Newsflash

The drive for lightweight materials to reduce overall cost and environmental impact for automotive manufacturers is nothing new.  Fuel economy attracts car buyers too. That is how majority of steel parts have been replaced in F-150 pickup truck by aluminum parts, reducing overall weight over 500 pounds. Then there are alloys, carbon fiber and plastics composites.The ambition for lighter vehicles did not stop with alloys (magnesium, aluminum), and/or composites (glass, carbon fibers).  Recently, Japanese researchers at Kyoto University led by Professor Hiroaki Yano along with its industrial partners (Denso Corporation and Daikyo-Nishikawa Corporation) reported that they were developing cellulose nanofiber based materials for automotive as well as aircraft parts to reduce environmental footprint while increasing product performance.Inevitable questions are: 1) would these materials be cost effective? 2) What would be the service life of these products compared to the current ones? 3) How about the parts’ safety in situations like crash or fire?A final question that an automaker has to ask is: what would be the pay back time to replace current production line (machinery) to CNF based plastics line?Reference: https://www.japantimes.co.jp/news/2017/08/15/business/researchers-japan-use-wood-make-cellulose-nanofiber-auto-parts-stronger-lighter-metal/#.WbAIKeTXuUm...
We know polycarbonates mostly from its use in plastics water bottles, safety goggles, smart phones, structural panels (glazing) and the list goes on.  A quick look at Wikipedia gives a spectrum of applications.However, polycarbonates have its weaknesses along with the BPA (bis-phenol) controversy. Polymers such as polysulfates and polysulfonates have similar if not better mechanical properties than polycarbonates.  The issue has been how reliably scale-up the manufacturing process of polysulfates and polysulfonates?“Click chemistry” is a concept in organic chemistry by which highly reactive reactions provide high yielding products and require little to no purification.  The concept was introduced by Nobel Prize winner Professor K. Barry Sharpless in 2001.A recent work published in Nature Chemistry, by a team of researchers from The Scripps Research Institute (La Jolla), Lawrence Berkley National Laboratory (Berkley), California and Shanghai Institute of Organic Chemistry & Soochow University, China claimed that reduced cost of catalyst, product purity, and by-product recycling make their work ready to move from laboratory research to industrial process.Chemists are at work indeed!References:https://en.wikipedia.org/wiki/PolycarbonateK. Barry Sharpless et al; Nature Chemistry, 2017 DOI: 10.1038/nchem.2796...
In a recent The Atlantic interview Bill Gates made a wish on an energy miracle, “Here’s a source of energy that is cheaper than your coal plants, and by the way, from a global-pollution and local-pollution point of view, it’s also better”.  The race is on to find that source. One such energy source is solar energy. We all know that solar energy can be harnessed to generate thermal energy or electrical energy for use in the residential and/or in the commercial applications.  Any material that can store Solar Thermal Energy is called Solar Thermal Fuel (STF).  The quest to harvest solar energy, store the same and use it when needed has been the focus of research in industry and academia alike. For the first time, Professor Grossman’s team at MIT, Cambridge (USA) has come up with a new approach which uses polymer Solar Thermal Fuel (STF) storage platform utilizing STF in its solid-state.  According to the published article, researchers stated, “Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. This approach enables uniform films capable of appreciable heat storage of up to 30 Wh kg?1 and that can withstand temperature of up to 180 °C.”How the STF process works?Certain molecules (chemicals) can have 2 different stable structural forms. These structures are called conformations.  When original molecular conformation is exposed to sunlight, the molecule gets charged and the original conformation changes to the other and stay in that charged conformation for a long period.  The charged molecule snaps back to their original shape (conformation), when triggered by a very specific temperature or other stimulus generating heat in the process. Currently, developed polymeric film can release heat about 10 degree C above the surrounding temperature. Film property improvements are underway. German auto company BMW, has sponsored this research. Where the potential application lies - your guess is as good as mine.References:The Atlantic, p 56, November 2015Zhitomirsky, D., Cho, E. and Grossman, J. C. (2015), Solid-State Solar Thermal Fuels for Heat Release Applications. Adv. Energy Mater., 1502006. doi:10.1002/aenm.201502006...
In a recent The Atlantic interview Bill Gates made a wish on an energy miracle, “Here’s a source of energy that is cheaper than your coal plants, and by the way, from a global-pollution and local-pollution point of view, it’s also better”.  The race is on to find that source. One such energy source is solar energy. We all know that solar energy can be harnessed to generate thermal energy or electrical energy for use in the residential and/or in the commercial applications.  Any material that can store Solar Thermal Energy is called Solar Thermal Fuel (STF).  The quest to harvest solar energy, store the same and use it when needed has been the focus of research in industry and academia alike. For the first time, Professor Grossman’s team at MIT, Cambridge (USA) has come up with a new approach which uses polymer Solar Thermal Fuel (STF) storage platform utilizing STF in its solid-state.  According to the published article, researchers stated, “Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. This approach enables uniform films capable of appreciable heat storage of up to 30 Wh kg?1 and that can withstand temperature of up to 180 °C.”How the STF process works?Certain molecules (chemicals) can have 2 different stable structural forms. These structures are called conformations.  When original molecular conformation is exposed to sunlight, the molecule gets charged and the original conformation changes to the other and stay in that charged conformation for a long period.  The charged molecule snaps back to their original shape (conformation), when triggered by a very specific temperature or other stimulus generating heat in the process. Currently, developed polymeric film can release heat about 10 degree C above the surrounding temperature. Film property improvements are underway. German auto company BMW, has sponsored this research. Where the potential application lies - your guess is as good as mine.References:The Atlantic, p 56, November 2015Zhitomirsky, D., Cho, E. and Grossman, J. C. (2015), Solid-State Solar Thermal Fuels for Heat Release Applications. Adv. Energy Mater., 1502006. doi:10.1002/aenm.201502006...
Reliable and high performance lithium ion batteries commonly known as LIBS are highly sought after product by industries. We all have heard stories about laptops, electric vehicles, airplanes catching fires due to LIBS. Underlying problem is the battery overheating. Preventing batteries from overheating is crucial to the public safety.  Now a team of researchers at Stanford University designed a thermo-responsive (heat sensitive) plastic composite film made from polyethylene and spiky nickel microparticles coated with graphene which shuts down the battery if the temperature is too high.         In a recently published work led by Yi Cui and Zhenan Bao of Stanford University, USA concluded “Safe batteries with this thermoresponsive polymer switching (TRPS) materials show excellent battery performance at normal temperature and shut down rapidly under abnormal conditions, such as overheating and shorting.” How practical this design approach is? Time will tell.References: Y. Cui, Z. Bao et al Nature Energy vol.1, Article number: 15009 (2016); DOI: 10.1038/nenergy.2015.9Chemical & Engineering News, Page 7, January 18, 2016...
In aviation industry, the focus is how to improve fuel safety and handling. Mike Jaffe and Sahitya Allam gave their perspective on safer fuels by integrating polymer theory into design (Science, 350, No. 6256, p. 32, 2015).Mist (generated from the fuel) is much more flammable than the liquid and that is why anti-misting kerosene interferes with mist formation when a low percentage of a polymer is added into it.  The problem however, is that the polymer chain undergoes scission during handling and can’t assist in suppressing mist formation. The answer comes from a recent paper published in the Journal Science by Professor Julia Kornfield and her cross-functional team at Caltech, Pasadena, USA. The group designed a megasupramolecules having polycyclooctadiene backbones and acid or amine end groups (telechelic polymer) which is short enough to resist hydrodynamic chain scission while protecting covalent bonds through reversible linkages. Yes, polymers can be designed to suit our societal needs including aviation fuel safety.Reference: M-H Wei, B. Li, R.L. Ameri David, S.C. Jones, V. Sarohia, J.A. Schmitigal and J.A. Kornfield; Science, 350, (6256), pp. 72-75 (2015)...
At the TED conference, Carbon3D, a Vancouver based company touted a radical 3D printing technology and named it CLIP or Continuous Liquid Interface Product. CLIP grows parts instead of printing them layer by layer. It harnesses light and oxygen to continuously grow objects from a pool of resin.  The result: make commercial quality parts at game-changing speed.  CLIP is 25 to 100 times faster than traditional 3D printing technique.  To make the point, Carbon3D web site provides a head-to-head comparison of CLIP to Polyjet, SLS and SLA.[Press release: March 16, 2015, Vancouver, Canada.  www.carbon3D.com]...
Self-healing plastics has been around for a while. Applications include self-healing medical implants, self-repairing materials for use in airplanes and spacecrafts. Even scientists have made polymeric materials that can repair itself multiple times. A recent report in Science describes a significant advance in self-healing plastics. The authors describe a product that mimics how blood can clot to heal a wound. When the plastic is damaged a pair of pre-polymers in channels combines and rapidly forms a gel, which then hardens over 3 hours.The authors demonstrated that holes up to 8 millimeters wide can be repaired. The repaired parts can absorb 62% of the total energy absorbed by undamaged parts.  Science never stops.Reference:S. R. White, J. S. Moore, N. R. Sottos, B. P. Krull, W. A. Santa Cruz, R. C. R. Gergely; Science, Restoration of Large Damage Volumes in Polymers, Vol. 344 no. 6184 pp. 620-623; (9 May 2014). ...
Knowingly or unknowingly, flexible electronics has become a part of our daily life.  Transparent conductive films (TCFs) are used in mobile phones, tablets, laptops and displays.  Currently, Indium Tin Oxide or commonly known as ITO is the material of choice.  But use of ITO has some major disadvantages and these are brittleness, higher conductivity at greater transparency, and supply of Indium.  This is where non-ITO materials come into play. Based in St. Paul, Minnesota (USA), Cima NaoTech’s uses its SANTETM nanoparticle technology, a silver nanoparticle conductive coating which self-assembles into a random mesh like network when coated onto a flexible substrate such as PET and PC.  According to a recent press release, the company stated SANTETM nanoparticle technology enabled transparent conductors in a multitude markets from large format multi-touch displays to capacitive sensors, transparent and mouldable EMI shielding, transparent heaters, antennas, OLED lighting, electrochromic and other flexible applications.  Cima NanoTech is working with Silicon Integrated Systems Corp. (SIS) of Taiwan and using its highly conductive SANTE FS200TM touch films to develop large format touch screens.References: Press release, San Diego, June 03, 2014; www.cimananotech.com ; http://www.cimananotech.com/sante-technology ; http://www.sis.com/...
In an article appeared today (January 29, 2014) in The Guardian newspaper, Stuart Dredge wrote, “From jet parts to unborn babies, icebergs to crime scenes, dolls to houses: how new technology is shaking up making things”1. Mr. Dredge was speaking about 3D printing technology.  The heart of this technology is the 3D printer itself. Stratasys, a company headquartered in Minneapolis, USA is the manufacturer of 3D printers.  It recently announced the launch of Color Multi-material 3D Printer, the first and only 3D printer to combine colors with multi-material 3D printing.  According to the press release2, by using cyan, magenta, and yellow, multi-material objects can be printed in hundreds of colors.  The technology is based on proven Connex technology.  While the base materials are plastics and elastomers, they can be combined and treated to make finished products of wide ranging flexibility and rigidity, transparency and opacity.  Designers, engineers and manufacturers can create models, mold, and parts that match the characteristics of the finished production part. This includes achieving excellent mechanical properties.  According to the manufacturer, print job in the newly revealed printer can run with about 30 kg of resin per cycle and prints as fine as 16 micron layers for models.  No wonder why some call the new Color Multi-material 3D printer a groundbreaking stuff.References: 1. www.theguardian.com.technology/2014/jan/29/3d-printing-limbs-cars-selfies (January 29, 2014)2. http://investors.stratasys.com/releasedetail.cfm?ReleaseID=821134 (August 3, 2014)...
Instead of stitches or skin staples, doctors use skin glue to close wounds. The glue joinsthe edges of a wound together while the wounds heal underneath. Most of the timeskin glue is used for simple cuts or wounds. According to the paper published inScience Translational Medicine, there are no clinically approved surgical glues thatare non-toxic, bind strongly to tissue, and work well in wet and highly dynamicenvironments within the body. This is the reason why this published work is promisingwhere infants born with heart defects would benefit tremendously. Researchers at the Brigham and Women’s hospital in Boston have engineered ‘bio-inspired’ gluethat can bind strongly to tissues on demand, and work well in the presence ofactively contracting tissues and blood flow. The authors of the paper show howthe glue can effectively be used to repair defects of the heart and blood vessels during minimally invasive procedures. [References: P. J. del Nido et al; Sci. Transl. Med., DOI: 10.1126/scitranslmed.3006557; See also, www.geckobiomedical.com/news/gecko-biomedicals-co-founde.html]...
Stability of organic electronics in water is a major research challenge. For this reason,organic electronics has yet to see any sensing application in aqueous environment.However, as understanding of underlying mechanism of stability aspect is becomingclearer, new developmental efforts to make water compatible organic polymer devicesare taking place. Recently, Professor Zhenan Bao’s group in the department of chemical engineering at Stanforduniversity revealed in a paper published in the journal of Nature Communications thatsolution- processable organic polymer could be stable under both in freshwater andin seawater. Developed organic field-effect transistor sensor is able to detect mercury ionsin the marine environment (high salt environment). Researchers believe that the work hasthe potential to develop inexpensive, ink-jet printed, and large-scale environmental monitoring devices. [References: O. Knopfmacher, M.L. Hammock, A.L. Appleton, G. Schwartz, J. Mei, T. Lei, J. Pei,and Z. Bao; Nature Communications, 5, 2954, January 6, 2014; DOI: 10.1038/ncomms3954]...
Insulin, the wonder medicine for diabetes was discovered about a century ago.Since insulin does not get into the blood stream easily, diabetes patients oftenhave injected themselves with insulin. Now a group of scientists led by Dr. Sanyog Jainat the Center for Pharmaceutical Nanotechnology of National Institute of Pharmaceutical Education and Research in Punjab, India has designed a polymerbased package for oral insulin administration. The package design addresses two major obstacles, 1) digestive enzymes must notdegrade insulin prior to its action and 2) the insulin gets into the blood stream.The package contained folic acid functionalized insulin loaded in liposomes.To protect the liposomes (lipids or fat molecules) they were alternately coated withnegatively charged polyacrylic acid (PAA), and positively charged poly allylamine hydrochloride. Studies were conducted to compare the efficacy of bothdelivery systems: designed polyelectrolyte based insulin and standard insulinsolution. Effects of oral administration lasted longer than that of injectedinsulin, authors reported in a recent article in Biomacromolecules. [Reference: A.K. Agarwal, H. Harde, K. Thanki, and S. Jain; Biomacrmolecules, Nov. 27, 2013;DOI: 10.1021/bm401580k]...
Research in the area of stretchable electronics is heating up!  Thanks to polymers. Led by Professor George M. Whitesides of Harvard University (USA), a team of researchers have demonstrated in a recently published paper in Science that ionic conductors can be used in devices requiring voltages and frequencies much higher than commonly associated with devices using ionic conductors.  The team showed for the first time that electrical charges carried by ions and not electrons, can be utilized in fast-moving, high voltage devices.As a proof of concept, the authors of the study built a transparent loudspeaker that produces sound across the full audible range i.e., 20 Hz to 20 kHz.  Components [such as VHB 4910 tape (acrylic tape with PE liner), polyacrylamide hydrogel containing NaCl electrolyte] used for the high speed, transparent actuators are described in the paper.Tissues and cells are soft and require stretchable conductors for biological systems. Many hydrogels are biocompatible which makes this work particularly an important one. The design of gel-based ionic conductors is highly stretchable, completely transparent and offer new opportunities for designers of soft machines.   [Reference: C.Keplinger, J-Y. Sun, C.C. Foo, P. Rothemund, G.M. Whitesides, and Z. Suo; Science, 341 (6149), pp. 984-987 (2013); DOI: 10.1126/science.1240228]...
Interweaving biological tissue with functional electronics, one can make bionic ears.  NASA has tested 3D-printed rocket engine part.  Then why not 3D print yourself?Well, Twinkind, a German start-up company is now offering enthusiasts statues of themselves for display.  How this works?  A full body scanner takes an image of the customer’s body, transfers the file to the printer after which 3D printer laser sinters a composite powder layer by layer into the customer image.Can we dare to say that Madame Tussauds wax figure of Voltaire can now be 3D printed in polymers soon!  [Reference: www.twinkind.com ]...
Polymer membranes have become a leading contender in numerous separation processes.  Be it in gas (air, hydrogen etc.) or be it in water purifications (salinated water, waste water etc.).  Not only polymer membrane technology helps reducing the environmental impact but also it is cost-effective.  Fracking in shell gas is one of many examples. New advances in drilling technology (such as horizontal drilling) have led to new hydraulic fractures called fracking.  Hydraulic fracturing requires about 2.5 to 5 million gallons of water per well.  Water management and its disposal are major costs for producers.One major challenge, however, of the membrane technology is the fouling (damage caused by contaminants) mitigation.  This has been recently studied by a group of researchers from University of Texas at Austin led by Professor Benny Freeman to address efficiency and reuse of water for fracking in shale gas plays.Researchers modified polydopamine coated UF (ultrafiltration) module by grafting polyethylene glycol brushes onto it.  The result is more hydrophilic surfaces which in turn improved cleaning efficiency relative to unmodified modules. The coating improves the membrane life, and can easily be applied to membrane surface by rinsing it through the recycling system.[References: D.J. Miller, X. Huang, H. Li, S. Kasemset, A. Lee, D. Agnihotri, T. Hayes, D.R. Paul, and B. Freeman; J. Membrane Sci., 437, pp. 265-275 (2013); Also see www.advancedhydro.net ]...
Flexible electronics can change the way we use electronic devices.  It is a term used for assembling electronic circuits by mounting electronic devices on a flexible plastic. A recent review article captured the advancement of CNT and graphene based flexible thin film transistors from material preparation, device fabrication to transistor performance control compared to traditional rigid silicon1. Silicon is used almost exclusively in electronic devices.Now Prof. Ali Javey led a team at the University of California, Berkley to develop a printing process to make nanotube transistors at room temperature with gravure printer.  The plastics used is polyethylene terephthalate (PET). The device exhibited excellent performance with mobility and on/off current ratio of up to ~9 cm2/ (V s) and 105 respectively.  Also, maximum bendability is observed.  The paper authors conclude that this high-throughput printing process serves as enabling nanomanufacturing scheme for range of large-area electronic applications based on nanotube networks2. References:1. D-M. Sun, C. Liu, W-C. Ren and H-M Cheng; Small, DOI: 10.1002/smll.2012031542. P.H. Lau, K. Takei, C. Wang, Y. Zu, J. Kim, Z. Yu, T. Takahashi, G. Cho, and Ali Javey; Nano Letters, 13 (8), pp. 3864-3869 (2013); DOI. 10.1021/nl401934a...
Drinking coffee from paper cups are as common as drinking water from plastics bottle. The issue however, is recycling of disposable cups. The disposable cups are made up of 90-95% of high strength paper (fibers) with a 5% thin coating of plastic (PE).To address the recycling issue, James Cropper Speciality Papers of UK have developed a process which involves softening the cup waste, and separating the plastic coating from the fiber.  After skimming off the plastic, remains are pulverised and recycled, leaving water and pulp behind.  According to the company news release, the high grade pulp is reused in luxury papers and packaging materials.An innovative approach to address a common problem.[Reference: www.jamescropper.com/news ]...
A search for an alternative to rigid silicon wafers gave birth to the area of flexible or bendable electronics. Research has been intense for the past few years in the area flexible electronics as it opens up multitude of new applications. Polymers play an important role to exciting field of flexible electronics.In a recent research report, a team of scientist led by Prof. Ali Javey of University of California, Berkeley (USA)  has shown for the first time user-interactive electronic skin or e-skin can conformally wrap irregular surfaces and spatially map and quantify various stimuli through a built-in active matrix OLED display.  Three electronic components namely thin film transistor (uniform carbon nanotube based), pressure sensor, and OLED arrays (red, green, and blue) are integrated over a plastic substrate.  Spin coated and cured polyimide on a silicon wafer is used as the flexible substrate.  Details are in the paper.This work essentially provides a technology platform where integration of several components (organic and inorganic) can be done at a system level on plastic substrates. According to the paper, this e-skin technology could find applications in interactive input/control devices, smart wallpapers, robotics, and medical/health monitoring devices.    [Ref: C. Wang, D. Hwang, Z. Yu, K. Takei, J. Park, T. Chen, B. Ma, and Ali Javey; Nature Materials, Published online July 21, 2013; DOI: 10.1038/NMAT3711]...
Recent buzz in the technology world is 3D printing.  Researchers to designers are creating new products everyday using 3D printing technology.  Even eBay has unveiled its services to those looking to make their own creations using 3D printing App.Since ages composites have played a crucial role in our society. Inspired by natural (biological) composites such as bone or nacreous abalone shell, researchers from MIT (USA) and Stratasys have developed composite materials that have fracture behaviour similar to bones.  Using computer model with soft and stiff polymers, the team has come up with a specific topological arrangements (hierarchical structures) of polymer phases to boost the mechanical behaviour in the composites.Interestingly, the team has been able to manufacture (thanks to 3D printing) a composite material that is more than 20 times larger than its strongest constituent.  The referenced paper showed that one can use computer model to design composite materials of their choice, tailor the fracture pattern and then use 3D printing technology to manufacture the composites.[Ref: L.S. Dimas, G.H. Bratzel, I. Eylon, and M.J. Buehler; Advanced Functional Materials, Published online June 17, 2013; DOI: 10.1002/adfm.201300215]...
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Since graphene was isolated by a group of physicists from Manchester University, UK in 2004, interest in graphene research throughout the world has skyrocketed.  This huge activity stems from graphene’s unusual and extraordinary electrical, thermal, and mechanical properties.  Professor Geim, who was instrumental in the separation of graphene, recently commented, “Graphene is a wonder material with many superlatives to its name”.  Why such glorification of graphene as a material?  Because it is the thinnest known material in the universe and its strength is the highest ever measured1. Prior to its separation into platelets, graphene was a controversial material and the subject of much speculation.  Many believed that graphene could not exist as a freestanding sheet, and yet it was studied theoretically for over 6o years. The results of this intense work over the years have been comprehensively documented in an article by Geim and Novoselov2.  Particularly noteworthy is the research, at MIT, of Gene Dresselhaus and Mildred Dresselhaus who began work with graphite (multi-layered graphene) several decades ago.  The results, until 1980, of the Dresselhaus team on graphite intercalated compounds have been described by these authors themselves3.  Today graphene’s unique structure allows for a wide spectrum of applications in a variety of fields while giving researchers an unprecedented opportunity for fundamental physical science. Picture on the top left show false-color 3-D rendered TEM image of isolated hydrogen atoms (purple-tipped) and an isolated carbon atom (red-tipped) on a graphene membrane ("Courtesy Zettl Research Group, Lawrence Berkeley National Laboratory and University of California at Berkeley"). This article aims to capture and convey in a few words the excitement provided by some of the interesting trends observed in research on graphene and graphene-based polymer nanocomposites (GPNC).

 

 

Background

Invented in 1564, the familiar pencil-lead is graphite, a three dimensional allotrope of carbon. Graphite has a layer structure and is anisotropic.  As a result of this structure, one carbon layer can slide over another layer making graphite a valuable lubricant in addition to a material familiar to all school children.  If the planar, hexagonal arrangements of carbon atoms are stacked together, the result is graphite.  These individual building blocks are nothing but graphene layers.  In other words, graphene is a flat single layer of carbon atoms (sp2bonded) packed into a two-dimensional honeycomb lattice (hexagonal arrangement).  Additionally, graphene can be rolled into a cylindrical one-dimensional carbon nanotube or can be wrapped up into zero-dimensional fullrenes.

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Graphene is an atomic-scale honeycomb lattice made of carbon atoms (Coutesy: Dr Thomas Szkopek http://www.ece.mcgill.ca/~ts7kop/images/graphene_xyz.jpg )

Prior to 2004, whenever scientists tried to slice layers from graphite as thin as was then possible, they ended up with 100 or more layers of graphene together.  Andre Geim and Kostya Novoselov of Manchester University used a micromechanical cleavage technique to separate a single sheet from the three-dimensional graphite.  They put an infinitesimal amount of graphite between two layers of cellophane tape and peeled the tape apart; this process allowed them to whittle the graphite down to a single layer known as graphene4.  The process employed was conceptually very simple, but it allowed for a consideration of what one could expect from graphene in terms of real world applications. This was not a puzzle given the research that had already been done on exfoliated graphite and with carbon nanotubes.  The main challenge was how to produce a large quantity of graphene in a cost efficient manner?  That’s where the race begins!

Graphene production methods

The current literature describes several techniques for graphene production.  Each method has its own benefits and related drawbacks.  Another trend is whether one wishes to synthesize defect free graphenes (purity) or graphenes with defects (containing oxygen species onto the surface).   The drawback of graphene materials with defects is the loss of some of the interesting properties of graphene.  On the other hand, defects could provide numerous application opportunities.  Therefore, not only the quantity of graphene but the types of applications dictate graphene’s preparative methods.  Well practiced methods of making graphene today are mechanical exfoliation, chemical exfoliation, solvo-thermal reduction, and chemical vapour deposition (CVD) or a combination of these.  An overview of current synthetic trends for producing graphene has been reviewed recently5.   However, we like to draw the readers’ attention to some key synthetic work on graphene that has been taking place around the world.  
To produce graphene in bulk quantities, Princeton University researchers led by Prud’homme and Aksay successfully worked out a method through thermal expansion of graphite oxide which provided single functionalized graphene sheets6.   Separately, J.N. Coleman’s group in Trinity College, Dublin in Ireland produced graphene, utilizing their earlier strategy where they avoided aggregation of carbon nanotubes by the use of liquids whose surface energy matched that of nanotubes and yielded a stable dispersion of graphene7,8.  They termed the graphene production technique as liquid-phase exfoliation of graphite.  Czech and Greek researchers used a similar technique to produce a set of colloidal dispersions of solubilised graphenes9.  To avoid harsh oxidation chemistry (using liquids such as DMF or NMP), Rice University scientists recently claimed that they had obtained a high yield of homogeneous graphene dispersions by using ortho-dichlorobenzeneas as the solvent10.  Researchers from China utilized worm-like exfoliated graphite to make graphene sheets11 .    Looking ahead, another group of researchers electrochemically reduced exfoliated graphite oxides at a graphite electrode and reported the work as a green approach to the synthesis of graphene12.  Bucking the graphitic precursor trends, John A. Stride13 of the University of New South Wales, in Sydney, Australia allowed common laboratory reagents ethanol and sodium to react to produce an intermediate which was then pyrolized to give a fused array of graphene sheets only to be sonicated to disperse and separate.  Interestingly, because of graphene’s promising applications in the electronics area, Ajayan’s group at RPI focused their attention on cutting processes to controlling graphene’s shapes14.  Meanwhile, Martin Pumera of the National Institute for Materials Science of Tsukuba, in Ibaraki, Japan is leading the development of electrochemical enzyme biosensors using graphene15 .  All of these works have implications to graphene based polymer nanocomposites (GPNC).

Graphene based Polymer Nano-composites

Graphite is cheap and abundant in nature.  Property wise, graphite is superior to clay and therefore provides a unique opportunity for polymer reinforcement.  The key, however, is to exfoliate graphite’s layer structure and utilize it as a nano-reinforcement.   For the past 20 years, researchers have incorporated, intercalated, exfoliated, or expanded graphite platelets into polymers to produce nanocomposite materials.  Undoubtedly, the separation of graphene (a single and a flat layer of graphite) as a nano-material has opened-up new vistas as well as challenges for polymer nanocomposites research.

The main challenge in making GPNCs is to disperse the individual graphene sheets in the polymer matrix. Stankovitch and Dikin’s work showed that it was, indeed, possible to prepare a well dispersed homogeneous mixture of graphene nano sheets15 in polymer.  Furthermore, the researchers found that the percolation threshold of graphene in polystyrene-graphene composites was close to 0.1 vol% which was three times lower than that of any other two-dimensional filler.  A team of researchers from Northwestern UniversityPrinceton University (New Jersey), and from the University of Texas at Austin further confirmed the homogeneous dispersion by creating functionalized graphene-PMMA nanocomposites that even competed against single-walled carbon nanotube-PMMA composites16.  In fact, these works, along with earlier work of Ilhan and Prud’homme6, resulted in a patented technology that Vorbeck Materials is exploiting in their commercial products.   Recently, Vorbeck and BASF announced that they are developing dispersions of highly conductive graphene for producing electrically conductive coating and compounds, especially for the electronics industry17.   Yongsheng Chen’s group studied EMI shielding of graphene/epoxy composites and found a low percolation threshold of 0.52 volume%.  The group showed that these composites could be used as lightweight and effective EMI shielding materials18.   Rodney Ruoff reviewed19 different chemical methods to produce graphene and chemically modified graphenes (CMG).  His work has resulted in a start-up “Graphene Energy” which is exploiting the market for ultracapacitors where the CMG could be used to make electrodes.Another graphene nanoplatelet supplier is Angstron Materials.  This company is following Bor Jang’s (Wright State University, Dayton, Ohio) work who recently patented highly conductive nano-scaled graphene plate nanocomposites20.   This group is actively pursuing and patenting its work for varieties of graphene based polymer nanocomposites (GPNC).  Another active group in this arena is L.T. Drzal’s group from Michigan State University.  The work of this group is well documented in the literature21,22Drzal’s work provided the basis of XG Sciencesproduct lines. 

After the isolation of free standing graphenes, the floodgate of ideas to produce graphene and use them in real life applications has been opened.  Advantages of graphenes over carbon nanotubes stem from easy access to the graphitic precursor material, the cost, and the scalable method.  Creation of several start-ups confirms the commercial potential of graphene based nanocomposites (GPNC), and different applications are rapidly becoming a reality. 

References

1.    A.K. Geim, Science, 324, pp. 1530-1534 (2009)
2.    A.K. Geim and K.S. Novoselov, Nature Mater. 6, pp. 183-191 (2006)
3.    M.S. Dresselhaus and G. Dresselhaus, Advances in Physics, 30, pp. 139-326 (1981)
4.    K.S Novoselov et al. Science, 306, p.666 (2004)

5.    M. Jacoby, Chemical and Engineering News, pp. 14-20, March 02, 2009.

6.    R.K. Prud’homme, I.A. Aksay et al. Chem. Mater., 19, pp 4396-4404 (2007) 
7.    J.N. Coleman et al. Nat. Nanotechnol., 3, pp. 563-568 (2008)
8.    J.N. Coleman et al. J. Am. Chem. Soc., 131, pp. 3611-3620 (2009)
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10.   A.R. Barron, J.M. Tour et al., Nanoletters, to appear (2009)
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Rakesh K. Gupta

Dr. Rakesh Gupta is George B. and Carolyn A. Berry Professor and Department Chairman of Chemical Engineering at West Virginia University where he has been teaching since 1991. He has also taught at the State University of New York at Buffalo and worked for Monsanto. Dr. Gupta earned his B. Tech. Degree from the Indian Institute of Technology in Kanpur, India, and his Ph.D., also in chemical engineering, from the University of Delaware. His research is focused on polymer rheology, polymer processing and polymer composites. He has published 100 peer reviewed journal papers, 60 conference papers and 10 book chapters on these topics. He also holds two U.S. patents. He is the author of Polymer and Composite Rheology, the coauthor of Fundamentals of Polymer Engineering and the co-editor of Polymer Nanocomposites Handbook.

Prithu Mukhopadhyay

Dr. Mukhopadhyay is scientist with IPEX Technologies Inc., Quebec, Canada.  He earned his doctorate in polymer chemistry from the Indian Institute of Technology, Kharagpur, India.  He has spent 6 years as a research scientist at the Ecole Polytechnique of University of Montreal, Canada.
Dr. Mukhopadhyay is a senior member of Society of Plastics Engineers (SPE), member of American Chemical Society (ACS), and Division members of Polymer Chemistry and Polymeric Materials: Science & Engineering (PMSE). He is a past Chairman of New Technology Committee (NTC) and a past Chairman of the Publication Committee of Society of Plastics Engineers.

He has authored numerous research publications and technical articles in polymers and plastics journals and has chaired many technical programs and sessions in international conferences. Dr. Mukhopadhyay is the founding editor of the Plasticstrends site.

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