Abstract: The inventive composition first is highly viscous, remaining in place when administered to a patient. Then it decreases in viscosity and liquefies, facilitating easy removal, after a period of time ranging from minutes to weeks, such as after a change in temperature or other trigger; or after another component is added to cause liquefaction. Such compositions have many different medical uses, optionally with a treating agent contained in, or held in place by, the composition, such as, without limitation, prevention or reduction in scarring or adhesions after surgery involving the uterus or other body or organ cavities or other sites, by keeping raw areas of the tissue or tissue walls separated from each other during healing; delivery or retention of treating agents in body or organ cavities or other sites of administration; protection of wounds, burns, and other injuries; and holding tissue grafts in place. Even cosmetic uses are available.