diff --git a/docs/releasehistory.md b/docs/releasehistory.md
index a62cb731..28ce5a75 100644
--- a/docs/releasehistory.md
+++ b/docs/releasehistory.md
@@ -27,6 +27,7 @@ Please note that all releases prior to a version 1.0.0 are considered pre-releas
 ### Performance improvements
 
 * #1097 Migrates version handling to `versioningit`, which should result in shorter import times.
+* #1122 Improves performance of Interchange.from_smirnoff on polymers.
 
 ### Documentation improvements
 
diff --git a/openff/interchange/components/toolkit.py b/openff/interchange/components/toolkit.py
index 36159755..12629795 100644
--- a/openff/interchange/components/toolkit.py
+++ b/openff/interchange/components/toolkit.py
@@ -1,19 +1,35 @@
 """Utilities for processing and interfacing with the OpenFF Toolkit."""
 
+from functools import lru_cache
 from typing import TYPE_CHECKING, Union
 
 import networkx
 import numpy
 from openff.toolkit import ForceField, Molecule, Quantity, Topology
 from openff.toolkit.topology._mm_molecule import _SimpleMolecule
-from openff.toolkit.typing.engines.smirnoff.parameters import VirtualSiteHandler
+from openff.toolkit.typing.engines.smirnoff.parameters import ParameterHandler, VirtualSiteHandler
 from openff.toolkit.utils.collections import ValidatedList
 from openff.utilities.utilities import has_package
 
+from openff.interchange.models import (
+    PotentialKey,
+)
+
 if has_package("openmm") or TYPE_CHECKING:
     import openmm.app
 
 
+_IDIVF_1 = Quantity(1.0, "dimensionless")
+_PERIODICITIES = {
+    1: Quantity(1, "dimensionless"),
+    2: Quantity(2, "dimensionless"),
+    3: Quantity(3, "dimensionless"),
+    4: Quantity(4, "dimensionless"),
+    5: Quantity(5, "dimensionless"),
+    6: Quantity(6, "dimensionless"),
+}
+
+
 def _get_num_h_bonds(topology: "Topology") -> int:
     """Get the number of (covalent) bonds containing a hydrogen atom."""
     n_bonds_containing_hydrogen = 0
@@ -202,3 +218,42 @@ def _lookup_virtual_site_parameter(
         raise ValueError(
             f"No VirtualSiteType found with {smirks=}, name={name=}, and match={match=}.",
         )
+
+
+@lru_cache
+def _cache_angle_parameter_lookup(
+    potential_key: PotentialKey,
+    parameter_handler: ParameterHandler,
+) -> dict[str, Quantity]:
+    parameter = parameter_handler.parameters[potential_key.id]
+
+    return {parameter_name: getattr(parameter, parameter_name) for parameter_name in ["k", "angle"]}
+
+
+@lru_cache
+def _cache_torsion_parameter_lookup(
+    potential_key: PotentialKey,
+    parameter_handler: ParameterHandler,
+    idivf: float | None = None,
+) -> dict[str, Quantity]:
+    smirks = potential_key.id
+    n = potential_key.mult
+    parameter = parameter_handler.parameters[smirks]
+
+    if idivf is not None:
+        # case of non-standard default_idivf in impropers
+        _idivf = idivf
+    elif parameter.idivf is None:
+        # This appears to only come from imports
+        _idivf = _IDIVF_1
+    elif parameter.idivf[n] == 1.0:
+        _idivf = _IDIVF_1
+    else:
+        _idivf = Quantity(parameter.idivf[n], "dimensionless")
+
+    return {
+        "k": parameter.k[n],
+        "periodicity": _PERIODICITIES[parameter.periodicity[n]],
+        "phase": parameter.phase[n],
+        "idivf": _idivf,
+    }
diff --git a/openff/interchange/interop/openmm/_import/_import.py b/openff/interchange/interop/openmm/_import/_import.py
index 2a0a6389..c8604e48 100644
--- a/openff/interchange/interop/openmm/_import/_import.py
+++ b/openff/interchange/interop/openmm/_import/_import.py
@@ -135,8 +135,6 @@ def from_openmm(
 def _convert_constraints(
     system: "openmm.System",
 ) -> ConstraintCollection | None:
-    from openff.toolkit import unit
-
     from openff.interchange.components.potentials import Potential
     from openff.interchange.models import BondKey, PotentialKey
 
@@ -164,7 +162,7 @@ def _convert_constraints(
         potential_key = PotentialKey(id=f"Constraint{index}")
         _keys[distance] = potential_key
         constraints.potentials[potential_key] = Potential(
-            parameters={"distance": distance * unit.nanometer},
+            parameters={"distance": Quantity(distance, "nanometer")},
         )
 
     for index in range(system.getNumConstraints()):
diff --git a/openff/interchange/smirnoff/_nonbonded.py b/openff/interchange/smirnoff/_nonbonded.py
index 453f60c0..38f4f3da 100644
--- a/openff/interchange/smirnoff/_nonbonded.py
+++ b/openff/interchange/smirnoff/_nonbonded.py
@@ -53,6 +53,17 @@
     LibraryChargeHandler,
 ]
 
+_ZERO_CHARGE = Quantity(0.0, unit.elementary_charge)
+
+
+@functools.lru_cache(None)
+def _add_charges(
+    charge1: float,
+    charge2: float,
+) -> "Quantity":
+    """Add two charges together."""
+    return Quantity(charge1 + charge2, "elementary_charge")
+
 
 def _upconvert_vdw_handler(vdw_handler: vdWHandler):
     """Given a vdW with version 0.3 or 0.4, up-convert to 0.4 or short-circuit if already 0.4."""
@@ -362,7 +373,6 @@ def _get_charges(
                         # the "charge" and "charge_increment" keys may not appear in that order, so
                         # we "add" the charge whether or not the increment was already applied.
                         # There should be a better way to do this.
-
                         charges[atom_index] = charges.get(atom_index, 0.0) + parameter_value.m
 
                     else:
@@ -781,7 +791,6 @@ def _find_reference_matches(
     @classmethod
     def _assign_charges_from_molecules(
         cls,
-        topology: Topology,
         unique_molecule: Molecule,
         molecules_with_preset_charges=list[Molecule] | None,
     ) -> tuple[bool, dict, dict]:
@@ -851,7 +860,6 @@ def store_matches(
             unique_molecule = topology.molecule(unique_molecule_index)
 
             flag, matches, potentials = self._assign_charges_from_molecules(
-                topology,
                 unique_molecule,
                 molecules_with_preset_charges,
             )
diff --git a/openff/interchange/smirnoff/_valence.py b/openff/interchange/smirnoff/_valence.py
index 63d5ae08..b97318d4 100644
--- a/openff/interchange/smirnoff/_valence.py
+++ b/openff/interchange/smirnoff/_valence.py
@@ -20,6 +20,7 @@
     ProperTorsionCollection,
 )
 from openff.interchange.components.potentials import Potential, WrappedPotential
+from openff.interchange.components.toolkit import _cache_angle_parameter_lookup, _cache_torsion_parameter_lookup
 from openff.interchange.exceptions import (
     DuplicateMoleculeError,
     InvalidParameterHandlerError,
@@ -448,15 +449,16 @@ def store_potentials(self, parameter_handler: AngleHandler) -> None:
 
         """
         for potential_key in self.key_map.values():
-            smirks = potential_key.id
-            parameter = parameter_handler.parameters[smirks]
-            potential = Potential(
-                parameters={
-                    parameter_name: getattr(parameter, parameter_name)
-                    for parameter_name in self.potential_parameters()
+            self.potentials.update(
+                {
+                    potential_key: Potential(
+                        parameters=_cache_angle_parameter_lookup(
+                            potential_key,
+                            parameter_handler,
+                        ),
+                    ),
                 },
             )
-            self.potentials[potential_key] = potential
 
 
 class SMIRNOFFProperTorsionCollection(SMIRNOFFCollection, ProperTorsionCollection):
@@ -550,11 +552,11 @@ def store_potentials(self, parameter_handler: ProperTorsionHandler) -> None:
 
         """
         for topology_key, potential_key in self.key_map.items():
-            smirks = potential_key.id
-            n = potential_key.mult
-            parameter = parameter_handler.parameters[smirks]
-
             if topology_key.bond_order:  # type: ignore[union-attr]
+                smirks = potential_key.id
+                n = potential_key.mult
+                parameter = parameter_handler.parameters[smirks]
+
                 bond_order = topology_key.bond_order  # type: ignore[union-attr]
                 data = parameter.k_bondorder[n]
                 coeffs = _get_interpolation_coeffs(
@@ -580,12 +582,7 @@ def store_potentials(self, parameter_handler: ProperTorsionHandler) -> None:
                     {pot: coeff for pot, coeff in zip(pots, coeffs)},
                 )
             else:
-                parameters = {
-                    "k": parameter.k[n],
-                    "periodicity": parameter.periodicity[n] * unit.dimensionless,
-                    "phase": parameter.phase[n],
-                    "idivf": parameter.idivf[n] * unit.dimensionless,
-                }
+                parameters = _cache_torsion_parameter_lookup(potential_key, parameter_handler)
                 potential = Potential(parameters=parameters)  # type: ignore[assignment]
             self.potentials[potential_key] = potential
 
@@ -734,11 +731,11 @@ def store_potentials(self, parameter_handler: ImproperTorsionHandler) -> None:
                     # Assumed to be a numerical value
                     idivf = _default_idivf * unit.dimensionless
 
-            parameters = {
-                "k": parameter.k[n],
-                "periodicity": parameter.periodicity[n] * unit.dimensionless,
-                "phase": parameter.phase[n],
-                "idivf": idivf,
-            }
-            potential = Potential(parameters=parameters)
-            self.potentials[potential_key] = potential
+            # parameter keys happen to be the same as keys in proper torsions
+            self.potentials[potential_key] = Potential(
+                parameters=_cache_torsion_parameter_lookup(
+                    potential_key,
+                    parameter_handler,
+                    idivf=idivf,
+                ),
+            )