Solomon Lectures
The Polymer Division in association with the Australian Academy of Technological Sciences and Engineering has established a prestigious lecture series to promote polymer science and engineering in Australia to be known as the Solomon Lectures. The lectures are given by a prominent polymer scientist, and are usually held in Adelaide, Brisbane, Melbourne and Sydney. The 2007 Solomon Lecturer is Professor Mitsuo Sawamoto of Kyoto University and an abstract of his Solomon Lectures may be found here.
Presentation of a memento crystal to Prof Mitsuo Sawamoto by Prof David Solomon at the Melbourne Solomon Lecture, 19th November 2007.
In his research career, Mitsuo Sawamoto has made two major breakthroughs in the field of chain-growth polymerization where precision reaction control (living polymerization) has been considered inherently difficult: (A) Lewis acid-catalyzed living cationic polymerization in 1983 and (B) Transition metal-catalyzed living radical polymerization in 1993.
These two discoveries rejuvenated cationic and radical polymerizations, where fundamental studies were considered to have matured, triggering a fast increase in publications as well as active efforts in industry for potential commercialization. Before metal-catalyzed living radical polymerization, few organometallic chemists, as well as polymer chemists, considered employing transition metal complexes for catalysis in radical polymerization. Sawamoto's mechanistic studies have contributed critically to the establishment of a general principle of polymerization control, “Dormant–Active Species Equilibrium”, inspired a rapid proliferation of world-wide research activities .
Living cationic polymerization is a chain-growth polymerization mechanism initiated with acid compounds for a variety of electron-rich alkenes. Mechanistically, it is akin to electrophilic addition reactions in organic chemistry and is mediated by carbocationic intermediates, which are active but unstable and prone to undergo chain transfer reaction via beta-proton elimination. Because of this, it was believed that cationic living polymerization would be beyond our reach. Sawamoto’s living cationic polymerization employs protonic acid/Lewis acid (initiator/catalyst) initiating systems which suppress chain-transfer reactions in cationic polymerization. He has demonstrated that, by employing such designed combinations of initiator and catalyst, vinyl ethers, styrenics, and other electron-rich monomers can be polymerized into living polymers with controlled molecular weights and very narrow (uniform) molecular weight distributions. Historically, this discovery heralded a general principle for precision control of chain-growth polymerizations, namely, the dynamic equilibrium between dormant and active species, which turned out to be relevant to other living processes of different mechanisms, such as group-transfer and living radical polymerizations. Sawamoto’s finding has really rejuvenated the field of cationic polymerization, where fundamental research was once pessimistically considered almost over, primarily because of the difficulty in controlling chain-transfer reactions of carbocations.
Living radical polymerization is perhaps more important in industry and academia. Radical polymerization proceeds via carbon radical species, and the intermediates tend to undergo termination (bimolecular radical coupling and disproportionation), making it difficult to achieve living radical polymerization. Sawamoto solved this long-standing problem by employing halogen-capped dormant species and transition metal complexes as catalysts.A large variety of monomers (acrylates, methacrylates, styrenes, acrylamides, etc.) can now be polymerized in a controlled fashion to form polymers of controlled molecular weights and narrow distributions. The key to these findings was the use of transition metal complexes (Ru, Fe, Ni, etc.) as catalysts. Systematic search in Sawamoto’s and other groups then led to a large variety of metal catalysts and initiators, and helped generalization of the principle of dormant species for precision polymerization.
Living cationic and radical polymerizations have also opened new vistas in polymer synthesis with high precision. First, because of the fine reaction control, these processes lead to a variety of new polymers with controlled architectures and topology. Second, these polymerizations can be applied to a variety of functional monomers and in turn to give a new family of functional polymers carrying ester, carboxylic acid, hydroxyl, amine, sugar, perfluoroalkyl and other functionalities.
The previous Solomon Lecturers have been:
