Macromolecules, Vol.53, No.10, 4047-4054, 2020
Quantitative Structure Analysis of a Near-Ideal Polymer Network with Deuterium Label by Small-Angle Neutron Scattering
Partially deuterated poly(ethylene glycol) (PEG) networks were fabricated by cross-linking a protonated four-arm PEG prepolymer (4hPEG) with a deuterated linear PEG (2dPEG) via a cross-end-coupling reaction. The structure of the resulting partially deuterated 4h-2dPEG networks and the corresponding non-cross-linked polymer solutions, i.e., a mixture of 4hPEG and 2dPEG homopolymers, was investigated in D2O solvent by small-angle neutron scattering (SANS) in a contrast-matched condition. The observed SANS profiles were analyzed with an extended random phase approximation (RPA) model, where the RPA theory was expanded for three-component multiarm star block copolymer systems, e.g., 4hPEG, 2dPEG, and solvent. A correlation-hole peak was exclusively observed in 4h-2dPEG gels but not in solutions of the homopolymer mixture of 4hPEG and 2dPEG. The extended RPA theory well reproduced the scattering profiles of both gels and polymer solutions. The Flory interaction parameter between PEG and water and the segment length of PEG were in good agreement with literature values. In addition, the behavior of the theoretical scattering function of the partially labeled multiarm star block copolymer was examined with respect to the fraction of polymer volume, the fraction of protonated chains in the star block copolymer, and the Flory interaction parameter between polymer chains and solvent molecules.