Penultimate-unit effect

{
  "id": "MLC-T-CHM-008603",
  "term": "Penultimate-unit effect",
  "field": "Chemistry",
  "definition": "The influence of the monomer unit located second-to-last from the growing end of a polymer chain on the reactivity of the terminal monomer unit. This effect considers that the reactivity of the chain end is not solely determined by the last unit, but also by the chemical nature of the unit preceding it. It is often observed in copolymerization reactions where the identity of the two most recent monomer additions affects the rate of subsequent monomer incorporation.",
  "subject": "Polymer",
  "see_also": [
    "chain-end reactivity ratio"
  ],
  "references": [
    "PAC, 2008, 80, 2163. 'Glossary of terms related to kinetics, thermodynamics, and mechanisms of polymerization (IUPAC Recommendations 2008)' on page 2180 (https://doi.org/10.1351/pac200880102163)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/penultimate-unit-effect/"
}