Bond lengths crosslinking

Figure 17.23 A traceless Staudinger ligation process involves the formation of an intermediate aza-ylide with subsequent attack of the nucleophilic nitrogen atom on the neighboring electrophilic group. The formation of an amide bond then occurs concomitant with the loss of the phosphine component, thus forming a zero-length crosslink between the two molecules.

The crystal structure of silver oxalate may be considered to be made up of a series of chains held together in sheets by Ag—O crosslinks (28). Ag—O bond lengths were 217-230 pm and between chains the Ag—O separation was 258-261 pm.260... 

Carbodiimides are zero length crosslinking agents which mediate amide bond formation between carboxylie aeid groups and amino groups present in the protein. The crosslinking reaction can be intramolecular or intermolecular. Intramolecular crosslinking is often used... 

When the complexes were treated with EDC, a zero-length crosslinker, which forms a covalent bond between carboxyl and amino groups, a distinct product band appeared at a position corresponding to molecular mass of about 90 kDa (Fig. 1-1-2). The band was also detected on crosslinking of NaCl-washed preparation (Fig.l-II), but not when MgCl2-washed preparation had been treated with EDC (Fig.l-III). Because the extrinsic 33 kDa protein is removed with MgCl2 but... 

Of even more interest is a comparison of bond lengths and energies given in Table 4.3 for primary and secondary bonds which assists in understanding the differences between linear and crosslinked polymers. 

Crosslinking, as previously mentioned, occurs primarily in the amorphous phase of UHMWPE. In the crystalline domains the chain segments are not in close enough proximity to allow the recombination of the free radicals— in fact the lattice spacing is smaller than the carbon-carbon bond length. Therefore, for a crosslink to form in the... 

When a dry, hydrophilic crosslinked network is placed in water, the chains between two consecutive junctions are initially in their unperturbed (Flory) state and exhibit an end-to-end distance, rg, which can be calculated from the characteristic ratio, Cp, or from knowledge of the bond length, /, the bond angle, 0, and the possible rotation angles, ( >, of the macromolecular backbone chain. The relevant equations, which have been discussed before [15,27], are summarized here. 

As has been shown above, a polymeric chain can be simulated with the aid of Equation 2.10. This equation allows both crosslinked polymer topology (the values and are functions of the chemical crosslinking density v ) and its molecular characteristics (the value is defined by skeletal bond length f and characteristic ratio C, which serves as an indicator of the chain statistical flexibility and also depends on Z ) to be accounted for [131]. 

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