n e w s of t h e w e e k
ONE-POT POLYMER PASTA Synthesis and processing combined in one step yield polymer with unique properties
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y using porous nanoscale reactors, ultrahigh molecular weight polyethylene can be prepared directly in the form of crystalline nanofibers. Such oriented polymers generally have better mechanical properties than other polymers for material applications. But to acquire that desirable orientation, polymers usually must undergo postpolymerization processing, such as extrusion or spinning. A new method developed at the University of Tokyo by Takuzo Aida, a professor of chemistry and biotechnology, and graduate students Keisuke Kageyama and Jun-ichi Tamazawa, enables the polymer to be extruded as it is synthesized [Science, 2 8 5 , 2113 (1999)]. The technique not only saves time and money in the production of functional materials, but it also opens doors to polymers with new properties. Aida and coworkers polymerize ethylene in mesoporous silica fiber reactors consisting of uniformly sized (27 A) hexagonal pores arranged in parallel. Molecules of the classic polymerization catalyst titanocene (Cp2Ti, Cp = cyclopentadienyl) are supported by the wall of each pore. After activating the catalyst, the vessel containing the reactors is pressurized with ethylene gas. Confined within the narrow pores, the polymer chains formed at the activated titanocene sites have no space in which to fold. They are forced to grow out of the framework, like spaghetti extruding from a pasta maker. "Combining synthesis and processing is a problem in all areas of materials science," David A. Tirrell, a professor of chemistry and chemical engineering at California Institute of Technology, notes. "It would be an advantage if we could learn how to make both the bonds and the superstructures at the same time, and that's clearly what's been done" by the Japanese researchers. The approach also "demonstrates the importance of proper design of a catalytic system and its spatial surround10
SEPTEMBER 27,1999 C&EN
Honeycomb-like nanoreactors simultaneously synthesize and extrude ultrahigh molecular weight polyethylene chains, which assemble into nanofibers (right).
they are able to fabricate and test macroscopic samples, they'll find that the polymers do have" better mechanical properties than polyethylene fibers prepared by conventional methods. Polyethylene in fully extended conformation previously could be obtained only by spinning from the gel phase or by stretching under pressure. In either case, an ultrahigh molecular weight polymer is required. Some strategies already exist for synthesizing fully extended polymers, notes Virgil Percec, a professor of chemistry at the University of Pennsylvania. But they are specific to particu| lar monomers and 1 polymers, he adds. 1 "Aida's method is the % first to produce fully % extended polyethyl^ ene directly from synthesis and may have universal applicability because other polymerization reactions can be carried out in mesoporous silica," he comments. Maureen Rouhi
ing," says Krzysztof Matyjaszewski, a chemistry professor at Carnegie Mellon University, Pittsburgh. Aida and coworkers call their approach "extrusion polymerization" and note that it mimics the way some organisms make naturalfibers.For example, highly crystalline cellulosefibersproduced by the bacte- Flood water swirled thick with sewage, rium Acetobacter xylinum are extruded gasoline, industrial chemicals, and through nanopores in the cellular mem- wastes flushed from garages in the afbrane where they are made. termath of Hurricane Floyd's visit to the The polyethylene produced by extru- U.S. East Coast on Sept. 16 and 17. Hardest hit were North Carolina and sion polymerization is unique. The fibers, with diameters ranging from 30 to northern New Jersey, where the flood50 nm, are the thinnest prepared so far ing claimed lives; caused extensive from a synthetic polymer, Aida says. property damage to homes and busiThe polymer's high density (1.01 g per nesses; and knocked out electric, gas, cu cm) suggests it contains less branch- and telephone service. The flooding ing than polyethylene produced in a ho- also disabled sewage treatment plants mogeneous system under similar condi- and compromised supplies of clean water for drinking and industrial use. tions (0.97 g per cu cm). Hurricane Floyd dumped 20 inches Furthermore, the polymer chains are regularly oriented in an extended fash- of rain on eastern North Carolina. Chemion, unlike ordinary polyethylene crys- ical industry plants in the Cape Fear River tals, which are folded to form a lamellar Basin in and around Wilmington were packing—a very interesting aspect, Tir- mostly shut because of the extensive rell says. High orientation ordinarily flooding, but many are now back in leads to desirable material properties, operation. such as high modulus and high strength, In Acme, N.C., HoltraChem plant he explains. Aida and coworkers "haven't manager John O. Foster says he called shown that yet, but I would guess that if local officials for help in shoring up
Floods release heavy metals from settling ponds, close facilities
Record floods swamp Bound Brook, N.J., in wake of Hurricane Floyd.
earthen retaining walls of two holding ponds containing mercury-contaminated wastewater at the plant site. HoltraChem had operated mercury-cell chloralkali production units until April, when they were decommissioned in favor of membrane-cell units that will soon come on-line. National Guard soldiers, U.S. Envi-
ronmental Protection Agency teams, and local hazardous material crews responded, working to sandbag weak spots as the storm came through. HoltraChem also secured regulators' permission to speed treatment of the mercury-contaminated water in the ponds in order to lower water levels in advance of the storm. The treatment was carried out at an adjacent site owned by International Paper. Floodwater did, however, flush waste lagoons at Occidental Chemical's chromium chemicals plant in Castle Hayne. Company officials estimated that as much as 100 million gal of river water washed over the lagoons, causing the release of approximately 225 lb of total chromium. However, plant manager Gene Renzaglia says the company tested river water near the plant and could find no trace of chromium. "It's a drop in the bucket," Renzaglia says. "It's so small, we can't even find it." The bigger threats to humans and marine life now are dissolved farm-animal wastes, untreated sewage, and the millions of
drowned chickens, hogs, and turkeys floating in the floodwater. As the hurricane moved up the coast into New Jersey, it became a tropical storm that dumped up to 18 inches of rain in the northern part of the state. Union Carbide's Bound Brook polyolefins compounding facility near the Raritan River was shut down until early last week. The facility sustained no damage, and a skeleton crew kept steam equipment running, but most employees could not get to work because of flooded roads, a Carbide spokesman says. Labs on-site were shut down because of limited water service. Hoechst Marion Roussel's labs and administrative offices in Bridgewater, N.J., were officially closed for a few days at the urging of local government officials to ease demand for potable water. Although Bridgewater did not lose telephone service, most northern New Jersey residents and businesses lost telephone service when a Bell Atlantic and AT&T switching hub in Rochelle Park was flooded. Marc Reisch
Earthquake rocks Taiwan
time on Tuesday, Sept. 21. Following the earthquake, most of TaiTaiwan's most serious earthquake this wan's electricity supply failed. Some century has killed more than 2,000 peo- buildings toppled and collapsed in ple and injured almost 8,000. Chemical in- Taipei, but the damage was concendustry infrastructure has been relatively trated in central Taiwan. As C&EN unaffected by the tremor, but chemical went to press, hopes were fading of industry workers will definitely be affect- finding many more survivors. An ed by deaths and injuries to relatives and estimated 400 people are missing, friends in the Puli and T'aichung area, presumably buried under tons of rubble. where the quake was centered. The earthquake, measuring 7.6 on the The Nantou area where Puli is loRichter scale, occurred at 1:45 AM local cated is a mix of tall mountains, farmers' fields, vil— ^ ^ ^ ~ — " lages, and small cities. The largest Earthquake-toppled building in Nantou area, uli was epicenter of earthquake city in the area is southwest of Puli. T'aichung, a oneand-a-half-hour drive most structures are built to withstand T'aoyuan. O Taipei from Puli. T'aichung is them. A spokesman for Taiwan's EnvironHINA Hslnchu^ home to some of Tai- mental Protection Agency tells C&EN C wan's best universities, that, so far, there have been no reports of and it was comparatively toxic spills or environmental disaster. T'aichung -J ( Taiwan Strait much less damaged by Taiwan's chemical industry is one of • Puli the quake than the Puli Asia's most developed. Most facilities are Mailiao TAIWAN area. located within 30 miles of the west coast. complex Philippine Sea Having prepared for About two-thirds of Taiwan's petrochemi( an invasion by China for cal industry is near Kaohsiung, where Tainan.? 50 years, Taiwan quickly quake damage was light, and the harbor, • Jen vyu complex mobilized an effective Taiwan's largest, is still operating. ForKaohsiungij • Linyrfan petrochemical rescue operation. Fur- mosa Plastics Corp., a Formosa Group -^complex South China Sea thermore, earthquakes company participating in the construcare a frequent occur- tion of the Mailiao petrochemical com^50 mi rence in Taiwan, and plex, reports no damage or injuries. ChiSEPTEMBER 27,1999 C&EN
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