Organo Modified Siloxanes (OMS)

Structurally, organomodified siloxanes (OMS) are derived from polydimethyl siloxanes (PDMS), better known as silicone fluids, methyl silicone oils or simply silicone oils.

Pure silicone oils are characterized by their chemical inertness, good temperature stability and excellent surface activity. Their surface tension is very low (21 mN/m), much lower than that of hydrocarbon surfactants. However, the incompatibility of silicones in most matrices prevents the full utilization of their advantageous properties.

Therefore it is necessary to modify the polydimethyl siloxane in order to improve their compatibility with, or solubility in, aqueous or organic systems. This is achieved by attaching various organic moieties. This type of modification makes it possible to produce specific physicochemical interactions or chemical reactivity with, or in, a substrate phase.

Due to the presence of siloxane segments, many OMS are highly surface active. This enables OMS to reduce surface tension much better than organic surfactants. OMS are also active in non-aqueous systems where organic products fail to work.

In addition to their pronounced surfactant properties, organomodified siloxanes are primarily characterised by their multifunctionality. Their properties include: levelling, wetting or dewetting; releasing and/or debonding; foaming or defoaming; emulsifying or demulsifying; hydrophilic or hydrophobic; dispersing or coagulating. A release agent can also be a good emulsifier, depending on the matrix.

Generic structures of siloxanes (R = organic ligand)

2) comb-like siloxane