Segmental orientation and chain relaxation of polymers by fourier transform infrared dichroism

Fourier transform infrared dichroism has been used to investigate molecular orientation in polymeric materials. It is first applied to characterize network behavior in some elastomeric systems such as model networks of poly(dimethylsiloxane). The strain dependence of segmental orientation is analyzed through networks of known degree of cross-linking and experimental results are compared with calculation predictions based on the rotational isomeric state formalism. Infrared dichroism spectroscopy has also been used to analyze orientational relaxation in binary blends of long and short polystyrene chains. The effect of short deuterated chains (M_w = 3000 to 72000) on the orientational relaxation of long entangled chains (Mw = 2 000 000) is examined in the bidisperse melts uniaxially deformed above the glass transition temperature. While the long chain relaxation is found to be dependent on the short-chain concentration, the local orientational order of the latter is molecular weight dependent in agreement with the classical relaxation theories.     

Characterization of polystyrene networks by small-angle neutron scattering

Polystyrene networks prepared by anionic polymerization have been characterized by small-angle neutron scattering. Two kinds of systems have been examined: (A) networks with labelled branch points allowing characterization of the spatial distribution of crosslinking points; (B) networks containing a low proportion of chains labelled with perdeuterated polystyrene in order to characterize the conformation of individual elastic chains of the polymeric network. The dependence of the results on swelling and uniaxial extension is discussed.     

Analysis of the conformation of wormlike chains by combination of small-angle x-ray and small-angle neutron scattering

An analysis of the conformation of a wormlike polymer by small-angle scattering is presented. By a combined investigation of small-angle X-ray and of small-angle neutron scattering the effect of the finite size of the repeating units can be eliminated. The procedure suggested herein therefore allows to obtain the scattering function for a respective infinitely thin chain. The latter quantity is compared to current models of the scattering function of wormlike chains.     

High-temperature fourier transform infrared study of polystyrene/poly(vinyl methyl ether) blends

Fourier transform infrared (FTIR) studies of polystyrene (PS)/poly(vinyl methyl ether) (PVME) miscible blends as a function of temperature are presented. Below the lower critical solution temperature (LCST) little change is observed in the interaction spectrum obtained via digital subtraction techniques. Once above the LCST, the magnitude of the interaction spectrum decreases as a result of the phase separation process. Comparison of the behavior of the ether C? O stretching band in the reference PVME and in the blends has yielded a lower limit estimate for the interaction energy of about 0.15 kcal/mol.     

A small-angle x-ray scattering study of blends of isotactic and atactic polystyrene

Small-angle x-ray scattering (SAXS) from blends of isotactic and atactic polystyrene has been studied. Results have been interpreted and compared using the Tsvankin, Vonk, and Hosemann techniques. The studies suggest that segregation of the atactic component occurs during crystallization within the growing spherulite of the isotactic component. However, since the interlamellar distance does not increase with atactic content, segregation is believed to occur with the formation of domains larger than interlamellar but smaller than spherulite size.     

Preparation and determination of the structure of high-performance polymer blends by small-angle neutron scattering

Amorphous blends from a deuterated polyaryletherketone and a polyetherimide have been prepared and investigated by neutron scattering. The used components differ remarkably in their structure and their solution properties. The blends on the other hand are combinatorial mixtures: the scattering quantity ϕ₁ϕ₂/S(q) is independent of the composition of the blends if the polymer chains have the same length.     

Structural investigation of polyaniline/Nylon 6 blends by small-angle neutron scattering and small- and wide-angle X-ray scattering

The structure of blends of Nylon 6 with deuterated polyaniline emeraldine base (D-PANI-EB) and fully doped D-PANI salts (D-PANI-ES) formed from camphorsulfonic acid (CSA), methanesulfonic acid (MSA), or dodecyl benzenesulfonic acid (DBSA) were investigated by small-angle neutron (SANS) and X-ray scattering. The blends were formed from hexafluoro-2-propanol solutions and had volume fractions of 0.038, 0.20, and 0.40 for D-PANI/CSA, 0.20 and 0.40 for D-PANI/MSA, 0.24 and 0.44 for D-PANI/DBSA, and 0.07, 0.14, and 0.31 for D-PANI-EB. The SANS results are compared with a number of standard models for two-phase systems. No evidence was found for significant molecular mixing. In some cases the inverse power law model is in reasonable agreement with observations, and in the case of the lowest concentration of D-PANI/CSA there is an indication of mass fractal structure. This was not found at the higher concentrations. The results establish that the blends with the smaller more polar dopants CSA and MSA behave similarly and are unlike either the D-PANI/DBSA blends or those with D-PANI-EB. There is evidence that the simple picture of two pure phases is inadequate for these materials. With the exception of the D-PANI/DBSA blend which has a relatively low scattering contrast, the results indicate that the lower limit of volume fraction for application of SANS is a few percent D-PANI-ES in Nylon 6. X-ray scattering was used to demonstrate the presence of Nylon 6 lamellae and residual peaks attributable to the pure components. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2765–2774, 1997     

Orientation and relaxation of polymer–clay solutions studied by rheology and small-angle neutron scattering

The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay [montmorillonite, i.e., Cloisite NA+ (CNA)] was investigated with rheology and small-angle neutron scattering (SANS). The steady-state viscosity and SANS were used to measure the shear-induced orientation and relaxation of the polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates, and the CNA clay platelets aligned with the flow, with the surface normal parallel to the gradient direction. The cessation of shear led to partial and slow randomization of the CNA platelets, whereas extremely fast relaxation was observed for laponite (LRD) platelets. These PEO–CNA networklike solutions were compared with previously reported PEO–LRD networks, and the differences and similarities, with respect to the shear orientation, relaxation, and polymer–clay interactions, were examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3102–3112, 2004     

Thermodynamic interactions in blends of poly(4-tert-butyl styrene) and polyisoprene by small-angle neutron scattering

The thermodynamic interactions between poly(4-tert-butyl styrene) [P(4tBS)] and 1,4-polyisoprene (PI; both hydrogenous) were obtained as functions of the temperature, PI molecular weight, and blend composition through the examination of miscible ternary blends of these two components with a common miscible labeled polymer [90% 1,2-deuterated polybutadiene (dPBD)] with small-angle neutron scattering. The thermodynamic interaction parameters between P(4tBS) and dPBD and between P(4tBS) and PI increased with increasing temperature and were consistent with lower critical solution temperature behavior. Although the binary blends of P(4tBS) and dPBD exhibited phase separation at elevated temperatures, the thermodynamic interaction parameters between P(4tBS) and PI remained large and negative and independent of the PI molecular weight. Finally, the thermodynamic interactions for PI and P(4tBS) depended strongly on the ratio of PI to P(4tBS) and were also sensitive to the amount of dPBD present in the ternary blend. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3204–3217, 2004     

Structure and dynamics of halogenoethanol-water mixtures studied by large-angle X-ray scattering, small-angle neutron scattering, and NMR relaxation

To clarify the structure of solvent clusters formed in halogenoethanol-water mixtures at the molecular level, large-angle X-ray scattering (LAXS) measurements have been made at 298 K on 2,2,2-trifluoroethanol (TFE), 2,2,2-trichloroethanol (TCE), and their aqueous mixtures in the TFE and TCE mole fraction ranges of 0.002 < or = x(TFE) < or = 0.9 and 0.5 < or = x(TCE) < or = 0.9, respectively. The radial distribution functions (RDFs) for TFE-water mixtures have shown that the structural transition from inherent TFE structure to the tetrahedral-like structure of water takes place at x(TFE) approximately 0.2. In the TCE-water mixtures inherent TCE structure remains in the range of 0.5 < or = x(TCE) < or = 1. Small-angle neutron scattering (SANS) experiments have been performed on CF(3)CH(2)OD- (TFE-d(1)-) D(2)O and CF(3)CD(2)OH- (TFE-d(2)-) H(2)O mixtures in the TFE mole fraction range of 0.05 < or = x(TFE) < or = 0.8. The SANS results in terms of the Ornstein-Zernike correlation length have revealed that TFE and water molecules are most heterogeneously mixed with each other in the TFE-water mixture at x(TFE) approximately 0.15, i.e., both TFE clusters and water clusters are most enhanced in the mixture. To evaluate the dynamics of TFE and ethanol (EtOH) molecules in TFE-water and ethanol-water mixtures, respectively, (1)H NMR relaxation rates for the methylene group within alcohol molecules have been measured by using an inversion-recovery method. The alcohol concentration dependence of the relaxation rates for the TFE-water and ethanol-water mixtures has shown a break point at x(TFE) approximately 0.15 and x(EtOH) approximately 0.2, respectively, where the structural transition from alcohol clusters to the tetrahedral-like structure of water takes place. On the basis of the present results, the most likely structure models of solvent clusters predominantly formed in TFE-water and TCE-water mixtures are proposed. In addition, effects of halogenation of the hydrophobic groups on clustering of alcohol molecules are discussed from the present results, together with the previous ones for ethanol-water and 1,1,1,3,3,3-hexafluoro-2-propanol- (HFIP-) water mixtures.     

Interaction of blockcopolymer micelles as probed by small-angle neutron and by small-angle X-ray scattering

 The analysis of the interaction of micelles formed by a blockcopolymer is given by means of small-angle X-ray (SAXS) and small-angle neutron scattering (SANS). The blockcopolymer consists of poly(styrene) and poly(ethylene oxide) (molecular weight of each block: 1000 g/mol) and forms well-defined micelles (weight-association number: 400, weight-average diameter: 15.4 nm) in water. The internal structure has been studied previously (Macromolecules 29:4006 (1996)) by SAXS. There it has been shown that the micelles are spherical objects. The structure factor S(q) as a function of the scattering vector q (q=(4π/λ) sin (θ/2); λ: wavelength of the radiation in the medium; θ: scattering angle) can be extracted from both sets of small-angle scattering data (SANS: q≤0.4 nm^-1; SAXS: q≤0.6 nm^-1). It is shown that particle interaction in the present system can be described by assuming soft interaction which is modeled by a square-step potential. Received: 12 May 1997 Accepted: 9 July 1997     

Small-angle neutron scattering studies on binary mixtures of polystyrene and perfluorinated particles

Small-angle neutron scattering measurements (SANS) studies have been carried out on binary mixtures of small polystyrene particles (radius 315 Å) and larger perfluorinated particles (radius 664 Å). Both types of particles were spherical, monodisperse and negatively charged in the aqueous conditions used. Electrostatic interactions between the particles in each type of dispersion were examined by determining the structure factor of the dispersions. Good agreement with the experimental data and theory were obtained with the rescaled mean-spherical-approximation-model (RMSA). An alternative approach for predicting the structure factor using an equivalent hard-sphere model also gave good agreement with the experimental data. In the case of binary mixtures, with the FEP particles contrast matched, the radial distribution function indicated extensive ordering of the polystyrene particles. In addition there was evidence, at high number ratios of small particles, of cluster formation of small particles with some rejection of these from the ordered arrangement.     

Small-angle neutron scattering study of homopolymer blends and blockcopolymers of polystyrene/polyparamethylstyrene

Small angle neutron scattering (SANS) experiments were carried out at one mixture and two block copolymers of polystrene (PS) and poly(p-methylstyrene)(PpMS) at different temperatures ranging from 107 to 295°C. Both block copolymers show a maximum in scattering intensity, which increases with decreasing temperature approaching the spinodal point. Theoretical curves from Leibler's mean field theory agree very well with the experimental points with (XN) as the only fitting parameter, where χ is the Flory-Huggins interaction parameter and N is the degree of polymerization. The reciprocal value of I(q_m)⁻¹ of the maximum intensity for the block copolymers as well as the reciprocal intensity at zero scattering vector (I(q=0)⁻¹) for the mixture obey well the ansatz I = A + B/T within the experimental temperature range. The spinodal values of (X^N)_S are in good agreement with the theoretical values from Leibler.     

Local structure of a phase-separating binary mixture in a mesoporous glass matrix studied by small-angle neutron scattering

The mesoscopic structure of the binary system isobutyric acid + heavy water (D(2)O) confined in a porous glass (controlled-pore silica glass, mean pore width ca. 10 nm) was studied by small-angle neutron scattering at off-critical compositions in a temperature range above and below the upper critical solution point. The scattering data were analyzed in terms of a structure factor model similar to that proposed by Formisano and Teixeira [Eur. Phys. J. E 1, 1 (2000)], but allowing for both Ornstein-Zernike-type composition fluctuations and domainlike structures in the microphase-separated state of the pore liquid. The results indicate that the phase separation in the pores is shifted by ca. 10 K and spread out in temperature. Microphase separation is pictured as a transition from partial segregation at high temperature, due to the strong preferential adsorption of water at the pore wall, to a tube or capsule configuration of the two phases at low temperatures, depending on the overall composition of the pore liquid. Results for samples in which the composition of the pore liquid can vary with temperature due to equilibration with extra-pore liquid are consistent with this picture.     

Determination of micelle structure and charge by neutron small-angle scattering

We present a general method of determining the structure and charge of globular ionic micelles, using neutron small-angle scattering. The micellar solutions may have any concentration within the micellar phase. The method is based in part on an analytic calculation of the interparticle correlations between monodisperse spherical micelles, and we discuss the theory in some detail to justify its application to polydisperse globular particles. Experimental results are presented for several cationic and anionic micellar systems.     

Thermal properties and mixing state of ethylene glycol-water binary solutions by calorimetry, large-angle X-ray scattering, and small-angle neutron scattering

Thermal properties and mixing states of ethylene glycol (EG)-water binary solutions in the entire mole fraction range of EG, 0 < or = x(EG) < or = 1, have been clarified by using differential scanning calorimetry (DSC), large-angle X-ray scattering (LAXS), and small-angle neutron scattering (SANS) techniques. The DSC curves obtained have shown that the EG-water solutions over the range of EG mole fraction 0.3 < or = x(EG) < or = 0.5 are kept in the supercooling state until approximately 100 K, and those in the range of 0.6 < or = x(EG) < or = 0.8 are vitrified, and those in the ranges of 0 < x(EG) < or = 0.2 and 0.9 < or = x(EG) < 1 are crystallized. The radial distribution function (RDF) for pure EG obtained from the LAXS measurements has suggested that a gauche conformation of an EG molecule is favorable in the liquid. The RDFs for the EG-water solutions have shown that the structure of the binary solutions moderately changes from the inherent structure of EG to the tetrahedral-like structure of water when the water content increases. The SANS intensities for deuterated ethylene glycol (HOCD2CD2OH) (EGd4)-water solutions at x(EG) = 0.4 and 0.6 have not been significantly observed in the temperature range from 298 to 173 K, showing that EG and water molecules are homogeneously mixed. On the other hand, the SANS intensities at x(EG) = 0.2 and 0.9 have been strengthened when the temperature decreases due to crystallization of the solutions. On the basis of all the present results, a relation between thermal properties of EG-water binary solutions and their mixing states clarified by the LAXS and SANS measurements has been discussed at the molecular level.     

Small-angle neutron scattering of polymer blends of polyvinylmethylether at dilute concentration in deuterated polystyrene

Small-angle neutron scattering was used to measure the radius of gyration and thermodynamics of blends of poly(vinylmethylether) (PVME) at dilute concentration in deuterated polystyrene (PSD). The data were analyzed using the Zimm equation and the random phase approximation theory. For PVME with a weight-average molecular weight of 38,400 the value of the radius of gyration, R_g, was found to be 47 Å in the limit of the concentration of PVME extrapolated to zero. Analysis of the temperature dependence of the Flory interaction parameter, χ/v₀, indicates that phase separation should occur at approximately 300°C for a sample with ϕ_PVME ≅ 9%. No significant temperature dependence of R_g was found over the experimental range studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 1–9, 1998     

The destruction-free analysis of polymers by fourier transform infrared photoacoustic and fourier transform Raman spectroscopy: A comparison

With the introduction of rapid–scanning Fourier transform infrared (FTIR) and recently Raman (FT–Raman) spectroscopy, vibrational spectroscopy has been launched into a new era of applications in polymer chemistry and physics. Thus, the increase in sensitivity provided by multiple scanning has led to the breakthrough of new, destruction–free sampling techniques, such as photoacoustic and Raman spectroscopy. This paper provides a comparison between data produced by FTIR photoacoustic and FT–Raman analysis of a range of polymers, and structural information available from both techniques is discussed.     

Scattering structure factor of colloidal gels characterized by static light scattering, small-angle light scattering, and small-angle neutron scattering measurements

The scattering structure factor of a colloidal gel in a q range of 5 orders of magnitude has been determined by combining static light scattering, small-angle light scattering, and neutron scattering measurements. It exhibits simultaneously two types of structure information: a mass fractal scaling within the clusters that constitute the gel and a surface fractal scaling for length scales larger than that of the clusters. Such scattering behavior can be well interpreted by the pair-correlation function proposed in the literature to model an ideal structure constituted of mass fractal objects inside surface fractal objects.