Direct imaging of the surface distribution of immobilized cleavable polyethylene oxide-polybutadiene-polyethylene oxide triblock surfactants by atomic force microscopy


Karl F. Schilke, Gleeson Hall Rm. 102, Oregon State University, Corvallis, OR 97331, USA.



Cleavable amphiphilic triblock surfactants with methoxypolyethylene oxide (PEO) side-chains attached to polybutadiene (PBD) center blocks by ester linkages were synthesized. The PEO–PBD–PEO triblocks were adsorbed on hydrophobic silicon wafers and covalently stabilized by γ-irradiation. The PEO side-chains were then cleaved from the PBD backbones by acid hydrolysis. Decoration of the immobilized centerblocks with β-cyclodextrin allowed direct imaging by standard atomic force microscopy techniques. Widely varied surface coverage, layer morphology and distributions of the PBD centerblocks were observed on surfaces coated with different triblock concentrations and PEO:PBD ratios. Surfaces coated from 1 mg/mL solutions of triblocks (near the critical aggregation concentration (CAC), 0.28–0.53 mg/mL) were sparsely coated, and triblocks containing 75–85% PEO exhibited negligible surface coverage, possibly due to poor adsorption or facile desorption during rinsing. Dense surface packings, albeit some with evident defects sufficiently large to allow for protein adsorption, were produced from 10 mg/mL triblock solutions (an order of magnitude above the CAC). This proof-of-concept report describes a method that may be useful in optimizing surface coatings on model substrates, and thus lend insight into optimization of coating conditions for economical production of non-fouling triblock-based PEO coatings on clinically relevant biomedical materials. Copyright © 2012 John Wiley & Sons, Ltd.