INCI name

ISOBUTYL POLYSILSESQUIOXANE

1,3,5,7,9,11,13,15-Octakis(2-methylpropyl)pentacyclo[9.5.1.1~3,9~.1~5,15~.1~7,13~]octasiloxane

Nail conditioningBasic data from CosIng

This entry shows data from the EU CosIng database. An editorial description has not been written and reviewed yet.

Functions

Nail conditioning: Improving and/or enhancing the cosmetic characteristics of the nail (moisturizing, increasing sheen, reducing brittleness and flaking, etc.).

This ingredient is not listed in the annexes of Regulation (EC) No 1223/2009 in the CosIng data.

CAS: 221326-46-1
Chemical name: Pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane, 1,3,5,7,9,11,13,15-octakis(2-methylpropyl)-
CosIng: Isobutyl Polysilsesquioxane is a resinous material composed of a mixture of three-dimensional siloxane polymers and oligomers with cage structures. For the oligomers, each silicon atom in the polysilsesquioxane is connected via oxygen atoms to three other silicon atoms and can be represented by the empirical formulation RSiO3/2 where R represents the isobutyl group. For the larger polymeric polysilsesquioxanes, some of the silicon atoms are not connected to other silicon atoms and instead have a silanol (SiOH) group. Isobutyl Polysilsesquioxane is prepared by the hydrolysis and condensation of 2-methylpropyl trimethoxysilane.
Sources: Wikidata Q82922018 (CC0)
CosIng – European Commission database of cosmetic ingredients (3 November 2026)