Microscopic and macroscopic thermodynamic observations in swollen poly(dimethylsiloxane) networks

Abstract

Poly(dimethylsiloxane) (PDMS) networks swollen in toluene are investigated both by smallangle neutron scattering (SANS) and by swelling pressure measurements. The scattering signal from the gels, measured as a function of swelling, is resolved into two components, a solution-like part and a static part. The forward scattering intensity of the solution-like part contains all the thermodynamic information relevant to the gel. The absolute intensity is obtained by calibrating against that of a standard water sample. The Flory-Huggins theory of polymer solutions is adopted to derive the swelling pressure of the gel from the scattering measurements. In addition, the swelling pressure is determined independently at different degrees of dilution of the gels. A comparison is made between these direct macroscopic observations and the results deduced from the scattering intensity.

Nanoscopic Polymer Particles with a Well‐Defined Surface: Synthesis, Characterization, and Properties

“…This quantity has been measured from macroscopic networks, in which it is found to be of the order a few nanometers. [27,72] Hence, x is much smaller than the length of the entire particle. Its contribution in a scattering experiment is therefore expected to be located at larger scattering angles.…”

“…[13] Similar effects of x on the volume fraction have been found for other networks as well. [72] It may be explained by the small osmotic compressibility of more concentrated systems if no critical phenomena are present. It may therefore be stated that the PNIPA network in the shell behaves more or less like the macroscopic networks far away from a phase transition.…”

Calcium-induced volume transition in polyacrylate hydrogels swollen in physiological salt solutions

“…For gels composed of flexible polymer coils the scattering intensity can be described as a sum of dynamic and static components [10][11][12][13][17][18][19] IðqÞ ¼ I dyn ðqÞ þ I stat ðqÞ ð 5Þ…”

Small-Angle X-Ray Scattering Studies on Nucleation Formation of Dextran Precipitation in the Presence of Boron

“…For a neutral polymer such as dextran at equilibrium, the Lorentzian form describes the scattering intensity in the region z Q ≤ 1. On the other hand, due to the variations in static concentration caused by puckering of the network by the cross-links, a contribution from the regions of the sample whose movement is restricted by the cross-links must also be included, and these regions have a Gaussian spatial distribution (7). Thus, analysis of the total scattering intensity curves was performed by taking both modes into account (7):…”