Polystyrene foam sticks with a square or rectangular profile will not fit into a round target hole (e.g., the opening of a soda bottle) at room temperature. However, they do contract sufficiently in contact with liquid nitrogen to fit into the hole and produce a simple demonstration of Charles’s Law. Many other polymer foams do not shrink under these conditions, but still provide opportunities to discuss and explore their structure and chemistry.
The theme to the 2022 National Chemistry Week, observed October 16-22, is “Fabulous Fibers: The Chemistry of Fabrics”. A visit to Natural Fiber Welding, Inc. in Peoria, IL, revealed how that company is using ionic liquids to solvent weld cellulose fibers together to produce more durable yarn which can then be made into more durable fabric. The production method and “greenness” of the product is discussed, from the cellulose itself to the recycling of the solution used in the welding process. Macroscopic demonstrations of the fiber solvent welding process are also described.
Why does the "Whoosh Bottle" experiment behave differently at different temperatures?
Thin sheets of polystyrene can be patterned with permanent markers to represent repeating units of the polymer and then shrunk down in size using heat. The shrunken models of the repeating units can be connected with a string and then flipped into positions to demonstrate different types of polymer tacticity.
The differing electrostatic and solubility properties of starch and polystyrene foam packing peanuts are used in various demonstrations to describe aspects of microplastics and their interactions with the environment. Their differing responses to exposure to liquid nitrogen and iodine solutions are also described.
During the last few semesters, a small survey has been deployed at Bradley University where students were to describe and classify items of litter that they found. The purposes of the surveys were to get students thinking about some of the chemical implications of solid waste and give the students some experience with a citizen science project. The most recent iteration of the survey, and some of its results, are described.
The solution to Chemical Mystery #15: The Leaky Cup is shown here.
I’ve always been fascinated by advanced polymeric materials; it’s amazing how materials that are generally considered “plastics” have such stunning properties. I recently watched a couple of movies about Batman and it came out that some of his devices and protections are made of advanced polymers. In particular, the suit is almost entirely made of Kevlar.
What happens if you cool a Scrub Daddy sponge in liquid nitrogen (or dry ice) and subsequently strike it with a hammer? Let's find out!
The science behind the incredibly popular Scrub Daddy sponge is investigated. Part of the appeal of the Scrub Daddy sponge is that it changes from soft to hard depending upon temperature. This allows a single sponge to be transformed into a hard scrubber or soft sponge, depending upon the temperature of water into which it is placed.