A POLYMER MAN'S HERCULEAN EFFORT
Edwin Vandenberg is honored by ACS for his extensive contributions to polymer science and the polymer chemistry community
STEPHEN K. RITTER, C&EN WASHINGTON
PHOTO BY TIM TRUMBLE/ASU
dwin J. Vandenberg's career as a polymer chemist reminds him of a comment made by J. Paul Getty when the famous oil baron was asked how to be successful. Getty responded with three important requirements, Vandenberg relates: "Rise early--which I did. Work hard--which I also did. And discover an oil well!
"Although I didn't accomplish that last one," Vandenberg muses, "I did discover important and useful polymer chemistry and materials for which my company, Hercules, benefited financially--many times beyond the best oil well. In return, I received financial and other recognition from my company as well as many personal benefits, including intellectual stimulation and research freedom."
Vandenberg, 84, is the recipient of the 2003 Priestley Medal, the American Chemical Society's highest award. He is best known for his work at Hercules in the 1950s through the 1970s that included the independent discovery of isotactic polypropylene and the development of Ziegler-type catalysts for its manufacture.
He further discovered the hydrogen chain-transfer method of controlling the molecular weight of polyolefins, which resulted in one of the most important patents related to polyolefin production. Vandenberg also devised alkylaluminoxane catalysts that are useful for ring-opening polymerization of epoxides and oxetanes to form polyether elastomers.
Vandenberg retired from Hercules in 1982 and has held a research position at Arizona State University since then. At ASU, he has continued his work with the alkylaluminoxane catalysts to prepare hydroxypolyethers that are analogs of polyvinyl alcohol and cellulose.
"Edwin Vandenberg's outstanding research accomplishments and his contributions to the advancement of polymer science during his long and distinguished career at Hercules were invaluable to our company," says Hercules Chairman and CEO William H. Joyce. "The Priestley Medal is a fitting tribute to an individual whose accomplishments are highly regarded in the international scientific community. We at Hercules congratulate him on this great honor and are proud to have had the benefit of his extraordinary knowledge for more than four decades."
"Ed is an extremely creative polymer chemist," adds Eli M. Pearce, a chemistry professor at Polytechnic University and ACS immediate past-president. "His accomplishments in polymer science are legion, as is his devotion to professional activities, primarily with the Division of Polymer Chemistry."
Vandenberg and Pearce served together as chair and chair-elect of the Polymer Division in 1979. "He set a high standard of participation as chair and was an active supporter of innovative programs for polymer education," Pearce says. "All of us knew that we could count on Ed whenever a difficult problem occurred--he would pitch right in to help work everything out successfully. The Priestley Medal is a wonderful honor to recognize his scientific accomplishments and his professional involvement."
Vandenberg was born on Sept. 13, 1918, and he grew up in Hawthorne, N.J., about 15 miles northwest of New York City, where his father owned a hay and feed business. Like many chemists, Vandenberg became interested in chemistry at an early age. While he was a teenager, his friend Gordon Hoffman had a small lab set up in his home, inspiring Vandenberg to do the same. "I became intrigued with the unique role of chemistry in all things, and I spent much time before going to college doing experiments and reading about chemistry," Vandenberg says.
ONE EXPERIMENT almost ended with disastrous results, he recalls. Hoffman and Vandenberg had decided to prepare manganese metal by heating a mixture of manganese dioxide powder and aluminum metal powder in a crucible. They were looking at it closely when the reaction occurred in a flash, right in their faces and unprotected eyes. "That wasn't a very bright thing to do," he says in hindsight. "Fortunately, neither of us were injured, but the reaction was successful since the recovered crucible pieces were coated with manganese metal."
By the time Vandenberg finished high school, he had decided on chemistry as a career. "My life goal listed in my senior yearbook was 'To be a good chemist,' " he says. But that was in 1935, just as the U.S. was struggling to recover from the Great Depression, so he wasn't sure that his family could afford for him to go to college.
"My father suggested that I attend Stevens Institute of Technology, an engineering school in Hoboken," Vandenberg notes. "He thought I could learn chemistry there and costs could be minimized by my living at home and commuting to school." So he ended up taking a train 20 miles from home to Jersey City, catching the subway to Hoboken, then walking a mile to Stevens--every school day for four years.
Although mechanical engineering had not been his goal, Vandenberg ended up studying it at Stevens. "I was pleased to be able to go to college," he adds. "Stevens was a good choice, an excellent school that provided a broad-based, interdisciplinary engineering background, which was unique at the time." He excelled at Stevens and was elected to the Tau Beta Pi engineering honor society. Vandenberg had few extracurricular activities, but he did play violin and was in the university's orchestra.
His undergraduate days at Stevens were not devoid of chemistry, however. During the summer before his senior year, Vandenberg arranged to do a research project with organic chemistry professor and department chairman Francis J. Pond. Since Vandenberg had not had a formal organic course, Pond spent considerable time tutoring him. Vandenberg subsequently took an organic course as an elective and continued to do research in Pond's lab.
Vandenberg received a degree with distinction in mechanical engineering in 1939. His career accomplishments were later recognized in 1965 with an honorary doctorate of engineering from his alma mater.
With a recommendation from Pond, Vandenberg was hired for a chemistry research position with Hercules Powder Co. at the company's Wilmington, Del., research center. His first assignment was to work with Harold M. Spurlin, one of the top polymer chemists at the time and a specialist in cellulose, Vandenberg recalls. He started on an investigation of the electrostatic retention mechanism of an aluminum resinate, [Al(OOCC19H30)2]+, during the rosin sizing of paper.
In this process, the aluminum resinate is precipitated in wood pulp where it becomes associated with cellulose fibers, he explains. The resinate helps ensure that the paper has sufficient hydrophobic surface characteristics to prevent written or printed ink from "feathering."
Vandenberg continued to work with rosin soaps in several projects during the 1940s, including one during World War II on stabilizing soil to quickly develop aircraft landing strips in remote areas with minimal raw materials. After a brief stint working on loan from Hercules at a munitions factory in Kansas in 194445, he returned to Wilmington and began work on emulsion polymerization--his first polymer synthesis research activity.
One of Hercules' rosin soaps had been discovered to be a good emulsifier for the free-radical polymerization of styrene-butadiene rubber, Vandenberg relates. With this rosin soap, he quickly discovered and patented a new redox emulsion polymerization system based on cumene hydroperoxide (CHP) as a free-radical initiator and a small amount of iron pyrophosphate and a reducing sugar as the redox couple. It increased polymerization rates 50-fold, he says, which significantly boosted styrene-butadiene production.
As an offshoot of this work, Vandenberg and his coworkers discovered during a mechanistic study that CHP could be cleaved by acid catalysts under mild conditions to give nearly quantitative yields of phenol and acetone. "I was intrigued by these mild conditions and high yields and continued to work on this facile cleavage," he says. "However, my supervisor thought I was wasting my time since CHP was too expensive for a phenol process." Eventually, however, Vandenberg's persistence led Hercules to develop a new process based on this reaction, and it has become the principal industrial route to prepare phenol.
During the emulsion polymerization research, Vandenberg learned from other Hercules researchers about using pressure bottles that have caps with self-sealing rubber liners as reaction vessels. This apparatus used hypodermic needles to inject reactants and remove products, Vandenberg says, and allowed him to run 10 to 20 experiments in one day.
"This proved to be a big part of my success," he notes. "I was able to cover new ground really fast, similar to combinatorial chemistry today." This technique was to prove valuable for handling reactive organometallic reagents under low pressure and in the absence of air, he says, which became essential in his future work on Ziegler-type catalysts.
In 1951, in the course of looking for applications for the hydroperoxide redox system, Vandenberg developed a low-temperature, low-pressure procedure to polymerize ethylene. The optimized procedure used an insoluble ferrous complex of ethylenediaminetetraacetic acid with CHP in tert-butyl alcohol. "Conversions were only a few percent, molecular weight was low, and the product brittle," Vandenberg says. "But this product was clearly a more linear polyethylene than that known from the commercial high-temperature, high-pressure product at the time."
IN RETROSPECT, Vandenberg believes that the product was linear high-density polyethylene, which was reported in 1953 by German chemist Karl Ziegler. "Our molecular weights were too low for us to recognize its value," Vandenberg adds.
Hercules licensed the Ziegler trialkylaluminum-titanium tetrachloride catalyst discovery for producing polyethylene in mid-1954, and Vandenberg began to work on it later that year. "I examined some of the longer range aspects and worked in this area for a couple of years," Vandenberg says. "Needless to say, these were very exciting times in the lab."
Initially unknown to Vandenberg and others, the Ziegler catalysts gave rise to a new type of polymerization. With addition polymerizations involving hydroperoxide-initiated free radicals, acid-catalyzed polymerizations (cationic), and base-catalyzed polymerizations (anionic), the catalyst is remote from the growing polymer chain and promotes activation of the monomer, which adds to the end of the polymer chain. But with the new Ziegler method, termed coordination polymerization, polymer chain growth was later proposed to occur by insertion of a monomer unit between a carbon-metal bond of the growing polymer chain and the catalyst, which controls the geometry of the polymer.
Within a week of starting work on the Ziegler process, Vandenberg carried out on the same day both an experiment to polymerize propylene and a separate experiment using hydrogen in an ethylene polymerization. The results of both experiments seemed to be inconsequential at first, he notes, but he continued to pursue the ideas.
In the case of propylene, Vandenberg obtained a small amount of an insoluble, crystalline polymer. He observed that ordinary Ziegler catalysts gave low yields of the crystalline polymer, but in time he came up with a modified catalyst (TiCl3nAlCl3, n = 01.0) and determined the reaction conditions needed for a high yield of the polymer. It turned out to be stereoregular polypropylene with all the methyl groups on the same side the of carbon chain.
At about the same time, chemistry professor Giulio Natta of the Polytechnic Institute of Milan also reported that the polymer was stereoregular and coined "isotactic" to describe the structure. Natta had a slight head start on Vandenberg, working as a consultant for Italian firm Montecatini (later Montedison), which also had licensed Ziegler's technology (C&EN, Feb. 10, page 26; March 3, page 8).
"Natta and I were unknowingly competing," Vandenberg says. "I did a lot of the same things that he did. But he got publications, and we were not able to publish, except by patent."
Vandenberg and Hercules filed a patent on the high-yield method to prepare polypropylene, which became involved in an interference proceeding among several parties to determine who could claim the discovery, he notes. But Natta showed that he had an earlier discovery date, Vandenberg says, so the Hercules patent was removed from the interference.
However, both Vandenberg and Natta are credited with independently discovering isotactic polypropylene. Natta went on to carry out important crystallographic studies on titanium-based catalysts used to make stereoregular polymers. Ziegler and Natta shared the 1963 Nobel Prize in Chemistry for their work on coordination polymerization, including development of what became known as Ziegler-Natta catalysts.
Because of Hercules' interest in high-density polyethylene, the company did not immediately produce polypropylene. But in 1957, in collaboration with Hoechst, Hercules developed a commercial process for isotactic polypropylene based on Vandenberg's work. Hercules became the first U.S. producer and ultimately the world's largest producer of polypropylene, a distinction that it would later relinquish.
In the polyethylene experiment involving hydrogen, Vandenberg found that a small amount of added hydrogen affected the molecular weight of the polymer produced. He later tried it on polypropylene and found similar results. The hydrogen was acting as a chain-transfer agent to separate the growing polymer chain from the catalyst and to cap the catalyst metal and the polymer end with hydrogen atoms, which halted polymer growth. The molecular weight could thus be controlled by adjusting the amount of hydrogen used.
The patent sought by Vandenberg and Hercules on the hydrogen control method also became involved in an interference proceeding, "but in this case we prevailed," Vandenberg points out. This simple, economic method of controlling molecular weight is still being used today, he says.
"In general, Hercules recognized that I was being successful and gave me a free hand to pursue areas that I thought were potentially important and interesting."
DURING HIS CAREER at Hercules, Vandenberg worked alone or with a small group of researchers, and he didn't have any particular interest in taking his career in any direction other than working in the lab. "Everyone thought I was better at doing research," he says. For that reason, he believes, Hercules allowed him to pursue his ideas in the manner that he thought was best.
||POLYMERIZERS Hercules' principal area of growth in the post-World War II era was in polyolefins, and Vandenberg (right) was one of the company's key researchers. Vandenberg poses with Spurlin (center) and colleague Howard G. Tennent (left) as they look at a pressure bottle containing the results of a polymerization reaction.
"In general, Hercules recognized that I was being successful and gave me a free hand to pursue areas that I thought were potentially important and interesting," Vandenberg says. "Many of the projects were never developed commercially--although some were near misses--but I did get many patents. It's difficult to publish in a timely manner as an industrial chemist, if at all, and the difficulty increases with the importance of the work. But I was able to eventually publish some of the work."
Vandenberg's research on coordination polymerization also included epoxides. In 1957, he noticed that some of his catalysts were similar to aluminum-zinc catalysts that were newly described by others for polymerizing propylene oxide. He thought that the epichlorohydrin analog would be a good candidate to try using his various catalyst systems, and he quickly determined that the epoxide polymerization worked better using triisobutylaluminum without an accompanying transition metal.
It turned out that in his early studies on epichlorohydrin, the starting material came from an old bottle that had been in the lab for some time, Vandenberg explains. When he needed more starting material, Vandenberg obtained a new bottle. However, he found that the earlier work could not be reproduced. "We immediately suspected that there was probably water in the old epichlorohydrin bottle," Vandenberg relates.
With the possibility of a wet reaction system in mind, he next tried reacting triisobutylaluminum with water in less than stoichiometric amounts and discovered that it formed an isobutylaluminoxane, R2AlOAlR2. This compound turned out to be the first of a new class of catalysts and provided high yields of polymers. In the course of studying the polymerization mechanism of this catalyst, Vandenberg and coworkers used acetylacetone as a chelating agent to see if it would block the coordination sites on aluminum to prevent polymerization. Indeed it did, but only partially. "Much to our surprise, when we tried this we obtained an even better catalyst," he says.
The aluminoxane catalyst and its derivatives, also known as Vandenberg catalysts, soon became some of the most versatile catalysts for making elastomers from epoxides and oxetanes. Among those polymers made at Hercules were polyepichlorohydrin homopolymers and copolymers with ethylene oxide, which are oil-resistant rubbers. Vandenberg also prepared a variety of other related zinc and magnesium catalysts for epoxide polymerizations.
"Elastomers were a difficult sell at Hercules since we would have been competing with customers who bought our rosin emulsifiers," Vandenberg says. But his persistence in pursuing the basic research again paid off, and after nearly 10 years Hercules came out with its Herchlor line of polyepichlorohydrin elastomers and licensed the technology to BFGoodrich, which developed its Hydrin line. The epichlorohydrin polymers received an Industrial Research 100 Award (now called R&D 100 Awards) in 1965 as one of the best new products of the year.
During the later years of his career at Hercules, Vandenberg became more active in ACS governance. "I liked working with people in ACS and helping to get others involved," he says. "I found it very instructive."
Vandenberg served in several capacities within the Division of Polymer Chemistry, notes Kenneth J. Wynne, a professor of chemical engineering at Virginia Commonwealth University and current chair of the division. Beyond his pioneering work in the synthesis of commercial polymers, Wynne says, Vandenberg was a leader of the polymer community through his division activities.
Vandenberg served as the division's secretary from 1975 to 1977 before becoming chair-elect in 1978 and chair in 1979. During Vandenberg's tenure as chair, Wynne remarks, the first division topical workshop was held. "The topic was water-soluble polymers and biomedical polymers, an area where Ed made seminal contributions. These topical workshops have become one of the centerpiece activities of the division and are characterized by a synergistic mixing of industrial and academic scientists discussing cutting-edge research."
While chair, Vandenberg was instrumental in founding the division's Industrial Sponsors Group, serving as its coordinator for nearly 20 years, according to Robert S. Moore, a retired researcher at Eastman Kodak and the group's current chair. Made up of 30 polymer producers, the group has a goal of supporting polymer education and improving the public perception of polymers through scholarships, grants, awards, short courses, and publication of the Polymer Education Newsletter.
"My life goal listed in my senior yearbook was: 'To be a good chemist.' "
"IN RECOGNITION of his exceptional service to the Division of Polymer Chemistry," Moore says, "Vandenberg was given its Distinguished Service Award in 1983 'to recognize many years of continuing service to the division,' and the division's Special Service Award in 1995 'to recognize outstanding contributions in service to the division.' "
PHOTO BY TIM TRUMBLE/ASU
Following his retirement from Hercules at the end of 1982 after 43 years with the company, Vandenberg moved west to suburban Phoenix and became a visiting professor of chemistry and later a research professor at Arizona State University. His goal was to enjoy retirement from industry and to continue work on some old research leads, he says, especially on hydroxypolyethers.
"In my prior Hercules work, interesting water-soluble, high-molecular-weight polymers were made from glycidol and 1,2-bis(hydroxymethyl)ethylene oxide," he explains. "In this same work, I discovered an interesting base catalyst rearrangement polymerization of glycidol to yield low-molecular-weight, water-soluble poly(3-hydroxyoxetane)." This work later led to a host of linear and branched polyethers.
At ASU, Vandenberg worked with then-postdoctoral researcher Jeffrey C. Mullis to further study poly(3-hydroxyoxetane), which led to a route to make the high-molecular-weight polymer. It's essentially a copolymer of vinyl alcohol and formaldehyde, Vandenberg notes, so it can be considered an analog of polyvinyl alcohol. It has some advantages over polyvinyl alcohol, such as being easy to fabricate into a tough translucent film, he adds. Although the polymer has not been commercialized, Vandenberg believes it could have a variety of applications if an economical production route can be found.
A subsequent polymer prepared by Vandenberg and Mullis is poly[3,3-bis(hydroxymethyl)oxetane], an analog of cellulose. It differs from cellulose in that the hydroxyl groups are all primary, the oxygens in the main chain are ethers rather than acetals, and there are no asymmetric carbons, Vandenberg says. But it's more stable to hydrolysis and probably oxidation than cellulose and potentially more readily fabricated, he adds. "In my view, there is still a large need for a hydrophilic fiber like cellulose that is much more durable," Vandenberg notes.
Vandenberg has spent less time on research during the past few years because of health problems and his commitment to caring for Mildred, his wife of more than 50 years with whom he had a son and a daughter. In his most recent work, he has been focusing on hydroxypolycarbonates and their copolymers with polylactic acid and other polymers. These materials could be used to bind drugs, proteins, or carbohydrates to facilitate drug delivery, Vandenberg believes.
He recently moved from the chemistry department to the bioengineering department to pursue the biomedical polymers. He has a new office but has yet to set up a lab and get back to work. "I've always enjoyed chemistry," Vandenberg says, "and I still have some ideas that I want to pursue."
In his more than 60 years of chemical research, Vandenberg has published about 50 papers and edited four books. He has amassed 116 patents, on most of which he is the sole inventor. He also served on the editorial advisory board of the Journal of Polymer Science (196793) and Macromolecules (197981).
In addition to the Priestley Medal, Vandenberg has received the ACS Award in Polymer Chemistry (1981) and the ACS Award in Applied Polymer Science (1991). He also has received the ACS Rubber Division's Charles Goodyear Medal (1991), the Polymer Division's Herman F. Mark Award (1992), and the Society of Plastics Engineers International Award (1994).
"Being announced winner of the Priestley Medal is an important day in my career," Vandenberg says. "I have been most fortunate to be able to make my research contributions to polymer chemistry." Beyond the hard work, he emphasizes that his achievements have depended on important contributions by many others from different areas of Hercules and ASU--as well as "a little bit of magic."
At C&EN press time, Vandenberg was scheduled to receive the Priestley Medal on March 25 during the awards ceremony at the ACS national meeting in New Orleans; a video showing of his award address was planned.