Directional stem

{
  "id": "MLC-T-CHM-003270",
  "term": "Directional stem",
  "field": "Chemistry",
  "definition": "The stem of a directional chain, that is, the straight crystalline segment of a chain whose two possible orientations along the chain axis are distinguishable. Such a stem has an up or down sense, so whether neighbouring stems in a lamella point the same way or opposite ways matters for packing and for disorder. Stems of isotactic polypropylene, which can pack with up or down orientation in the lattice, are an example.",
  "subject": "Polymer",
  "see_also": [
    "directional chain"
  ],
  "references": [
    "PAC, 2011, 83, 1831. 'Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)' on page 1839 (https://doi.org/10.1351/PAC-REC-10-11-13)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/directional-stem/"
}