Nicholas L. Abbott

Surface‐Initiated Polymerization for Amplification of Self‐Assembled Monolayers Patterned by Microcontact Printing

Patterned polymer brushes can be prepared by a novel strategy that combines surface-initiated polymerization and microcontact printing (see picture; μCP SAM indicates the self-assembled monolayer formed by microcontact printing). The living nature of the polymerization process permits the thickness of the polymer brush and its physical properties to be accurately controlled.

Planar anchoring of nematic 4‐n‐pentyl‐4′‐cyanobiphenyl on self‐assembled monolayers formed from alkanethiols on gold

We report measurements of planar anchoring of nematic 4‐n‐pentyl‐4′‐cyanobiphenyl (5CB) on self‐assembled monolayers (SAMs) formed from CH3(CH2)mSH (7⩽m⩽17) on films of gold (prepared without oblique deposition) by using reflection interferometry. The anchoring observed contrasts with past reports of homeotropic anchoring of 5CB by surfaces, such as monolayers formed from octadecyltrichlorosilane on silica, with energies as low as alkanethiols on gold (19 mN/m). The anisotropic dispersion force acting between 5CB and gold was calculated to favor planar anchoring of 5CB on SAMs formed from CH3(CH2)15SH by ∼0.1 mN/m, and can, therefore, override self‐interactions of 5CB that lead to homeotropic anchoring. Electric field‐induced Freederiksz transitions of 5CB supported on bare gold, and on SAMs formed from CH3(CH2)15SH on gold, confirm weaker (planar) anchoring of 5CB on SAMs on gold as compared to bare gold.

Oberflächeninitiierte Polymerisation zur Verstärkung selbstorganisierter, durch Mikrokontakt‐Druck gemusterter Monoschichten

Gemusterte Polymerbursten lassen sich durch eine neue Strategie erhalten: durch oberflacheninitiierte Polymerisation, kombiniert mit Mikrokontakt-Drucken (siehe Bild; μCP steht fur die selbstorganisierte Monoschicht, die durch Mikrokontakt-Drucken erhalten wird). Da es sich hierbei um eine lebende Polymerisation handelt, konnen die Dicke der Polymerburste und ihre physikalischen Eigenschaften genau eingestellt werden.

Surface effects on orientation of liquid crystals

Optical second harmonic generation (SHG) is now being used to measure the orientations of mesogens adsorbed at a variety of polar organic surfaces (e.g. rubbed films of polyimides). For some surfaces, at least, these measurements can be used to predict the anchoring of bulk liquid crystals. Few rules exist, however, to guide the design of surfaces for manipulation of the orientations of adsorbed mesogens (and thus bulk anchoring). These rules are difficult to establish on surfaces as complicated as those of rubbed polymers. Self-assembled monolayers formed from functionalized alkanethiols on semi-transparent films of gold and silver do permit the synthesis of well defined surfaces, and these surfaces are now being used in studies of the anchoring of liquid crystals. Orientations of liquid crystals on these surfaces differ substantially from orientations observed in the past on surfaces formed from organosilanes.

Observation of Long-Range Orientational Ordering in Metal Films Evaporated at Oblique Incidence onto Glass

We studied long-range orientational ordering in polycrystalline Au films (10 nm - 30 nm) that are evaporated at oblique incidence onto a glass substrate at room temperature. By measuring the averaged optical second-harmonic response from the films over a 6-mm diameter region, we observed a transition from the expected in-plane mirror symmetry at 10 nm to a surprising three-fold in-plane rotational symmetry at 30 nm. X-ray pole figure analysis performed on these films showed the strong fiber texture typical of fcc films, but with a restricted, three-fold symmetric, distribution of crystallite orientations about the fiber axis.