Macromolecules, Vol.28, No.20, 6860-6864, 1995
Small-Angle Neutron-Scattering Study on End-Linked Poly(Tetrahydrofuran) Networks
The relationship holding between the degree of polymerization between cross-links, N, the volume fraction at swelling equilibrium, phi, and the correlation length, xi, for end-linked poly(tetrahydrofuran) (PTHF) networks having a fairly narrow molecular weight distribution was studied by swelling and small-angle neutron scattering (SANS) experiments. A scaling rule, phi similar to N--0.74, was obtained for the PTHF networks swollen in toluene. This result agrees with the scaling prediction, phi similar to N-blob(-4/5), for semidilute polymer solutions, where N-blob is the degree of polymerization for a subchain in a blob. SANS spectra from PTHF networks swollen in deuterated toluene indicated the presence of two types of concentration fluctuations, i.e., solution-like fluctuations characterized by the correlation length, xi, and solid-like fluctuations due to screening breakdown of cross-links. xi was found to be given by xi similar to N-0.59. This led to xi similar to phi(-0.79), which was also in good agreement with the scaling prediction (xi similar to phi(-3/4)).