Control over molecular weight and polydispersity of condensation polymers by chain-growth polycondensation

Abstract

Polycondensation normally proceeds in a step-growth reaction manner to give polymers with a wide range of molecular weights. Chain-growth polycondensation (CGP) process like the synthetic process of natural polymeric materials such as polypeptides, DNA, RNA, cis-polyisoprene rubber, etc. has been developed to yield artificial condensation polymers having controlled molecular weights and low polydispersities. The requirement for CGP is the selective reaction of monomers with polymer end group without the reaction of monomers with each other. Two approaches to CGP are carried out: (1) the activation of propagating end group by different substituent effects on the reactive site between monomer and polymer, and (2) the prevention of reaction of monomers with each other in solid phase and successive reaction of monomers with polymer end group via phase transfer of monomers. Well-defined aromatic polyamides and polyethers with low polydispersities (Mw/Mn ≤ 1.1) were produced in approach (1), whereas aliphatic polyesters with low polydispersities (Mw/Mn ≤ 1.3) were obtained in approach (2).