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The physics of photons and neutrons with applications of deuterium labeling methods to polymers

Description: Over the past decade small-angle neutron scattering (SANS), has found numerous applications in the fields of biology, polymer science, physical chemistry, materials science, metallurgy, colloids, and solid state physics. A number of excellent references are available which contain basic neutron scattering theory though these text books reflect the origins of the technique and the examples are largely drawn from physics e.g., single crystals, simple liquids, monatomic gases, liquid metals, magnetic materials, etc. in view of the large numbers of nonspecialists who are increasingly using neutron scattering, the need has become apparent for presentations which can provide rapid access to the method without unnecessary detail and mathematical rigor. This article is meant to serve as a general introduction to the symposium ''Scattering Deformation and Fracture in Polymers,'' and is intended to aid potential users who have a general scientific background, but no specialist knowledge of scattering, to apply the technique to provide new information in areas of their own particular interests. In view of space limitations, the general theory will be given in the case for neutron scattering and analogies and differences with photon scattering (x-rays) will be pointed out at the appropriate point. 90 refs., 6 figs.
Date: December 1, 1986
Creator: Wignall, G.D.
Partner: UNT Libraries Government Documents Department

SANS Studies of Polymers

Description: Before small-angle neutron scattering (SANS), chain conformation studies were limited to light and small angle x-ray scattering techniques, usually in dilute solution. SANS from blends of normal and labeled molecules could give direct information on chain conformation in bulk polymers. Water-soluble polymers may be examined in H/sub 2/O/D/sub 2/O mixtures using contrast variation methods to provide further information on polymer structure. This paper reviews some of the information provided by this technique using examples of experiments performed at the National Center for Small-Angle Scattering Research (NCSASR).
Date: October 1, 1984
Creator: Wignall, G. D.
Partner: UNT Libraries Government Documents Department

The morphology of blends of linear and branched polyethylenes in solid state by SANS

Description: In a previous paper, the authors have shown how small-angle neutron and X-ray scattering (SANS, SAXS) can be used to determine the melt compatibility of different polyolefins, including high-density (HD), low-density (LD), and linear low density (LLD) polyethylene. Such blends have attained widespread commercial applications, though the understanding of the mechanical and melt-flow properties of such blends has hitherto been handicapped by the absence of a consensus concerning the degree of mixing of the components, both in the melt and solid states. Recent SANS data indicate that for HDPE/LDPE blends, the melt is homogeneous for all compositions after proper accounting for H/D isotope effects. In this publication the authors use complementary SANS, DSC, and SAXS to examine the types of morphologies and the different degrees of phase separation which may arise via crystallization effects on cooling from a homogeneous melt.
Date: March 1, 1995
Creator: Wignall, G.D.; Londono, J.D.; Alamo, R.G. & Mandelkern, L.
Partner: UNT Libraries Government Documents Department

Characterization of fullerenes and fullerene derivatives by small-angle neutron scattering and transmission measurements

Description: Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes (1) in solvents with strong SANS contrast (e.g. CS{sub 2}) and we have extended initial studies of C{sub 60} (1) to include C{sub 70} and C{sub 84} moieties. Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60}, so there is virtually no SANS contrast with the solvent. Hence, these particles are practically {open_quotes}invisible{close_quotes} in such media, though the negative scattering length of hydrogen means that SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs and this paper describes the first results on cyclohexane-substituted fullerenes.
Date: January 1, 1997
Creator: Melnichenko, Y.B.; Wignall, G.D. & Affholter, K.A.
Partner: UNT Libraries Government Documents Department

SANS study of phase separation in solid {sup 3}He-{sup 4}He

Description: Small angle neutron scattering has been used to study phase separation in a quantum alloy, solid {sup 3}He{sub x}-{sup 4}He{sub 1{minus}x}. The onset of phase separation is marked by a dramatic increase in the measured scattering. A simple interpretation of the results suggests that the late-stage phase separation kinetics are dominated by an increase in the concentration of {sup 3}He atoms in preexisting precipitate regions.
Date: December 31, 1994
Creator: Koster, J.P.; Nagler, S.E.; Adams, E.D. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Small-angle neutron scattering from polystyrene-DVB networks containing a delta fraction of deuterated polystyrene: evidence for aggregation during polymerization

Description: Sample No. 1 yielded a mol wt of 70,000 g/mole and a Z-average radius of gyration of 121 A. The delta fraction of polystyrene of interest has a mol wt of 50,000-72,000 g/mole, depending on position, and suggestive of aggregation. Some speculation is made on the aggregation mechanism. (DLC)
Date: January 1, 1983
Creator: Fernandez, A.M.; Widmaier, J.M.; Wignall, G.D. & Sperling, L.H.
Partner: UNT Libraries Government Documents Department

SANS (small-angle neutron scattering) evaluation of the RPA (random phase approximation) theory for binary homopolymer mixtures

Description: A well characterized binary mixture of normal (protonated) and perdeuterated monodisperse 1,2 polybutenes has been studied by small-angle neutron scattering (SANS). For scattering wavevectors q greater than the inverse radius-of-gyration R/sub g//sup -1/, the SANS intensity is quantitatively predicted by the random phase approximation (RPA) theory of deGennes over all measured values of the segment-segment interaction parameter Chi. In the region (Chi s-Chi)Chi s/sup -1/ > 0.5 the interaction parameter determined using the RPA theory for q > R/sub g//sup -1/ is greater than that calculated from the zero-angle intensity based on an Ornstein-Zernike plot, where Chi s represents the limit of single phase stability. These findings indicate a correlation between the critical fluctuation length xi and R/sub g/ which is not accounted for by the RPA theory.
Date: December 1, 1986
Creator: Bates, F.S.; Koehler, W.C.; Wignall, G.D. & Fetters, L.J.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering study of the micelle structure of amphiphilic block copolymers

Description: The amphiphilic block copolymers of vinyl ether were prepared by living cationic polymerization. The partially deuterated copolymers for SANS experiments were especially synthesized by introducing deuterated phenyl units in the hydrophobic chain. SANS measurements were performed for aqueous solutions of these copolymers by changing H{sub 2}O/D{sub 2}O ratios. The SANS profiles indicate that the micelles in the present system exhibit a core-shell structure and that the size and shape of micelles are largely dependent on the length of hydrophobic chain. The micelle of shorter hydrophobic chain was found to be nearly spherical, whereas the micelle of longer hydrophobic chain was confirmed to have an ellipsoidal shape.
Date: July 31, 1994
Creator: Yamaoka, H.; Matsuoka, H.; Sumaru, K.; Hanada, S.; Imai, M. & Wignall, G. D.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering studies of critical phenomena in a three-component microemulsion

Description: Critical density fluctuations of a ``water-in-oil`` microemulsion consisting of water, benzene, and BHDC (benzyldimethyl-n-hexadecyl ammonium chloride) were observed near the phase boundary by SANS. Observed profiles were well described by product of a form factor of spherical droplets and a structure factor, consisting of a term describing the inter-droplet correlations and also an Ornstein- Zernike component describing the droplet density fluctuations. Allowance was also made fro droplet polydispersity,though the width of the distribution turned out to be very small (1-2%). Observed temperature dependence of osmotic compressibility was fitted using the crossover function proposed by Belyakov et al., and the Ginzburg numbers were obtained on the order of 10{sup -2}. This indicates that long range interdroplet forces are not significant in this system, which displays upper critical solution temperature behavior. In contrast, previous studies of systems displaying lower critical solution temperature behavior (e.g., water, n-decane, and dioctyl sulfosuccinate sodium salt) indicate that long range interactions appear to dominate the phase separation behavior.
Date: December 31, 1996
Creator: Seto, H.; Komura, S.; Wignall, G.D.; Triolo, R. & Chillura-Martino, D.
Partner: UNT Libraries Government Documents Department

The morphology of blends of linear and branched polyethylenes in solid state by SANS

Description: In a previous paper the authors have shown how small-angle neutron and X-ray scattering (SANS, SAXS) can be used to determine the melt compatibility of different polyolefins, including high-density (HD), low-density (LD), and linear low density (LLD) polyethylene. Such blends have attained widespread commercial applications, though the understanding of the mechanical and melt-flow properties of such blends has hitherto been handicapped by the absence of a consensus concerning the degree of mixing of the components, both in the melt and solid states. Recent SANS data indicate that for HDPE/LDPE blends, the melt is homogeneous for all compositions after proper accounting for H/D isotope effects. In this publication the authors use complementary SANS, DSC, and SAXS to examine the types of morphologies and the different degrees of phase separation which may arise via crystallization effects on cooling from a homogeneous melt.
Date: December 31, 1994
Creator: Wignall, G.D.; Londono, J.D.; Alamo, R.G.; Mandelkern, L. & Stehling, F.C.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) analysis of polyaniline salts and blends

Description: Doped polyaniline emeraldine salts (PANI-ES) exhibit good environmental stability with a high level of conductivity (1 to 300 S/cm). However, they suffer from the fact that they have poor mechanical properties and must be blended with an insulating host polymer to be useful in industrial applications. Polyaniline blends are a new type of conducting material that typically show very low onsets of conductivity unlike that of metal filled blends. This is primarily due to the unique cellular geometry of the PANI-ES that is formed within the insulating host polymer. The formation of this immiscible polymer network may be due in part to structural and conformational differences in the blend components.
Date: June 1, 1996
Creator: Hopkins, A.R.; Rasmussen, P.G.; Basheer, R.A.; Annis, B.K. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Phase Behavior of Blends of Linear and Branched Polyethylenes on Micron-Length Scales via Ultra-Small-Angle Neutron Scattering (USANS)

Description: SANS experiments on blends of linear, high density (HD) and long chain branched, low density (LD) polyethylenes indicate that these systems form a one-phase mixture in the melt. However, the maximum spatial resolution of pinhole cameras is approximately equal to 10<sup>3</sup>Å and it has therefore been suggested that data might also be interpreted as arising from a bi-phasic melt with large a particle size (~ 1 µm), because most of the scattering from the different phases would not be resolved. We have addressed this hypothesis by means of USANS experiments, which confirm that HDPEILDPE blends are homogenous in the melt on length scales up to 20 µm. We have also studied blends of HDPE and short-chain branched linear low density polyethylenes (LLDPEs), which phase separate when the branch content is sufficiently high. LLDPEs prepared with Ziegler-Natta catalysts exhibit a wide distribution of compositions, and may therefore be thought of as a �blend� of different species. When the composition distribution is broad enough, a fraction of highly branched chains may phase separate on µm-length scales, and USANS has also been used to quantify this phenomenon.
Date: May 17, 1999
Creator: Agamalian, M.M.; Alamo, R.G.; Londono, J.D.; Mandelkern, L. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Role of dopant counter-anion functionality in polyaniline salts/blends and implications to morphology

Description: In this paper, wide and small angle X-ray scattering techniques (i.e., WAXS and SAXS) and light microscopy are used to characterize the influence of the dopant`s structure on the morphology of both polyaniline salt and blend. In an attempt to modify the morphology of the PANI-ES, the authors have evaluated a number of doping acids (i.e., methane sulfonic acid (HMSA), butane sulfonic acid (HBSA), dodecyl benzene sulfonic acid (HDBSA) and camphor sulfonic acid (HCSA)) that vary in size and polarity to better understand the role of the acid in PANI-ES`s morphology and the resulting electrical conductivity. These salts were solution blended with polycaprolactam using hexafluoro-2-propanol (HFIP) as a solvent. The other goal was to investigate the effect of the counter-anion structure on the nature of the phase separated PANI-ES network. The shape of the PANI-ES network in the host polycaprolactam has important implications on the nature of conduction behavior and the final electrical conductivity of the blend.
Date: March 1, 1997
Creator: Hopkins, A.R.; Rasmussen, P.G.; Basheer, R.A.; Annis, B.K. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

SAXS and SANS studies of surfactants and reverse micelles in supercritical CO{sub 2}

Description: Surfactants promise to extend the applicability of supercritical CO{sub 2} (SC-CO{sub 2}) to processing of insoluble materials such as polymers and aqueous systems. In this short paper the authors summarize the techniques for studying surfactants and reverse micelles in SC-CO{sub 2} using SAXS and SANS; they will describe the scattering instruments and the pressure cells for conducting these studies; they will describe the types of measurement that yield the desired characterizations; they will describe the methods of data analysis and interpretation; and they will provide illustrative results from this laboratory. Industry seeks to replace common organic solvents now used in many reaction and separation processes; SC-CO{sub 2} is a potential solvent substitute widely favored by both government and industry. The currently available surfactants are limited in number and performance. In ongoing work the authors are coupling their SAXS and SANS scattering studies with complementary molecular simulations in efforts to understand, at a molecular level, what surfactant characteristics lead to improved performance. They hope that superior surfactants for use in SC-CO{sub 2} can be designed and synthesized based on this new level of understanding.
Date: March 1, 1997
Creator: Londono, J.D.; Dharmapurikar, R.S.; Wignall, G.D. & Cochran, H.D.
Partner: UNT Libraries Government Documents Department

Role of dopant counter-anion functionality in polyaniline salts/blends and implications to morphology

Description: Polyanilines are of particular current interest primarily due to their relative ease of synthesis, low cost and stable conductivity in air. The insulating, polyaniline emeraldine base (PANI-EB) form becomes electrically conducting by preferential protonation or doping the imine nitrogen sites to yield an electrically conducting polyaniline emeraldine salt (PANI-ES). In this paper, wide and small angle X-ray scattering techniques (i.e., WAXS and SAXS) and light microscopy are used to characterize the influence of the dopant`s structure on the morphology of both polyaniline salt and blend. In an attempt to modify the morphology of the PANI-ES, the authors have evaluated a number of doping acids (i.e., methane sulfonic acid (HMSA), butane sulfonic acid (HBSA), dodecyl benzene sulfonic acid (HDBSA) and camphor sulfonic acid (HCSA)) that vary in size and polarity to better understanding the role of the acid in PANI-ES`s morphology and the resulting electrical conductivity. The other goal was to investigate the effect of the counter-anion structure on the nature of the phase separated PANI-ES network. The shape of the PANI-ES network in the host polycaprolactam has important implications on the nature of conduction behavior and the final electrical conductivity of the blend.
Date: April 1, 1997
Creator: Hopkins, A.R.; Rasmussen, P.G.; Basheer, R.A.; Annis, B.K. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Comparison of the Behavior of Polymers in Supercritical Fluids and Organic Solvents Via Small Angle Neutron Scattering

Description: Small-angle neutron scattering has been used to study the effect of temperature and pressure on the phase behavior of semidilute solutions of polymers dissolved in organic and supercritical solvents. Above the theta temperature (To), these systems exhibit a ''good solvent'' domain, where the molecules expand beyond the unperturbed dimensions in both organic solvents and in COZ. However, this transition can be made to occur at a critical ''theta pressure'' (PO) in CO2 and this represents a new concept in the physics of polymer-solvent systems. For T &lt; To, and P &lt; Po, the system enters the ''poor solvent'' domain where diverging concentration fluctuations prevent the chains from collapsing and allow them to maintain their unperturbed dimensions.
Date: May 17, 1999
Creator: Melnichenko, Y.B.; Kiran, E.; Heath, K.D.; Salaniwal, S.; Cochran, H.D.; Stamm, M. et al.
Partner: UNT Libraries Government Documents Department

National facility for small-angle neutron scattering: five years' operating experience. Draft

Description: At the time of this Conference on Neutron Scattering, the ORNL-NSF-DOE National Facility for Small-Angle Neutron Scattering will have been operating routinely in a full-time user mode for nearly five years. The Facility, located at the High Flux Isotope Reactor at ORNL, is part of the National Center for Small-Angle Scattering Research. Operating experience and scientific highlights for the past five years are surveyed.
Date: June 1, 1985
Creator: Koehler, W.C.; Bunick, G.J.; Child, H.R.; Hayter, J.B.; Lin, J.S.; Maddox, L. et al.
Partner: UNT Libraries Government Documents Department

The morphology of emulsion polymerized latex particles

Description: Under monomer starved feed conditions, emulsion polymerization of perdeuterated methyl methacrylate and styrene in the presence of preformed polymethylmethacrylate latexes resulted in particles with a core-shell morphology, as determined by small-angle neutron scattering (SANS) analysis for a hollow sphere. The locus of polymerization of the added deuterated monomer is therefore at the particle surface. In similar measurements a statistical copolymer of styrene and methyl methacrylate was used as seed particles for further polymerization of trideuteromethyl methacrylate. The resulting polymer latex was again shown to have a core-shell morphological structre as determined by SANS. SANS experiments were also undertaken on polystyrene latexes polymerized by equilibrium swelling methods, with deuterated polymer forming the first or second step. The experiments covered a molecular weight range of 6 x 10/sup 4/ < M < 6 x 10/sup 6/ g/mol. For M > 10/sup 6/ the molecular weights are consistent with the experimental errors, indicating that the deuterium labeled molecules are randomly distributed in the latex. These results led to the finding that the polymer chains were constrained in the latex particles by factors of 2 to 4 from the relaxed coil dimensions. For M < 10/sup 6/ g/mol SANS gave zero angle scattering intensities much higher than expected on the basis of a random distribution of labeled molecules. Several models were examined, including the possible development of core-shell structures at lower molecular weights. 25 refs., 6 figs., 3 tabs.
Date: November 1, 1987
Creator: Wignall, G. D.; Ramakrishnan, V. R.; Linne, M. A.; Klein, A.; Sperling, L. H.; Wai, M. P. et al.
Partner: UNT Libraries Government Documents Department

Structural characterization of a polymer substituted fullerene (flagellene) by small angle neutron scattering

Description: Small-angle neutron scattering (SANS) can structurally characterize fullerenes in solvents with strong SANS contrast (e.g. CS{sub 2}). Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60} and C{sub 70} moieties. Hence, there is virtually no SANS contrast with the solvent and these particles are practically ``invisible`` in such media. On the other hand, the negative scattering length of hydrogen means that the SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs such as the polymer-substituted fullerenes, or flagellenes. These consist of C{sub 60} cores to which 1-4 polystryene chains (with a molecular weight, MW {approx_equal} 2000) are attached. The extrapolated cross section at zero angle of scatter [d{Sigma}/d{Omega}(0)] is a function of the number of pendant chains, so SANS can be used to assess the number of ``arms`` which are covalently attached to the fullerene ``sphere.`` Close agreement ({plus_minus}4%) between measured and calculated values of d{Sigma}/d{Omega}(0) along with independent estimates of the radius of gyration (R{sub g}) and second virial coefficient (A{sub 2}) for a calibration linear polystyrene sample serves as a cross check on the validity of this methodology.
Date: December 31, 1994
Creator: Affholter, K.A.; Bunick, G.J.; Wignall, G.D.; Desimone, J.M.; Hunt, M.O. Jr.; Menceloglu, Y.Z. et al.
Partner: UNT Libraries Government Documents Department