Trimethylpentyl Polysilsesquioxane

AKA: Isooctylsilsesquioxane, Cage mixture
Synthetic
Skin Conditioner
Not Clean
OriginSynthesized from silica and organic silane precursors through condensation polymerization reactions. Produced by hydrolyzing and cross-linking silane monomers to form a cage-like polymeric structure.
Trimethylpentyl 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 trimethylpentyl group. For the larger polymeric polysilsesquioxanes, some of the silicon atoms are not connected to other silicon atoms and
CAS #
190732-67-3, 444619-08-3
Form
Liquid
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
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.
UV Protection
Strengthens nails
The paper trail
🔬Peer-reviewednone on file
⚖️Regulatory0 listings
🛡️Safety-assessed1 review →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
EWG
4
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Skin Irritant in Testing
1 study / 1 irritating (CIR 743)
Concentration Guide
CIR lists it as not reported to be in use.
CIR · report published 2017
Regulatory Status
USA✔ permitted
EU⚠ restricted
JAPAN⚠ restricted
CANADA⚠ restricted
Verified Jun 2026
Data: CosIng · EWG · CIR