Deuterium labeled crosslinks

Figure 28.3 The homobifunctional crosslinkers BS2G and BS3 can be used to capture protein interactions through amide bond formation. The deuterium-labeled analogs of these reagents can be used to differentiate...

Star-shaped macromolecules have also been synthesized by using the monofunctional "living" precursor as an Initiator for the polymerization of a small amount of a divinyl monomer. A small crosslinked nodule is formed, which is connected with the p chains that have contributed to Its Initiation. It turns out that fluctuations on the value of p within a sample remain rather small, and consequently the star polymers obtained by this method can also be considered as tailor-made polymers. Recently star molecules with deuterium labeled central nodule have been synthesized according to the... 

For a given network the intercrosslink distance d should be proportional to G1/3. This is exactly what was found by neutron scattering on networks with deuterium-labelled nodules. In particular dc is the distance between neighbor crosslinks in the nascent network, the swelling ratio being Qc (Fig. 2). 

In the latter two phases backbones have the spindle-like conformation, i.e., the prolate shape with (R%) > R p), the characteristic of main chain liquid crystalline polymers. Important means of investigating the conformations of side chain liquid crystalline polymers include small angle neutron scattering from deuterium-labeled chains (Kirst Ohm, 1985), or small angle X-ray scattering on side chain liquid crystalline polymers in a small molecular mass liquid crystal solvent (Mattossi et al., 1986), deuterium nuclear resonance (Boeffel et al., 1986), the stress- or electro-optical measurements on crosslinked side chain liquid crystalline polymers (Mitchell et al., 1992), etc. Actually, the nematic (or smectic modifications) phases of the side chain liquid crystalline polymers have been substantially observed by experiments. 

The size and shape of polymer chains joined in a crosslinked matrix can be measured in a small angle neutron scattering (SANS) experiment. This is a-chieved by labelling a small fraction of the prepolymer with deuterium to contrast strongly with the ordinary hydrogenous substance. The deformation of the polymer chains upon swelling or stretching of the network can also be determined and the results compared with predictions from the theory of rubber elasticity. 

Deuterium NMR is very sensitive to orientational behavior and order there are a number of papers dealing with constrained polymeric networks. For example, 2H NMR (in both, solid state and solution) is used in the study of the orientational order generated in uniaxially strained rubbers as a function of the crosslink density. Two sets of rubbers (model end-linked silicone rubbers and randomly crosslinked diene networks) were investigated directly (on perdeuterated silicone labelled chains) and indirectly, via C6D6 as an NMR probe for diene rubbers 45). 

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