Single-molecule atomic force microscopy (AFM) was used to study the statistical distribution of contour lengths (polydispersity) of polymer chains grafted to a surface. A poly(dimethylsiloxane) (PDMS) monolayer was grafted on a flat silicon substrate by covalently bonding Cl-terminated PDMS (M w ) 15000-20000) to an OH-silicon surface and characterized using contact angle measurements, ellipsometry, and single-molecule AFM. A model for the single-chain dynamics is presented. The statistical distributions of the polymer contour lengths were found to depend on the concentration of the PDMS polymer used in the grafting solutions. Shifts of the statistical distributions toward higher contour lengths indicated preferential adsorption of longer chains with increasing PDMS:CH 2 Cl 2 volume ratios of 0.005-0.16. The gel permeation chromatography (GPC) profile was found to correlate with the most dilute (0.005 volume ratio) AFM data. The polydispersity index (PI) calculated using AFM data was found to be 1.56 compared to 1.62 by GPC. A surface grafted with two PDMS polymer samples of average molecular weights, 3000 and 15000-20000, was found to have a bimodal distribution of contour lengths, with peaks corresponding to the two grafting samples. † Part of the special issue "John T. Yates, Jr. Festschrift". * To whom correspondence should be addressed. PI ) M h w /M h n (1) 3965

No abstract

Single-molecule studies under poor solvent conditions show that atomic force microscopy (AFM) measurements of contour lengths of polystyrene 12K and 17K relate well to gel permeation chromatography (GPC) data when grafting concentrations are low (not greater than 0.7 mM). Contact angles and ellipsometry have been used to characterize the surfaces and indicate low grafting densities at this grafting concentration. Persistence lengths (p) of different length polystyrene chains, when fitted to a WLC (worm-like chain) model, show values of p ¼ 0.23 nm AE 0.10 nm and p ¼ 0.25 nm AE 0.13 nm, for 12 K and 17 K polystyrene, respectively, when the persistence lengths are fitted to log-normal distributions. These values are close to the expected theoretical value of 0.23 nm and further confirm that mostly single molecules were studied on these polystyrene surfaces. Higher grafting concentrations (!1 mM) resulted in pulling multiple molecules.

No abstract

This mini-review reports efforts to develop new scanning probe microscopies to characterize the function and aging of textured, minimally adhesive polymer surfaces used for antifouling applications in the marine environment. Novel atomic force and infrared near field microscopy techniques have been used to characterize the polymer surface adhesion and structural properties. These techniques may find promise for characterizing the deposition of the extracellular matrix of organisms as well as aging of the polymer coating itself. The reported work is part of a larger effort to reduce biofouling on ships' hulls through the development and use of improved coating materials.