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Books > Science & Mathematics > Chemistry > Organic chemistry > Polymer chemistry
In many cases rheological measurements are carried out in the
simplest of geometries, but the interpretation involved in
obtaining the rheological parameters of the test fluids from these
measurements is surprisingly complex. The purpose of this book is
to emphasise the points on which most workers in the field agree,
and to let the authors deal with the contentious points according
to their own beliefs and experience. This work represents a summary
of the current thought on rheological meas urement by experts in
the various techniques. When making measurements and obtaining from
them parameters that describe the flow behaviour of the test
fluids, it is essential that the experimentalist understands the
underlying theory and shortcomings of the measurement technique,
that he is aware of the likely microstructure of the fluid, and
that from this he can appreciate how the fluid and the measuring
system will interact with each other. It is this interaction that
gives both the required rheological parameters of the fluids and
the artefacts that confuse the issue. This book covers the main
rheological measurement techniques from capillary, slit and
stretching flows to rotational and oscillatory rheometry in various
geometries including sliding plate measurements. These topics are
backed up by chapters on more practical aspects, such as commercial
instruments, and on computer control and data acquisition. The
chapters deal with the basic methods, how the measurements are
taken, and what assumptions and interpretations are made to obtain
valid data on the test fluids."
Most of the untreated surfaces of polymers used in industry are not
hydrophilic but hydrophobic. It is, therefore, difficult to bond
these nonpolar polymer sur faces directly to other substances like
adhesives, printing inks, and paints because they generally consist
of polar compounds. On the other hand, polymer surfaces generally
adsorb proteins when brought into direct contact with a bio logical
system, resulting in cell attachment or platelet aggregation. The
protein adsorption and attachment of biological components trigger
a subsequent series of mostly adverse biological reactions toward
the polymeric materials. Therefore, the technologies for surface
modification of polymers or regulation of the polymer surface
interaction with other substances have been of prime importance in
polymer applications from the advent of polymer industries. Some of
the technologies have been directed to introduction of new function
alities onto polymer surfaces. The new functionalities introduced
include improved surface hydrophilicity, hydrophobicity, bio
compatibility, conductivi ty, anti-fogging, anti-fouling, grazing,
surface hardness, surface roughness, adhesion, lubrication, and
antistatic property. Theoretically, there is a large dif ference in
properties between the surface and the bulk of a material and only
the outermost surface is enough to be taken into consideration when
the sur face properties are concerned. However, this is not the
case for polymer surfaces, as the physical structure of the
outermost polymer surface is generally not fixed but continuously
changing with time due to the microscopic Brownian motion of
polymer segments."
After epoxy resins and polyimides, cyanate esters arguably form the
most well-developed group of high-temperature, thermosetting
polymers. They possess a number of desirable performance
characteristics which make them of increasing technological
importance, where their somewhat higher costs are acceptable. The
principal end uses for cyanate esters are as matrix resins for
printed wiring board laminates and structural composites. For the
electronics markets, the low dielectric loss characteristics, dimen
sional stability at molten solder temperatures and excellent
adhesion to conductor metals at temperatures up to 250 DegreesC,
are desirable. In their use in aerospace composites, unmodified
cyanate esters offer twice the frac ture toughness of
multifunctional epoxies, while achieving a service tem perature
intermediate between epoxy and bis-maleimide capabilities.
Applications in radome construction and aircraft with reduced radar
signatures utilize the unusually low capacitance properties of
cyanate esters and associated low dissipation factors. While a
number of commercial cyanate ester monomers and prepoly mers are
now available, to date there has been no comprehensive review of
the chemistry and recent technological applications of this
versatile family of resins. The aims of the present text are to
present these in a com pact, readable form. The work is primarily
aimed at materials scientists and polymer technologists involved in
research and development in the chemical, electronics, aerospace
and adhesives industries. It is hoped that advanced undergraduates
and postgraduates in polymer chemistry and technology, and
materials science/technology will find it a useful introduc tion
and source of reference in the course of their studies.
How did life begin on the Earth? The units of life are cells, which
can be defined as bounded systems of molecules that capture energy
and nutrients from the environment -- systems that expand,
reproduce, and evolve over time, often into more complex systems.
This book is the proceedings of a unique meeting, sponsored by NATO
and held in Maratea, Italy, that brought together for the first
time an international group of investigators who share an interest
in how molecules self-assemble into supramolecular structures, and
how those structures may have contributed to the origin of life.
The book is written at a moderately technical level, appropriate
for use by researchers and by students in upper-level undergraduate
and graduate courses in biochemistry and molecular biology. The
overall interest of its subject matter provides an excellent
introduction for students who wish to understand how the
foundational knowledge of chemistry and physics can be applied to
one of the most fundamental questions now facing the scientific
community. The editors are pioneers in defining what we mean by the
living state, particularly the manner in which simple molecular
systems can assume complex associations and functions, including
the ability to reproduce. Each chapter of the book presents an
up-to-date report of highly significant research. Two of the
authors received medals from the National Academy of Science USA in
1994, and other research reported in the book has been featured in
internationally recognized journals such Scientific American, Time,
and Discover.
The broad field of conformational motion disorder in crystals is
described with particular attention to the separation from the well
known mesophases of liquid crystals and plastic crystals.
Structure, thermodynamics and motion of a larger number of small
and large molecules are discussed. Of special interest are the
borderlines between smectic and high viscosity liquid crystals and
condis crystals and between plastic crystals and condis crystals as
complicated by pseudorotation, jumping between symmetry-related
states and hindered rotation. This paper illustrates the wide
distribution of conformational disorder in nature. Condis crystals
and glasses ("Con"formational "Dis"order) can be found in small and
large molecule systems made of organic, inorganic and biological
compounds. The condis state was newly discovered only four years
ago. In this article over 100 examples are discussed as example of
the condis state. In many cases the condis state was suggested for
the first time. Motion in the Condensed State, Condis Crystals and
their Relation to Plastic Crystals, Condis Crystals of Flexible
Macromolecules, Condis Crystals and their Relation to Liquid
Crystals, Condis Crystals of Stiff Macromolecules.
Viscoelasticandtransportpropertiesofpolymersintheliquid(solution,melt)or
liquid-like (rubber) state determine their processing and
application to a large extent and are of basic physical interest
[1-3]. An understanding of these dynamic properties at a molecular
level, therefore, is of great importance.
However,thisunderstandingiscomplicatedbythefactsthatdi?erentmotional
processes may occur on di?erent length scales and that the dynamics
are governed by universal chain properties as well as by the
special chemical structure of the monomer units [4,5]. The earliest
and simplest approach in this direction starts from Langevin
equations with solutions comprising a spectrum of relaxation modes
[1-4]. Special features are the incorporation of entropic forces
(Rouse model, [6]) which relax uctuations of reduced entropy, and
of hydrodynamic interactions (Zimm model, [7]) which couple
segmental motions via long-range back ow elds in polymer solutions,
and the inclusion of topological constraints or entanglements
(reptation or tube model, [8-10]) which are mutually imposed within
a dense ensemble of chains. Another approach, neglecting the
details of the chemical structure and
concentratingontheuniversalelementsofchainrelaxation,isbasedondynamic
scalingconsiderations[4,11].Inparticularinpolymersolutions,thisapproach
o?ers an elegant tool to specify the general trends of polymer
dynamics, although it su?ers from the lack of a molecular
interpretation. A real test of these theoretical approaches
requires microscopic methods, which simultaneously give direct
access to the space and time evolution of the segmental di?usion.
Here, quasi-elastic scattering methods play a crucial role
sincetheyallowthemeasurementofthecorrespondingcorrelationfunctions.In
particular,thehigh-resolutionneutronspinecho(NSE)spectroscopy[12-15]is
very suitable for such investigations since this method covers an
appropriate range in time (0.005)t/ns)40) and space (r/nm [15).
Furthermore, the
possibilityoflabellingbyhydrogen-deuteriumexchangeallowstheobservation
of single-chain behavior even in the melt.
The renewed and increasing interest in lipid self-assembly, phase
behaviour and interfacial properties can be related to both a much
improved insight in biological systems and the applications of
lipids in food and pharmaceutical industry; in the latter, the
development of drug delivery systems based on lipids has become in
focus. Amphiphilic systems comprise lipids, surfactants as well as
different types of polymers, including block and graft copolymers.
Research on biological amphiphiles has often been conducted
separate from research on synthetic ones. However, in recent years
a very fruitful convergence between the two fields has evolved.
These new perspectives on fundamental research and applications of
lipids are discussed in these proceedings from an international
symposium on "Lipid and Polymer Lipid-systems," October 2000 in
Chia Laguna in Italy - a joint undertaking of Prof. Maura Monduzzi
at Cagliari University, Italy and Camurus Lipid Research
Foundation, Lund, Sweden.
The incessantly interest in aqueous polymer dispersions (APD)
since more than 90 years can be related to the almost unlimited
possibilities to tailor APD to specific needs.
These proceedings from an international symposium on "Polymer
Colloids: Preparation & Properties of Aqueous Polymer
Dispersions" held at the Swabian Conference Center (Kloster Irsee,
Germany) witness this statement.
The 33 contributions cover important aspects of APD such as control
of particle size and stabilization, different polymerization
technologies, applications as binders, paints, or as supports for
proteins and hence, span the whole range from academic to
practical.
Leading Nordic-Baltic scientists and their colleagues from other
countries present recent research on a broad range of topics in
surface and colloid science: adhesion, adsorption processes,
characterization of solid/liquid and solid/polymer interfaces,
chemical and particle depositions, colloid stability,
emulsification and encapsulation, interfacial reactions, new
surfactants, polymer-surfactant interactions, self-assembly
processes, and functionalized surfaces for bio- and chemosensors.
The papers were presented at the 1st Nordic-Baltic Meeting on
Surface and Colloid Science, which was held in Vilnius, Lithuania
on August 21-25, 1999, as a continuation of the traditional
Scandinavian Symposium on Surface Chemistry.
The two volumes "New Developments in Polymer Analytics" deal with
recent progress in the characterization of polymers, mostly in
solution but also at s- faces. Despite the fact that almost all of
the described techniques are getting on in years, the contributions
are expected to meet the readers interest because either the
methods are newly applied to polymers or the instrumentation has
achieved a major breakthrough leading to an enhanced utilizaton by
polymer scientists. The first volume concentrates on separation
techniques. H. Pasch summarizes the recent successes of
multi-dimensional chromatography in the characteri- tion of
copolymers. Both, chain length distribution and the compositional
h- erogeneity of copolymers are accessible. Capillary
electrophoresis is widely and successfully utilized for the
characterization of biopolymers, particular of DNA. It is only
recently that the technique has been applied to the
characterization of water soluble synthetic macromolecules. This
contributrion of Grosche and Engelhardt focuses on the analysis of
polyelectrolytes by capillary electopho- sis. The last contribution
of the first volume by Coelfen and Antonietti sum- rizes the
achievements and pitfalls of field flow fractionation techniques.
The major drawbacks in the instrumentation have been overcome in
recent years and the"triple F techniques" are currently advancing
to a powerful competitor to size exclusion chromatography.
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