Small angle neutron scattering networks

In addition to the above techniques, inverse gas chromatography, swelling experiments, tensile tests, mechanical analyses, and small-angle neutron scattering have been used to determine the cross-link density of cured networks (240—245). Si soHd-state nmr and chemical degradation methods have been used to characterize cured networks stmcturaHy (246). H- and H-nmr and spin echo experiments have been used to study the dynamics of cured sihcone networks (247—250). 

Small Angle Neutron Scattering from Polymer Networks... 

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. 

Small angle neutron scattering (SANS) of "marked" (isotopically labeled) chains in unmarked networks has proven to be of potential value in... 

Zhou, W., Islam, M.F., Wang, H., Ho, D.L., Yodh, A.G., Winey, K.I., and Fischer, J.E. (2004) Small angle neutron scattering from single-wall carbon nanotube suspensions Evidence for isolated rigid rods and rod networks. Chem. Phys. Lett. 384, 185-189. 

The temperature dependences of the small-angle neutron scattering (SANS) from solutions and networks of poly(N,N -diethylacrylamide) or from copolymer of DEAAm and MNa (xMNa = 0.05) in deuterated water were measured [41]. Experimental dependences of the effective scattering cross-section... 

Further characterization of the mechanical properties and structures of such zeolite-reinforced PDMS elastomers by Wen and Mark [139] also utilized small-angle neutron scattering (SANS) [141, 143, 214—220] and transmission electron microscopy (TEM). The neutron-scattering profiles of the pure and zeolite-filled PDMS networks were identical, which indicated negligible penetration of the polymer into the zeolite pores. The TEM pictures showed that the zeolite with the larger pore size had a somewhat smaller particle size, and this is probably the origin of its superior reinforcing properties [62, 139]. 

As explained in Sec. 7.1, epoxy networks have been and are still the subject of controversy. This is mainly based on the particular interpretation of results obtained using microscopy techniques. On the contrary, results obtained with small-angle neutron scattering (SANS) proved that typical diepoxy-diamine networks were homogeneous (Wu and Bauer, 1985). 

In PB networks, the variation of the line shape as a function of the applied stress was interpreted in terms of a chain length distribution. Shorter chains may be more oriented than longer ones, at a given elongation [18], which may lead to a non-affine behaviour at the chain scale. The question of the spatial scale to which the deformation is affinely transmitted, has been investigated intensively by small angle neutron scattering [64]. However, it may happen as well that the chain portions close to junction points are more oriented (have a more restricted mobility) than those in the middle of the chains [19]. 

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