This case was written by Juan D. Rogers. Comments or questions should be directed to Juan D. Rogers at (404) 894-6697 or, by email, juan.rogers@pubpolicy.gatech.edu. The research was sponsored by the Department of Energy, Office of Basic Energy Sciences, Contract ER45562. The views presented here are the case author’s and do not necessarily represent those of the Department of Energy or Georgia Institute of Technology.

The Organic Chemistry of Conducting Polymers case examines the research on charge distribution in polymer molecules and the mechanisms of charge transfer in these materials. The work was conducted, until very recently, under the supervision of a single PI, Dr. Laren Tolbert. DOE support began in 1985, but the foundations of this research stream were set during the previous 8 years of work by Tolbert in carbanion chemistry while at the University of Kentucky and with the support of NSF.

It is a fairly typical case of "small" basic science in an academic setting led by a single highly productive university professor. Two important characteristics of the research stream must be mentioned in this summary. First, the main scientific impact was the result of cross-disciplinary fertilization occasioned by the communication patterns of the PI with various audiences. Second, the career paths of students show some peculiarities in that they are almost exclusively hired by industry, especially when they worked on the DOE sponsored component of the research.

Sources: The Organic Chemistry of Conducting Polymers case was written based on an interview with the PI, Laren Tolbert, and proposals, reports and a CV he provided.

The research activities described in this case are mainly the effort of a single PI, Laren Tolbert, with the participation of a postdoc and a few graduate students at a time. The work has been supported by both BES and NSF at roughly the same level and, between the two, make up between 80 and 90% of total research funding. This research work consists in the application of conceptual frameworks and techniques from chemistry to an area mainly addressed by physicists. The focus of chemists on the chemical bond allowed for an increased theoretical understanding of the mechanisms of conduction in polymers and the synthesis of molecules of controlled lengths in order to enhance their mechanical and electrical properties.

The discovery by Heeger and MacDiarmid that polyacetylene can be doped to high conductivity by a variety of acceptors and donors constitutes one of the main background findings for this stream of research. Subsequent work by Schrieffer and others has established the basic characteristics of the conduction mechanism in this material, which is fundamentally different from other metals and semiconductors. These properties result from the unique character of the soliton, the mobile charge carrier in these materials, which can be described with reference to the properties of carbanions, radicals, and carbocations. The soliton model of polymer conduction is derived from concepts used by physicists in the study of solid state. At the beginning of this research stream, Tolbert proposed to study these phenomena by using the chemistry of carbanions to characterize the solitons.

The physical model suggests that high conductivity polymers result from the pre-formation of a neutral polymer followed by doping to the desired conduction with reducing metals. This process yields the material almost intractable. The carbanion approach led to a significant simplification of the synthesis and study of conducting polyacetilene. The generation of n-doped polyacetilene involves not a true doping but a deprotonation. The charge carriers themselves are generated first and, then, their length is extended systematically until the desired conducting regime is reached.

The potential uses of these materials are many, though they have not yet found widespread commercial applications. They could be very important in future micro-miniaturization of electronic circuits, selective metal replacement, batteries and photovoltaics.

The origins of this stream of research go back to 1978, to Tolbert’s work on the chemistry of carbanions while at the University of Kentucky. During this time, and until 1986, his work was funded almost exclusively by NSF. During a stay at Berkeley for a sabbatical year in 1984, he was able to articulate the connections between the knowledge base he had developed in carbanion chemistry and the work of physicists in conducting polymers who approached them from the point of view of solid state materials. The key realization came from exchanges during lectures on his work at Bell Labs where resident researchers first pointed out the analogies. The approach derived from chemistry significantly simplified the problems posed by the physicists and suggested new models for the phenomena of distribution of charge in molecules.

The new interdisciplinary context for Tolbert’s work seems to have led to the first proposal for DOE support submitted in 1985 and granted in 1986. The proposal contained a plan to verify experimentally the advantages that a carbanion chemistry approach to conducting polymers seemed to have. Together with the theoretical interest in fully characterizing the properties of these materials, the approach suggested a better way of generating the materials and experimental techniques to work with them. The expected theoretical results included a better understanding of the charge transfer mechanisms. Within a year, the main goals of the proposed research were achieved which resulted in a publication in a cross-disciplinary journal co-authored with a graduate student.

By the second year of DOE support, the research on conducting polymers was divided into four areas: (a) thin film formation, "doping" through organometal deprotonation, and conductivity measurements; (b) synthesis and chemical characterization; (c) new polyacetylene derivatives; (d) a new class of charge-transfer potentially intrinsically conducting polymers (rather than a result of "doping"). Area (a) continued to offer difficulties in producing tractable materials using "doping" techniques. The results in area (b) confirmed hypotheses. A new substance with a reversible thermochromism effect was discovered when developing syntheses in area (c). And a new class of polymers was developed in area (d), which had not yet been characterized completely. With the DOE support, a new post-doctoral researcher was hired, Janusz Kowalik, who would carry half the load of the DOE sponsored research from that time to the present.

By the time the DOE grant was due for renewal in 1989, most remaining obstacles had been overcome. A successful process for thin film formation of conductive polyacetilene had been devised, the characterization of the new materials and validation of the soliton model of conduction had been completed, and the new conducting copolymers had been formed and characterized.

The success of the first stage of this component of Tolbert’s research program led to a more general perspective on the research questions being addressed and this was reflected in a change of title for the new proposal. It changed from "A Carbanion Approach to Polyacetilene" to "The Organic Chemistry of Conducting Polymers." The advances toward elucidation of a soliton model of charge transport and the generation of new copolymers with their full characterization justified this more general framing. The success in thin film formation enabled precise conductivity measurements and a classification of variants of the polymers.

The elucidation of the charge transport mechanisms in polymers was a significant success at the fundamental level of the second cycle of the BES sponsored research. This theoretical result, with experimental validation, together with the success in developing techniques for thin film formation grounded the application for grant renewal to a third three-year cycle. In sum, previous sponsored research had (a), demonstrated the benefits of the discrete molecule approach to the chemistry of conductive polymers, (b), demonstrated proton-transfer doping of polyacetilene, and (c), established a new class of conductive heteropolymers. The research in the new period intended to continue advancing in the four areas outlined in previous proposals. These were: (1) the use of polymethine dyes to explore the possibility of switching between degenerate ground states; (2) determining the utility of proton-transfer doping by direct synthesis of segmented polyacetylene; (3) exploring the possibility of increasing effective polymer chain length by molecular "solder;" (4) extending the synthesis of heteropolymers for improving processability and electrical properties.

The grant was renewed by BES in 1991 and after the first year of the new cycle remarkable progress was made toward two of the stated objectives: (1) development of "molecular switches" based upon cyanine dyes degenerate ground states; (2) adhesive conductive polymer films. The advances are reported to have resulted serendipitously from work on the soliton structure and on heteropolymers. The potential applications of the second area of work is then separated from the main line of BES supported work and slated for development in a new interdisciplinary program.

The second year of this cycle continued along the same lines by completing the synthesis of the highest member of the series of cyanine dyes and with studies of adhesive conductive polymers that produced forms that attach covalently to metals. A review article published in Accounts of Chemical Research and a chapter on "Synthesis of Conductive Polymers" in Textbook in Conductive Polymers are evidence of an established reputation in this field of research.

In 1994, a proposal for renewal of the grant to a fourth three-year cycle was submitted and awarded. A significant difference in the context for research introduced with this proposal is the fact that the proposal was submitted with a Co-PI, Lawrence Bottomley, an associate professor at Georgia Tech. The proposal suggests that, at this point, viable commercial applications of the materials they have been studying either exist or could be easily foreseen. This presented the PIs with a more pressing decision in this area than had been the case in previous stages. Rather than pursue some of the possible commercial applications of their results, they decided to continue to orient their research toward answering the fundamental questions in mechanistic organic chemistry that remained open. The main focus of the research was to relate the properties of the substances that were already understood at a molecular level with the bulk properties of electroactive materials. Armed with the techniques to manipulate the molecular chains, they proposed to construct chains of increasing lengths and study how the properties converged to those of polymers as the length of the molecule increases. The basis for this technique still contrasted with the solid state approach introduced by physicists that studied the static structures of the material in their final form. This process had already allowed for the design of "molecular switches." Proposed research would extend these results to (a), demonstrate molecular "switching" in cyanines, (b), synthesize dinuclear complexes of cyanines to measure rates of communication between nuclear centers, (c), synthesize and examine layered devices, and (d), form electroactive surfaces patterned on the molecular scale.

After the first year of the new cycle, scientific results were reported in the following areas: (1) synthesis and investigation of a novel set of binuclear complexes that indicate soliton-like communication between the two metal centers, which can be used as molecular wires in the molecular architecture of electroactive systems; (2) synthesis of new soluble polyheterocycles which demonstrate remarkable conjugation lengths. The research would continue to: (1) measure the rates of soliton propagation down a polyene chain; (2) string together polymers and olygomers consisting of solitonic chains between ferrocene centers, which can be viewed as molecular neural networks; (3) apply soluble conductive films to incorporation in commercial fibers, which can be used in antistatic applications.

At the time of our interview with Dr. Tolbert, the DOE grant was approaching the end of its fourth funding cycle and the research had coalesced along two lines: (1) the synthesis of discrete electroactive molecules, which represent solitonic systems connected by two redox active end groups (important in the search for nanostructured materials and devices); (2) the search for soluble precursors to conducting materials.

In mid 1997, a proposal for renewal was in preparation for a fifth funding cycle by BES.

The outputs reported here correspond to those mentioned in the reports and proposals to have resulted from DOE sponsored work. The PI maintained that he was very careful in keeping separate work that was supported by different sources of funds. Therefore, he was able to distinguish between outputs resulting from the different streams of work. There was, however, a unifying theme to all the research done under his leadership, namely, the distribution of charge in molecules. In the PI’s estimation, the main scientific impact of this research was theoretical and, at the time of our interview, its contribution to the field was widely recognized and the subject of important discussions. Evidence of this was a theoretical review paper in which a leader in the field engaged in constructive criticism of their models and drew considerable attention to their results.

Year	DOE Supported	Other Sources
1986	3	4
1987		5
1988	1	1
1989	4	3
1990	2	3
1991	4	4
1992	1	1
1993	2	1
1994	1	1
1995	2	4
1996	2	4

Tolbert attributed great significance to the meetings he attended, not as an indication of the productivity of his work, but as the occasion for interactions that had proved, over the years, to be very significant for choosing the direction of research. An invited lecture at Bell Labs in 1983 was the occasion for an exchange with people aware of relevant work in physics that created the opportunity for the carbanion approach to conducting polymers. Since then, as well as attenting the main conferences in his discipline, he has attended meetings where the problems of interest to him are discussed interdisciplinarily. In terms of frequency of attendance, the reports show, on average, 4 meetings a year, 2 of which are attributed to DOE work and 2 to NSF sponsored research.

The list of personnel working on the project since 1986 to the present is the following:

The table charts the years during which they worked with support of the DOE grant. There are almost an equal number of PhD students, 2 more MS students and 6 Postdocs, with stays of 1 or 2 years each, that worked on research supported by other sources of funds.

Year	PhD	MS	Postdoc
1986	S, O		K
1987	S, O		K
1988	S, O, H		K
1989	S, O, H	Si	K
1990	S(g), O(g), H	Si(g)	K
1991	H		K
1992	H(g),Z		K
1993	Z		K
1994	Z, T		K
1995	Z(g), T, N, E		K
1996	T, N, E		K

NOTE: Each person is identified with the first initial of their last name, as indicated in brackets in the list of names, and (g) after an initial indicates that the individual graduated that year.

Relations with private companies do exist but have not been a major component of the research pursued in this case. A grant received from the Sandoz Foundation is documented and broad collaboration agreements with Hoechst and Hercules were reported during the interview. The PI mentioned that the intellectual property agreement required in the first case was reached after very difficult negotiations especially due to the requirements of the legal advisers at Georgia Tech. This experience was used to improve the process in the next two cases for which broad agreements are in place so that small grants can be received over time without requiring new negotiations. There is no report of the way in which these companies use knowledge gained by the DOE sponsored research of this case.

The first independent variable that we can account for in some detail is funding by source and year. The following table charts the available information:

The care with which the PI maintained work supported by different streams of funding separate establishes correlations between funding and publication patterns, meeting attendance and student training. Publications resulting from DOE funding are identified and, in some cases, they are directed to a more interdisciplinary audience. This goes together with the regular attendance of the PI at meetings in chemical physics that are mostly populated by physicists interested in solid state analysis of materials. The division of labor of students and postdocs is also rigorously established according to the source of funds for their assistanships and fellowships. In this regard, the only students and postdocs working under this PI to continue in an academic track were not funded by DOE but by NSF.

The PI also reported during the interview that he perceived the research agenda of the DOE to be more oriented toward practical applications and that he should keep abreast of the possibilities for the application of his work. He would not include the more exploratory and risky components of his research program under the DOE grant proposals and would use mostly his work under NSF sponsorship or small, undirected industry grants for that purpose. However, he believed all his work was equally fundamental, in terms of the spectrum of types of R&D, and that applications, even those that justified or inspired some of the research agenda, were not a concern of his.

The research reported in this case is an example of "small science" conducted, untill very recently, under the supervision of a single PI in an academic position. According to the available evidence, the scale of research is mostly the result of the work style of the PI who is aware of potential applications and the possibilities for larger scale ventures but has made a conscious decision not to pursue those himself.

The research performed in this case has not directly led to the commercialization of any products nor to the creation of new businesses to exploit the knowledge it created. However, it has had significant impact outside of the academic scientific community through the training of students that were hired by industry.

The scientific impact has been quite significant and can be interpreted as the result of inter-disciplinary fertilization of ideas, in this case, between organic chemistry and physics. Significantly different conceptual frameworks used in looking at the same problem resulted in the ability to manipulate certain substances in new ways and to elucidate the mechanisms that created their most desirable properties.

The case shows some interesting peculiarities of the career paths of students and postdocs. First, almost all the students that worked with Tolbert were hired by industry rather than continuing an academic career. There are only three students mentioned in the evidence available that went on to take positions in universities but did their graduate research on other parts of Tolbert’s program and not on the DOE sponsored research. Second, a single postdoctoral fellow has been working on the entire period of 12 years that DOE support has been awarded.