Side reactions in the synthesis of triblock copolymers of nylon-6 with telechelic oligomers

BACKGROUND: The polymerization of hexanelactam (HL) is complicated by numerous side reactions: chain transfer to monomer, termination of the polymer chain, exchange as transamidation and formation of beta-ketoimides and beta-ketoamides. The generation of by-products and their effect on the anionic polymerization of HL in the bulk in the presence of functionalized tetrahydrofuran oligomers as polymeric activators (PACs) were investigated. RESULTS: In order to consider how side reactions influence the process of HL polymerization, qualitative and quantitative determination of the by-products obtained and their exhaustion were carried out. An investigation of the polymerization kinetics and the formation of low molecular weight by-products through the polymerization was performed. The products are further involved in the polymerization process and consumed until an equilibrium level is reached. The mechanism of their generation is discussed. These processes were followed during the first polymerization stage by means of gel permeation chromatography. A mechanism of by-product formation and consumption is proposed. CONCLUSION: The investigation of the polymerization kinetics and the formation of low molecular weight by-products through the polymerization has shown that the side reaction yields oligomeric HL-based products. The products are further involved in the polymerization process and consumed until an equilibrium level is reached. The equilibrium values depend on the HL/PACs ratio. (C) 2008 Society of Chemical Industry.