manufactured at two plants—one in Puerto Rico and one in Pennsylvania. These two plants and four other manufacturing facilities have since been recertified "by FDA and are in full production for all products/' says company spokeswoman Jennifer A. Mann. There have been "no reports of consumer injury" from use of unstable Dilantin, Mann stresses. Indeed, FDA reassured the public in a recent advisory that Dilantin on the market "is safe and effective for the treatment of certain seizure disorders." Warner-Lambert is the only producer of Dilantin. George J. Shields, vice president for investor relations, explains it "is a terribly complicated drug to make. It's been on the market since 1936, and no one has a generic version of it." He adds that Dilantin manufacturing problems have cost the company "more than $1 billion in net present value"—including a loss of $130 million in sales revenue each year. But the bulk of the loss comes from what he calls "manufacturing expenses." Neither Shields nor Mann expects this case to affect company stock prices.
In fact, the share price has risen slightly since announcement of the fine. Company projections for 1995 growth in earnings per share are unchanged— estimated at 6 to 8% in both 1995 and 1996, says Mann. For a number of years, Warner-Lambert has been mentioned as a takeover target. A security analyst who asked not to be identified says the guilty plea makes Warner-Lambert—with its "premier consumer products business"—a more likely candidate for takeover "within a few years." Benadryl, Rolaids, and Listerine are among its overthe-counter products. Meanwhile, a federal grand jury last week indicted the firm's former vice president for quality assurance, Allan H. Doane, for conspiracy, causing shipment of adulterated Dilantin, and obstructing FDA proceedings. He faces a maximum prison sentence of 19 years and $1.25 million in fines. Mann says Doane was a loyal and productive employee for more than 30 years, and the company "will continue to pay his legal fees." Lois Ember
New model proposed for surfactant aggregation Direct images of single-chain surfactants on solid surfaces reveal highly curved structures that contradict prevailing models of surfactant aggregation, according to research carried out at the Technical University of Munich. The work also shows that the aggregates exhibit periodicity on certain substrates, which could be exploited
to make nanometer-scale patterns on surfaces. These results challenge current thinking about how molecules assemble, notes Ralph G. Nuzzo, chemistry professor at the University of Illinois, UrbanaChampaign. The findings will influence how people think about such diverse processes as adsorbate-mediated elec-
Surfactants form curved, not flat, structures on solids Proposed structures
Current models
Graphite (hydrophobic surface)
Mica (hydrophilic surface)
Note: Structures on the left are those proposed by Manne and Gaub on the basis of atomic force microscopy images. Structures on the right are those predicted by current models.
trodeposition and lipid assembly at planar interfaces, he tells C&EN. Srinivas Manne, now a research staff member at Princeton Materials Institute in New Jersey, and physics professor Hermann E. Gaub, now at Ludwig Maximilian University, Munich, used a technique called noncontact atomicforce microscopy to image surfactant aggregates on various types of solid surfaces in aqueous solutions [Science, 270, 1480 (1995)]. Using a single-chain quaternary ammonium surfactant called tetradecyl trimethylammonium bromide (C14TAB), the researchers obtained images showing striped patterns. They believe these images are consistent with curved, rather than flat, aggregates. On mica—a negatively charged hydrophilic surface—C14TAB molecules form full cylinders that bend and meander over the substrate. But on graphite and molybdenum disulfide—hydrophobic surfaces—the same molecules form straight parallel half-cylinders regularly spaced about 5 nm apart. This is the first report of cylindrical aggregates, but halfcylinders on a graphite surface were observed earlier by the same researchers and their coworkers at the University of California, Santa Barbara [Langmuir, 10, 4409 (1994)]. Manne points out that most models predict that surfactants will form flat monolayers or bilayers on solid surfaces. Though surprising, the curved structures actually represent a good compromise between opposing forces: The molecules naturally tend to form spheres because of intermolecular attraction, whereas the surface pulls them toward as flat an arrangement as possible for maximum interfacial contact. A cylinder can be thought of as an intermediate between a sphere and a flat layer, Manne notes. The regular spacing of half-cylinders on hydrophobic surfaces could be the basis for a new way of patterning surfaces. If the patterned aggregates could be fashioned as a template, Manne says that wires could be made that have the same width as the spacing between aggregates. To create a template, however, the aggregates somehow must be made rigid so they are not destroyed once the surfactant solution is removed. One way to do this is to polymerize tail groups after the aggregate is formed. Maureen Rouhi DECEMBER 4,1995 C&EN 9
