Two generations of amphiphilic membranes synthesized in our laboratories for biological/medical applications are highlighted. Recent results obtained with representative 2nd generation membranes designed specifically for immunoencapsulation of pancreatic islets and cells are summarized. The latter tri-component membranes comprise well-defined hydrophilic poly(ethylene glycol) and hydrophobic/oxyphilic polydimethylsiloxane segments crosslinked by oxyphilic polycyclosiloxane domains, which also provide reinforcement. Select membranes are demonstrated to allow the diffusion of glucose and insulin but prevent the permeation of immunoglobulin G. These membranes remain permeable despite long incubation in IgG solution.

The electrostatic surface potential of self-assembled monolayers (SAMs) of aliphatic and aromatic thiols has been measured using electrostatic force microscopy. The variation of the surface potential of chemisorbed alkanethiols, with respect to bare Au(111), is observed to increase with increasing chain length. The trend is similar to that observed in the literature. A preliminary theoretical model, based on treating the monolayer as a sheet of dipoles, has been used to calculate the surface potential of alkanethiols. Similar measurements on several aromatic thiols, with a symmetric and non-symmetric molecular structure, reveal that non-symmetric systems have significantly higher potential (≥ 170mV) than the symmetric molecules.