SYNTHESIS OF NARROWLY DISTRIBUTED LOW MOLECULAR WEIGHT POLYETHYLENE AND POLYETHYLENE MIMICS WITH CONTROLLED STRUCTURES AND FUNCTIONALITIES

Abstract

<p>The controlled synthesis of functional low molecular weight polyethylene and polyethylene mimics is important in tuning polymer properties and is of great industrial interests. Living polymerization is a method that allows for precise control in polymer structure. Although high molecular weight polymers with controlled structures can be efficiently produced via living polymerization, the production of low molecular weight polymers faces the challenges of the use of large amounts of expensive catalyst and the broadening of polydispersity.</p> <p>The synthesis of well-defined functional low molecular weight polyethylene and polyethylene mimics is studied. Promising polymerization systems, including living ring opening metathesis polymerization (ROMP), living coordination polymerization, coordinative chain transfer polymerization (CCTP), and living C1 polymerization, are identified and are analyzed based on product properties, efficiency, cost, and safety.</p> <p>Within the identified systems, living ROMP is selected for study due to the industrial relevance of ROMP polymers, the availability of raw materials, and the ease of reaction setup. The efficiency of ROMP is challenged by polydispersity broadening resulting from slow initiation and poor reactor volume efficiency due to its implementation as a solution polymerization process. The challenges are addressed by the use of excess phosphine and the realization of ROMP as a bulk polymerization process.</p> <p>Experimental results demonstrate that bulk ROMP with and without phosphines yield product with similar or enhanced molecular weight distribution control as solution ROMP. Kinetic studies confirm living polymerization behaviour of bulk ROMP. A mathematical model is developed for the first time using method of moments to describe the kinetics and development of molecular weight distribution of ROMP. The model is a useful tool in preliminary research and commercialization of ROMP. The success of bulk ROMP and the development of a representative model yield ROMP as a promising method for the production of low molecular weight polymers with controlled architecture.</p>