US Patent No. 12,048,760 B2 (Soo-Young Kang, Zhaoxia Ji, Ling-Fang Tseng, Dinara A. Villanueva); Living Proof, Inc., Boston, MA, has patented a hair treatment composition comprising a polyurethane-urea crosslinked by at least one hydrocarbon based triol or tetraol, wherein the polyurethane-urea is a salt of the formula: [Q, W, V, Y and Z]X.

• Q is the product formed from polyisocyanate;

• W is the product formed from polycarbonate polyol monomer;

• V is the product formed from hydrocarbon based triol or tetraol;

• Y is the product formed from C3-C8 alkyldiol optionally substituted with —C(O)OH or a mono-amino C3-C8 alkyldiol;

• Z is the product formed from C3-C8 alkyldiamine optionally substituted with —C(O)OH; and

• X is a neutralizer.

The Young’s modulus of the polyurethane-urea is above 150 MPa. The elongation at break of the polyurethane-urea is from about 15% to about 300. The moisture uptake of the polyurethane-urea is less than 10%.