What is a polymer?
Polymers are materials made of long, repeating chains of molecules.
Materials have unique properties, depending on the type of molecules that are linked and how they are linked. Some polymers bend and stretch, such as rubber and polyester. Others are hard and resistant, such as epoxies and glass.
Polymers touch almost every aspect of modern life. Chances are, most people have been in contact with at least one product containing polymers—from water bottles to gadgets to tires—in the last five minutes.
Polymer
Polymer, any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, that are multiples of simpler chemical units called monomers.
Polymers make up many of the materials of living organisms, including, for example, proteins, cellulose, and nucleic acids.
In addition, they constitute the base of minerals such as diamond, quartz and feldspar and of artificial materials such as concrete, glass, paper, plastics and rubber.
The term polymer is often used to describe plastics, which are synthetic polymers.
However, there are also natural polymers; Rubber and wood, for example, are natural polymers consisting of a simple hydrocarbon, isoprene, according to the Encyclopedia Britannica.
Proteins are natural polymers made up of amino acids, and nucleic acids (DNA and RNA) are polymers of nucleotides – complex molecules made up of nitrogen-containing bases, sugars, and phosphoric acid, for example.
Polymer uses
Polymers are used in almost all areas of modern life. Grocery bags, water and soda bottles, textile fibers, phones, computers, food packaging, auto parts, and toys all contain polymers.
Even more sophisticated is the technology that uses polymers. For example, «membranes for water desalination, carriers used in controlled drug release, and biopolymers for tissue engineering all use polymers,» according to the ACS.
The most popular polymers for manufacturing include polyethylene and polypropylene. Its molecules can consist of 10,000 to 200,000 monomers.
future of polymers
Researchers are experimenting with many different types of polymers, with the goal of furthering drug development and improving the products we already use.
For example, carbon polymers are being developed and improved for the automotive industry.
«Carbon fiber reinforced polymer (CFRP) composites – also called carbon fiber laminates – are the next generation materials for making cars lighter, more fuel efficient and safer.»
According to a 2016 Live Science column by Nikhil Gupta, an associate professor, and Steven Zeltmann, a research student.
Both in the Composite Materials and Mechanics Laboratory in the Department of Mechanical and Aerospace Engineering at New York University’s Tandon College of Engineering.
«Carbon layup is extremely strong and rigid due to its woven layers of nearly pure carbon fibers held together by a hardened plastic, such as epoxy resin.»
Polymers are also used to enhance holograms. Scientists at the University of Pennsylvania created a hologram on a flexible polymeric material called PDMA that was embedded with gold nanorods.
According to a study published online in early 2017 in the journal Nano Letters. This new holographic device can hold multiple images instead of just one.
«The question we asked is, ‘Can we encode multiple bits of information in a hologram?'» Ritesh Agarwal, research leader and professor of materials science and engineering at the University of Pennsylvania, told Live Science.
«It’s important work, because it’s the first time anyone has shown you that you can record multiple holographic images, and just by stretching the polymer, you can basically change the image.»
Artificial skin made from a silicone polymer may be the future of antiaging efforts.
In the form of two creams, the polymer may be able to tighten a person’s skin, reduce the appearance of wrinkles and diminish bags under the eyes, according to a study published in May 2016 in the journal Nature Materials.
Such artificial skin can also be used to help people with skin conditions, such as eczema, or used as a sunscreen.
«We’re excited; it’s a totally new material,» study co-author Robert Langer, a professor at the Massachusetts Institute of Technology, told Live Science.
The structure of polymers
Many common classes of polymers are composed of hydrocarbons, compounds of carbon, and hydrogen.
These polymers are specifically made of carbon atoms linked together, from one to another, in long chains that are called the backbone of the polymer.
Due to the nature of carbon, one or more atoms may be attached to each carbon atom in the backbone.
There are polymers that only contain carbon and hydrogen atoms. Polyethylene, polypropylene, polybutylene, polystyrene, and polymethylpentene are examples.
Polyvinyl chloride (PVC) has chlorine bonded to the carbon backbone. The Teflon has fluorine bonded to the carbon backbone.
Other common manufactured polymers have backbones that include elements other than carbon. Nylons contain nitrogen atoms in the backbone of the repeating unit.
Polyesters and polycarbonates contain oxygen in the backbone. There are also some polymers that, instead of having a carbon backbone, have a silicon or phosphorous backbone. These are considered inorganic polymers.
Depending on the desired use, polymers can be tuned to take advantage of certain advantageous properties.
These include
reflectivity: Some polymers are used to produce reflective film, which is used in a variety of light-related technologies.
Impact Resistance: Tough plastics that can withstand rough handling are perfect for luggage, protective cases, car bumpers, and more.
Brittleness: Some forms of Styrofoam are hard and brittle, and these materials are easily deformed by heat.
Translucency: Transparent polymers, including polymer clay, are often used in arts and crafts.
Ductility: Unlike brittle polymers, ductile polymers are those that can be deformed without falling apart.
Metals like gold, aluminum, and steel are known for their ductility, and ductile polymers, while not as strong, are still useful for many purposes.
Elasticity: Natural and synthetic rubbers have elastic properties that make them ideal for automobile tires and other products.
Polymer characteristics
Most manufactured polymers are thermoplastic, which means that once the polymer is formed, it can be heated and reformed over and over again.
This property allows for easy processing and facilitates recycling. The other group, the thermosets, cannot be remelted. Once these polymers form, reheating will eventually cause the material to degrade, but not melt.
Each polymer has very different characteristics, but most polymers have the following general attributes.
Polymers can be very resistant to chemicals. Consider all the cleaning fluids in your house that are packaged in plastic.
Reading warning labels that describe what happens when the chemical comes into contact with the skin or eyes or is swallowed will emphasize the need for chemical resistance in plastic packaging.
While solvents easily dissolve some plastics, other plastics provide safe, unbreakable packages for aggressive solvents.
thermal
Polymers can be thermal and electrical insulators. A walk through your home will reinforce this concept as you will take into account all appliances, cords, outlets and wiring that are made of or coated with polymeric materials.
Heat resistance is evident in the kitchen with polymer handles for pots and pans, coffee pot handles, the foam core of refrigerators and freezers, insulated mugs, refrigerators, and microwave cookware.
The thermal underwear that many skiers wear is made of polypropylene, and the fiberfill in winter jackets is acrylic and polyester.
Polymers are generally very light in weight with significant degrees of strength.
Consider the range of applications, from toys to the frame structure of space stations, or from the delicate nylon fiber in pantyhose to Kevlar, which is used in bulletproof vests. Some polymers float on water while others sink.
But compared to the density of stone, concrete, steel, copper or aluminium, all plastics are lightweight materials.
Polymers can be processed in various ways. Extrusion produces fine fibers or heavy tubes or films or food bottles.
Injection molding can produce very complex parts or large body panels. Plastics can be drummed or mixed with solvents to become adhesives or paints.
Elastomers and some plastics stretch and are very flexible. Some plastics are stretched in the process to keep their shape, like soda bottles. Other polymers can be foamed like polystyrene (Styrofoam™), polyurethane and polyethylene.
Polymers are materials with a seemingly limitless range of characteristics and colors.
Polymers have many inherent properties that can be further enhanced with a wide range of additives to broaden their uses and applications.
Polymers can be made to mimic the fibers of cotton, silk, and wool; porcelain and marble; and aluminum and zinc. Polymers can also make possible products that do not easily come from the natural world, such as transparent sheets and flexible films.
Polymers are often made from petroleum, but not always. Many polymers are made from repeating units derived from natural gas or coal or crude oil.
But building block repeating units can sometimes be made from renewable materials like polylactic acid from corn or cellulosics from cotton linings.
Some plastics have always been made from renewable materials, like the cellulose acetate used for screwdriver handles and gift ribbon.
When the blocks of…