since heparin itself does not coat the plastic catheter surface , a complex of heparin with tridodecylmethylammonium chloride ( tdmac ) was used which results in hydrophobic association of hydrocarbon chains of the tdmac with the catheter leaving the quaternary ammonium moiety of tdmac exposed to the surface forming ionic bonds with the highly anionic sulfate groups of heparin .
C0003075
anionic
C0038720
sulfate