Above are listed many common polymers, the basic type of polymerization to produce them, and some of their uses.
Inaddition polymerization, polymers are formed through the addition of monomers, without any byproducts. There are many different types of addition polymerizations, including free-radical and ionic.
Incondensation polymerization, when the monomers join together, byproducts are produced, such as water or hydrochloric acid. Condensation polymerization is a form of step-growth polymerization.
Copolymerization is when two or more different monomers join together to form a polymer. Any type of polymerization has the potential to produce a copolymer, as long as two different monomers are used.
A skin-like polymeric material is using carbon nanotubes (CNTs) to bring a sense of touch to robotic and prosthetic devices. Developed by researchers at Stanford University and Xerox Palo Alto Research Center, the flexible, polymeric skin or ‘digital tactile system’ (DiTact) incorporates CNT pressure sensors and flexible organic printed circuits to mimic human response [Tee et al., Science 350 (2015) 313].
‘‘We wanted to make a sensor skin that communicates in the same way as the body,’’ explains research student Alex Chortos, one of the lead authors of the work. ‘‘The goal is to make skin for prosthetics that can feel touch in a natural way and communicate that information to the person wearing the prosthetic device.’’
In the body, receptors in the skin relay sensing information directly to the brain in a series of voltage pulses rather like Morse code. Artificial devices employ tactile sensing to improve the control of neuroprosthetics and relieve phantom limb pain. But, to date, prosthetic skin devices have had to use a computer or microprocessor to turn the output from sensors into a signal compatible with neurons.
The new approach, by contrast, combines these operations in a single system of piezoresistive pressure sensors embedded in a flexible circuit layer. The sensors are made from a CNT composite dispersed in a flexible polyurethane plastic and molded into pyramidal structures. The pyramidal shape is crucial because it allows the pressure range of the sensor to be tuned to that of skin.
Self-compacting high-performance concrete (SCHPC) has till now suffered from one weakness: when exposed to fire it flakes and splits, which reduces its loadbearing capacity. Empa scientists have now developed a method of manufacturing fire-resistant self-compacting high-performance concrete which maintains its mechanical integrity under these conditions.
Wood crackles as it burns in a chimney or campfire. When concrete is exposed to fire it chips and flakes – a process known as spalling. Both effects are due to the same phenomenon: water trapped within the piece of wood or concrete element vaporizes due to the high temperature. As more water vapour is produced the pressure within the wood or concrete structure increases. In wood this causes the cells to burst with a crackling sound, creating cracks in the logs. In concrete structures, chips split away from ceilings, walls, and supporting pillars, reducing their loadbearing capacity and increasing the risk of collapse in a burning building.
The resistance of conventional vibrated concrete to the heat of a fire can be optimized by adding a few kilograms of polypropylene (PP) fiber per cubic meter of concrete mixture. When exposed to fire the fibers melt, creating a network of fine canals throughout the concrete structure. These allow the water vapour to escape without increasing the internal pressure, so the concrete structure remains intact.
What has chemistry ever done for me, you might ask? Just as Dustin Hoffman was told by one of his would-be mentors in The Graduate, one answer is plastics – one of the greatest chemical innovations of the 20th century.
Most plastic items are made of chemicals such as polyethylene (PET), polypropylene (PP), polyurethane, or polyvinylchloride (PVC) which are all derived from oil. These monomers are obtained industrially from the fractional distillation of crude oil, and polymerised in great quantities with catalysts in a process developed in the 1950s and 60s. Chemists Karl Ziegler and Giulio Natta shared the 1963 Nobel Prize in Chemistry for their titanium catalyst process, which for cost-effectiveness has yet to be bettered.
So the industrial feedstocks and methods of manufacturing plastics have not changed significantly for more than 60 years. But the situation has: oil is harder to come by and (usually) more expensive, and environmental pressures are growing. If we want to keep plastics, we will need to find new ways of making them.
Both an important mineral for health as a solid but poisonous as a gas, sulfur usually conjures up vivid images of fire, volcanoes and, through its archaic name brimstone, even hell itself. But in fact sulfur is a waste product from many industrial processes and could be an alternative to oil from which to manufacture plastics.
For all the good they do, eye drops and ointments have one major drawback: It’s hard to tell how much of the medication is actually getting to the eye. Now in a study appearing in ACS Applied Materials & Interfaces, scientists report that they have developed a contact lens that changes color as drugs are released. This visual indicator could help eye doctors and patients readily determine whether these medications are where they should be.
Eyes are adept at keeping things out. When something ventures into or toward an eye, the lids blink and tears start rapidly flowing to avoid infection and damage from foreign objects. These processes are usually helpful, but they can hinder the uptake of much-needed medications. Studies suggest that less than 5 percent of drugs in eye drops and ointments are absorbed, and much of the absorbed medication ends up in the bloodstream instead of the eye, causing side effects. Contact lenses may be a more effective way to deliver drugs directly to the eye, but real-time monitoring of drug release is still a challenge. So Dawei Deng and Zhouying Xie sought to create a drug-delivering contact lens that would change color as the medication is released into the eye.
You can now 3D print lithium-ion batteries in any shape.
Lithium-ion batteries are normally either cylindrical or rectangular shaped, which forces manufacturers to dedicate a certain size and place for the battery in its design. This way of making electronic devices such as laptops and mobile phones may cause a waste of both space and options to branch out with design.
InACS Applied Energy Materials, researchers present their method of 3D printing which can create the whole structural device, including the battery and with all the electronic components – in almost any shape.
Since the polymers used for printing, like poly(lactic acid) (PLA) are not ionic conductors, the researchers infused PLA with an electrolyte solution as well as adding graphene into the anode or cathode to boost the battery’s electrical conductivity.
Showing the capacity of the printed battery, the team printed a bracelet with an integrated battery. As of now, the battery could only power the green LED for approximately 60 seconds – making the battery circa two orders of magnitude lower than already commercially available batteries. Although this makes the battery capacity too low to use at the moment, the researchers have multiple ideas to fix the low capacity such as, replacing the PLA materials with 3D printable pastes.
Recipes for three-dimensional (3D) printing, or additive manufacturing, of parts have required as much guesswork as science. Until now.
Resins and other materials that react under light to form polymers, or long chains of molecules, are attractive for 3D printing of parts ranging from architectural models to functioning human organs. But it’s been a mystery what happens to the materials’ mechanical and flow properties during the curing process at the scale of a single voxel. A voxel is a 3D unit of volume, the equivalent of a pixel in a photo.
Now, researchers at the National Institute of Standards and Technology (NIST) have demonstrated a novel light-based atomic force microscopy (AFM) technique – sample-coupled-resonance photorheology (SCRPR) – that measures how and where a material’s properties change in real time at the smallest scales during the curing process.
20 years ago, Stephanie Kwolek became only the fourth woman to enter the US National Inventors Hall of Fame, 30 years after she first synthesised a material for the purpose of making strong but light tyres.
That material is now used in more than 200 different applications. It protects undersea optical cables, suspends bridges with ultra-strong ropes and creates super-taut drumheads. But Kevlar is perhaps best known for saving countless lives as a protective material in bulletproof vests and helmets.
Kwolek, a chemist at American company DuPont, created a solution of para-phenylenediamine and terephthaloyl chloride in 1965 that was ‘cloudy, opalescent upon being stirred and of low viscosity’. Polymer solutions are normally syrupy, but Kwolek’s was thin and watery.
DuPont technician Charles Smullen refused to run the solution through a spinneret, the apparatus used to spin a polymer solution into a fibre, saying it was too watery and interpreting the opalescence as particles that would clog the machine. Thankfully, Kwolek was persistent, and Smullen agreed to spin the fibre.
‘We spun it, and it span beautifully,’ Kwolek beamed in a 2012 interview. ‘It was very strong and stiff – unlike anything we had made before. I knew that I had made a discovery. I didn’t shout “Eureka!” but I was very excited, as was the whole laboratory excited, and management was excited, because we were looking for something new. Something different. And this was it.’
The high tensile strength-to-weight ratio of Kevlar is five times that of steel. When layered together, it can absorb the velocity of shrapnel or a bullet, distributing its force across the fibres instead of being pierced. It is used in tennis rackets, skis, boats, ropes and cables and, as first intended, in tyres.
Kwolek, who also developed the nylon rope trick classroom demonstration, died in 2014 at the age of 90, having lived to see her invention take more forms than she could have possibly anticipated. Kwolek’s was a rare discovery with perhaps the most rewarding property a material can possess. As she put it, ‘I don’t think there’s anything like saving someone’s life to bring you satisfaction and happiness.’
For my final line-up I would love to use some smart fabrics and after having a look around I found a lot that I think would be great to use.
Temperature sensitive fabrics Clothings main job is to keep up warm or cool so it makes sense that the smart material industry is looking into making fabrics that can regulate body temperature. These types of fabrics are mostly seen in windbreakers and beanies. Junor Campbell design and development manager for Mountain Designs says its hats, beanies and jackets are often treated with paraffins.“Paraffin changes its character. As you get hot it becomes more liquid and all that heat to pass out,” says Campbell. “As the body gets cold it solidifies and keeps heat back with the wearer.” Other fabrics that are also starting to appear are ones that conduct electricity to monitor your body temperature but because they are still so new they are very expensive but one company that wants to launch in this market with a more reasonable price range, Australian Wool Innovators, want to make socks that will be able to keep your toes toastie at 30 degrees centigrade but also feel like any other sock and being washable.
Odour Eaters There are also fabrics that are being developed that are suited for more health reasons, fabrics with anti-bacterial treatments. Materials that are treated with silver seem to be working best and the garment that seems to be best for this type of fabric is underwear, you can treat underwear with anti-bacterial but it washed out but they have found that if it has silver added to it, the same effect happens but it is permanent. Microencapsulation technology, which allows a whole swathe of substances including aloe vera, vitamins or insect repellents to be added to the fabric, is creating endless possibilities.
Medical Material Microencapsulated fabrics is best for medical treatments, mainly in the natural health sector. Materials with vitamin E are great for scarring and theres also a good market in materials for diabetes and improving circulation. There has been development in smart fabrics called bio-therapeutic textiles where they look to isolating the chemical properties of gold fly maggots that are known to combat wound infection, this could be extremely useful when it comes to dressings and bandages. For electrically conductive smart fabrics there is a much greater medical use, for example, in hospitals they could be used to create life vests that would monitor your heart rate, ECG and body temperature and you could have every patient wearing one with the results all going back to the nurses in a central office to be monitored. Though it would be a very long time until this could be seen as a reality because this type of technology is still extremely expensive.
Before and after comparisons don’t tell the full story of chemical reactions in flowing fluids, such as those in a chemical reactor, according to a new study from a collaboration based in Japan.
The researchers published their paper on May 6 in the Journal of Physical Chemistry B, a journal of the American Chemical Society. The results were featured on the journal’s cover.
The team examined how a solution of dissolved polymers changed after the addition of Fe3+ solution. These types of solutions are used to better control variables in several fields, including manufacturing. In automobile manufacturing, for instance, the solutions help achieve a thorough evenness of paint coverage and control over how much a material expands or contracts under various temperatures.
Traditionally, researchers examine a solution before a reactant, such as Fe3+solution, is added, and again after the reaction takes place.
One-dimensional nanomaterials with highly anisotropicoptoelectronic properties can be used within energy harvesting applications, flexible electronics and biomedical imaging devices. In materials science and nanotechnology, 3-D patterning methods can be used to precisely assemble nanowires with locally controlled composition and orientation to allow new optoelectronic device designs. In a recent report, Nanjia Zhou and an interdisciplinary research team at the Harvard University, Wyss Institute of Biologically Inspired Engineering, Lawrence Berkeley National Laboratory and the Kavli Energy Nanoscience Institute developed and 3-D printed nanocomposite inks composed of brightly emitting colloidal cesium lead halide perovskite (CsPbX3, where X= Cl, Br, or I) nanowires.
They suspended the bright nanowires in a polystyrene-polyisoprene-polystyrene block copolymer matrix and defined the nanowire alignment using a programmed print path. The scientist produced optical nanocomposites that exhibited highly polarized absorption and emission properties. To highlight the versatility of the technique they produced several devices, including optical storage, encryption, sensing and full color displays. The work is now published on Science Advances.
A category of polymers technically defined as any polymer which contains a sulfonyl group, the term polysulfone is actually most often used in reference to polyarylethersulfones, in which the following structure is present: aryl-SO2-aryl. These polymers are thermoplastics, and known for their toughness and stability at high temperatures.
Polysulfones are amorphous polymers typically prepared through condensation polymerizations and are rigid and high-strength. They stand up well in high-pressure environments and are often considered to be high-performance polymers. These polymers are often semi-transparent and resistant to creep and deformation at high temperatures under continuous loads.
These polymers are fairly uncommon, due to the relatively high costs of production and the raw materials involved, and as such applications of polysulfones tend to be highly specialized. Because of their high service temperatures, they are sometimes used as flame retardants, or in medical applications requiring autoclave or steam sterilization. Another common application is in the form of membranes, with controllable poor sizes.
Artificial muscles made from polymers can now be powered by energy from glucose and oxygen, just like biological muscles. This advance may be a step on the way to implantable artificial muscles or autonomous microrobots powered by biomolecules in their surroundings. Researchers at Linköping University, Sweden, have presented their results in the journal Advanced Materials.
The motion of our muscles is powered by energy that is released when glucose and oxygen take part in biochemical reactions. In a similar way, manufactured actuators can convert energy to motion, but the energy in this case comes from other sources, such as electricity. Scientists at Linköping University, Sweden, wanted to develop artificial musclesthat act more like biological muscles. They have now demonstrated the principle using artificial muscles powered by the same glucose and oxygen as our bodies use.
The researchers have used an electroactive polymer, polypyrrole, which changes volume when an electrical current is passed. The artificial muscle, known as a “polymer actuator,” consists of three layers: a thin membrane layer between two layers of electroactive polymer. This design has been used in the field for many years. It works when the material on one side of the membrane acquires a positive electrical charge and ions are expelled, causing it to shrink. At the same time, the material on the other side acquires a negative electrical charge and ions are inserted, which causes the material to expand. The changes in volume cause the actuator to bend in one direction, in the same way that a muscle contracts.
In a paper to be published in a forthcoming issue of Nano, a team of researchers from Henan University have investigated the flame retardant performance of epoxy resin using a boron nitride nanosheet decorated with cobalt ferrite nanoparticles.
Polymers are widely used in our daily lives due to good physical and chemical stability, corrosion resistance and other superior properties. However, most polymers, due to their organic nature, are inherently flammable which is a potential threat to the safety of human life and property. In order to avoid or reduce the flammability of polymers, it is a good strategy to add flame retardants to the polymers.
Among them, two-dimensional (2-D) layered inorganic nanomateirals (nanosheets), represented by graphene oxide,molybdenum disulfide, and boron nitride nanosheets (BNNS), exhibit excellent flame retardant performance due to their good physical barrier effects. However, the flame retardance is not enough in the use of such 2-D inorganic flame retardants alone, and in particular, the ability to suppress toxic gases and smoke is weak.
The research team of researcher Hyunseon Seo and senior researcher Dr. Donghee Son of the Korea Institute of Science and Technology’s Biomedical Research Institute, postdoctoral candidate Dr. Jiheong Kang and Professor Zhenan Bao of Stanford University (chemical engineering) announced a new material with high stretchability and high electrical conductivity, with the ability to self-heal even after being subjected to severe mechanical strain. The material could have application in wearable electronic devices.
Prior to this study, Dr. Donghee Son, Dr. Jiheong Kang, and Prof. Zhenan Bao developed a polymer material that is highly elastic, can self-heal without the help of external stimuli even when exposed to water or sweat, and has a mechanical strength similar to that of human skin, making it comfortable to wear for long periods of time.
In its most recent study, the KIST-Stanford research team developed the new material, which can be used as an interconnect, as it has the same properties as existing wearable materials and high levels of electrical conductivity and stretchability, characteristics which allow the stable transmission of electricity and data from the human body to electronic devices.
Composite materials are increasingly popular. One of the primary composite materials for modern structures is glass fiber reinforced plastic (GFRP), which is commonly used in aviation, modern transport and wind power plants. Scientists of South Ural State University have carried out extensive studies of ballistic properties of GFRP to improve the efficiency of its use.
GFRP is relatively cheap and has high strength. However, practically all well-known results regarding ballistic characteristics of GFRP do not take into account various loads occurring when operating the structures or consider comparatively low-impact loading speeds. At the same time, a more frequently encountered problem is impacts at high speed. The team of scientists from SUSU’s Institute of Engineering and Technology have determined ballistic characteristics of glass fiber reinforced plastic under exposure to operational loads at a high speed of impact loading.
“Often, noses of modern trains, which are produced out of composite materials, are exposed to impacts during the train’s movement. We have studied the influence of the impact force on a plate made of composite material under the normal operational load. We stretched the sample, creating a strained condition, and then determined its ballistic properties in an impact,” says one of the project authors, Mikhail Zhikharev.
The group at Polymeric Materials has developed a simple way to regulate both dispersity and sequence in highly complex multiblock copolymers, and the results have been published in Nature Chemistry.
Controlling monomer sequence and dispersity in synthetic macromolecules is a major goal in polymer science as both parameters determine materials’ properties and functions. However, synthetic approaches that can simultaneously control both sequence and dispersity remain experimentally unattainable.
In this contribution from the group at Polymeric Materials we present a simple, one pot and rapid synthesis of sequence-controlled multiblocks with on-demand control over dispersity while maintaining a high livingness, and good agreement between theoretical and experimental molecular weights and quantitative yields.
Introducing a simple step to the production of plant-derived, biodegradable plastic could improve its properties while overcoming obstacles to manufacturing it commercially, says new research from the University of Nebraska-Lincoln and Jiangnan University.
That step? Bringing the heat
Nebraska’s Yiqi Yang and colleagues found that raising the temperature of bio-plastic fibers to several hundred degrees Fahrenheit, then slowly allowing them to cool, greatly improved the bio-plastic’s normally lackluster resistance to heat and moisture.
Its thermal approach also allowed the team to bypass solvents and other expensive, time-consuming techniques typically needed to manufacture a commercially viable bio-plastic, the study reported.
Yang said the approach could allow manufacturers of corn-derived plastic – such as a Cargill plant in Blair, Nebraska – to continuously produce the biodegradable material on a scale that at least approaches petroleum-based plastic, the industry standard. Recent research estimates that about 90 percent of U.S. plastic goes unrecycled.
This year’s latest Nobel Prize winners have been announced, as scientists and researchers across the world are recognised for their outstanding discoveries.
The winner for chemistry category went to 3 researchers for improving the resolution of optical microscopes. Eric Betzig, Stefan Hell and William Moerner used fluorescence to extend the limits of the light microscope.
While the Nobel Prize for Physics celebrated their success for the invention of blue light emitting diodes (LEDs) made in the early 1990s.
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