Necklace-like microstructure in shallow-quenched aqueous solutions of poly( n -isopropylacrylamide), detected by advanced small-angle neutron scattering methods

The microstructure of aqueous poly(N-isopropyl acrylamide) (PNIPA) gel and solution was investigated by small-angle neutron scattering (SANS) in the vicinity of the gel volume phase transition at TV (= 34 °C). The SANS technique was reinforced by refractive neutron lenses and perfect single crystals in order to get access to μm length scales. At 31 °C SANS shows Ornstein–Zernike (OZ) type scattering in the swollen gel which at 32 °C starts to deviate from the OZ-formalism, exhibiting excess scattering and at the wave number qc ≅ 5 × 10−3 Å−1 a crossover to Porod's asymptotic q−4 power law. For shallow quenches of ΔT 1.0 K) the globules are aggregating to larger objects of R ≅ 0.24 μm size as determined from a strong intensity upturn in the small q-region of USAN

Editorial on Special Issue “New Era in the Volume Phase Transition of Gels”

The Special Issue of gels titled “Advancements in Gel Science” has been published from MDPI in 2019 [...