The Society For Polymer Science, India, Thiruvananthapuram Chapter, Kerala
Some of the latest developments in polymer science around the world
17-01-2014
Shape memory polymers regaining shape at body temperature UPDATED 17/01/2014
Scientists have discovered shape memory polymers that regain shape at temperatures close to human body temperature. This discovery has important implications in biomedical applications such as stents and artifical arteries. They can be implanted in their compact form, regaining the required shape naturally. Mechanical Engineering Professor Lih-Sheng (Tom) Turng and his PhD students Hao-Yang Mi and Xin Jing have used inexpensive polymer materials commonly used in injection molding environments. They used amorphous polylactic acid (PLA), derived from corn starch, and thermoplastic polyurethane (TPU). The key to the research is combining both brittle and elastic polymers in the mix. Like many other breakthroughs in polymer research, this discovery is also accidental!
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Polymer cis-trans isomerism to write on water UPDATED 17/01/2014
Now we can write on liquids, literally. University of Helsinki researchers have manufactured photochemically active polymers which can be dissolved in water or certain alcohols. Vladimir Aseyev and his colleagues at the University of Helsinki used a 365-nm laser to aim at a solution into which the polymer was partially dissolved. When exposed to light, the polymer switched to its cis conformation, dissolving completely and leaving a clear form which was visible in the cloudy solution. The polymer under investigation was based on poly (azocalix[4]arene). Scientists found that the two isomers of this polymer have different solubility parameters at the same temperature. For example, at 20 deg C, the trans form is barely soluble in ethanol, but the cis isomer dissolves easily. The azobenzene groups in these polymer backbones cause the polymer to switch between a cis and trans isomer when excited by light. As the two conformations are different in solubility, a ray of light can "draw" in an ethanol-based dispersion of the polymer. The switch from trans to cis happens in the entire polymer chain. This effect where light causes the polymer to dissolve completely and be made visible can last several hours depending, for example, on the concentration of the solution. Macromolecules 2013, 46 (15), pp. 6209
25-12-2011
Triple Shape Nanocomposites-a new class of shape memory polymers
A German research team from the Helmholtz-Zentrum Geesthacht (HZG) Centre for Biomaterial Development in Teltow developed, what they call "Triple-shape polymers". These polymers are able to perform two distinct changes in shape when heated if the shape changes are properly programmed. These composites can memorize two distinct shapes. By the application of magnetic fields with different field strengths, the switching temperatures of these composites can be adjusted in a controlled manner. These "Triple-Shape Composites" consist of a polymer matrix with two different crystallisable chain segments and also contain iron oxide nanoparticles. Each crystallisable segment can memorize one specific shape. The iron oxide nanoparticles, in presence of magnetic field, serve as additional heating source and the lower the temperature required for specific shape change.
Hydrogels by Click Chemistry
Click chemistry, which is a chemical philosophy introduced by K. B Sharpless of The Scripps Research Institute, in 2001 is a concept that mimicks nature. It describes a method in chemistry which will enable generation of substances quickly and reliably by joining small units together. This is, in fact, a concept inspired from nature because nature also generates substances by joining small modular units. Note that Click Chemistry is not a specific chemical reaction; it is a concept that mimicks nature. Now Yusuf Yagci and co-workers of Istanbul Technical University developed a simple and rapid synthetic approach to prepare hydrogels possessing reactive sites to incorporate any molecules of interest by "Click Chemistry". Synthesis of hydrogels by redox or photopolymerization of water soluble monomers, though simple to use and flexible, has the drawback of requiring additional modification steps for tuning or introducing properties for specific purposes. However, the strategy based on "Click Chemistry", by using propargyl acrylamide (PAm) as comonomer together with acrylamide (AAm) and N,N'-methylene bisacrylamide (BAAm) as crosslinker in photoinitiated polymerization, eliminates this drawback. With the selective reactivity of photochemically generated free radicals towards the acrylic function of PAm, hydrogels with clickable acetylene groups can be prepared in a one pot, one step manner.
Self mending polymers - no more glues!!
Scientists working at AkzoNobel, in collaboration with Eindhoven University of Technology, have developed a material that is able to heal itself when it is broken or cut. It is not the conventional self-healing polymers we know. The new plastic, which has been called Supra B, takes advantage of hydrogen bonding - large number of hydrogen bonding sites are introduced in the polymer. Andrew Burgess, chief scientist at AkzoNobel, told that new scratch resistant coatings for vehicles, laptops and other portable equipment can also be developed using these polymers.
Click here for more details. It is also interesting to see some of the comments below the article.
Raman Spectroscopy to detect explosives in plastic bottles
Researchers of VU University, Amsterdam, have developed a method that uses Raman spectroscopy to detect and identify concealed hazardous materials concealed in plastic bottles. They used time-resolved Raman spectroscopy (TRRS) for this purpose. The concept of TRRS is that, after a laser excites a sample, the first photons back to the spectrometer are those emitted from the molecules on the sample's surface, because they have the shortest distance to travel. Thus by opening the gate in front of the spectrophotometer quickly, the signals corresponsing to those of the plastic containers can be collected. Then by delaying the opening for longer and longer, the signature signal corresponding to the explosive (for example, dinitrotoluene) can be collected. However, they caution that the method won't work, if the explosives are hidden in metal or cardboard: "If it's not plastic, the laser won't go through at all."
Stretchable polymer LEDs based on carbon nanotube
Researchers at the UCLA Henry Samueli School of Engineering and Applied Science have demonstrated for the first time an intrinsically stretchable polymer light-emitting device based on carbon nanotube-polymer composite electrodes.The metal-free devices can be linearly stretched up to 45 percent and the composite electrodes can be reversibly stretched by up to 50 percent with little change in sheet resistance.
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Retinal implants with waterproof coating based on polymers
Researchers at the University of Alabama, Huntsville, have developed waterproof coatings based on block copolymers of polyethylene glycol and amino acid-based polymers that both protect electronic retinal implants and the sensitive eye tissue of the wearer.
Click here for more details. Aptly titled "Polymer Vision"!
Polymer heals itself with a "light" touch
Self-healing materials are not totally new. But scientists at the University of Fribourg in Switzerland have developed a type of rubbery plastic that 'self heals' when exposed to ultraviolet light. "It's a clever, novel self-healing method which could find many applications in medical, electronic and composite applications," said Richard Wool, a materials engineer at the University of Delaware though this technique has a drawback that it works only with thin plastics- a shortcoming which can be avoided in future by proper engineering
Click here for more details. Yes a "light touch" is only what requires sometimes to heal a polymer!
NASA successfully tested world's largest and most powerful solid rocket motor
World's largest and most powerful solid rocket motor, DM-2,was successfully completed its testing in Utah, USA, by NASA on 31-08-2010. The motor is designed to provide up to 3.6 million pounds of thrust.
Click here for more details. Don't forget to watch the video, but remember to turn down the speakers before the countdown hits zero!
Moisturizer and plastic bottles from biomass - No more petroleum?!
An accidental chemistry discovery could lead to a new method for making antifreeze, moisturizer and plastic bottles out of biomass rather than petroleum, according to researchers at Iowa State University.
Click one of the latest issues of "Popular Science" here for more details
Graphene/polyaniline nanofiber composites as supercapacitor electrodes
A specific capacitance of as high as 480 F/g at a current density of 0.1 A/g was achieved when graphene/polyaniline nanofiber composites are tested as supercapacitor electrodes. An article published in the recent issue (January 2010) of Chemistry of Materials describes the method of preparation and characterization of such nanocomposites.
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Organosoluble polyimides
A paper published in Polymer Journal (30 June 2010) describes synthesis and identification of fluorescent organosoluble polyimides prepared from a new diamine, 4-(4-(4-amino-2-(4,5-diphenyl-1H-imidazol-2-yl)phenoxy)phenoxy)-3-(4,5-diphenyl-1H-imidazol-2-yl)benzenamine, and three tetracarboxylic dianhydrides.The new symmetrical diamine was successfully synthesized by the nucleophilic substitution reaction of hydroquinone with 2-(2-chloro- 5-nitrophenyl)-4, 5-diphenyl-1H-imidazole (I). The PIs synthesized here are amorphous and soluble in polar aprotic solvents and demonstrate the ability to form films; their inherent viscosities ranged from 43 to 82 mlg-1
Polyethylene with thermal conductivity of the order of 100 W/m.K!!
Scientists have made polyethylene thermally conductive-conductivity larger than half of the pure metals! High-quality ultra-drawn polyethylene nanofibres with diameters of 50 to 500 nm and lengths in millimetre range will have thermal conductivity as high as ~104 W/(m.K). The high thermal conductivity is due to the restructuring of the polymer chains by stretching, where single crystalline fibre will be obtained. They can be used as heat-spreaders and could supplement conventional metallic heat-transfer materials.
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Review paper on Polymer Nanocomposites
A new review on "Polymer nanocomposites based on functionalized carbon nanotubes" is published in Progress in Polymer Science (Volume 35, Issue 7, July 2010, Pages 837-867)
Organic photovoltaic cells based on nanorods of copper phthalocyanine
Researchers at Indian Institute of Technology, Kharagpur, have fabricated organic photovoltaic cells that uses nanorods of copper phthalocyanine. Maximum power conversion efficiency of 2.57% is claimed to be obtained from the vertically aligned nanorods. Read Journal of Physics B: Applied Physics, Volume 43, No. 24, 2010 for more details.
Click here for the abstract of the paper
