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able starting materials protects the environment by partially or completely substituting for petroleum-based inputs. Furthermore, Andjelkovic pointed out, polymers made from biorenewable materials have been shown to have properties that are comparable with or better than those of widely used industrial polymers. "Soybean oil is available in large quantities from soybean oilseeds and represents one of the cheapest and most abundant annually renewable natural resources," Andjelkovic said "We have recently shown that a variety MICHAEL FREEMANTLE, C&EN LONDON ofpromising new polymeric materials—rangHE OPPORTUNITIES FOR DESIGNFollowing Young's presentation, Dejan ing from soft rubbers to hard, tough, rigid ing polymers and developing D. Andjelkovic, a graduate student working plastics—can be prepared by cationic copopolymerization processes that with organic chemistry professor Richard C. rymerization of readily available soybean oils are safe, prevent pollution, and Larock at Iowa State University, Ames, de- with styrene and divinylbenzene." are more efficient in the use of scribed how novel rubbers can be prepared This approach, developed by Larock's materials and energy are enormous, judging from a renewable feedstock: soybean oil. group, relies on the catalyst boron trifluoride by the breadth of topics discussed several "Recent years have witnessed an increas- diethyl etherate to initiate the cationic poweeks ago at a symposium on green polymer ing interest in biomaterials derived from lymerization of the oil. To facilitate homochemistry. renewable resources," he said. geneous copolymerization, the researchers modify the initiator with a fatty acid The symposium, held at the ester from Norwayfishoil. American Chemical Society's national meeting in Washington, D.C., The approach can be used to cowas sponsored by the Division of polymerize soybean oil triglyceride Polymeric Materials: Science & with dicyclopentadiene, a cheap, Engineering and organized by Elreadily available comonomer. Dicyliot P. Douglas, associate professor clopentadiene "is a good cross-linker of materials science and engineerthat impartsrigidityto the resulting ing at the University of Florida, thermosetting materials," AndjelkoGainesville. vic noted. "Our results show that the yield of the cross-linked polymers "The number of presentations increases very slowly with increasing that combined different aspects of amounts of the dicyclopentadiene. green polymer chemistry or that All the copolymers formed appear combined green polymer chemistry as dark brown plastics with a slight with another 'hot' topic suggests that odor. Almost all of them have glasswe are moving into a new phase of transition (softening) temperatures green polymer chemistry in which below ambient temperature and are the end goal is not the green chemtherefore in their rubbery states. istry," Douglas remarked. "Rather, the green chemistry is just another "As much as 85% by weight of available tool that can be used to adsoybean oil is used for the synthesis dress a variety of problems." of these biomaterials," Andjelkovic Jennifer L. Young, a senior readded. "The results show that our search chemist at ACS's Green approach offers a simple route toChemistry Institute in Washington, ward a range of new and exciting D.C., presented the opening lecture. biobased rubbery materials." She observed that green polymer UNDER STRESS Zhu tests the stress and strain of a At the University of Delaware, research can be seen increasingly biobased elastomer. Newark, Ph.D. student Lin Zhu in academia, industry, and governand professor of chemical engineerment. "The research tackles all aspects of One of the major initiatives has focused ing Richard P. Wool have prepared a series polymers and polymerization—everything on utilizing renewable and environmen- of polymeric materialsfromplant oils such from chemical feedstocks, synthetic path- tally benign starting materials obtained as soybean oil. "Triglycerides are the main ways, and reaction media to the nature of from agricultural, animal, and microbial components ofplant oils," Zhu told C&EN. the final polymer as related to its inherent resources for the synthesis of a wide range "Our research group has successfully denontoxicity or degradability," she said. of bioplastics. Deploying such biodegrad- veloped triglyceride-based composites,
GREEN POLYMER FIELD BLOSSOMING
Progress reported in making new materials from renewable feedstocks such as soybean oils
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"We are moving into a new phase of green polymer chemistry in which the end goal is not the green chemistry/' 36
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sized by coupling soybean fatty adhesives, foams, coatings, and acids with ethanolamine followed elastomers from plant oils." by ring closure in the presence of She described the use of acrya titanium catalyst. The resulting lated oleic methyl ester monomers soy-based 2-oxazoline is a mixture derived from plant oil triglycerides of 2-oxazolines with different fatty to synthesize biodegradable elas acid side chains. tomers. The groupfirstprepares "The process is green because high-molecular-weight linear microwave irradiation provides ef polymers by free-radical poly ficient, energy-saving heating and merization ofthe monomer. The also because the monomer is based elastomers are then prepared by on a renewable source: soybeans," cross-linking the polymers. explained Ph.D. student Richard The mechanical and thermal Hoogenboom, who carried out the properties ofthe elastomer are workwith professor of macromoimproved by adding methyl meth- BIOMATERIALISTS Larock (back, left) poses with lecular chemistry and nanoscience acrylate to modify the molecular members of his research group: Andjelkovic (back Ulrich S. Schubert and coworkers structure ofthe rubber chain. The right), postdoc Yongshang Lu (front, left), and graduate at Eindhoven University of Techmechanical properties can also be students Marlen Valverde and Phillip Henna. nology, in the Netherlands, and the dramatically improved by mixing the acrylated monomer with an organoclay: self-healing materials. We showed that the Dutch Polymer Institute. natural montmorillonite modified with a clay-loaded elastomers are biodegradable Aqueous solutions of poly(2-oxazoline) quaternary ammonium salt. and biocompatible." block copolymers aggregate into micelles "The organoclay has a nanolayered In related work, a group in the Nether that could potentially be used in applications structure that works as physical cross-links lands has shown that microwave irradiation such as micellar catalysis and drug delivery, and improves the tensile properties ofthe provides a green alternative to conventional Hoogenboom noted. elastomers," Zhu explained. "Mechanical heating for the cationic ring-opening poly "Polymerization of 2-oxazolines takes recovery ofthe nanocomposites is slow, merization of 2-oxazoline monomers from from several hours to several days," Hoogen but the layer structure has potential for soybean oils. The monomers are synthe boom observed. "These long reaction times
Extreme Pressure X-LC " Traditional HPLC Jasco offers the flexibility of doing b o t h extreme pressure LC (up to 15,000 p
