ionomer

Polymer composed of macromolecules in which a small but significant proportion of the constitutional units has ionic or ionizable groups, or both.
Note:
Ionic groups are usually present in sufficient amounts (typically less than 10% of constitutional units) to cause micro-phase separation of ionic domains from the continuous polymer phase. The ionic domains act as physical crosslinks.
Source:
PAC, 2006, 78, 2067 (Terminology of polymers containing ionizable or ionic groups and of polymers containing ions (IUPAC Recommendations 2006)) on page 2071