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Über dieses Buch

This volume summarizes the papers presented at the First Osaka University Macromolecular Symposium OUMS'93 on "Ordering in Macromolecular Systems", which was held at Senri Life Science Center, Osaka, Japan, on June 3 through June 6, 1993. The symposium covered the three topics, (1) Crystallization and Phase Transitions, (2) Polymer Liquid Crystals and (3) Block Copolymers, Polymer Blends and Surfaces, and invited leading scientists in these fields. At present any of these topics is a hot issue in itself and frequently taken up separately in many occasions. It is noted however that all these topics are correlated with each other with the keyword "Ordering" and their combination provides a unique feature of the present symposium in reflecting the interactions among investigators working in these important fields with the common ground expressed by the keyword "Ordering". Nineteen invited lectures and 40 posters of both experiment and theory were presented at the symposium, and the eighteen lectures and ten poster presentations contribute to this volume. In the first topic crystal structures and their transitions were discussed from kinetic as well as static points of view; attention was paid to give a molecular-level interpretation of the structure, phase transition and physical properties, using theories and simulations. The second topic was mainly concerned with static structures and thermodynamic properties of polymer liquid crystals including phase behaviours.

Inhaltsverzeichnis

Frontmatter

A Unifying Scheme for Polymer Crystallization Based on Recent Experiments with Wider Implications for Phase Transformations

Abstract
This lecture is aimed to link the “main stream” subject of chain folded polymer crystallization to the “speciality stream” of extended chain crystallization, the latter as typified by the crystallization of polyethylene under pressure. This is achieved through a scheme based on some new experimental material comprising the recognition of thickening growth as a primary growth process of lamellae and of the prominence of metastable phases, specifically of the mobile hexagonal phase in polyethylene. The scheme relies on the consideration of crystal size as a stability determining factor, namely on melting point depression, which in general is different for different polymorphs. It is shown that under specificable conditions phase stabilities can invert with size, i.e. a phase which is metastable for infinite size can become the stable one when the phase is sufficiently small. When applying this condition to crystal growth it follows that a crystal in such a situation will appear and grow in a phase that is different from that in its state of ultimate stability, maintaining this state as a metastable one or transforming into the ultimate stable state during growth according to circumstances. The consequences of such deliberations, of potential significance to all phase transformations also beyond polymer crystallization, are being developed throughout the paper.
A. Keller, M. Hikosaka, S. Rastogi, A. Toda, P. J. Barham

Order-Disorder Transitions in Crystalline Polymers with Characteristic Mechanical and Electric Properties

Abstract
Structural changes occurring in phase transitions of several polymers with characteristic physical properties have been investigated based on X-ray diffraction and infrared spectroscopic methods. (1) In the thermochromic phase transition of electrically conductive poly(3-alkylthiophene)s, the long alkyl side chains experience trans-gauche conformational change, which affects the planarity or the conjugation length of polythiophene skeletal chains, resulting in a drastic change of sample color. Alkyl chains were found to play an important role in determining the conjugation length and the cooperativity of phase transition. (2) A side-chain-type ferroelectric liquid crystalline polymer was found for the first time to show a variety of layer stacking structure or polytype phenomenon by changing a cooling rate from the isotropic state only slightly. A complicated transition scheme was clarified by measuring the temperature dependence of X-ray diffractions.
Kohji Tashiro, Masamichi Kobayashi

Computer Simulation of Macromolecular Crystals and Their Defects

Abstract
Computational results on the dynamics of polyethylene, derived by our research group during the last five years are reviewed and connected to experimentally known facts. It could be demonstrated that conformational defects can be created at temperatures as much as 100 K below the melting point and that the concentration continues to increase exponentially with temperature, ultimately leading to disordered crystals along the polymer chains (high temperature CONDIS crystals). Although the rate of formation of these defects is high, approximately 1×1010 s−1 at 350 K, the defects do not, by themselves, lead at low temperature to macroscopic motion that could give rise to lamellar thickening or deformation. The diffusion mechanisms involve coupling of large-amplitude torsional motion with transverse and longitudinal vibrations of the crystal, which lead to the formation of disclinations, dispirations, and twists. Such defects can, under proper conditions, move towards the end of the crystal, thereby causing a chain diffusion process that is probably at the root of lamellar thickening and deformation processes. Collective twisting of the chains without major influence of conformational defects leads to hexagonal or pseudo-hexagonal structures of the asymmetric motifs, involving dynamic multidomain arrangements of the chains. The especially efficient molecular dynamics simulation-code developed for this research produces reasonable agreement with experimental data on density, defect concentration, heat capacity, vibrational spectra (including stress-induced frequency shifts), melting temperature, and speed of sound. The simulations produced data on crystals of up to 30,000 atoms for times of up to 100 picoseconds (10−10 s). The total simulation efforts needed a massive effort of approximately 8,000 hours of supercomputer CPU time between 1988 and 1993.
Bernhard Wunderlich, Bobby G. Sumpter, Donald W. Noid, Guanghe L. Liang

AFM Observation of Surface Morphology for Oriented PET Films

Abstract
The atomic force microscopy (AFM) was used to examine surface morphologies for biaxially oriented PET films, and the results were discussed from the view point of strain induced structure formation. For the most of oriented films, the nodular microstructure was observed. Its height and diameter were several nm and 20–50nm, respectively. Although the microstructure was observed also on the surface of as-cast film, its height was less than lnm. The plot of surface roughness measured by AFM as a function of the draw ratio showed that the microstructure had developed gradually with drawing until a certain draw ratio (λ c), but the development had declined after λ c. The AFM images and the behavior of roughness change also showed that a higher order structure like a spherullite was easily formed by annealing for the films undrawn or drawn less than λ c, while the films drawn more than A c were little influenced by the annealing. The strain induced crystallization were examined by wide angle X-ray scattering (WAXS), density and average refractive index measurements. The experimental results suggested that the development of surface microstructure was closely related to the strain induced crystallization, and the strain induced crystallization in the bulk slightly delayed compared with the development of surface microstructure.
Y. Sasaki, X. J. Shao, T. Suzuki, H. Ishihara

Characterization of Polymer Interface by Micro Raman Spectroscopy

Abstract
Micro Raman spectroscopy was applied to characterize the interface region of multi-layered film specimens in which ethylene-propylene random copolymer(EPR) was sandwiched with polyethylene(PE) or polypropylene(PP) sheets. Micro Raman line scan of the interface region for PE/EPR pair indicated that PE molecules migrated into the EPR phase and crystallized there, forming a mixed phase where the PE crystallites were embedded in EPR matrix. Apparent diffusion constant(D) evaluated from the thickening rate of the mixed phase strongly depended on the chemical composition of EPR, i.e., D increased with increasing the ethylene content of EPR. On the contrary, the mixed phase thickness of PP/EPR pair showed the opposite dependence on the composition of EPR.
S. Hosoda, S. Hoshi, K. Kojima, A. Uemura, H. Yamada, M. Kobayashi

Supramolecular Assemblies of Cyclodextrins with Polymers and Preparation of Polyrotaxanes

Abstract
Cyclodextrins (CDs) have been found to form inclusion complexes with various polymers with high selectivities to give stoichiometric compounds in crystalline states. α-CD formed complexes with poly(ethylene glycol)(PEG) of molecular weight higher than 300, although β-CD did not form complexes with PEG of any molecular weight. However, β-CD formed complexes with poly(propylene glycol)(PPG), although α-CD did not form complexes with PPG of any molecular weight. γ-CD formed complexes with poly(methyl vinyl ether)(PMVE), though α- and β-CD did not form complexes with PMVE. Polyrotaxanes in which many CDs are threaded on a single PEG chain were prepared by capping the chain ends of the complex with bulky groups. The neighboring CDs in a polyrotaxane are crosslinked by epichlorohydrin and then stoppers at the both ends and the polymer chain of the crosslinked polyrotaxane were removed by strong base to give a tubular polymer, a molecular tube.
A. Harada, J. Li, M. Kamachi

Case II Diffusion in Polystyrene Fiber: In-situ Measurement of a Moving Sharp Front

Abstract
In-situ measurement of a moving sharp front formed in a polystyrene fiber- organic vapor system was presented by using optical microscopy and light scattering technique. The diffusion of acetone vapor with the relative vapor pressure of 0.92 into the physically aged polystyrene fiber of 25 μm diameter was measured at 25°C. The system showed following characteristics; (1) an induction time, (2) formation of a sharp front after the induction time, (3) nearly constant rate of the sharp advancing front, (4) step-like distribution of the penetrant concentration at the sharp front, (5) uniform state of swelling behind the sharp front. These findings strongly suggested Case II diffusion. The effect of the physical aging on the polymer glass to get front formation was also discussed based on Thomas and Windle model.
Mitsuhiro Fukuda

“Liquid Crystallization” Mechanism of Liquid Crystalline Polymers

Abstract
Morphology of the liquid crystals of thermotropic main chain liquid crystalline polymers isothermaly formed at atmospheiric pressure from the melt and their formation mechanism was studied. Materials used were a copolyether based on 1,2-Bis (4-hydroxy phenyl) ethane (BPE-8/12) and poly [bis (trifluoro ethoxy) phosphazenel, (PBFP). Morphology of liquid crystals observed by polarizing microscopy and that of the quenched liquid crystals into crystalline phase oberved by transmission electron microscopy was very similar to that of extended chain crystals (ECCs) of crystalline polymers, such as polyethylene (PE). Therefore it is concluded that extended chain liquid crystals (ECLCs) are formed from the melt, which suggests that lamellar thikening growth is fast within the liquid crystalline phase. The lateral growth rate (V) of an ECLC showed the same degree of supercooling (ΔT) dependence as has been observed on crystalline polymers, that is V ∝ exp(\( - \frac{C} {{\Delta T}} \)) where C is a constant This indicates that the lateral growth of the liquid crystals is a nucleation controlled process, as has been proposed by Papkov et al. Combination of these two results leads to a conclusion that the liquid cyrstals are formed by the coupling of the thickening growth and the nucleation controlled lateral growth, which we proposed to term “liquid crystallization” mechanism.
M. Hikosaka, K. Mabuchi, K. Yonetake, T. Masuko, G. Ungar, V. Percec

Thermotropic Liquid Crystals in Polypeptides

Abstract
Several types of the liquid crystal (LC) polymers have been synthesized and the mesomorphic properties and structures have been studied. Among these LC polymers, the polypeptide is of special interest since it has comprised a peculiar class of hard-rod polymers by pretending the stable α-helical conformation. By this reason, the mesomorphic behavior and structure have been extensively studied in the lyotropic solutions.
Junji Watanabe

Study on the Orientational Order of the Main Chain Liquid Crystalline Polymers

Abstract
The thermotropic liquid crystalline homo- or copolyesters based on 4-hydroxyacetophenone azine and diacyl chloride were synthesized. The liquid crystalline polymers(LCPs) were characterized by 1H NMR, DSC, GPC, polarizing microscopy experiments. We analyzed the molecular orientational order in LCPs by changing the length of polymethylene spacers, or combining the two different aliphatic spacers in the magnetic field. An odd-even oscillation of orientational order parameters(S) measured from 1H NMR spectra was observed in themotropic homopolyesters, and the nematic order parameters associated with the mesogens or the spacers were found to be quite high, about 0.85~0.97 near solid-nematic transition temperature. The orientational parameters of copolyesters with the two polymethylene spacers in equal molar amounts decreased dramatically as compared with those of the corresponding homopolymers, and the copolymers connecting both even numbered spacers were shown to have a higher order than those connecting by even-odd or odd-odd number parity.
Dong-Won Kim, Jung-Ki Park, Kwan-Soo Hong

Statistical Theory of Liquid Crystalline Orderings in Hard Rod Fluids

Nematic, Cholesteric, Smectic and Columnar Phases
Abstract
A review is given of theoretical studies on systems of rod-like molecule with simple shape ( cylinders, spherocylinders, square rods,...). The role of hard-core repulsion in liquid crystalline orderings are mainly discussed. It is shown that the excluded volume effect due to the hard-core repulsion stabilizes not only the orientational order but also positional ordering of the smectic A density wave in cylindrical molecules.
Hatsuo Kimura

Phase Diagram and Molecular Ordering of Dimer Liquid Crystals Dissolved in a Simple Nematic Solvent

Identification of the Nematic Spacer Conformation
Abstract
The RIS analysis of the deuterium quadrupolar splitting data have been performed for ether-type dimer liquid crystals NCPh2O(CD2)nOPh2CN (DLC) with n = 9 and 10 according to the simulation scheme previously established. The orientational as well as conformational characteristics of DLCs have been investigated under various conditions including binary mixtures with a low-molar-mass liquid crystal EtOPhCH=NPhCN. In the DLC systems studied, the intervening spacer -O(CH2)nO- was found to take spatial arrangements characteristic of the nematic phase. The nematic conformation thus identified remains quite stable over a wide range of concentration and temperature.
Akihiro Abe, Renato N. Shimizu, Hidemine Furuya

Phase Equilibria in Liquid Crystalline Polymer Solutions: Theory and Experiment

Abstract
We compared various statistical thermodynamic theories with experimental results for isotropic—liquid crystal phase behaviors in many stiff-chain liquid-crystalline polymer solutions. Among the theories, the scaled particle theory for wormlike hard spherocylinders most successfully explained the experimental phase behaviors in neutral polymer systems, and the same theory considering the electrostatic interaction in a perturbative way was favorably compared with a phase diagram for a charged stiff polymer system. Good agreements between this theory and experiment were also obtained for the osmotic pressure and the orientational order parameter of poly(γ-benzyl L-glutamate) solutions.
Takahiro Sato, Akio Teramoto

Light Scattering Studies of a Nematic to Smectic — A Phase Transition in Rigid Rod Polymer Solutions

Abstract
An important approach to understanding phase transitions in liquid crystals is to study systems in which the dominant interparticle interactions are hard repulsion, rather than the complicated interparticle potentials found in most liquid crystals. Computer simulations have shown [1] that a nematic to smectic A phase transition may exist in a system as simple as monodisperse hard rods. Experimentally, Xin Wen, Robert Meyer and Donald Caspar [2] have reported the observation of the smectic A ordering in tobacco mosaic virus (TMV) suspensions, in which the dominant interparticle interactions are screened electrostatic repulsion. In this paper we present the first quantitative measurements of the nature of the nematic to smectic A phase transition in TMV. In solutions in which the concentration is just below the transition concentration to the smectic phase, large pretransitional smectic fluctuations are observed. We will describe the methods of measuring the correlation lengths of these presmectic fluctuations by light scattering. In addition, the concentration difference between the smectic and the nematic phase close to the transition point is determined to be very small, implying that the transition is very close to second order. This result is consistent with the conclusion of numerous theoretical approaches [3], such as density functional theory and scale particle theory, which have concluded that a nematic to smectic A transition in a system of rigid rods should be second order or very close to second order.
Jin-Hua Wang, Franklin Lonberg, Xiaolei Ao, Robert B. Meyer

Collective and Molecular Dynamics in Ferroelectric Liquid Crystals: From Low Molar to Polymeric and Elastomeric Compounds

Abstract
Broadband dielectric spectroscopy (10−2Hz – 1010Hz) is employed to analyse the collective and molecular dynamics in low molar weight and polymeric ferroelectric liquid crystals (FLC). Below 106Hz two collective dielectric relaxation processes are observed having the character of a soft — mode and that of a Goldstone — mode. The soft — mode is assigned to fluctuations of the amplitude of the helical superstructure, while the Goldstone — mode corresponds to fluctuations of the phase of the ferroelectric helix. In the frequency range between 106Hz and 1010Hz one dielectric relaxation process is observed, the β — relaxation, which is assigned to the libration (hindered rotation) of the mesogenes around their long molecular axis. At the phase transition smectic A / smectic C* this process does not show any deviations from an Arrhenius — like temperature dependence. In comparing low molecular mass and the polymeric side group FLC, the collective and molecular dynamics is found to be qualitatively similar. This open new possible applications for FLC as sensors, actuators or (polymeric) flexible displays.
F. Kremer, A. Schönfeld

The Rheology of PBLG Liquid Crystalline Polymers at High Concentrations

Abstract
The rheological behavior of most liquid crystalline polymers (LCP’s), especially thermotropic ones, is not yet well understood. This is true, despite notable progress towards a molecular-level understanding of the rheology of some lyotropic LCP’s, especially modestly concentrated solutions of poly(γ-benzylglutamate), or PBG, in the solvent metacresol. Many aspects of the rheology of PBG solutions seem to be well described by the Doi molecular theory,1 particularly the behavior of the first normal stress difference N1, which is negative in sign over a range of shear rates. In fact, semi-quantitative agreement between the Doi theory and measurements of N1 has been achieved for PBG solutions of modest concentration.2 However, the success of the Doi theory in describing the rheological behavior of some PBG solutions does not extend to many other LCP’s.
R. G. Larson, J. Promislow, S.-G. Baek, J. J. Magda

Microdomain Structures of Triblock Copolymers of the ABC Type

Abstract
To understand microdomain structures of triblock copolymers of the ABC type at the molecular level, we studied the variation of morphology of microdomain with composition, the molecular weight dependence of lamellar domain spacing and the chain conformation of middle-block polymer in lamellae by transmission electron microscopy(TEM), small-angle X-ray scattering(SAXS) and small-angle neutron scattering(SANS), in comparison with microdomain structures of diblock copolymers of the AB type, because the middle-block chain of the triblock copolymers has a bridge conformation, while the one end of block chain of diblock copolymers is always free.
Samples used here were isoprene(I)-styrene(S)-2-vinylpyridine(P) triblock copolymers of which the two end-block polymers have the same chain lengths and the corresponding triblock copolymers with deuterated middle-block polymers, prepared by a succesive anionic polymerization technique. Film specimens for TEM, SAXS and SANS were prepared by solvent-casting and annealing.
TEM and SAXS studies revealed that the morphologies of microdomains change in the order of spherical, cylindrical, ordered tricontinuous double-diamond and lameller structures as the S block polymer content decreases. The order is similar to that of diblock copolymers, but the composition ranges and the types of packing in lattice are different. SAXS studies revealed that the lamellar domain spacings of the triblock copolymers are larger than those of SP diblock copolymers at least for high molecular weight samples in accordance with the theories of microphase separation in the strong segregation limit. Moreover, SANS studies suggested that the middle-block polymer of the triblok copolymers is contracted along the direction parallel to lamellae at the almost same magnitude as the block chain of the diblock copolymers.
I. Noda, Y. Matsushita, Y. Mogi

Evolution of Ordering in Thin Films of Symmetric Diblock Copolymers

Abstract
The manner in which thin films of asymmetric diblock copolymer of polystyrene and poly(methyl methacrylate) form a multilayered structure has been investigated by transmission electron microscopy and neutron reflectivity. It is shown that spin coated films of the diblock copolymer are initially microphase separated with an average repeat period that is much smaller than the equilibrium period. Upon heating, two different relaxations were found. One involves a rapid, local relaxation of the copolymer chains in which the phase size increases to a size scale comparable to the equilibrium period. However, the microstructure is a bicontinuous network of polystyrene and poly(methyl methacrylate). Upon further heating the copolymer chains are transported within the bicontinuous network to form the multilayered structure.
T. P. Russell, A. M. Mayes, M. S. Kunz

Rheology of Polymeric Materials with Mesoscopic Domain Structure

Abstract
Computer simulation is carried out for theological properties of a hexagonally ordered mesophase of block copolymers. When the applied strain is small, the stress response is that of usual viscoelastic solid. On the other hand, when the applied strain is large, anomalous theological response is observed:(i) for an oscillatory shear of low frequency, the stress-strain curve becomes lozenge shape, and (ii) for a step shear, the stress relaxes in two steps. A simple model describing such behavior is proposed based on the observation that the anomalous behavior appears when the slippage of lattice planes takes place. The model reproduces many characteristic features found by the computer simulation. The possible relevance of this model to more general cases of ordered liquids is discussed.
Masao Doi, James Harden, Takao Ohta

Rheology, Dielectric, Relaxation, and Adhesion of Thermodynamically Confined Diblock Copolymer Chains

Abstract
Various thermodynamic requirements exist in strongly segregated A-B diblock copolymer systems. Some of them, e.g., an osmotic requirement of uniform segment density distribution in microdomains, impose a constraint on the block conformation. On the other hand, there always exists an elastic requirement of randomizing the conformation. These contradicting requirements thermodynamically confine the copolymer chains, thereby providing them some unique properties. Those properties are briefly reviewed and their thermodynamic origins are discussed.
H. Watanabe, T. Kotaka

Crystallization Kinetics and Microdomain Structures for Blends of Amorphous-Crystalline Block Copolymers with Amorphous Homopolymers

Abstract
Blends of a symmetrical diblock poly(ethylene-b-propylene) (DEP) and an atactic polypropylene (APP) were studied by calorimetry, small angle neutron scattering, and electron microscopy. Addition of APP to DEP drastically changed the crystallization kinetics of the polyethylene block. The results were interpreted on the basis of the morphological studies of the microdomain structure in both the crystalline state and the melt state of the blends.
K. Sakurai, D. J. Lohse, D. N. Schulz, J. A. Sissano, M. Y. Lin, M. Agamalyan, W. J. MacKnight

Reversible Heteropolymer Gelation -Phase Diagrams of Mixed Networks-

Abstract
This paper presents possible phase diagrams of binary polymer mixtures A/B in which mixed networks are formed. To ensure the thermal equilibrium of the system, we consider reversible cross-links which are created and destroyed by thermal motion of the chains. On the basis of the lattice-theoretical picture, we develop a statistical-mechanical theory of network-forming polymer solutions. We derive possible phase diagrams of alternating networks, interpenetrating networks and randomly mixed networks with special attention to the interference effects among different phase transitions.
F. Tanaka

SANS Studies of Early Stage Spinodal Decomposition

Abstract
Time-resolved small-angle neutron scattering (SANS) experiments were performed on the self-assembling process of a binary mixture of deuterated polybutadiene and protonated polybutadiene at the critical composition. Specimens held in the single-phase state at an initial temperature (Ti) were quenched to a point inside the spinodal phase boundary at a final temperature (Tf) to induce phase separation via spinodal decomposition (SD). The effect of the thermal concentration fluctuations on the SD was examined by changing Ti for a fixed Tf. The wave number and temperature dependence of Onsager kinetic coefficient were also investigated as a function of Ti and Tf.
T. Hashimoto, H. Jinnai, H. Hasegawa, C. C. Han

Dynamic Interplay Between Wetting and Phase Separation in Geometrically Confined Polymer Mixtures

Abstract
Here we study the interplay between wetting and phase separation for binary polymer mixtures confined in one-dimensional (1D) or two-dimensional (2D) capillaries. It is found that near the symmetric composition, the hydrodynamics unique to bicontinuous phase separation plays a crucial role on the wetting dynamics and the surface effect is strongly delocalized by the interconnectivity of the phases. The wetting dynamics is discussed on the basis of the hydrodynamic coarsening, focussing on the effect of the dimensionality of the geometrical confinement. We also discuss the possibility that the quick reduction of the interface area spontaneously causes double phase separation.
Hajime Tanaka

Wetting of Grafted Polymer Surfaces by Compatible Chains

Abstract
We discuss the way a droplet of a polymer melt spreads on a surface densely grafted by chains of same chemical nature. If the melt chains are short they invade the grafted layer and complete wetting is expected. On the other hand interpenetration should be very limited for long melt chains and partial wetting the rule. These considerations should apply for an A melt on the surface of a segregated AB block copolymer, and are in qualitative agreement with recent developping experiments.
Ludwik Leibler, Armand Ajdari, Ahmed Mourran, Ghislaine Coulon, Didier Chatenay

Surface Segregation and Wetting from Polymer Mixtures

Abstract
Coexisting binary polymer phases are characterised by very small interfacial energies even well below their critical solution temperature. By extension of Cahn’s ideas concerning critical point wetting, one expects that such low energies should readily lead to the exclusion of one of the phases from any interface which favours the other; this phenomenon has implications for practical surface-related effects, ranging from welding to wear properties. Using nuclear reaction analysis, we have now observed such complete wetting behaviour from two different classes of binary polymer mixtures. These are mixtures of statistical olefinic copolymers of structure -(C2H3(C2H5))x((CH2)4)1−x-, with differing x values, and an isotopic pair of deuterated and protonated polystyrene. In the former case we have been able to follow the growth with time t of the wetting layer thickness l; our results indicate l ~ logt.
Ullrich Steiner, Erika Eiser, Andrzej Budkowski, Lewis Fetters, Jacob Klein

Interfacial Properties of Mixed Polymer Films Spread at the Air/Water Interface

Abstract
Three binary mixtures of polymer films spread at the air/water interface have been investigated by surface pressure measurements and ellipsometry. Their compatibility and interfacial conformation are discussed as a function of the composition in the mixed polymer films.
M. Kawaguchi

Polymer Monolayer Dynamics

Abstract
Polymer chain dynamics at interfaces of vapor/liquid and liquid/liquid have been probed by confining macromolecules as monolayers or thin films and examining their field induced and spontaneous capillary waves in addition to their lateral diffusion and in-plane steady shear viscosity, all in a Langmuir trough in conjunction with simultaneous surface pressure measurements. Various experimental methods have been used to examine the chain dynamics and this paper deals with two of such, namely surface quasielastic light scattering and surface canal viscometry.
Focus has been place on thin film viscoelastic properties of monolayers as examined by retardation effects of the surface films on the propagation and damping characteristics of the capillary waves. With the aid of a dispersion equation, two viscoelastic parameters, i.e., the surface dilation elasticity ε and the corresponding viscosity κ, are deduced from the observed spatial wave length or wave propagation rate and the wave damping constant. By virtue of ε and κ representing short-ranged, local packing states and the attending dynamics of polymeric monolayers, they are independent of molar mass. Thus we have chosen to examine structural parameters of some vinyl polymers together with polyethers and poly(dimethyl siloxane).
Parallel with this effort to understand the monolayer dynamics in terms of structural parameters, we present a very recent endeavor in determining steady shear viscosity of monolayers by observing the surface flow rate of monolayers through a narrow canal on a Langmuir trough, rather analogous to capillary viscometry under a constant driving head. Here the aim is to confirm the hydrodynamic coupling model of Harkin and Kirkwood, and probe the molar mass dependence of the in-plane steady shear viscosity ηs of a vinyl polymer, poly(t-butyl methacrylate)
Hyuk Yu

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