Exploring the rules for selective deposition: Interactions of model polyamines on acid and oligoethylene oxide surfaces

New results using chemical force microscopy examine the relationships between polyions and both charged acid surface groups (COOH) and neutral oligoethylene oxide (EG) functionalized surfaces. Although poly(ethylene oxide) (PEO) and its derivatives have been known to resist protein deposition, our data indicate that certain hydrophobic polyelectrolytes, including polyallylamine hydrochloride (PAH), are actually attracted to the EG surface under certain pH conditions. Polymer surface modified colloidal particles were used as force probes to examine the interactions of polyamines with hydrophilic backbones, such as linear polyethyleneimine, and those with hydrophobic backbones, such as PAH, on alkanethiol monolayers. The adsorption and force curves of these two model polyamines with COOH and EG surfaces at a range of pH values is discussed. It is thought that the behavior observed is related to conformational differences between the hydrophobic and hydrophilic polymers at certain degrees of ionization. The differences in adsorption behavior of these and other polymers can be used as a tool to effectively control the region of film deposition. In general, these studies of synthetic polyamines have implications in understanding the nature of PEO-functionalized bioinert surfaces and the interactions of more complex polyelectrolytes such as proteins with EO-functionalized surfaces.