Polymer comprising two or more networks that are at least partially interlaced on
a molecular scale but not covalently bonded to each other and cannot be separated unless chemical bonds are broken.
A mixture of two or more preformed polymer networks is not an IPN.
PAC, 2007, 79, 1801
(Definitions of terms relating to the structure and processing of sols, gels, networks, and inorganic-organic hybrid materials (IUPAC Recommendations 2007))
on page 1814
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook