Isobutyl Polysilsesquioxane
AKA “Pentacyclo(9.5.1.13, 9.15, 15.17, 13)octasiloxane, octakis(2-methylpropyl)-, 1, 3, 5, 7, 9, 11, 13, 15-octakis(2-methylpropyl)-, Pentacyclo[9.5.1.13, 13]octasiloxane, RefChem:859707, 221326-46-1, PSS-OCTAISOBUTYL SUBSTITUTED 97, MFCD31010095, 15-Octakis(2-methylpropyl)-2, 4, 6, 8, 10, 12, 14, 16, 17, 18, 19, 20-dodecaoxa-1, 15-octasilapentacyclo[9.5.1.13, 13]icosane, OctaIsobutyl-POSS
Ingredient
Ingredient Facts
Isobutyl polysilsesquioxane
AKA: Pentacyclo(9.5.1.13, 9.15, 15.17, 13)octasiloxane, Octakis(2-methylpropyl)-, 1, 3, 5, 7, 9, 11, 13, 15-octakis(2-methylpropyl)-, Pentacyclo[9.5.1.13, 13]octasiloxane, RefChem:859707, 221326-46-1, PSS-OCTAISOBUTYL SUBSTITUTED 97, MFCD31010095, 15-Octakis(2-methylpropyl)-2, 4, 6, 8, 10, 12, 14, 16, 17, 18, 19, 20-dodecaoxa-1, 15-octasilapentacyclo[9.5.1.13, 13]icosane, OctaIsobutyl-POSS
Ingredient · Nail Conditioning · EWG: 4
Synthetic
Skin Conditioner
Silicone
Not Clean
Pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane, 1,3,5,7,9,11,13,15-octakis(2-methylpropyl)-
Formula
C32H72O12Si8
Mol. Weight
873.60
CAS #
221326-46-1
Form
Liquid
See origin →
Functions
Nail Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Locks In Moisture
Antioxidant Protection
Strengthens nails
Traditional Use
Modern silicone-based polymer developed for cosmetics in the late 20th century. Used to provide a lightweight, silky texture and improved spreadability in skincare and color cosmetic formulations.
Skin Types
all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
EWG
4
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not a Sensitizer
medical-approval
all-shades-safe
Regulatory Status
USApermitted
EUrestricted
JAPANrestricted
CANADArestricted
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR