3 research outputs found
Design of a Dynamic Polymer Interface for Chiral Discrimination
Enantioselective wetting of a chiral
polymer film was demonstrated.
The contact angle of chiral liquids on the film was strongly dependent
on their chirality although their physical properties including surface
tension were identical. Such wetting behavior resulted from the enantioselective
surface reorganization involving local conformational change of the
polymer chains at the liquid interface. The concept of “dynamic
interface for chiral discrimination” has possible potential
for the development of materials capable of chiral sensing, optical
resolution, and asymmetric synthesis
Load-Induced Frictional Transition at a Well-Defined Alkane Loop Surface
Self-assembled
monolayers (SAMs) have attracted considerable attention
as a tool to confer desirable properties on material surfaces. So
far, molecules used for the SAM formation are generally limited to
linear ones and thus chain ends dominate the surface properties. In
this study, we have successfully demonstrated unique frictional properties
of a SAM composed of alkane loops from cyclic alkanedisulfide on a
gold substrate, where both sulfurs are bound to gold. The frictional
response was proportional to the load. However, once the load went
beyond a threshold value, the frictional response became more dominant.
Such a frictional transition was reversible and repeatable and was
not discerned for a corresponding SAM composed of <i>n</i>-alkyl chains. The load-induced change in the frictional response
from the alkane loops could be associated with the conformational
change of the alkane loops. The present results differ from most studies,
in which the surface properties are designed on the basis of functional
chain end groups
Structure and Mechanical Properties of Polybutadiene Thin Films Bound to Surface-Modified Carbon Interface
The
structure and mechanical properties of polybutadiene (PB) films
on bare and surface-modified carbon films were examined. There was
an interfacial layer of PB near the carbon layer whose density was
higher (lower) than that of the bulk material on the hydrophobic (hydrophilic)
carbon surface. To glean information about the structure and mechanical
properties of PB at the carbon interface, a residual layer (RL) adhering
to the carbon surface, which was considered to be a model of “bound
rubber layer”, was obtained by rinsing the PB film with toluene.
The density and thickness of the RLs were identical to those of the
interfacial layer of the PB film. In accordance with the change in
the density, normal stress of the RLs evaluated by atomic force microscopy
was also dependent on the surface free energy: the RLs on the hydrophobic
carbon were hard like glass, whereas those on the hydrophilic carbon
were soft like rubber. Similarly, the wear test revealed that the
RLs on the hydrophilic carbon could be peeled off by scratching under
a certain stress, whereas the RLs on the hydrophobic carbons were
resistant to scratching