SubstancePolymer — Polymer structure

One of the five chemical-substance structuring resources. Describes a polymer through its class, geometry, repeat units and starting monomers. Used for PEGs, polysorbates, copolymers, hydrogels, resorbable sutures.

Purpose of the resource

A polymer is not a molecule in the classical sense: it is a distribution of chains obtained by polymerisation, characterised by a molecular mass distribution (Mn, Mw, polydispersity), a geometry (linear, branched, star), a connectivity (homopolymer, alternating, statistical, block, grafted copolymer), and the nature and stereochemistry of its repeat units.

SubstancePolymer provides the structured vocabulary to carry that information into a medicinal-product registration dossier. Typical cases: PEG of a lipid nanoparticle (Comirnaty), polysorbate 80 of a flu vaccine, PLA / PLGA of a resorbable suture, viscosity agents in eye drops.

Key fields

JSON example

Linear polyethylene glycol (PEG), homopolymer of ethylene oxide, average mass 1000 Da — the common backbone of countless pharmaceutical formulations:

{
  "resourceType": "SubstancePolymer",
  "id": "example-peg",
  "class": {
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/polymer-class",
      "code": "polyether",
      "display": "Polyether"
    }]
  },
  "geometry": {
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/polymer-geometry",
      "code": "linear",
      "display": "Linear"
    }]
  },
  "copolymerConnectivity": [{
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/copolymer-connectivity",
      "code": "homopolymer"
    }]
  }],
  "modification": "Polyethylene glycol with hydroxyl termini",
  "monomerSet": [{
    "ratioType": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/ratio-type",
        "code": "molar"
      }]
    },
    "startingMaterial": [{
      "code": {
        "coding": [{
          "system": "http://www.nlm.nih.gov/research/umls/rxnorm",
          "code": "8061",
          "display": "Ethylene oxide"
        }]
      },
      "category": {
        "coding": [{
          "system": "http://terminology.hl7.org/CodeSystem/monomer-category",
          "code": "monomer"
        }]
      },
      "isDefining": true,
      "amount": { "value": 100, "unit": "%" }
    }]
  }],
  "repeat": [{
    "averageMolecularFormula": "(C2H4O)n",
    "repeatUnitAmountType": {
      "coding": [{
        "system": "http://terminology.hl7.org/CodeSystem/repeat-unit-amount-type",
        "code": "molar-mass-average"
      }]
    },
    "repeatUnit": [{
      "unit": "C2H4O",
      "orientation": { "coding": [{ "code": "head-to-tail" }] },
      "amount": { "value": 1000 }
    }]
  }]
}

Typical use cases

• IDMP registration: polymeric excipient of a medicinal product (PEG, polysorbate, PLGA…).
• mRNA vaccines: describe the PEG and SM-102 of an LNP.
• Implants: stents, sutures, resorbable prostheses — polymer characterisation for CE marking.
• Pharmaceutical cosmetics: silicone derivatives, acrylic copolymers.
• GSRS referencing: feeding normative substance ledgers.

Common pitfalls

• Polymer vs monomer confusion: PEG is the polymer, ethylene oxide is the monomer. Putting ethylene oxide inside repeat.repeatUnit instead of monomerSet.startingMaterial is a frequent mistake.
• Geometry omitted: a linear PEG and a star PEG (8 arms) have different pharmacokinetic properties. geometry is not optional in business terms.
• No mass distribution: for a polymer, giving only a developed formula ignores polydispersity. Always qualify the mass via repeat.repeatUnitAmountType.
• Copolymer without connectivity: distinguishing alternating, statistical, block and grafted is critical (a block PLGA and a statistical PLGA degrade at different rates).
• No normative monomer identifier: use RxNorm, UNII or CAS in monomerSet.startingMaterial.code; avoid free text.

Related resources

• SubstanceDefinition — references this block via structure.
• SubstanceNucleicAcid, SubstanceProtein, SubstanceReferenceInformation, SubstanceSourceMaterial.
• MedicinalProductDefinition — authorised product.
• Ingredient — ingredient of a medicinal product (excipient, active).

See also: Ingredient — medicinal product ingredient and SubstanceDefinition.