The disclosure provides a synthetic polymer that mimics the passive absorption kinetics of the human intestinal tract. More particularly, disclosed is a silicone-based polymer, e.g., poly(dimethyl siloxane), poly(dimethyl silicone) and poly siloxane, that meets the requirements of a robust, semipermeable, and in vivo-relevant membrane for use in an in vitro method for measuring the absorption of a chemical compound, such as a therapeutic, e.g., a small-molecule or a biologic, that can be expected to reflect the absorption properties of the chemical compound in the vertebrate gastrointestinal tract, thereby providing an assessment of absorption of the compound in the vertebrate GI tract.
