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Current Organic Chemistry
ISSN: 1385-2728
Current Organic
Chemistry,
Volume 9, Number 16, November 2005
Contents
Stimuli-Induced Functions
Guest Editor: Takayuki Suzuki
Editorial Pp.1615
Design of Functional Polymer Gels and Their Application
to Biomimetic Materials Pp.1617
Ryo Yoshida
[Abstract]
Electro- and Magneto-Rheological Materials: Stimuli-Induced
Rheological Functions Pp.1643
Keiji Minagawa & Kiyohito Koyama
[Abstract]
Electro- and Magneto-Responsible Chiral Polymers Pp.1665
Tomokazu Iwasaki & Hiroyuki Nishide
[Abstract]
Electrochemical Detection and Sensing of Reactive Oxygen
Species Pp.1685
Makoto Yuasa & Kenichi Oyaizu
[Abstract]
Abstracts
[Back to top]
Editorial
This is the first issue of Current Organic Chemistry dedicated
to “stimuli-induced functions”. Functional materials
currently cover a diverse range of applications. It is ideal
to activate these functions at any time and in any environment.
To realize this reality, I am convinced that it is necessary
to create systems with induced-function that respond to a
certain stimuli, e.g. light, heat, or physical force. When
people wish to apply the function of the material, they simply
input the appropriate stimuli. It is relatively easy to modify
the characteristics or add functionality to organic compounds
because there are many synthetic techniques already in place.
In this issue, I have tried to include a variety of approaches
to attaining “stimuli-induced functions.
Since the discovery of Tanaka’s gel, research into
“Polymer gels” has progressed rapidly as an example
of a stimuli-induced functional polymer. Because various stimuli
such as pH, temperature, and an electric field can induce
changes in the gels, many researchers have been studying these
gels intensively. The first contribution of this issue, by
Yoshida (The University of Tokyo, Tokyo, Japan), reviews the
design and recent applications of stimuli-induced gels, and
also describes his interesting self-oscillating gels, which
are promising as bio-mimetic artificial muscles.
The second paper by Minagawa (The University of Tokushima,
Tokushima, Japan) and Koyama (Yamagata University, Yonezawa,
Japan) describes electrorheological (ER), magnetorheological
(MR) and electromagnetorheological (EMR) materials. Such materials
include a number of compounds in the organic and inorganic
areas. In this paper, they emphasize organic polymers, of
which rheological functions are induced by electric and/or
magnetic fields. The preparation of the polymers, their field-induced
functions and their applications are described.
The molecular solenoid is one proposal to provide a new organic
material with electric and magnetic properties, both of which
are intimately connected with each other; one property should
induce the other. A helical and π–conjugated
polymer would be a potential candidate for such a functional
material, based on the well-defined chiral structure. In the
third paper, Nishide and Iwasaki (Waseda University, Tokyo,
Japan) focus on helicene derivatives and their interesting
optical properties that arise from the stiff structures and
molecular ordering. They also describe novel stiff helical
ladder polymers, the poly(thiaheterohelicene)s.
A material can be useful as a sensor if chemical bonding
of a specific species to the material induces an electron
transfer reaction. The fourth review by Yuasa and Oyaizu (Tokyo
University of Science, Noda, Japan) is a summary of detecting
and sensing of reactive oxygen species, which are found in
excess in the body as a result of cancer, brain and myocardial
infarction, and other diseases. They describe some biosensors
including all-synthetic sensors of reactive oxygen species,
of which the needle-type sensor is expected to be applicable
to certain sites in the living body.
I would like to thank all authors for their efforts in making
this first issue of “stimuli-induced functions”
interesting and informative. It was a great pleasure to be
involved in this issue of Current Organic Chemistry
as a Guest Editor and I hope you will enjoy reading the papers
as much as I have.
Takayuki Suzuki
Tokyo Denki University
Department of Environmental Materials of Science
Inzai, Chiba
JAPAN
[Back to top]
Design of Functional Polymer Gels and Their Application
to Biomimetic Materials
Ryo Yoshida
Over about the last two decades, many kinds of stimuli-responsive
polymer gels in response to the change in their surroundings
such as solvent composition, temperature, pH, and supply of
electric field, etc., have been developed. They have attracted
much attention as intelligent (or smart, biomimetic) materials
which have sensor, processor and actuator functions. Applications
to actuator (artificial muscle), biosensor, drug delivery
systems, purification or separation systems, etc. are extensively
studied. In this review, design of stimuli-responsive gels
and their application to bio- or biomimetic materials will
be discussed as well as our recent studies on novel self-oscillating
gels.
[Back to top]
Electro- and Magneto-Rheological Materials: Stimuli-Induced
Rheological Functions
Keiji Minagawa & Kiyohito Koyama
Various materials that show reversible changes in the rheological
properties in response to external stimuli, especially electric
and/or magnetic fields, have attracted attention because of
their possible applications to devices of transformation of
electric/magnetic stimulus into mechanical (passive) force.
These materials are called electrorheological (ER), magnetorheological
(MR), and electromagnetorheological (EMR) materials. The field-responsive
properties are regarded as ‘rheological functions’
induced by the field, which characterize these materials.
The ER/MR materials can be classified into some types, i.e.
suspensions, homogeneous or heterogeneous liquids, elastomers/gels,
etc. according to the rheological characteristics in the absence
and presence of the electric/magnetic fields. For each type,
the field-induced rheological properties are briefly summarized,
followed by some topics on the material preparation, stimuli-induced
functions, and/or practical applications are exemplified.
The materials chemistry, especially for organic/polymer materials,
are mainly focused on here.
[Back to top]
Electro- and Magneto-Responsible Chiral Polymers
Tomokazu Iwasaki & Hiroyuki Nishide
Helical polymers and macromolecules have precisely ordered
stereostructures, and their potential applications include
chiral separation and sensing based on molecular recognition
and liquid crystalline formation by molecular ordering. Among
them, π-conjugated
polymers with a helical structure have often exhibited unique
electro- and magneto-responsibilies. In this review, we describe
the helical π-conjugated
macromolecules as electro- and magneto-responsible materials
including our recent studies. In Chapter 2, the recent studies
of helical polymeric molecules with π-conjugated
structures are reviewed. We focus on “helicene”
derivatives, which consist of fused-benzene and/or thiophene
rings, in Chapter 3 and summarize their syntheses, characteristics,
and optical properties based on the stiff structures and molecular
ordering. Helical ladder polymers, “poly(thiaheterohelicene)s”
comprised of fused-benzothiophene rings, are discussed in
Chapter 4 among their stiff helical structure and π-conjugation.
The combined functions of electro- and magneto-properties
of the chiral polymer are described using the example of poly(thiaheterohelicene)s,
such as electron transmission along the helical main-chain
and a molecule model of a molecular solenoid, in the final
section.
[Back to top]
Electrochemical Detection and Sensing of Reactive Oxygen
Species
Makoto Yuasa & Kenichi Oyaizu
Reactive oxygen species (ROS) such as superoxide anion radical
(O2-×) play an essential role
on normal cellular growth and homeostasis. However, excess
ROS generated by perturbing O2-×
homeostasis under various conditions of oxidative stress induce
high radical toxicity, resulting in many diseases such as
cancer, brain and myocardial infarction, and inflammation.
Quantitative analysis of O2-×
by a convenient method is a subject of intense research, since
most of ROS are derived from O2-×.
In situ real-time measurement of O2-×
is very important to understand the relevance of ROS to many
diseases. Recent progress in electrochemical sensors for the
facile detection of O2-× including
biosensors utilizing a variety of metalloproteins as sensing
elements for O2-× and very recently
developed all-synthetic sensors with a high selectivity for
O2-× detection, is reviewed. Emphasis
is placed on the possibility of the all-synthetic sensor for
convenient in vivo measurement of ROS.
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