SME's are surface-active oligomers covalently bonded to the base polymer during synthesis. SMEs-which include silicone (S), sulfonate (SO), fluorocarbon (F), polyethylene oxide (P), and hydrocarbon (H) groups-control surface chemistry without compromising the bulk properties of the polymer. The result may be the improvement of key surface properties, such as thromboresistance, biostability, and abrasion resistance. The base polymer is permanently enhanced without expensive post-fabrication treatments or topical coatings.

SMEs provide a series of (biomedical) base polymers that can achieve a desired surface chemistry without the use of additives. The added mobility of end groups relative to the backbone is thought to facilitate the formation of uniform overlayers by the surface-active (end) blocks. The use of the surface-active end groups leaves the original polymer backbone intact so the polymer retains strength and processability. Surface modified polymers have been made with tensile strengths exceeding 5000 psi containing only 0.5 wt. % or less of end groups. This patented technology is applicable to a wide range of polymers. However, modification with highly surface-active end groups is particularly adapted to the synthesis of polymers that incorporate low molecular weight mono-functional end groups for molecular weight control: e.g. polyurethanes and other step-growth polymers.

The SME approach also allows the incorporation of mixed end groups on a single polymer. For example, the combination of hydrophobic and hydrophilic end groups gives the polymer 'amphipathic' characteristics in which the hydrophobic-to-hydrophilic balance may be easily controlled.

Surface-Modifying End GroupT (SME™)	Possible Advantages
Silicone (S)	Hydrophobic, non-adhesive surface, self-lubricious, may increase biostability under certain conditions, may increase infection resistance
Flurocarbon (F)	Hydrophobic, non-adhesive surface, chemically-stable surface, may increase biostability under certain conditions, may increase infection resistance
Polyethylene Oxide (P)	Hydrophilic, affects material permeability, reduced protein adsorption
Sulfonate (SO)	Hydrophilic, may be thromboresistant, can react or bind to proteins and peptides
Hydrocarbon (H)	Hydrophobic, may increase biostability under certain conditions, may bind albumin
Mixed SMEs™	Example: Silicone (S) and PEO (P) - amphipathic structure-hydrophilic and hydrophobic polymer depending on the surrounding environment