resolution 13C NMR study of pressure effects on the main phase transition in L-alpha-dipalmitoyl phosphatidylcholine vesicles.

The effects of pressure on the liquid-crystalline to gel transition in vesicles of L-alpha-dipalmitoyl phosphatidylcholine were investigated by high-resolution proton-decoupled natural-abundance 13C NMR spectroscopy. The linewidths of several 13C resonances, including the choline methyl groups, carbonyl carbons, and choline methylene groups and the palmitoyl methyl groups are reported as a function of pressure at 52.7 degrees C. These preliminary NMR experiments clearly demonstrate that high-pressure, high-resolution proton-decoupled natural-abundance 13C NMR spectra are a promising tool to study the phase-transition behavior and the dynamics of model membrane systems.

A High-resolution 13C NMR Study of Some Ethylene Oxide Oligomers, Cryptands and Crown Ethers Complexed with a Variety of Metal Ions in the Solid State. Conformational Change of Ligand Molecules as Viewed from the Conformation-dependent Displacements of 13C Chemical Shifts

Abstract We recorded high-resolution solid-state 13C NMR spectra of ethylene oxide oligomers, cryptands, and crown ethers complexed with metal ions, determined by cross polarization-magic angle spinning (CP-MAS) NMR method. It is found that peak-intensities of these complexes are significantly enhanced by the presence of metal ions which act toward conformational fixation of flexible ligand molecules. The 13C chemical shifts of ethylene oxide oligomers complexed with HgCl2 or CdCl2 as open-chain analogues of crown ethers were successfully related with a pair of torsion angles of nearby single bonds. 13C Chemical shifts of cyclic ionophores were displaced (up to 6 ppm) together with conformational changes of ligand molecules. In addition, the 13C chemical shifts of the carbons neighbored with nitrogen atoms of cryptands [2.2.2] and [2.2.1] were well related with a pair of torsion angles of neaby bonds. Further, we found that several kinds of metal complexes with cis-syn-cis and cis-anti-cis isomers of dicyclohexano-18-crown-6 gave rise to substantially different spectral profiles, resulting in the occurrence of significant conformational changes of these ligand molecules as a result of complex formation.