Special Issue "NMR in Polymer Science"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (20 April 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Roberto Simonutti

Dipartimento di Scienza dei Materiali, Università Milano Bicocca, via R. Cozzi 53, 20125 Milano, Italy
Website | E-Mail
Interests: synthesis and characterization of polymers, polymeric nanocomposites, micro- and mesoporous materials; solid state nuclear magnetic resonance spectroscopy

Special Issue Information

Dear Colleagues,

Since their early days, Nuclear Magnetic Resonance (NMR) and Polymer Science have had a strong and enduring liaison. Many times, the discovery of a new class of polymers required the development of new NMR techniques or the set-up of new interpretative paradigms, as in the case of the precise determination of the polymer tacticity. On the other hand, the possibility of using both Cross Polarization (CP) and Magic Angle Spinning (MAS) for recording 13C NMR spectra was demonstrated for the first time on polymer samples. Nowadays, NMR is widely used in all different areas of polymer science, from chemical analysis in solution and in the solid state, including but not limited to composition, tacticity, branching and end group determination, to morphology of semicrystalline polymers, blends, micro- and nanoparticles. NMR is also extremely sensitive to molecular mobility thus polymer dynamics and chain conformation in solution or in bulk can be accurately described. Additionally, relevant processes, closer to the final application of the polymer materials, like diffusion of a penetrant or self-diffusion, can be monitored.

This Special Issue intends to collect original papers and reviews at the forefront of research in NMR of polymers and to provide a comprehensive view of the multifaceted opportunities that NMR offers to the polymer science community in academia and industry. The topical subjects to be addressed include: high resolution solution and solid state NMR techniques, in particular for polymer identification and reaction monitoring; MAS NMR based techniques for the determination of crystalline structures, phase morphology in polymer blends, block copolymers and nanocomposites; Time Domain (TD) NMR for the characterization of chain dynamics and diffusion in polymer melts, elastomers and gels. Finally, papers focused on exotic methodology development (hyphenated techniques, hyperpolarization, 129Xe NMR, Rheo-NMR) are strongly invited.

Prof. Dr. Roberto Simonutti
Guest Editor

Manuscript Submission Information

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Keywords

  • Nuclear Magnetic Resonance
  • high resolution
  • multidimensional
  • solid state
  • magic angle spinning
  • cross-polarization
  • time domain
  • relaxation times
  • hyphenated techniques
  • hyperpolarization
  • 129Xe NMR
  • polymers
  • microstructure
  • branching
  • end groups
  • crystalline phase
  • morphology
  • dynamics
  • block copolymers
  • blends
  • nanocomposites
  • nanoparticles
  • melts
  • elastomers
  • gels
  • diffusion
  • rheology

Published Papers (8 papers)

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Research

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Open AccessArticle
NMR Analysis of Poly(Lactic Acid) via Statistical Models
Polymers 2019, 11(4), 725; https://doi.org/10.3390/polym11040725
Received: 20 March 2019 / Revised: 15 April 2019 / Accepted: 16 April 2019 / Published: 19 April 2019
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Abstract
The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. [...] Read more.
The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. In this work, we prepared several PLA samples with a tin catalyst at different L,L-lactide and D,D-lactide ratios. Upon analysis of the tetrad intensities with the pair-addition Bernoullian model, we found substantial deviations between observed and calculated intensities due to the presence of transesterification and racemization during the polymerization processes. We formulated a two-state (pair-addition Bernoullian and single-addition Bernoullian) model, and it gave a better fit to the observed data. The use of the two-state model provides a quantitative measure of the extent of transesterification and racemization, and potentially yields useful information on the polymerization mechanism. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Open AccessArticle
Rubber-Filler Interactions in Polyisoprene Filled with In Situ Generated Silica: A Solid State NMR Study
Polymers 2018, 10(8), 822; https://doi.org/10.3390/polym10080822
Received: 30 June 2018 / Revised: 21 July 2018 / Accepted: 23 July 2018 / Published: 25 July 2018
Cited by 3 | PDF Full-text (1646 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we used high- and low-resolution solid state Nuclear Magnetic Resonance (NMR) techniques to investigate a series of polyisoprene samples filled with silica generated in situ from tetraethoxysilane by sol-gel process. In particular, 1H spin-lattice and spin-spin relaxation times allowed [...] Read more.
In this paper we used high- and low-resolution solid state Nuclear Magnetic Resonance (NMR) techniques to investigate a series of polyisoprene samples filled with silica generated in situ from tetraethoxysilane by sol-gel process. In particular, 1H spin-lattice and spin-spin relaxation times allowed us to get insights into the dynamic properties of both the polymer bulk and the bound rubber, and to obtain a comparative estimate of the amount of bound rubber in samples prepared with different compositions and sol-gel reaction times. In all samples, three fractions with different mobility could be distinguished by 1H T2 and ascribed to loosely bound rubber, polymer bulk, and free chain ends. The amount of bound rubber was found to be dependent on sample preparation, and it resulted maximum in the sample showing the best dispersion of silica domains in the rubber matrix. The interpretation of the loosely bound rubber in terms of “glassy” behaviour was discussed, also on the basis of 1H T1 and T1ρ data. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Open AccessArticle
Local Order and Dynamics of Nanoconstrained Ethylene-Butylene Chain Segments in SEBS
Polymers 2018, 10(6), 655; https://doi.org/10.3390/polym10060655
Received: 21 May 2018 / Revised: 7 June 2018 / Accepted: 8 June 2018 / Published: 11 June 2018
Cited by 1 | PDF Full-text (3783 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Subtle alterations in the mid-block of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene (SEBS) have a significant impact on the mechanical properties of the resulting microphase separated materials. In samples with high butylene content, the ethylene-co-butylene (EB) phase behaves as a rubber, [...] Read more.
Subtle alterations in the mid-block of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene (SEBS) have a significant impact on the mechanical properties of the resulting microphase separated materials. In samples with high butylene content, the ethylene-co-butylene (EB) phase behaves as a rubber, as seen by differential scanning calorimetry (DSC), time domain (TD) and Magic Angle Spinning (MAS) NMR, X-ray scattering at small (SAXS), and wide (WAXS) angles. In samples where the butylene content is lower—but still sufficient to prevent crystallization in bulk EB—the DSC thermogram presents a broad endothermic transition upon heating from 221 to 300 K. TD NMR, supported by WAXS and dielectric spectroscopy measurements, probed the dynamic phenomena of EB during this transition. The results suggest the existence of a rotator phase for the EB block below room temperature, as a result of nanoconfinement. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Open AccessArticle
Microstructure of Copolymers of Norbornene Based on Assignments of 13C NMR Spectra: Evolution of a Methodology
Polymers 2018, 10(6), 647; https://doi.org/10.3390/polym10060647
Received: 18 May 2018 / Revised: 4 June 2018 / Accepted: 7 June 2018 / Published: 9 June 2018
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Abstract
An overview of the methodologies to elucidate the microstructure of copolymers of ethylene and cyclic olefins through 13C Nuclear magnetic resonance (NMR) analysis is given. 13C NMR spectra of these copolymers are quite complex because of the presence of stereogenic carbons [...] Read more.
An overview of the methodologies to elucidate the microstructure of copolymers of ethylene and cyclic olefins through 13C Nuclear magnetic resonance (NMR) analysis is given. 13C NMR spectra of these copolymers are quite complex because of the presence of stereogenic carbons in the monomer unit and of the fact that chemical shifts of these copolymers do not obey straightforward additive rules. We illustrate how it is possible to assign 13C NMR spectra of cyclic olefin-based copolymers by selecting the proper tools, which include synthesis of copolymers with different comonomer content and by catalysts with different symmetries, the use of one- or two-dimensional NMR techniques. The consideration of conformational characteristics of copolymer chain, as well as the exploitation of all the peak areas of the spectra by accounting for the stoichoimetric requirements of the copolymer chain and the best fitting of a set of linear equation was obtained. The examples presented include the assignments of the complex spectra of poly(ethylene-co-norbornene (E-co-N), poly(propylene-co-norbornene (P-co-N) copolymers, poly(ethylene-co-4-Me-cyclohexane)s, poly(ethylene-co-1-Me-cyclopentane)s, and poly(E-ter-N-ter-1,4-hexadiene) and the elucidation of their microstructures. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Open AccessArticle
Evaluation of Band-Selective HSQC and HMBC: Methodological Validation on the Cyclosporin Cyclic Peptide and Application for Poly(3-hydroxyalkanoate)s Stereoregularity Determination
Polymers 2018, 10(5), 533; https://doi.org/10.3390/polym10050533
Received: 19 April 2018 / Revised: 9 May 2018 / Accepted: 15 May 2018 / Published: 16 May 2018
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Abstract
Band-selective (bs) HSQC, improving spectral resolution by restriction of the heteronuclear dimension without inducing spectral folding, has been recently used for polymer tacticity determination. Herein is reported an evaluation of various bs-HSQC and bs-HMBC sequences, first from a methodological point of view (selectivity, [...] Read more.
Band-selective (bs) HSQC, improving spectral resolution by restriction of the heteronuclear dimension without inducing spectral folding, has been recently used for polymer tacticity determination. Herein is reported an evaluation of various bs-HSQC and bs-HMBC sequences, first from a methodological point of view (selectivity, dependence to INEPT interpulse delay or relaxation delay), using the cyclic peptide cyclosporin selected as a model compound, and then from an applicative approach, comparing tacticity determined from bs-HSQC and bs-HMBC experiments to the one obtained from 1D 13C{1H} on poly(3-hydroxyalkanoate)s samples. For HSQC sequences, the 13C selectivity scheme consisting in substituting a 13C broadband refocalization by a selective one revealed itself problematic, with unwanted aliased signals, whereas the insertion of double pulsed field gradients spin-echo (DPFGSE) or the use of opposite sign gradients bracketing a selective refocalization gave satisfactory results. Determination of the probability of syndiotactic enchainments, Ps, by bs-HSQC is fully consistent and no precision loss was observed when decreasing acquisition time (37 min vs. 106 min for 1D 13C{1H}). Bs-HMBC, although not straightforwardly applicable for tacticity determination, could provide (after a calibration step) an alternative for compounds of which only 13C carbonyl signals are resolved enough for discriminating between syndiotactic and isotactic configurations. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Open AccessArticle
Solid-State Nuclear Magnetic Resonance (NMR) and Nuclear Magnetic Relaxation Time Analyses of Molecular Mobility and Compatibility of Plasticized Polyhydroxyalkanoates (PHA) Copolymers
Polymers 2018, 10(5), 506; https://doi.org/10.3390/polym10050506
Received: 19 April 2018 / Revised: 3 May 2018 / Accepted: 5 May 2018 / Published: 7 May 2018
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Abstract
The molecular mobility and compatibility of plasticized polyhydroxyalkanoates (PHA) were investigated, focusing on changes due to copolymerization using either flexible poly (butylene succinate) (PBS) or rigid poly(lactic acid) (PLA) units. For the case of a poly(3-hydroxybutyrate) (PHB) unit in plasticized PHA, copolymerization of [...] Read more.
The molecular mobility and compatibility of plasticized polyhydroxyalkanoates (PHA) were investigated, focusing on changes due to copolymerization using either flexible poly (butylene succinate) (PBS) or rigid poly(lactic acid) (PLA) units. For the case of a poly(3-hydroxybutyrate) (PHB) unit in plasticized PHA, copolymerization of either PBS or PLA decreased 1H and 13C spin-lattice relaxation times in the laboratory frame (T1H and T1C) in the same manner, while PBS produced a lower 1H spin-lattice relaxation time in the rotating frame (T1ρH) than PLA. Both the signals of 1H MAS (magic-angle spinning) and 13C PST (pulse saturation transfer) MAS nuclear magnetic resonance (NMR) spectra were sharpened and increased by copolymerization with PBS. A variable temperature relaxation time analysis showed that the decrease of T1H values was dominated by the 1H spin diffusion via the interface between PHB and the added polyester because of the good compatibility. Meanwhile, the decrease of T1C values was dominated by increasingly rapid molecular motions of PHB because of the lowered crystallinity due to the plasticization. Slow molecular motions (kHz order) were enhanced more by the addition of PBS than PLA, although rapid molecular motions (MHz order) were enhanced by either polyester. Several NMR parameters were beneficial for analyzing the manufacturing process as the indexes of polymer compatibility and molecular motions. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Open AccessArticle
Hydrogen-Deuterium Exchange Profiles of Polyubiquitin Fibrils
Polymers 2018, 10(3), 240; https://doi.org/10.3390/polym10030240
Received: 31 January 2018 / Revised: 23 February 2018 / Accepted: 24 February 2018 / Published: 27 February 2018
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Abstract
Ubiquitin and its polymeric forms are conjugated to intracellular proteins to regulate diverse intracellular processes. Intriguingly, polyubiquitin has also been identified as a component of pathological protein aggregates associated with Alzheimer’s disease and other neurodegenerative disorders. We recently found that polyubiquitin can form [...] Read more.
Ubiquitin and its polymeric forms are conjugated to intracellular proteins to regulate diverse intracellular processes. Intriguingly, polyubiquitin has also been identified as a component of pathological protein aggregates associated with Alzheimer’s disease and other neurodegenerative disorders. We recently found that polyubiquitin can form amyloid-like fibrils, and that these fibrillar aggregates can be degraded by macroautophagy. Although the structural properties appear to function in recognition of the fibrils, no structural information on polyubiquitin fibrils has been reported so far. Here, we identify the core of M1-linked diubiquitin fibrils from hydrogen-deuterium exchange experiments using solution nuclear magnetic resonance (NMR) spectroscopy. Intriguingly, intrinsically flexible regions became highly solvent-protected in the fibril structure. These results indicate that polyubiquitin fibrils are formed by inter-molecular interactions between relatively flexible structural components, including the loops and edges of secondary structure elements. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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Review

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Open AccessReview
Chain Trajectory, Chain Packing, and Molecular Dynamics of Semicrystalline Polymers as Studied by Solid-State NMR
Polymers 2018, 10(7), 775; https://doi.org/10.3390/polym10070775
Received: 3 June 2018 / Revised: 13 July 2018 / Accepted: 13 July 2018 / Published: 15 July 2018
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Abstract
Chain-level structure of semicrystalline polymers in melt- and solution-grown crystals has been debated over the past half century. Recently, 13C–13C double quantum (DQ) Nuclear Magnetic Resonance (NMR) spectroscopy has been successfully applied to investigate chain-folding (CF) structure and packing structure [...] Read more.
Chain-level structure of semicrystalline polymers in melt- and solution-grown crystals has been debated over the past half century. Recently, 13C–13C double quantum (DQ) Nuclear Magnetic Resonance (NMR) spectroscopy has been successfully applied to investigate chain-folding (CF) structure and packing structure of 13C enriched polymers after solution and melt crystallization. We review recent NMR studies for (i) packing structure, (ii) chain trajectory, (iii) conformation of the folded chains, (iv) nucleation mechanisms, (v) deformation mechanism, and (vi) molecular dynamics of semicrystalline polymers. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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