polymer chemistry

Demonstrating the Glass Transition of Polylactic Acid with a Rattle

Polylactic acid (PLA) exhibits a glass transition from hard and brittle to soft and rubbery when immersed in boiling water. PLA-based structures containing a small metal object can be used as rattles when they are shaken. The sound of the rattles change when they are heated above or cooled below their glass transition, enabling them to be used as demonstrations.

Laser-Cutting CDs into Snowflakes

Laser cutters can be used to cut and engrave a variety of thin materials. Compact discs, composed of layers of polycarbonate plastic and aluminum metal, were explored for their ability to be shaped with a laser cutter. The laser can successfully cut and engrave the compact discs into the shape of snowflake. However, each disc must first be coated with a material like glue in order to protect the plastic from discoloration and the byproducts from cutting the plastic that can accumulate on the disc surface.  

Surprising Shrinking Styrofoam Stick: Using the Gas Laws to Get a Square Peg into a Round Hole

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.

A Visit to Natural Fiber Welding: Demonstrating Green Chemistry in Action

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. 

A Polystyrene Model of Polystyrene Tacticity

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.

Microplastics, Liquid Nitrogen, and Iodine: Polystyrene vs. Starch Foam Packing Peanuts

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.

Surveying Litter as a Citizen Science Chemistry Activity

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.

How Chemistry Helped Batman: Kevlar - A short review

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.