Sticky situations: Thoughts on polymers in chewing gum

Can you name the only polymer that comes with baseball cards, comics and the approval of four out of five dentists?

Chewing gum has permanently stuck itself onto the face of mankind, be it pop culture – pun intended – or the list of great scientific accomplishments. After all, without the material engineering behind this polymer confection, you wouldn't even recognize the little pink blob you've grown so fond of chewing, but not swallowing.

"The molecular properties of gum's ingredients dictate its distinct profile."

What is chewing gum made of?
The ingredients in your average stick of chewing consists of two overarching traits: water-soluble versus not water-soluble. Sugars and other flavors comprise the soluble component, while the polymers remain no matter how long you chew. That's why your gum loses its flavor over time. Your saliva washes it away. The same idea applies to why a stick of gum will go from being rigid to squishy after a couple rounds of mastication.

Whatever doesn't break down in gum consists of polymers and stabilizers – additives that transform the polymer to meet certain characteristics. Like the name suggests, elastomers, the main polymer, derive their moniker from the elasticity they provide, according to the International Current Pharmaceutical Journal. Plasticizers – like natural, paraffin or fatty waxes – as well as modified resins act as stabilizers added to soften and bind the gummy compound together while also giving the substance its proper texture. Gum manufacturers also include antioxidants in the mix as a way to keep every chewy morsel from oxidizing and hardening on the shelf of your local candy shop.

The molecular properties of every component dictate the gum's distinct profile, but don't just think in terms of taste. You might be singing chewing gum's praises when you're gnawing away at your favorite brand, but what if you step in someone else's gum while walking down the sidewalk? Or get it in your hair?

We already know scrubbing doesn't help since the main ingredient to chewing gum resists water solubility. However, as LiveScience reported, scientists have engineered chewing gum polymers that can break down with water. Starting with a hydrophilic polymer that absorbs saliva helps promote a mushy, yet stable composition that will deteriorate naturally.

Science never tasted so sweet.Science never tasted so sweet.

How is chewing gum tested?
If you offer your friends sticks of gum and ask them to test it for you, chances are you won't enjoy the outcome. All you'll be left with is a giant soggy wad and a confused group of friends.

But chewing on different kinds of gum can tell you a lot about the ingredients inside. For example, size exclusion chromatography – otherwise known as gel permeation chromatography – can deduce the molecular weight distribution of a particular polymer. Why does this matter? The molecular weight of a piece of gum directly correlates to the size of the bubble a person can blow with it, according to Handbook on Size Exclusion Chromatography and Related Techniques. As the molecular weight of the polymer increases, the tougher the bonds within. Bubble gum bubbles can be blown bigger and bigger, while the thinly-stretched polymer resists the urge to pop.

SEC can also explain the effects chewing gum has on you and your mouth. Purdue University states polymers consist of long molecular chains comprised of thousands upon thousands of shorter, repeating units or monomers. However, within the network of long-chain polymers, there will also be oligomers, chains consisting of just a few monomers.

Polymer Solution's Senior Project Manager Beth Caba and her team experimented with SEC methods to discover the nature of how oligomers move from chewing gum into a person's saliva. The results were successful on many different levels.

"The in vitro portion of the study, conducted with a chewing machine, was pretty uneventful," she said. "The in vivo portion of the study, conducted with volunteers from PSI, was pretty memorable."

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