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Induced pluripotent stem cell reprogramming is inherently inefficient and understanding the molecular mechanisms underlying this inefficiency holds the key to successfully control cellular identity. Here, we report 16 novel reprogramming roadblock genes identified by CRISPR/Cas9-mediated genome-wide knockout (KO) screening. Of these, depletion of the predicted KRAB zinc finger protein (KRAB-ZFP) Zfp266 strongly and consistently enhanced iPSC generation in several iPSC reprogramming settings, emerging as the most robust roadblock. Further analyses revealed that ZFP266 binds Short Interspersed Nuclear Elements (SINEs) adjacent to binding sites of pioneering factors, OCT4 (POU5F1), SOX2 and KLF4, and impedes chromatin opening. Replacing the KRAB co-suppressor with a co-activator domain converted ZFP266 from a reprogramming inhibitor to a potent reprogramming facilitator. This work proposes SINE-KRAB-ZFP interaction to be a critical regulator of chromatin accessibility at enhancers for efficient cellular identity changes and also serves as a resource to further illuminate molecular mechanisms hindering reprogramming.

The tsunami that occurred at the 2011 Tōhoku earthquake caused a severe accident with a hydrogen explosion at the Fukushima Daiichi Nuclear Power Plant. The radioactive material leaked was the second largest compared to the Chernobyl accident in 1986. The risk of carcinogenesis due to low-dose radiation exposure was concerned, and many residents were evacuated. What is important for risk science is (1) to estimate the magnitude of risk as accurately as possible; (2) to provide it as a basis for citizens’ decision-making; and (3) to propose effective policies to reduce overall risk. Initially, the concentration of radioactive substances in agricultural and fisheries products sometimes exceeded the safety standards, but from around 2015, it was almost eliminated. Soil pollution does not diminish easily, but it can be dealt with by treating the soil. The food safety standard for radioactive cesium in Japan was set at 100 Bq/kg after the accident, but the actual exposure dose from food was sufficiently low. Issues will be discussed regarding how to set safety standards and the concept of risk based on the linear no-threshold model.

The identification of transcription factor (TF) binding sites in the genome is critical to understanding gene regulatory networks (GRNs). While ChIP-seq is commonly used to identify TF targets, it requires specific ChIP-grade antibodies and high cell numbers, often limiting its applicability. DNA adenine methyltransferase identification (DamID), developed and widely used in Drosophila, is a distinct technology to investigate protein-DNA interactions. Unlike ChIP-seq, it does not require antibodies, precipitation steps or chemical protein-DNA crosslinking, but to date it has been seldom used in mammalian cells due to technical impediments. Here we describe an optimised DamID method coupled with next generation sequencing (DamID-seq) in mouse cells, and demonstrate the identification of the binding sites of two TFs, OCT4 and SOX2, in as few as 1,000 embryonic stem cells (ESCs) and neural stem cells (NSCs), respectively. Furthermore, we have applied this technique in vivo for the first time in mammals. Oct4 DamID-seq in the gastrulating mouse embryo at 7.5 days post coitum (dpc) successfully identified multiple Oct4 binding sites proximal to genes involved in embryo development, neural tube formation, mesoderm-cardiac tissue development, consistent with the pivotal role of this TF in post-implantation embryo. This technology paves the way to unprecedented investigations of TF-DNA interactions and GRNs in specific cell types with limited availability in mammals including in vivo samples.

Background Along with the reorganization of epigenetic and transcriptional networks, somatic cell reprogramming brings about numerous changes at the level of RNA processing. These include the expression of specific transcript isoforms and 3’ untranslated regions. A number of studies have uncovered RNA processing factors that modulate the efficiency of the reprogramming process. However, a comprehensive evaluation of the involvement of RNA processing factors in the reprogramming of somatic mammalian cells is lacking. Results Here, we used data from a large number of studies carried out in three mammalian species, mouse, chimpanzee and human, to uncover consistent changes in gene expression upon reprogramming of somatic cells. We found that a core set of nine splicing factors have consistent changes across the majority of data sets in all three species. Most striking among these are ESRP1 and ESRP2, which accelerate and enhance the efficiency of somatic cell reprogramming by promoting isoform expression changes associated with mesenchymal-to-epithelial transition. We further identify genes and processes in which splicing changes are observed in both human and mouse. Conclusions Our results provide a general resource for gene expression and splicing changes that take place during somatic cell reprogramming. Furthermore, they support the concept that splicing factors with evolutionarily conserved, cell type-specific expression can modulate the efficiency of the process by reinforcing intermediate states resembling the cell types in which these factors are normally expressed. Electronic supplementary material The online version of this article (10.1186/s12864-019-5438-2) contains supplementary material, which is available to authorized users.

Flow cytometry is a technology commonly used in biomedical research to measure physical and chemical properties of single cells. Cells in suspension are stained with various fluorescent dyes that bind to a specific macromolecule and pass through a laser beam one by one. Next, the equipment measures scattered and emitted light intensity that can be translated to size, granularity, expression levels of protein, RNA, or DNA content. In this chapter, we explain the principles of flow cytometry and provide a basic protocol to measure cell surface protein expression levels with fluorescent antibodies. As a practical example, we demonstrate how flow cytometry can be used to detect changes of cellular populations during the process of induced pluripotent cell generation.

The generation of induced pluripotent stem cells (iPSCs) with Oct4, Sox2, Klf4, c-Myc has been described as 'direct' reprogramming in contrast to reprogramming via nuclear transfer. Interestingly, recent studies have suggested that the conversion process itself includes transient up-regulation and down-regulation of hundreds of genes, making unique intermediate populations. In a sense, the process of 4 factor reprogramming is indirect. Like in vitro differentiation, iPSC generation efficiency and kinetics largely depend on the external environment, as well as the amount and stoichiometry of exogenously expressed reprogramming factors. However, accumulating evidence indicates that when reprogramming succeeds, the process is not random but progresses in an ordered, step-wise manner. In this review, we summarize current knowledge detailing how somatic cells reach a pluripotent state.

Summary The Nucleosome Remodeling and Deacetylase (NuRD) complex is essential for embryonic development and pluripotent stem cell differentiation. In this study, we investigated whether NuRD is also involved in the reverse biological process of induction of pluripotency in neural stem cells. By knocking out MBD3, an essential scaffold subunit of the NuRD complex, at different time points in reprogramming, we found that efficient formation of reprogramming intermediates and induced pluripotent stem cells from neural stem cells requires NuRD activity. We also show that reprogramming of epiblast-derived stem cells to naive pluripotency requires NuRD complex function and that increased MBD3/NuRD levels can enhance reprogramming efficiency when coexpressed with the reprogramming factor NANOG. Our results therefore show that the MBD3/NuRD complex plays a key role in reprogramming in certain contexts and that a chromatin complex required for cell differentiation can also promote reversion back to a naive pluripotent cell state., Graphical Abstract, Highlights • Mbd3 facilitates the initiation of neural stem cell reprogramming • Mbd3 is also required for efficient iPSC generation from EpiSCs and preiPSCs • Overexpression of Mbd3/NuRD facilitates reprogramming in a context-dependent manner, dos Santos et al. show that Mbd3/NuRD plays a positive role in reprogramming in certain contexts and that overexpression of Mbd3 facilitates Nanog-mediated reprogramming.

The generation of induced pluripotent stem (iPS) cells presents a challenge to normal developmental processes. The low efficiency and heterogeneity of most methods have hindered understanding of the precise molecular mechanisms promoting, and roadblocks preventing, efficient reprogramming. Although several intermediate populations have been described, it has proved difficult to characterize the rare, asynchronous transition from these intermediate stages to iPS cells. The rapid expansion of minor reprogrammed cells in the heterogeneous population can also obscure investigation of relevant transition processes. Understanding the biological mechanisms essential for successful iPS cell generation requires both accurate capture of cells undergoing the reprogramming process and identification of the associated global gene expression changes. Here we demonstrate that in mouse embryonic fibroblasts, reprogramming follows an orderly sequence of stage transitions, marked by changes in the cell-surface markers CD44 and ICAM1, and a Nanog-enhanced green fluorescent protein (Nanog-eGFP) reporter. RNA-sequencing analysis of these populations demonstrates two waves of pluripotency gene upregulation, and unexpectedly, transient upregulation of several epidermis-related genes, demonstrating that reprogramming is not simply the reversal of the normal developmental processes. This novel high-resolution analysis enables the construction of a detailed reprogramming route map, and the improved understanding of the reprogramming process will lead to new reprogramming strategies.

Reprogramming of cellular identity using exogenous expression of transcription factors (TFs) is a powerful and exciting tool for tissue engineering, disease modeling, and regenerative medicine. However, generation of desired cell types using this approach is often plagued by inefficiency, slow conversion, and an inability to produce mature functional cells. Here, we show that expression of constitutively active SMAD2/3 significantly improves the efficiency of induced pluripotent stem cell (iPSC) generation by the Yamanaka factors. Mechanistically, SMAD3 interacts with reprogramming factors and co-activators and co-occupies OCT4 target loci during reprogramming. Unexpectedly, active SMAD2/3 also markedly enhances three other TF-mediated direct reprogramming conversions, from B cells to macrophages, myoblasts to adipocytes, and human fibroblasts to neurons, highlighting broad and general roles for SMAD2/3 as cell-reprogramming potentiators. Our results suggest that co-expression of active SMAD2/3 could enhance multiple types of TF-based cell identity conversion and therefore be a powerful tool for cellular engineering.

The early history of fiber structure in molecular level is closely related to the history of development of the so-called macromolecular theory or the concept of macromolecules. After a long debate, it ended in victory of the macromolecular theory in 1936, concluding that the substances consist of many monomers connected by covalent bonds. Through the discussions of the macromolecular theory, the study of fiber structure was greatly activated. In this article we review the history of fiber structure. In the first section we describe the research history of structure of natural fibers, especially natural cellulose fiber, starting from a micelle model to a fringed-micelle model. In the second section, we focus on the history of the structural study of synthetic fibers from fringed-micelle microfibril model to shish-kebab model.

Summary Oct4 is an essential regulator of pluripotency in vivo and in vitro in embryonic stem cells, as well as a key mediator of the reprogramming of somatic cells into induced pluripotent stem cells. It is not known whether activation and/or repression of specific genes by Oct4 is relevant to these functions. Here, we show that fusion proteins containing the coding sequence of Oct4 or Xlpou91 (the Xenopus homolog of Oct4) fused to activating regions, but not those fused to repressing regions, behave as Oct4, suppressing differentiation and promoting maintenance of undifferentiated phenotypes in vivo and in vitro. An Oct4 activation domain fusion supported embryonic stem cell self-renewal in vitro at lower concentrations than that required for Oct4 while alleviating the ordinary requirement for the cytokine LIF. At still lower levels of the fusion, LIF dependence was restored. We conclude that the necessary and sufficient function of Oct4 in promoting pluripotency is to activate specific target genes., Graphical Abstract Highlights ► Function of Oct4 as an activator is sufficient to induce and maintain pluripotency ► When Oct4 is converted to a strong activator, it supports pluripotency more effectively ► When Oct4 is converted to a repressor, it induces differentiation, Oct4 is a key transcription factor involved in both the maintenance of embryonic stem cells (ESCs) and the reprogramming of somatic cells to an ESC-like pluripotent state (induced pluripotent stem cells; iPSCs). How does Oct4 support and induce these states? Here, Brickman and colleagues show that activation of a network of gene expression by Oct4 is sufficient to both maintain and reprogram pluripotent cell states.

In situ observation of the formation process of mesophase of isotactic polypropylene (iPP) is reported in structural point of view. Combining a rapid temperature jump and a high-flux synchrotron radiation X-ray scattering techniques, very rapid transformation from the molten amorphous state to the mesophase has been observed. The transformation proceeded very quickly in a narrow temperature range accompanied by instantaneous fluctuations in micrometer scale, suggesting the mesophase formation proceeds similarly to spinodal decomposition.

Structure studies were performed on PVA gels in mixtures of dimethyl sulfoxide (DMSO) and water using various scattering methods to see the hierarchic structure. It was found that the crosslinking points are crystallites, the nearest-neighboring distance is 180–200 A and the bicontinuous structure due to phase separation is in μm scale for the gel in DMSO/water (60/40). Dynamics of three kinds of PVA gels were also studied in nm scale using neutron spin echo technique.

Time-resolved light-scattering measurements have been performed on poly(vinyl alcohol) (PVA) in mixed solvents of dimethyl sulfoxide (DMSO) and water with various mixing ratios after quenching from...

The force required to stretch a polymer chain by 1% (f value) was calculated from experimental values of elastic moduli E1 in the direction of molecular axis and the cross-sectional area of the molecule of 25 well known polymers. The f value is mainly dependent on the conformation of a molecule and almost independent of side groups. The f values of polymers of various types of conformation may be summarized as follows: T type, 4−5 × 10−5 dyne; TGTG type, 1.5 × 10−5 dyne; TG(3/1) type, 1 × 10−5 dyne; T′G′ (7/2) type, 0.58 × 10−5 dyne; T′G′ (4/1) type, 0.36 × 10−5 dyne; TTGG type, 0.29 × 10−5 dyne; where T, G, and G mean trans, gauche and minus gauche, respectively, and the numbers in the parentheses denote helical structures. The reason for an anomalous apparent E1 value of nylon 6 (α-form) previously reported was elucidated; it was confirmed that E1 exhibits a value expected for a polymer with a nearly extended zigzag conformation.

Summary Since the first generation of induced pluripotent stem cells (iPSCs), several reprogramming systems have been used to study its molecular mechanisms. However, the system of choice largely affects the reprogramming efficiency, influencing our view on the mechanisms. Here, we demonstrate that reprogramming triggered by less efficient polycistronic reprogramming cassettes not only highlights mesenchymal-to-epithelial transition (MET) as a roadblock but also faces more severe difficulties to attain a pluripotent state even post-MET. In contrast, more efficient cassettes can reprogram both wild-type and Nanog−/− fibroblasts with comparable efficiencies, routes, and kinetics, unlike the less efficient reprogramming systems. Moreover, we attribute a previously reported variation in the N terminus of KLF4 as a dominant factor underlying these critical differences. Our data establish that some reprogramming roadblocks are system dependent, highlighting the need to pursue mechanistic studies with close attention to the systems to better understand reprogramming., Graphical Abstract, Highlights • Distinct reprogramming cassettes yield different reprogramming intermediates • MET is not a major rate-limiting step in reprogramming with high KLF4 expression • A lack of endogenous Nanog becomes trivial in efficient reprogramming systems • Roadblocks toward iPSCs depend on the reprogramming systems, In this article, Kaji and colleagues demonstrate that different reprogramming systems with distinct reprogramming efficiencies yield clearly distinguishable intermediate populations and, thus, potentially biased mechanistic views. For example, mesenchymal-to-epithelial transition and lack of endogenous Nanog are obstacles for iPSC generation only in inefficient reprogramming systems. This work highlights the importance of re-assessing molecular mechanisms of reprogramming in the literature heeding the reprogramming systems.

One of the most popular crystalline morphologies is a spherulite. An evidence is reported that the spherulite is crystallized through a dense packing state of small particles appearing in a droplet, which is caused by the primary phase separation of the melt in the metastable region of a phase diagram proposed by Olmsted et al. [Olmsted PD, Poon WCK, McLeish TCB, Terrill NJ, Ryan AJ. Phys Rev Lett 1998; 81: 373]. According to this phase diagram, the crystallization from the metastable state causes the nucleation and growth (N & G) of nematic domains, here named droplets, in the isotropic matrix. As a next step, the secondary phase separation of spinodal decomposition (SD) type into smectic and amorphous domains occurs inside the droplet where entanglements are excluded from the smectic to the amorphous domain; then such an SD structure turns into a densely packing structure of many small particles owing to surface tension. At this final stage of the induction period a long period peak of small-angle X-ray scattering (SAXS), so-called SAXS before WAXS, appears, which may be due to the average distance between these small particles. Furthermore, it is considered that crystalline lamellae are formed by radial and azimuthal fusion of these small particles inside the droplet, resulting in a spherulite. Such a type of crystallization occurs most commonly when flexible polymers are crystallized under the usual conditions. This tentative concept of spherulitic growth, which is completely different from a theory by Keith and Padden [Keith HD, Padden FJ. J Appl Phys 1963; 34: 2409], would give a new insight into problems of spherulites.

Cells of early mammalian embryos have the potential to develop into any adult cell type, and are thus said to be pluripotent. Pluripotency is lost during embryogenesis as cells commit to specific developmental pathways. Although restriction of developmental potential is often associated with repression of inappropriate genetic programmes1, the role of epigenetic silencing during early lineage commitment remains undefined. Here, we used mouse embryonic stem cells to study the function of epigenetic silencing in pluripotent cells. Embryonic stem cells lacking Mbd3 — a component of the nucleosome remodelling and histone deacetylation (NuRD) complex2,3 — were viable but failed to completely silence genes that are expressed before implantation of the embryo. Mbd3-deficient embryonic stem cells could be maintained in the absence of leukaemia inhibitory factor (LIF) and could initiate differentiation in embryoid bodies or chimeric embryos, but failed to commit to developmental lineages. Our findings define a role for epigenetic silencing in the cell-fate commitment of pluripotent cells.

Small-angle neutron scattering (SANS) measurements were performed on poly(vinyl alcohol) (PVA) gels in a mixture of deuterated dimethyl sulfoxide (DMSO-d 6 ) and D 2 O with volume ratio of 60/40 to see the structure changes of the crosslinking points, which are crystallites, and of the gel network during the melting process. The observed SANS intensities were fitted to the Ornstein-Zernike (OZ) formula and a power law in scattering vector Q ranges from 0.01 to 0.035 and 0.05 to 0.1 A -1 , respectively, to evaluate the correlation length ξ and the power law exponent n. It was found that the exponent n is 4 and the correlation length ξ is ∼ 150 A below 70°C, suggesting that the crystallite surface is smooth and the average distance between the neighboring crystallites is 150A. On the other hand, they begin to decrease >70°C. The decrease of n suggests that the surface of the crystallites becomes rougher with increasing temperature. As for the correlation length ξ, analyses in terms of distance distribution function suggested that the decrease of ξ is apparent, and the intercrystallite distance increases with temperature >70°C because the crystallites decrease in number because of melt.

This study was performed to determine the current situation and future prospects regarding the information, techniques, and educational methods of Interprofessional Education (IPE) that are needed throughout the world. The authors contacted a number of schools with physical therapy faculties that have introduced IPE into their curricula as well as credits designated by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). The IPE-related credits under the present curriculum were reviewed. In Japan, only 5 of 36 physical therapy faculties have adopted IPE into their curricula. In Japan, ninety-three credits are designated by MEXT in schools that train physical therapists. The Designated Regulation of Education of Japanese Physical Therapists was revised in 1989, and IPE-related clauses were added. This takes into account the social needs of physical therapists and recognizes the need for interprofessional knowledge. Furthermore, other clauses were added to train competent therapists: clauses regarding increased human understanding, sympathy for patients, understanding and cooperation in human relationships, understanding of patients' families, and understanding of support education methods. These are all part of the "joint education for training physical therapists," which is a small part of the curriculum.

The effect of isotacticity on the mesomorphic phase-forming properties of isotactic polypropylene (iPP) is reported. Only iPP having high isotacticity (iPP-HT) can form the mesomorphic phase by a rapid quench, but iPP having low isotacticity (iPP-LT) cannot form the mesomorphic phase though it crystallizes by the same quenching rate. These results suggest that the mesomorphic phase of iPP is closely related to the stereoregularity of the polymer chain. The mesomorphic phase in the iPP-HT shows longer regular 3/1 helices than in the crystalline iPP-LT. The structure and formation mechanism of the mesomorphic iPP are considered analogous to those of liquid crystals since the average length of the long regular 3/1 helices in the mesomorphic iPP acting as rodlike segments is sufficiently large to fulfill a criterion for the formation of liquid crystalline phase. From this criterion, the minimum requirement of isotacticity to form the mesomorphic phase is also estimated.

Novel morphology of isotactic polypropylene (iPP) crystal, which is quite different from that of usual spherulite, has been observed by scanning electron microscope (SEM). The crystals show ‘bamboo leaf-like (BL)’ shape with α-monoclinic high crystallinity. The BL crystals are formed by neither melt nor glass crystallization, but by a complicated annealing process that goes through mesomorphic phase of iPP. Substrates are not essential for the formation of BL crystals, since the BL crystals are formed both on glass surface and free surface as well as in bulk. Along with the annealing process, a possible explanation for the mechanism of the formation of the BL crystal is proposed.

The origin of the variety of characteristics of the reduced viscosity of aqueous suspensions of charged spherical particles has been an unsolved problem. To solve the problem, the reduced viscosity due to interparticle electrostatic interactions between charged spherical particles are calculated as a function of particle concentration with scanning various parameters, such as diameter of particle, number of charges per particle, and added-salt concentration. The result successfully reproduced the variety of characteristics. Of all the scanned parameters, the diameter of the particle has a significant role to display the variety of characteristics when other parameters are fixed. When the diameter is very small (∼0 A), the calculated reduced viscosity of aqueous suspensions of charged spherical particles increases with decreasing particle concentration and it shows a maximum. This behavior is very similar to the reduced viscosity of linear chain polyelectrolyte solutions. Whereas, when the diameter is large (>2000 A), the calculated reduced viscosity decreases with decreasing particle concentration and it does not show a maximum. When the diameter is

It has been considered that crystallization of polymer from melt proceeds via the coexistence of molten matrix and growing crystals that have once overcome a nucleation barrier to a critical size. The nucleation process has often been explained analogously with so-called nucleation and growth (NG) behavior of the phase separation of a binary mixture in metastable conditions, although the crystallization in one-component polymer is not a real component separation but a phase transition. Among the mechanisms of polymer crystallization, the topic is whether a liquid-liquid transition between states of different densities within one-component polymers takes place before the aforementioned nucleation process. The liquid-liquid transition between states, which is probably driven by chain orientation, is also categorized into NG and the controversial spinodal decomposition (SD) type processes depending on the quenching depth. This article provides the optical microscopic observations that favor the occurrence of the SD-like process when a one-component polymer melt is very rapidly quenched below a stability limit, including a drastic morphological change from a spherulitic to a spinodal pattern at the critical (or spinodal) temperature.

An unexpected type of primary crystal nucleation is described, involving spinodal decomposition (SD) type microphase separation due to the orientation fluctuations of rigid segments prior to crystal nucleation. This type of mechanism was found by the present authors about 10 years ago, and recently, it was theoretically revealed by Olmsted et al. to be one of three types of primary crystal nucleation: the well-known homogeneous crystal nucleation directly from the liquid–crystal coexistence domain, which occurs at higher temperatures above the binodal temperature T b , crystal nucleation after binodal microphase separation between T b and spinodal temperature T s , and that after SD below T s . The detailed experimental results for the spinodal-type crystal nucleation, especially the temperature dependence of characteristic wavelength in SD, are explained as well.

We studied the rates of gelation and phase separation of poly(vinyl alcohol) (PVA) solutions in mixtures of dimethyl sulfoxide (DMSO) and water at 25 °C and found that both the rates show a maximum at a volume fraction of DMSO φDMSO=0.60 while gelation was not observed either in pure DMSO or pure water, suggesting that water–DMSO is a cononsolvent system for PVA. On the basis of the data by Cowie [Can J Chem 36 (1961) 2240] we concluded that the 1:2 stable complex between one DMSO molecule and two water molecules is the main cause of this cononsolvency.

Preface to the special issueConceptual Innovation in Polymer Science: Ichiro Sakurada Special Issue

CD9 is a membrane protein belonging to the tetraspanin family. Despite CD9's broad tissue distribution, the only abnormality observed in CD9-deficient mice was infertility of females, which was responsible for a defect in the sperm-egg fusion process. However, the function of CD9 in sperm-egg fusion is not clear at all because the technique to analyze the activity of molecules in sperm-egg fusion has not been established. We demonstrated that the exogenous mouse CD9, expressed by polyadenylated mRNA injection at the germinal-vesicle stage oocytes, was precisely localized to the egg plasma membrane, and the expression reversed the infertility of CD9(-/-) eggs. Then, two other tetraspanins, human CD9 and mouse CD81, overexpressed with this technique on CD9(-/-) eggs restored the fertilization rate up to approximately 90 and approximately 50% against that of wild type eggs, respectively. Moreover, in the presence of an anti-mouse CD9 mAb, which blocks sperm-egg fusion, expression of human CD9 or mouse CD81 on eggs also rescued the fusibility. These results suggested that human CD9 plays a crucial role in human fertilization, and mouse CD81 has the potential to compensate for CD9 function in sperm-egg fusion. In addition, the polyadenylated mRNA injection is effective for molecular analysis of sperm-egg fusion.

The local dynamics of 10 substituted polyacetylenes in the glassy state have been investigated using a quasielastic neutron scattering technique in a time range of picoseconds to several tens of picoseconds to see a relationship between the local mobility and the gas permeability of these polymers. Even in the glassy state, these polymers show quasielastic scattering components, suggesting that certain stochastic motions occur in the glassy state. The dynamic scattering laws S(Q,ω) of the quasielastic components were well fitted to the sum of two Lorentzians, i.e., the narrow (slow) and broad (fast) components. It was found that both the relaxation rate Γn and the fraction An of the narrow (slow) component show positive correlations with oxygen permeability coefficient (PO2), suggesting that the local mobility of the matrix polymers plays an important role in gas permeability. We then defined local flux F, which is the product of Γn and An, as a measure of the local mobility to find that F is proportional...

Intramolecular hydrodynamic contribution ηintra/C to the reduced viscosity ηSP/C of polyelectrolyte solutions is derived as a function of polymer concentration C by separating the theoretically calculated intermolecular electrostatic contribution ηinter/C from the observed reduced viscosity, assuming an additivity, ηSP/C=ηintra/C+ηinter/C. The resulting intramolecular part ηintra/C reflects nearly the net effect of the polyion conformation; it increases monotonously with decreasing polymer concentration and levels off to a constant in sufficiently dilute concentrations. The leveling-off value of ηintra/C corresponds to the intrinsic viscosity [η]. From the estimated values of [η], the ionic strength I dependence of the polyion conformation has been visualized, resulting in a similarity between two relations, ηintra/C vs. C and [η] vs. I.

The intermolecular correlation due to electrostatic repulsion in flexible polyelectrolyte solutions as a function of ionic strength has been studied using small-angle neutron and X-ray scattering (SAXS and SANS) techniques. The ionic strength was changed by adding low molecular weight salts at a fixed polyion concentration (C = 0.25 mol/L). To solve the controversy about the added salt effect on the characteristic maximum in small-angle scattering of polyelectrolyte solutions, separation of the total scattering function into the intra- and intermolecular parts has been performed. With increasing the ionic strength of the solution the maximum position qm in the total scattering function of SAXS and SANS slightly shifts toward the lower scattering vector and subsequently disappears, whereas the maximum position in the intermolecular scattering function slightly shifts to the higher scattering vector, but the peak itself does not disappear even for the highest ionic strength of the present study though it be...

Dynamics of poly(vinyl alcohol) (PVA) gel have been investigated using a neutron spin echo technique. The intermediate scattering function I ( Q , t ) of the gel shows a very rapid decay and a non-decaying component in time ranges shorter and longer than about 3 ns, respectively, in the Q range of 0.03-0.1 A m 1. This Q range corresponds to the so-called Porod's region, suggesting that we are seeing the dynamics of cross-linking points of the gel. We therefore analyzed the data assuming that the cross-linking point performs a random motion in a restricted region around its quasi-equilibrium position.

Small-angle neutron scattering measurements have been carried out on transparent and opaque poly vinyl alcohol (PVA) gels formed in a mixture of dimethyl sulfoxide and water with a volume ratio 60/40 to investigate the network structure of the gels. It was found that the correlation length of the network, which corresponds to an average distance between the nearest neighboring cross-linking points, is independent of the PVA concentration for the opaque gel, while it depends on the concentration for the transparent gel. This result is discussed by taking into account the previous findings that spinodal decomposition type liquid–liquid phase separation takes place before the gelation in the opaque gel, but does not in the transparent gel. The size of the cross-linking points, which are crystallites in the present gel, is also discussed on the basis of the distance distribution analysis of the scattering data.