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Interactions atactic polystyrene

This category includes such polymers as atactic polystyrene (25-291 or poly(vinylchloride) (30.31 and references therein). A closely related problem is the gelation of non-block copolymers (5), which share with atactic polymers the feature that chemically and conformationally homogeneous sequences may be relatively short, so that when two or more chains interact, large crystalline domains are prevented from forming. [Pg.6]

Ozaki and co-workers (99) applied 2D-FT Raman correlation spectroscopy to examine conformational changes and specific interactions in blends of atactic polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE). [Pg.186]

Odani, H., J. Hayashi and M. Tamura Diffusion in glassy polymers. II. Effects of polymer-penetrant interaction diffusion of methyl ethyl ketone in atactic polystyrene. Bull. Chem. Soc. Japan 34, 817 (1961). [Pg.47]

However, as we shall see, the results in the asymptotic domain should reveal a different property of polymer chains. Criticism came from Yoon and Flory,10 disturbed by the absence of local chemical structure effects. These authors modelled the atactic polystyrene chain of N beads as realistically as they could (see Chapter 1). Thus, Yoon and Flory accounted for interactions between nearest neighbour monomers in particular, these interactions are responsible for the fact that the three orientations of a bond j, relative to bonds j — 1,/ — 2, are weighted differently in relation to the stereochemical composition. Moreover, we have seen in Chapter 1 that, for atactic polystyrene, pairs of successive benzene rings are slightly more frequent in syndiotactic than in isotactic positions. [Pg.727]

The thermic correlation lengths , derived from the interaction b are given in Table 15.6. Let us recall that the persistence length of atactic polystyrene is equal to 2 nm. Condition (15.3.29) is therefore satisfied. [Pg.746]

All the previous systems were polydisperse in nature, so that the coil-stretch transition was broad (because the relaxation time depends upon molecular weight). Also, only a part of the molecular weight distribution (the longest molecules) becomes stretched by the flow. It therefore proved impossible to determine the dependence of the coil-stretch or interaction behavior upon molecular weight. For these reasons, we examine the behavior of a model system, monodisperse atactic polystyrene (a-PS) in the 0 solvent decahydronaphthalene. We will explore separately, both by assessment of molecular strain and macrorheology, the onset of interaction behavior, particularly as a function of molecular weight, and the associated flow-induced degradation. [Pg.236]

No.19,21st Sept.1999, p.6307-18 TWO-DIMENSIONAL FOURIER TRANSFORM RAMAN CORRELATION SPECTROSCOPY STUDIES OF POLYMER BLENDS CONFORMATIONAL CHANGES AND SPECIFIC INTERACTIONS IN BLENDS OF ATACTIC POLYSTYRENE AND POLY(2,6-DIMETHYL-l,4-PHENYLENE ETHER)... [Pg.57]

LL phase separation may play a key role in the gelation of some noncrystalline polymers such as atactic polystyrene (a-PS) [34-36]. For a-PS, the physical junctions are not crystals and there are no specific interchain interactions, yet a-PS can form gels. Amauts and Berghmans were the first to explain the gelation of a-PS in terms of LL phase separation combined with vitrification [36]. In this case, vitrification acts as the agency responsible for arrest of the LL phase separation, and locks the system in a metastable state. [Pg.168]

Such phase-separated polymer mixtures serve as an excellent model system where molecular-level interactions between components are small. The system studied here is a film made of an immiscible binary mixture of atactic polystyrene and low-density polyethylene [2], The dynamic IR measurement was carried out as before by mechanically stimulating the system at room temperature with a 23-Hz dynamic tensile strain with an amplitude of 0.r/>. The time-dependent fluctuations of IR absorbance induced by the strain were recorded at a spectral resolution of 4 cm. ... [Pg.21]

Differential scanning calorimetry (DSC) experiments indicated that atactic polystyrene and polyvinyl methyl ether (PVME) form miscible blends [8,9]. Syndiotactic and isotactic polystyrene when blended with PVME, phase separate at aU temperatures above the glass transition temperature of PVME. Only weak van der Waals interactions between the phenyl rings in polystyrene with the methoxy group of PVME were detected using 2-dimensional nuclear magnetic resonance (NMR) spectroscopy. [Pg.7]

Poly(cyclohexyl acrylate) was shown to be miscible with PS with ucst behavior [720]. Random copolymers of cyclohexyl acrylate with n-butyl acrylate showed miscibility with PS above 50% cyclohexyl acrylate[721]. Poly(cyclohexyl methacrylate)/isotactic PS blends showed miscibility based on calorimetry and NMR studies [722]. The NMR results showed homogeneous behavior at a scale of 2.5-3.5 nm. Poly(4-trimethylsilyl styrene) miscibility with polyisoprene was observed with a lest behavior (critical temperature = 172 ° C at degree of polymerization of 370) [723]. The interaction parameter, showed the following relationship = 0.027—9.5/T. Isotactic and syndiotactic polystyrene both exhibit crystallinity, whereas atactic polystyrene is amorphous. Atactic PS/isotactic PS blends exhibited crystallization kinetics, which decreased linearly with atactic PS addition indicating miscibility [724]. The TgS of aPS and iPS are identical, thus Tg methods could not be employed to assess miscibility. Atactic PS/syndiotactic PS blends were also noted to be miscible with rejection of atactic PS in the interfibrillar region between the lamellar stacks of sPS [725]. [Pg.173]

This section presents the evaluation of the segmental interaction of polystyrene blends with different tacticities using the SANS technique and the discussions about the tacticity effect on polymer mixtures in comparison with their interaction parameters. Furthermore, the properties of blends of syndio-tactic polystyrene (SPS) and atactic polystyrene (APS) are presented focusing on the improvement of chemical resistance. [Pg.361]

Typically, the temperature dependence of o is not large, but it may be either positive or negative. For example, 10 d In Rl Q/dTis —1.1 for polyethylene, 0.4 for atactic polystyrene, —0.1 to —0.3 for polyisobutylene, —0.2 for poly(ethyl acrylate), 2.2 for poly(hexyl methacrylate) and 0.5 for poly(vinyl alcohol). A large compendium of chain dimension parameters is available in the Polymer Handbook . A 1969 monograph by Flory gives a comprehensive summary of the application of the rotational isomeric state concept with near neighbor interactions to a great variety of real-chain model structures. [Pg.74]


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See also in sourсe #XX -- [ Pg.236 ]




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