Noncovalent materials

Keywords Supramolecular polymer gels Stimuli-responsive materials Noncovalent interactions Supramolecular network dynamics Self-assembly... 

Himdin [8001-27-2] is a polypeptide of 66 amino acids found ia the saUvary gland secretions of the leech Himdo medicinalis (45). It is a potent inhibitor of thrombin and biads to y-thrombia with a dissociation constant of 0.8 x 10 ° M to 2.0 x lO " M. Himdin forms a stable noncovalent complex with free and bound thrombin completely iadependent of AT-III. This material has now been cloned and expressed ia yeast cells (46,47). Its antigenic poteatial ia humans remains to be estabUshed. 

B. Sellergren, Noncovalent molecular imprinting antibody-like molecular recognition in polymeric network materials . Trends. Anal. Chem. 16 310-320 (1997). 

Self-Assembly and Noncovalent Strategy for the Synthesis of Soft-Materials... 

The metal leached from the support is re-adsorbed to a guard bed of ion exchange material. This shows that the concept of noncovalent anchoring is very attractive, especially if the homogeneous catalyst needs no further modification. 

One good example of noncovalent functionalization for subsequent hybridization is the use of benzyl alcohol (BA) [118]. n-n interactions between the aromatic ring of BA and the CNT sidewalls result in a good dispersibility in ethanol. Furthermore, BA offers a well-ordered and well-distributed functionalization [119] of hydroxyl groups on the sidewalls of the CNTs that can be used to hybridize the material with a large number of metal oxides using conventional chemical methods [60]. 

Encapsulation of different entities inside the CNT channel stands alone as an alternative noncovalent functionalization approach. Many studies on the filling of carbon nanotubes with ions or molecules focus on how the presence of these fillers affects the physical properties of the tubes. From a different point of view, confinement of materials inside the cylindrical structure could be regarded as a way to protect such materials from the external environment, with the tubes acting as a nanoreactor or a nanotransporter. It is fascinating to envision specific reactions between molecules occurring inside the aromatic cylindrical framework, tailored by CNT characteristic parameters such as diameter, affinity towards specific molecules, etc. 

These novel carbon nanostructures can also be modified by (a) doping, that is the addition of foreign atoms into the carbon nanostructure, (b) by the introduction of structural defects that modify the arrangement of the carbon atoms and (c) by functionalization involving covalent or noncovalent bonding with other molecules. These modifications opened up new perspectives in developing novel composite materials with different matrices (ceramic, polymer and metals). For example, polymer composites containing carbon nanostructures have attracted considerable attention due to... 

Summarizing, noncovalent functionalization methods can be used to prepare materials with specific biological properties because they are quick, efficient and clean. In order to increase biocompatibility of carbon nanostructures, these materials now need to be integrated into living systems and to be potentially used as tissue regeneration scaffolds, prostheses or drug deliverers. 

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