MATSE 81
Materials in Today's World

What are Scientists Doing Now to Improve Polymers?

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Now that you have read about the classical usages of polymers let us take a look at two short videos that discuss two areas that scientists are working in to improve or increase the usage of polymers in our daily lives.

To Watch

The first is a video about designer polymers (3:45).

Click for the transcript of What Are Designer Polymers.

Polymers have been around for a long time. Some of the commonly named examples are found in clothes. Things like nylon, polyesters, and acrylic. Others are plastics like PVC, polyethylene, and polycarbonates. Whereas some act as coatings on saucepans like PTFE, more commonly known as Teflon. The key thing is that different polymers have different properties.

More recently, chemists have developed a branch of polymers called designer polymers. A designer polymer is one that has been designed to respond to a change in environment or uses properties that are better than traditional polymers. Nylon, a traditional polymer used to make some clothes, has desirable properties he may even wear a jacket that's made from nylon. Nylon is tough lightweight and waterproof sadly it's missing a desirable property in that it doesn't allow sweat to pass through so when the person is wearing a Garmin they can become quite uncomfortable. If only there was a way of making a material breathable able to allow the sweat to pass through without losing the waterproofing on the outside of the jacket. The answer is that designers have started to use gore-tex a design a polymer. Gore-tex uses layers of different polymers they include an outer layer typically made from nylon or polyester. This makes the outer layer strong inner layers are made from polyurethane and miss provides water resistance.

Other membranes are made of PTFE which has millions of holes. These holes are small enough to allow the water vapor or sweat to pass out but does not allow larger water droplets from the outside to pass into the soft lining. Designer polymers come up in many everyday situations. Contact lenses, the traditional polymer PMMA, did not allow oxygen to pass through and touch the eye. This is because no blood visits the cornea this would block your vision. Therefore, all of the oxygen needed for the cells comes from the air. It was rigid and uncomfortable and the cells were starved of oxygen. How do you think the design of this polymer was improved? Pause and continue when you're ready.

The answer is the polymer used now is a special hydrogel. It's more flexible, softer, and is breathable. This improves the health of the eye to fillings. If you have a traditional filling the chances are it is made of silver amalgam this looks false as it contrasts against the tubes natural color. Designer polymers use a composite polymer resin which is tough, contains no dangerous chemicals like the mercury metal found in your tradition of silver amalgam fillings. The designer polymer can be matched at the tooth's natural color it's a photopolymer and when treated with lights will harden and match the color of the tooth. In summary, a designer polymer is one that has been designed to respond to a change in environment or uses properties that are better than the traditional polymers.

Some examples of these minor polymers include breathable clothing made from gore-tex, hydrogels found in contact lenses, in babies nappies, and finally tooth fillings.

 

The second video (4:28) is about research into how to make flexible and lightweight electronics.

Click for the transcript of Plastic Electronics: Inventing the Future.

Plastic electronics are electronic devices in which the active components are made out of carbon-based materials. So these are plastics, or polymers, or small molecules and the reason you want to make plastic electronics is because you want to make use of the attributes of these plastic materials. These include their mechanical flexibility, they're lightweight, they can be produced with tunable properties, and this is something you can't easily do with inorganic materials. My name is Yu Lin Lieu and I work in the field of plastic electronics.

In the field of plastic electronics, it all starts with chemistry. We need to make or synthesize new materials that are conductive or semiconductive, so they have the electrical properties that we would like so that when we incorporate them into electronic devices they're active. So in our group, some of the researchers make new materials, some of the researchers characterize the structures are these materials, and some other incorporate these materials to understand their potential in applications like transistors and solar cells.

Polyaniline is a conducting polymer that changes color. In here, this color change is triggered by applying a voltage to the sample. So the potential applications for polyaniline, in addition to being electrodes, we can use it as electrochromic displays, as well as sensors that change color when exposed to a specific chemical or reagent.

We use a process called spin coating to make thin layers of these compounds. The layers end up to be about a hundred nanometers thick that's about a thousand times thinner than my hair.

Here we examine the films we make under the microscope to see how the crystals grow during spin coating. We try to control the size of the crystals in the film. The bigger the crystals, the better the devices will turn out.

To make devices, we have to make electrical contact to the film by evaporating gold. Gold is evaporated through a mask. The pattern of the mask determines where gold is cooled. After the placement of a mask, we put the sample in the gold evaporator. Alternatively, we can evaporate gold electrodes on a clear silicone rubber-stamp, and laminate the rubber stamp onto the polymer film to make our devices. The structure of the devices depends on their function. In my opinion, their beauty derives from their functionality. Compared to inorganics like silicon, classics had unique attributes which include their lightweightness and their mechanical flexibility, their potential in their tunability in terms of their properties and soon to incorporate all these attributes into electronic devices would be really nice.

Well, the field's really exciting because it's a young field and it's growing and it's directly tied to applications that can have direct implications on the quality of our lives. Imagine electronic wallpaper that changes patterns from green stripes to pink polka dots at a click of a switch. Imagine tinted windows that can also generate power during the day. Imagine disposable sensors that would change color if the water sources contaminated or yet think of smart plastic patches that can monitor your health and deliver medication when you're sick. The possibilities are endless.

Now that you have finished these videos please proceed to the next page of our course which will introduce the video for this lesson, Plastics: The Secret Life of Materials. This video will tie together the history, concepts, and usages of polymers that we have been discussing in this lesson, as well as, highlight some possible future usages of plastic.