Neutron scattering from polymer networks

Small Angle Neutron Scattering from Polymer Networks... 

Another important statement of French authors from their neutron scattering experiments was that the size of polystyrene strands in dry model networks is equal to the size of the precursor chains dissolved under -conditions (see Table 1.5). At first sight, this result confirms the idea [136, 137], expressed by Flory [138] in the middle of the last century and later picked up by De Gennes [139], that in bulk polymer the chain retains its unperturbed dimension characteristic of its solution in a -solvent. Flory believed to have experimentally confirmed his idea [140]. By analyzing elastic neutron scattering from a mixture of linear protonated and deuterated polyisobutylene with a molecular weight of 48,000+ 3,000 Da, he found that the gyration radii of the macromolecules... 

Up to this time, it has not been possible to compare the results of experimental studies of elastic small angle neutron scattering (SANS) from polymer networks with labeled crosslinks with theoretical treatments of this scattering. This problem existed because polymer networks are essentially infinite in extent and an infinite sample is expected to... 

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. 

The parameters of neutron scattering theory of polymer networks are A, the macroscopic stretching of the sample, or linear degree of swelling, f, the network functionality, K. which accounts for restricted junction fluctuations and a, a measure of the degree to which chain extension parallels the macroscopic sample deformation. The functionality is known from knowledge of the chemistry of network formation, and A is measured. Both K and a must be extracted from experiments. 

---