NMR Spectroscopy

Research People Equipment Publications

 

Nuclear Magnetic Resonance

Nuclear magnetic resonance (NMR) is one of the most important spectroscopic methods currently used to describe the structure and dynamics of a variety of molecular and macromolecular systems. The importance of this method is clearly illustrated by the fact that six Nobel Prizes have been awarded for the development of NMR (O. Stern (1943), I.I. Rabi (1944), F. Bloch and E.M. Purcell (1952), R.R. Ernst (1991), K. Wüthrich (2002), P.C. Lauterbur and P. Mansfield (2003)). Today one can find important applications of NMR spectroscopy in structural biology describing the structure and function of nucleic acids or proteins, or in industry identifying new drugs or the products of their metabolism. NMR spectroscopy is thus an indispensible part of the current protemic and metabonomic research. In addition, recent methodology and hardware developments significantly increase the resolution and selectivity of solid-state NMR experiments that now provide detailed information on the structure and dynamics of a wide range of organic and inorganic solids. In many cases, solid-state NMR spectroscopy became quite comparable with well-established x-ray diffraction techniques, thus opening new ways  to characterize nanocrystalline and microcrystalline powdered solids. The time has come for NMR crystallography.

 

Current Research Topics

The research interest of the  department of NMR spectroscopy is focused on the development and application of specific techniques of liquid-state and solid-state NMR spectroscopy to probe the structure and dynamics of a variety of polymer systems.  As a result of our close  cooperation with other groups in  the IMC, the research projects currently solved at the dept. of NMR cover a wide rage of materials and phenomena. Among others, we extensively deal with the investigation of the process of self-organization of macromolecules driven by cooperative inter-polymer H-bonds, we probe structural changes in thermo-responsive polymers, and we  try to develop new experimental techniques of NMR crystallography. The main research topics are  listed below:

 

 

 

Recent results of our investigations

The name is Bond H-Bond

In a  series of three consecutive studies the main factors of the cooperative behavior of intermolecular hydrogen bonds were rigorously described: i) the entropic contribution resulting from  the release of low-molecular-weight ligands; and ii) the proximity effect resulting from  the coupling of neighbouring structure units. These findings open a new insight on the formation of hydrogen bonds between polymer chains, e.g., in DNA. Subsequently, the key role of the entropy-driven cooperative hydration of methyl groups in the thermo-responsive conformational transformations of amphiphilic polymer systems has been, for the first time, evidenced and theoretically explained. The phenomenon of the attack of water molecules on polymer chains has priority in comparison with hydrophobic interactions. This finding considerably changes our understanding of the  thermo-responsive behaviour of natural and synthetic polymers. And, finally, using combined NMR techniques and quantum-chemical calculations, the interaction between hydrated protons (H3O+, H5O2+) and macro-cycle receptors was, for the first time, clearly evidenced. The dynamics and physical nature of this bonding were  rigorously described.  The extent of dominated charge-enhanced multiple hydrogen bonds depends on the cavity size of the receptor. The results seem to be important for the development of molecular sensors of the acidity of solutions and are particularly applicable in medicine.

  • Kříž, J., Dybal, J., Makrlík, E., Vaňura, P., Moyer B., A., J. Phys. Chem. B, 115, 7578 (2011).
  • Kříž, J., Dybal, J, Chem. Phys., 382, 104 (2011).
  • Kříž, J.; Dybal, J. J. Phys. Chem. B, 114, 3140 (2010).
  • Kříž, J.; Toman, P.; Makrlík, M.; Budka, J.; Shukla, R.; Rathore, R. J. Phys. Chem. A, 114, 5327 (2010).
  • Kříž, J.; Dybal, J.; Makrlík, E.; Budka, J.; Vaňura, P. J .Phys. Chem A, 113, 5896 (2009).
  • Kříž, J.; Dybal, J.; Tuzar, Z.; Kadlec, P.  J . Phys. Chem. B, 113, 11950 (2009).
  • Kříž, J., Dybal, J. J. Phys. Chem. B, 111, 6118 (2007).
  • Kříž, J., Dybal, J., Brus, J. J. Phys. Chem. B, 110, 18338 (2006).
  • Kříž, J., Dybal J. J. Phys. Chem. B, 109,13436 (2005).

 

 

An insight into the world of polymer nanocomposites 

Since 2000 we systematically develop the advanced solid-state NMR techniques for detail characterization of complex heterogeneous systems like polymer blends and nanocomposites. Quite recently the domain-selective techniques of 2D separated-local-field experiment designed to measure one-bond dipolar couplings were developed. As these couplings carry information about motional amplitudes of polymer segments the proposed measurements have been successfully applied to describe internal dynamics of polymer segments in semicrystalline nanocomposites. The developed experimental technique opened new way how to discover relations between segmental dynamics and mechanical properties of complex semicrystalline systems. The epoxy networks reinforced by polyhedral oligomeric silsesquioxanes (POSS) provide a typical example of polymer nanocomposites with hierarchical architecture. Investigations of molecular dynamics yielded information making possible the assignment of the contribution of molecular segments to thermomechanical properties like glass transition temperature and storage shear modulus, and to predict the products’ ability to absorb mechanical energy. At last but not least, the recently performed structural study of biodegradable polymers opened the way how to enhance miscibility and mutual interactions between synthetic polymers and natural starch. Using the advanced techniques of solid state NMR spectroscopy the phase structure in wide range of starch/polycaprolactone blends was described in detail. The research opened tight cooperation with our colleagues from Laboratoire Polymères, Propriétés aux Interfaces et Composites, Université de Bretagne-Sud, Lorient, France.

  • Matějíček, P., Brus, J., Jigounov, A., Pleštil, J., et al., Macromolecules 44, 3847 (2011).
  • Brus, J., Čubová Urbanová, M., Šeděnková, I., Brusová, H., Int. J. Pharm. 409, 62 (2011).
  • Spěváček, J., Hanyková, L., Labuta, J., Macromolecules 44, 2149 (2011).
  • Spěváček J., Current Opinion in Colloid & Interface Science 14, 184-191, (2009).
  • Brus J, Urbanova M, Strachota A. Macromolecules 41 (2), 372-386 (2008).
  • Spěváček J.,  Brus J., Divers T.,  Grohens Y. Eur. Polymer J. 43, 1866 (2007).
  • Brus J, Urbanova M, Kelnar I, Kotek J. Macromolecules 39 (16): 5400, (2006).
  • Brus J, Urbanova M. J. Phys. Chem. A 109 (23): 5050, (2005).
  • Brus J., Jegorov A. J. Phys. Chem. A, 108(18); 3955, (2004).
  • Brus J., Spirkova M, Hlavata D, Strachota A. Macromolecules 37, (4) 1346 (2004).

 

 

Additional information

More information about news, job offers, PhD and postdoc. positions, UNESCO/IUPAC studies, research projects, and the results and publications resulting from our research can be found at the web site of Joint Laboratory of Solid State NMR.

BIOpolymer POstdoctoral Laboratory and educational center - BIOPOL

Otto Wichterle Centre of Polymer Materials and Technologies - CPMTOW

Centre of Biomedicinal Polymers - CBMP

Centre of Polymer Sensors - CPS

Polymers for Power Engineering - Energolab


 

Institute of Macromolecular Chemistry AS CR, v.v.i.
Heyrovského nám. 2
CZ-162 06 Praha 6
Czech Republic
phone:+420 296 809 111
fax:+420 296 809 410

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