Styrene neutron scattering

Experimentally, the stretching of block copolymer chains has been addressed in two ways by measuring L as a function of N, and by measuring the components of Rg of the block chains both parallel and perpendicular to the interface. The domain dimensions have been studied most extensively for styrene-isoprene and styrene-butadiene block copolymers X-ray and neutron scattering are the methods of choice. The predicted SSL scaling of L N2/3 has been reported for spheres, cylinders and lamellae [99,102-106], but not in all cases. For example, Bates et al. found N0 37 for styrene-butadiene spheres [100], and Hadziioannou and Skoulios observed N0 79 for styrene-isoprene lamellae [107], In the sphere case, kinetic limitations to equilibration were felt to be an important factor [100],... 

Systematic studies on micellar size and structure have been published for poly(styrene-h-acrylic acid) (PS-PAAc) [7, 8], poly(styrene-fr-sodium acrylate) (PS-PAAcNa) [9], or quaternized poly(styrene-h-4-vinyl-pyridine) (PS-P4VPMeI) [10, 11]. It was concluded that the polyelectrolyte chains in the micellar corona are almost fully stretched [8]. The effect of salt concentration was investigated by Guenoun et al. on poly(f-butylstyrene-fr-sodium styrene sulfonate) (PtBS-PSSNa) who observed a weak decrease of micellar size and aggregation number when the salt concentration was increased beyond 0.01 mol/1 [12]. Using small-angle neutron scattering (SANS), the authors could provide additional support for the rod-like conformation of the polyelectrolyte chains in the micellar corona [13]. 

For the pair styrene/isoprene, various other dependences of x or temperature have been reported in the literature, which give values of x that at 100°C differ by almost a factor of two, from 0.06 to around 0.14 (see Fig. 13-3) (Lin et al. 1994 Han et al. 1995). These estimates of x ot obtained by direct calorimetric measurements (the energetic effects are too minute to measure), but by fitting the predictions of thermodynamic theories (such as that of Leibler or Fredrickson and Helfand see below) to x-ray or neutron scattering data for diblock copolymers or blends. The values of / thereby obtained are only as accurate as the theories to which the data are fitted. 

In TEM studies by Fernandez, et al. (9) on thin-sliced materials, it was shown that early in the polymerization of the styrene in PB/PS IPN s the domains tended to be spherical, while later in the polymerization the domains tended to be ellipsoidal in nature. The latter were modeled as irregularly shaped cylinders, which resemble ellipsoidal structures on thin sectioning. In more recent experiments involving small-angle neutron scattering, SANS, it was concluded that the phase separation involved a mixture of nucleation and growth, and spinodal decomposition kinetics (10). 

Structural studies of polymer materials often use neutron scattering techniques. In such circumstances the use of deuterated chains can be necessary because it overcomes problems associated with inelastic scattering. In this example, a commercial sample of polystyrene-d7 is polymerized in such a way as to maximize yield due to the high cost of the monomer. There is lillle advantage in polymerizing styrene in solution unless large quantities are required (where heat transfer becomes a problem). Polystyrene can be polymerized in the... 

Most of the research effort on the ionomers has been devoted to only a small number of materials, notably the ethylenes the styrenes, the rubbers(9)5 and those based on poly(tetra-fluoroethylene), the last of which is the subject of the present volume. As a result of these extensive investigations, it has become clear that the reason for the dramatic effects which are obsverved on ion incorporation is, not unexpectedly, the aggregation of ionic groups in media of low dielectric constant. Small angle X-ray and neutron scattering, backed up by a wide range of other techniques, have demonstrated clearly the existence of ionic... 

The colloidal properties of anionically prepared poly(styrene-g-ethylene oxide) graft copolymers were studied by Candau et al. in different water/toluene/ alcohol mixtures by light and neutron scattering, NMR, and viscometry [307-309]. Aggregation numbers depend on mixture compositions with the highest values attained for water-rich systems. The micelles formed seem to have a core and shell conformation, with PS cores, in all cases studied. Dialysis experiments showed that the enhanced water-oil solubility was due to preferential solvation of the two segregated components of the copolymers by the solvent mixture and not to one specific solvent entrapment as is the case of classical microemulsions. 

Figure 5.19 Small-angle neutron scattering intensity obtained with a styrene-butadiene diblock copolymer having spherical butadiene microdomains. The peaks at very small q are due to a body-centered cubic lattice structure of ordered microdomains. The solid curve is the calculated intensity of independent scattering from solid spheres of mean radius 124 A. (From Bates etal.34)...

Yang et al. [27], using small-angle neutron scattering (SANS), reported the formation of supermolecular structures in polystyrene latex particles prepared by the seeded emulsion polymerization of styrene onto deuterated polystyrene particles. The recorded scattering intensities, which were much higher than those expected on the basis of the Debye random coil model, indicate the presence... 

Mehta, R., and Dadmun, M. D. 2006. Small angle neutron scattering studies on miscible blends of poly(styrene-rfln-vinyl phenol) with liquid ciystalline polyurethane. Macromolecules 39 8799-8807. 

Yurekli, K., and R. Krishnamoorti. 2004. Thermodynamic interactions in blends of poly(4-tert-butyl styrene) and polyisoprene by small-angle neutron scattering. /. Polym. Set. Part B Polym. Phys. 42 3204-3217. 

Such definitive forecasts do not result from the theories of Leibler or Hong and Noolandi. However, the latter theory describes in detail the phase diagram for copolymer — homopolymer mixtures and is therefore pertinent to the X-ray work of Roe Similarly, Leibler s theory provides a detailed description of a microphase separation mechanism and thus is of value in the interpretation of experiments investigating this phenomenon. Small angle neutron scattering data reported to date has been maitily concerned with pure styrene-diene block copolymers which are fully microphase separated and thus examined D, dj, and interfadal layer thickness as a function of molecular weight and composition and therefore comparison has usually been made with the MIA theory of Helfand. 

Schmitt, Kirste, and Jelenic utilized neutron scattering to determine the coil sizes and the second virial coefficients with mixtures containing two styrene/acrylonitrile copolymers, one of which was deuterated. The interaction parameter calculated... 

The morphology of blends of block copolymer with homopolymer was studied by means of electron microscopy and small-angle X-ray or neutron scattering by Hashi-moto et al. and by Bates et al. The first group prepared blends of styrene/isoprene... 

The structures of TPNR and their composites with carbon black were investigated by SAXS, and small-angle neutron scattering (SANS). Thomas et al. studied the deformation of cylindrical PS domains of a near single crystal styrene-isoprene-styrene (SIS) triblock copolymer by SAXS. The structural changes in the hexagonal lattice of cylinders on uniaxial tensile deformation were related to the macroscopic mechanical behaviour. 

NC Inceoglu, S., Young, N.P., Jackson, A.J., Kline, S.R., Costeux, S., and Balsara, N.P., Effect of supercritical carbon dioxide on the thermodynamics of model blends of styrene-acrylonitrile copolymer and poly(methyl methacrylate) studied by small-angle neutron scattering, Macrowro/ecM/ex, 46, 6345, 2013. 

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