Skip to main content

Über dieses Buch

Structural organization or disorganization in macromolecular systems has been an important subject of polymer physical chemistry during the last one or two decades. This volume summarizes the main lectures presented at the Osaka University Macromolecular Symposium OUMS '98 on Molecular Interactions and Time-Space Organization in Macromolecular Systems, where the following topics were discussed:crystallization kinetics, liquid crystals, phase separation, gelation, adhesion, complex formation, and self-organization, with emphasis on molecular interactions. Both these topics are hot issues at present and frequently are taken up as a main theme at a particular symposium. The present symposium invited leading theorists and experimentalists in these fields as guest speakers and is expected to attract the interest of a significant range of readers.



Synchrotron SAXS and WAXD Study of Polymer Crystallization in Confined Microdomains

Crystallization of polymers in confined microdomains could exhibit different features, including crystalline structure, morphology and novel dynamic processes. Two different such systems have been investigated. They are crystallizable mixtures of a block copolymer with a corresponding homopolymer and miscible semicrystalline/semicrystalline homopolymer blends. In a compatible blend of an AB diblock copolymer and its corresponding homopolymer A, spherical, cylindrical, lamellar, hexagonally-perforated (catenoid) lamellar, bicontinuous lad cubic (gyroid) and bicontinuous Pnm cubic (double diamond) microphases[l-4] can be formed. In AB/A compatible blends with one of the two blocks crystallizable, the crystallization behavior, the structure and the morphology could be very different from the extensively studied miscible polymer blends [5,6]. In this lecture, the AB/A blends with hard amorphous microdomains, meaning that the glass transition temperature, Tg, of the domains is higher than the melting point, Tm, of the crystallizable block, has been studied. Schematic diagrams of the systems are shown in Figure 1.
Li-Zhi Liu, Benjamin Chu

Structure Development in Side Group Liquid Crystalline Diblock Copolymers

In side-chain liquid crystalline diblock polymers, driving forces for ordering of the material may be provided by the chemical incompatibility between the blocks and the liquid crystalline nature of one of the blocks. We study the microstructure and its development from initially isotropic solutions in side group liquid crystalline copolymers based on styrene-isoprene diblocks. Hierarchical structure from the 5 Å to the 500 Å length scale is observed, the product of coherent block copolymer microphase separation and liquid crystalline mesophase formation. The development of structure in these materials is discussed
Chinedum O. Osuji, John T. Chen, Guoping Mao, Christopher K. Ober, Edwin L. Thomas

Crystallization Behavior and Properties of Polyolefins

An overview of thermodynamic properties and crystallization kinetics of linear chains and random copolymers based on polypropylenes is given. The details of the discrete isothermal thickening of monodisperse low molecular weight species are discussed in relevance to the interpretation of the crystallization kinetics. Emphasis is given to the need to distinguish the crystallites formed from the initial melt from those transformed from them during thickening. When this distinction is made the nucleation process of either extended or folded crystallites is found to have the same temperature coefficient.
The effect of adding structural irregularities to the chain on the crystallization kinetics and lamellar morphology of high molecular weight species, is discussed by analyzing the behavior of well characterized metallocene isotactic polypropylenes. The analysis of the growth rates indicates the general behavior observed for random copolymers. However, the break found in the analysis of the kinetics according to classical nucleation theory is primarily related to a unique morphological change and may not be specific of a II – III regime transition. A dynamic morphological change due to the progressive development of the crosshatched morphology with time has been investigated as a function of crystallization temperature, crystallization time and concentration of defects.
R. G. Alamo, C. Chi

Modeling of Side-Chain Liquid Crystal Polysiloxanes

Molecular dynamics (MD) simulations of polysiloxanes havm& cholesterol and methoxynitrostilbene (MONS) substituents tethered 10 the siloxane backbone by an allyloxybenzoate spacer group demonstrated that ordering involving all of the substituents developed quite rapidly, even though only the cholesterol group by itself inherently mesogemc The observed ordering varied with the nature and arrangement of the substituents Generally, strong interactions between cholesterol groups iesulted in the longest lived pair-wise associations. MONS substituents also showed orientation, aosing primarily from their associations with cholesterol mesogens The overall order parameter was typically unaffected by the incorpoiation of MONS at tractions of the order of 25% The polymer having alternating MONS and cholesterol substituents did not develop any significant order Association lifetimes were not simply related to order parameter Polymers which achievea the highest ordei parameters did not exhibit the longest association lifetimes Cholesterol - cholesteiol associations tended to be the longest, MONS - MONS association the shortest.
B. L. Farmer, G. M. Podojil, R. Pachter, W. W. Adams

Polymorphic and Polytypic Transformations during Crystallization of Long-Chain Compounds

Crystallization processes of long-chain compounds have been studied with FT-IR spectroscopy, which is highly sensitive to structural differences in functional groups. It has been found that several types of structural changes take place during the crystallization of fatty acids. In the solution crystallization of stearic acid, single crystals of the E form transform to the B form. This transformation starts with a heterogeneous nucleation of the B form on the faces of the single crystal of E, and the B domains spread to the whole region of the single crystal through a solid-state phase transition. Screw dislocations incorporated into a mother phase in the early stages of crystallization provide a field for the emergence of the product B phase and a channel for the E solid-state transition. In addition, the polytypic transformation from a single-layer to a double-layer structure takes place during the crystallization of the E form. A similar polytypic transformation also occurs in petroselinic acid.
Fumitoshi Kaneko

Fluorescence Studies on Molecular Interaction and Dynamics of Liquid Crystalline Polymers

Fluorescence measurements on several main-chain biphenyltype liquid crystalline polyesters were carried out to investigate the temperature dependence of molecular interaction between mesogenic groups and the dynamics around the mesogenic groups in the time range of nano-seconds. A blue shift of fluorescence during heating was observed for BB-6 with 4,4’-biphenyldicarboxylate mesogen, while a red shift with strong excitation wavelength dependence was observed forPB-10 with 4,4’-diearbonyloxybiphenyl mesogen. The difference is attributed to the difference in the temperature dependence of packing patterns for these polyesters. Fluorescence depolarization in a liquid crystalline polymer was measured for the first time by using perylene in BB-5 with 4,4’- biphenyldicarboxylate mesogen. Rotational diffusion coefficient increases gradually with the increase in temperature and jumps at the liquid crystal-isotropie transition temperature.
Kazuyuki Horie, Hsu-Wen Huang, Masaki Shimada

Molecular Rheology of Glassy Polymers

Simultanuos measurement of stress birefringence in oscillatory deformation were revealed to privide information of the deformation of polymer chains and origins of stress in glassy state.The stress was composed of the glassy stress similar to that of ordinary glass forming liquid and the rubbery stress due to the entropic force of chains.The relaxation behavior of these sterss components were discussed in details.
K. Osaki, T. Inoue

Polymer-solvent organization in relation to chain microstructure

Most polymers possess a microstracture (helicity, special sites bearing fractional charge arising from bonds polarization..) that has dramatic consequences on the manner they interact with solvent molecules to form organized systems. Here are reviewed some experimental results obtained on different varieties of polystyrenes (isotactic, syndiotactic), on atactic polyvinyl chloride and on chemically-modified polyvinyl chloride (chlorine atoms replaced either by hydrogen atoms or by thiophenate groups) that cast some light on these effects.
Jean-Michel Guenet

Polymer-surfactant interaction in thermoreversible gels

The influence of low molecular weight surfactants on the sol/gel transition of hydrophobically modified water-soluble associating polymers is studied on the basis of the recent theory of thermoreversible gelation with multiple junctions. It is shown that the existence of a lower and an upper bound in the aggregation number of hydrophobes at the network junctions leads to non-monotonic polymer gelation concentration as a function of the surfactant concentration. There is a certain surfactant concentration where gelation is most promoted, thereby exhibiting a peak in the viscosity and modulus. Relation between this peak concentration and the critical micelle concentration of the added surfactant is detailed. The number of elastically active network chains is calculated in the postgel regime as a function of the surfactant concentration, and compared with the experimental data on the high frequency storage modulus of HEUR/SDS systems
Fumihiko Tanaka

Viscoelastic Phase Separation and Transient Formation of Spongelike Patterns

It has so far been believed that phase separation in isotropic condensed matter can be classified into either solid or fluid models, including some modification due to elastic effects. Contrary to this common belief, we recently found unusual phase separation, which can be described by neither of the above models, in a mixture whose components have a large difference in their dynamics. Thus, we proposed that a new model of phase separation, namely, “viscoelastic model”, is necessary to describe phase separation in such dynamically asymmetric mixtures. This model is likely a general model that can describe all types of isotropic phase separation including solid and fluid model as special cases. Viscoelastic phase separation in dynamically asymmetric mixtures can be characterized by the order-parameter switching phenomena: The primary order parameter switches from the composition to the deformation tensor as in gel, and back to the composition again, reflecting viscoelastic relaxation between a characteristic deformation time of phase separation and the slowest rheological time of the system. This unusual behavior can be explained by the above general nature of a viscoelastic model. It is remarkable that orderparameter switching can occur even during an ordering process driven by a ‘single’ thermodynamic driving force. We argue that spongelike patterns observed in phase separation of many materials may be produced by a common physical mechanism of viscoelastic phase separation. For example, spongelike patterns formed during polymerization-induced phase separation can also be explained by our viscoelastic model.
Hajime Tanaka

Dielectric Studies of Order-Disorder Transition in Solutions of Styrene-Isoprene Block Copolymers

We investigated the dielectric normal mode relaxation of the polyisoprene (PI) block chain of styrene-isoprene diblock copolymer (SI) and styrene-isoprene-styrene triblock copolymers (SIS) in semi dilute and concentrated solutions. Solvent was a common good solvent toluene (TOL). The order-disorder transition (ODT) was reflected on the dielectric loss curves ɛ″: In the ordered state, SI solutions exhibited a bimodal ɛ″ curve but a single peak in the disordered state. In this paper we investigated the molecular mechanism of the bimodal relaxation spectra in the ordered phase using solutions of non-symmetrical SI, triblock copolymers SIS, and styrene-butadiene-isoprene triblock copolymers (SIB and SBI). In order to detect the ODT we also carried out the measurements of heat capacity on an SI/TOL system. The bimodal relaxation spectra in the ordered state was ascribed to the difference in mobility of the chain ends of the PI block. From the dielectric data for solutions of SIS, SIB, and SBI in TOL, we concluded that the high and low frequency peaks of the ɛ″ curves can be ascribed to the motion of the end at the interface and that of the free end, respectively.
Keiichiro Adachi

Long wavelength composition fluctuations in diblock copolymers

We examine the effect of composition polydispersity on the dynamic structure factor of diblock copolymers at low wavenumbers. Its bimodal relaxation shape in the case of a poly(styrene-b-isoprene) copolymer solution in the common good solvent toluene is preserved. The polydispersity is mainly manifested in the slow process associated with chain diffusion.
K. Chrissopoulou, F. Rittig, G. Fytas

Structure and Ordering Processes of Diblock Copolymer Associates in Solution

Experimental observation of micellar solution of deblock copolymer are presented to show non-monotonous changes of association number during micellation process,and reveal that some structural changes can be induced by completely kinetic factors. Thesefindings arebasically explained by the Aniansson-Wall (A-W) mechanism, which assumes only insertion/expulsion of unimers into/from micelles. It is demonstrated that phenomenological thermodynamic equations based on the A-W mechanism possibly reproduce a minimum in change of the association with time observed in the relaxation process induced by the imp. Furthermore, for more quantitative descriptions of kinetic behavior of the micellar solution, the time evolution of association-number distribution during micelle formation and relaxation is by evaluating the micelle free energy and the rate of expulsion of a unimer from micelles. The results clearly show the characteristic feature of the A-W mechanism, where the micellar relaxation takes place stepwise with two steps.
Takuhei Nose

Amphipathic Synthetic and Biological Macromolecules in Aqueous Media

Biological and synthetic amphipathic macromolecules are often capable of forming phase-separated microdomains in response to external stimuli, for example pH, ionic strength, shear stress, and temperature. In this manuscript, we discuss the aqueous solution behavior of two synthetic polymers and a biopolymer that possess microstructural features which allow reversible associations. The first synthetic series was prepared by hydrolyzing an octylamide-modified polymer of maleic anhydride [MA] and ethyl vinyl ether [EVE]. Responsiveness to pH has been studied via energy transfer utilizing photophysical probes. The second series of copolymers was synthesized by cyclocopolymerization of N,N-diallyl-N,N-dimethyl ammonium chloride [DADMAC] and 3-(N,N-diallyl-Nmethylammonio)-1-propanesulfonate [DAMAPS]. Electrolyte responsiveness of these novel sulfobetaine copolymers is discussed as a function of composition. The final amphipathic water-soluble polymer is hydrophobin, a fungal protein secreted by Schizophyllum commune. This protein is capable of self-assembly from water onto both hydrophilic and hydrophobic surfaces as demonstrated by contact angle and AFM studies.
C. L. McCormick, R. S. Armentrout, G. C. Cannon, G. G. Martin

The Interactions of Hydrophobically-Modified Poly-(N-Isopropylacrylamides)with Liposomes

The interactions between a random copolymer of N-isopropylacry amide (NIPAM), N-[4-(1-pyreny l)butyl]-N-n-octadecy lacry lamide and N-glycylacrylamide (Gly) (PNIPAM-Py-Gly) with a series of vesicles have been examined by fluorescence spectroscopy. The copolymer exhibits pH-sensitivity due to the carboxylic acid groups of the glycine residues (15 mol%), thermosensitivity due to the NIPAM residues (84 mol%), and amphiphilic characteristics due to the pyrenyl octadecyl moieties (1 mol%). In the presence of salts, complex formation was detected between the copolymer and cationic or anionic non-phospholipid liposomes based on the non-ionic surfactant, n-octadecyl-diethylene oxide ((EO)2CS18H37), and cationic phospholipid liposomes. Weak interaction was detected between the copolymer and neutral phospholipid liposomes under the same conditions. The binding of the copolymer to the liposomes is shown to be controlled primarily through hydrogen bond formation between the hydroxyl groups of the ((EO)2CS18H37) and the amide groups of the NIPAM residues, electrostatic interactions between the charged surfactants of the bilayer and the glycine residues and to, a lesser extent, by hydrophobic forces.
Françoise M. Winnik, Alla Polozova

Controlled Association of Macromolecules in Water: Hydrophobized Polymers and Proteins

In living systems, the association of biopolymers such as DNA, polysaccharides and proteins is controlled in a noncovalent manner, such as by electrostatic interaction, hydrogen bonding, and hydrophobic association. The amphiphilicity of biopolymers is an important factor in their self-organization in water. Various polymer amphiphiles such as amphiphilic block copolymers and hydrophobized polymers have been synthesized, and the structure-function relationships of these self-assemblies have been studied.[1-3]. In artificial systems, however, macromolecular association is still difficult to control. The supramolecular assembly of macromolecules is important in various fields for designing new materials. We describe here our recent studies on the self-assembly of hydrophobized polymers where water-soluble polymers are partly substituted by hydrophobic molecules.
Kazunari Akiyoshi, Yoshihiro Sasaki, Kenichi Kuroda, Atushi Ueminami, Junzo Sunamoto

Macro to Microdynamics of Threadlike Micelles

The dynamics of the entangling threadlike micelles formed with surfactants and additives in aqueous solution can be classified into three regimes. The first dynamics is the slowest one related to the entanglement release mechanism of threadlike micellar networks. The second dynamics is governed by bending motions of the threadlike micelle between entanglement points. These are macrodynamics of the threadlike micelle, which can be investigated by rheological techniques. The last dynamics of the threadlike micelle is micro dynamics, which is in time scale on the order of 10−9 s and is detectable by use of fluorescence probing techniques. Fast molecular motions for surfactants and additive molecules in the micelle are the origin of this dynamics. Rotational and translational motions for surfactants and additives in the threadlike micelle are twice slower than those in the spherical micelle.
Toshiyuki Shikata

Self-Organized Nanostructures with a Single Polymer Chain

The present article describes the new finding that various kinds of characteristic nanostructures are created spontaneously f r om the collapsing transition in single polymer chains. From theoretical study with Monte-Carlo simulation on single chains, it is predicted that toroid, rod, and spherical structures are generated as the most stable conformations under thermal equilibrium, depending on the stiffness, temperature (or effective interaction between the segments in a chain), and chain length. From the actual experiments on long DNA chains with the order of several tens of micrometers, the formation of these nonostructures have been confirmed, together with the formation of intrachain segregated structure. It is also indicated that kinetic effect, such as nucleation-growth and spinodal decomposition, plays an important role in the determination of the final structures with the collapsing transition.
Kenichi Yoshikawa

Solution Properties of Polymacromonomers Consisting of Polystyrene

Analyses are made of z-average radii of gyration <S 2>Z l/2 and intrinsic viscosities [η] for two series of polymacromonomer samples consisting only of polystyrene (PS) and having fixed side chain lengths of 15 and 33 styrene monomer units in cyclohexane at 34.5°C (the theta point) and in toluene at 15°C, on the basis of the wormlike chain with or without excluded volume. The current theories for this model are shown to be capable of consistently explaining the main-chain length dependences of <S 2>Z and [η] for the two polymacromonomers in the theta and good solvents. The chain stiffness is an increasing function of side chain length and higher in the good solvent than in the theta solvent. Thus, the semiflexibility of polymacromonomers under the theta condition arises from the high segment density near the main chain and monomer-monomer repulsions in good solvents further stiffen the polymer backbone.
Ken Terao, Yo Nakamura, Takashi Norisuye

Frictional behavior of Self-Assembled Polymer Brushes

The frictional response between polymer brush layers was studied as a function of solvent condition and degree of compression using a direct force measurement technique. The brush bearing surfaces were made by preferential adsorption of polystyrenepolyvinylpryridine (PS-PVP) block copolymers from a dilute solution. Parallel lateral motion was imparted to one surface, while the response was detected at the opposing brush-covered surface. It was observed, consistent with work published by other groups, that when contacting brushes bathed in a good solvent are sheared past one another, no frictional forces are detected until the polymer layers are strongly compressed. When the solvent is changed to a near-theta solvent, large frictional forces are measured at weaker compressions. The onset of these frictional forces occurs at distances comparable to the distance at which the opposing layers contact one another and rapidly increase as the brushes are compressed. Arguments are advanced that this behavior is attributable to frictional interactions between the polymer chains and the solvent.
S. M. Kilbey, P. Schorr, M. Tirrell
Weitere Informationen