We use static contact angle measurements and near-edge absorption fine structure to elucidate the surface structure and molecular orientation of hydrocarbon-based mechanically assembled monolayers (H-MAMs), structures formed by combination of assembly of alkyl moieties onto flexible elastomeric substrates and mechanical manipulation of the substrates. Specifically, we report that the organization of the grafted molecular array (“liquid”-like vs. solid-like) can be tailored by varying the degree of stretching of the elastomeric substrate. We also show that the H-MAM surfaces exhibit excellent stability.

We probed the glass transition temperature Tg at the surface of polystyrene (PS) samples with different molecular weights by embedding of gold nanoclusters. The embedding of the nano-clusters was monitored by x-ray photoelectron spectroscopy (XPS). The onset embedding temperature determined by XPS was taken as a measure for the Tg at the surface. We observed a small decrease of Tg at the surface relative to the bulk for all molecular weights (ΔTg= 2.5- 8.5 K). This decrease is small for short chains (MW = 3.6 kg/mol) and grows to a saturation for MW ≥ 44 kg/mol (ΔTg ≍ 8 K). This is in accord with the smaller relative increase in the number of degrees of freedom between bulk and surface for shorter chains.

This paper reports the result of a study of organic-inorganic network assembles as chemically sensitive interfacial materials. Core-shell gold nanoparticles of a 5 nm size and organic linkers such as 1,9-nonanedithiol and 1,5-pentadithiol are utilized as building blocks for constructing network assembles on planar substrates. To explore the responsive properties of such materials to volatile organic compounds, we utilized interdigitated microelectrodes as transducer. The responses at these nanostructured interfaces are demonstrated to be dependent on the chain length of the linking molecules. The difference of molecular interactions at the nanostructured interface has a significant impact to the response profile and sensitivity. The implications of the findings to the delineation of design parameters for constructing organic-inorganic network assemblies as chemically-sensitive interfacial materials are also discussed.