Polyethers and polyesters have desirable properties and can be produced by ring-opening polymerization (ROP) of epoxides, lactones, and lactides using a range of catalysts. Polyolefins are used in a variety of consumer products and industrial applications. There is a need in the market for a cost-effective, non-toxic, and highly active ring-opening polymerization catalyst. Also, single-site catalysts are desired for ring-opening and olefin polymerization to enable production of polymers with targeted properties. Herein, optimization of an alkylaluminophosphonate catalyst system for the ROP of epoxides, and extension of that catalyst system for the ROP of lactones and lactides, are reported. The preparation of dipyrromethene based complexes of zinc as a potential single-site catalyst for ring-opening polymerization of cyclic esters and ethers is also described. Moreover, the market needs and a customer discovery effort for polyolefin catalyst development is reviewed.
In chapter one, a brief review of polyethers, polyesters, and polyolefins is presented. The use of ring-opening polymerization catalysts to produce polyethers and polyesters is discussed, and the catalysts for polymerization of olefins are reviewed. Moreover, useful properties, commercial producers, and applications of these polymers are discussed. Also described are the commercial catalysts to produce such polymers and existing opportunities in the market to improve these catalysts.
Chapter 2 briefly reviews known catalyst systems for the ring-opening polymerization of cyclic ethers to polyethers and the shortcomings of these catalyst systems. The advantages of an alkylaluminophosphonate catalyst system for the polymerization of epoxides, previously reported by Dr. Mason’s group, are discussed. Consequently, efforts aimed at optimization of the alkylaluminophosphonate catalyst system to produce polyethers from cyclic ethers are presented, including investigation of the effects of water and aging on catalyst activity for polymerization of epichlorohydrin, and substitution of expensive tBu3Al with iBu3Al to produce a cost-reduced catalyst capable of scale-up. The results of an effort to expand catalyst application to polymerization of oxetane and oxepane are also reported.
In chapter 3, the demand for an improved catalyst for ring-opening polymerization of cyclic esters is discussed. Polymerization activity of alkylaluminophosphonates in the ring-opening polymerization of cyclic esters, including ε-caprolactone, lactide, glycolide, and ε-caprolactam, is reported. Three catalyst systems, tBu3Al/2MePO(OH)2, iBu3Al/2MePO(OH)2, and iBu3Al/2tBu3PO(OH)2 were found to polymerize ε-caprolactone to high molecular weight polycaprolactone with almost 100% conversion in an hour for moderate ratios of ε-caprolactone to catalyst. Moreover, end group analysis of polycaprolactone produced by alkylaluminophosphonate system confirmed that the first monomer ring opening is initiated by nucleophilic attack of an aluminum alkyl group.
The synthesis and characterization of 1,9-dimesityl-5-phenyldipyrromethene (abbreviated as (N,N)) complexes of zinc are discussed in chapter 4 as another potential catalyst system for the ring-opening polymerization of cyclic esters. Metal complexes similar or analogous to (N,N)ZnN(SiMe3)2 have been reported in the literature as good catalysts for the ring-opening polymerization of lactide and ε-caprolactone. Moreover, Dr. Mason’s group previously demonstrated polymerization activity of the (N,N)ZnnBu complex for ring-opening polymerization of ε-caprolactone. Synthesis of (N,N)ZnN(SiMe3)2 and [(N,N)Zn(μ-OiPr)2]2Zn is reported. These complexes were characterized by NMR spectroscopy and X-ray crystallography.
Olefin polymerization and the need for catalysts that produce polyolefins with improved properties are discussed in chapter 5. The emergence of single-site catalysts and the background of a patented constrained geometry ligand developed in Dr. Mason’s lab is reviewed. This patented technology can be used to synthesize a set of olefin polymerization catalysts and catalysts for other applications. Our National Science Foundation Innovation Corps (NSF I-Corps) project aimed at customer discovery, identification of customer needs, and development of value propositions for commercialization of this catalyst system is presented. Moreover, the key findings of the 244 customer discovery interviews from our I-Corps program, including the drivers for improved polymer properties in polyolefins, value propositions for our catalyst system, supply chain complexities and needs, target market size, and feasible revenue streams for a polyolefin catalyst development startup company are reported.