Poly phase behavior

The effect of lateral methyl groups in the spacer on the phase behavior has been studied in several polybibenzoates [18,19] derived from poly(tetramethy]ene p,p bibenzoate), P4MB. The branched polymers display transition temperatures significantly lower than P4MB. Moreover, the substituents have a clear effect on the kind of mesophase formed. Thus, P4MB displays a smectic A mesophase, while the lateral methyl groups... 

The phase behavior of several polybibenzoates with oxyalkylene spacers has been reported [11,14,15,20-27]. These spacers include the dimer of trimethylene glycol and different ethylene oxide oligomers. The most noticeable characteristic of these polybibenzoates with ether groups in the spacer is the considerable decrease of the rate of the mesophase-crystal transformation. Thus, Fig. 8 shows the DSC curves corresponding to a sample of poly[oxybis(trimethylene)p,p -bibenzoate], PDTMB, with a structure similar to that of P7MB but with the... 

FIGURE 11.12 Interaction energy density versus 4-methyl styrene content. (From Raboney, M., Gamer, R.T., Elspass, C.W., and Peiffer, D.G., Phase Behavior of Brominated Poly(Isobutylene-co-4-Methylstyrene)/ General Purpose Rubber Blends. Rubber Division, Proceedings of the American Chemical Society, Nashville, TN, Sept. 29-Oct. 2, 1998, Paper No. 36.)... 

Linse, P, Phase Behavior of Poly(ethylene oxide)-Poly(propylene oxide) Block Copolymers in Aqueous Solutions, Journal of Physical Chemistry 97, 13896, 1993. 

In addition to the crystal forms, X-ray scattering studies indicate that when unoriented PEN fiber was drawn at 120 °C ( 7 g), a mesophase is generated. In this form, the molecular chains are in registry with each other in the meridional direction but not fully crystallized in the equatorial direction. This conclusion was based on the presence of additional meridional peaks not accounted for by the crystal structure obtained by X-ray scattering. The mesophase is a intermediate phase and its existence is strongly dependent upon the processing conditions consequently, it could have implications with respect to the properties of commercially produced fibers and films, since it appears to be stable and not easily converted to the crystalline form, even at elevated temperature [25, 26], The mesophase structures of PET, PEN and poly(ethylene naphthalate bibenzoate) were compared by Carr et al. [27], The phase behavior of PEN and PEN blends with other polymers has also been studied [28-32],... 

Kenworthy AK, et al. Structure and phase behavior of lipid suspensions containing phospholipids with covalently attached poly (ethylene glycol). Biophys J 1995 68 1903. 

R Hansson and M. Akngren Interaction of Alkyltrimethylammonium Surfactants with Polyacrylate and Poly(Styrenesulfonate) in Aqueous Solution Phase Behavior and Surfactant Aggregation Numbers. Langmuir 10, 2115 (1994). 

The high-pressure phase behavior of polymer-solvent-supercritical carbon dioxide systems was investigated experimentally The polymers used were poly(methyl methacrylate), polystyrene, polybutadiene, and poly(vinyl ethyl ether) at concentrations ranging from 5 to 10% in mixtures with toluene or tetrahydrofuran. The experiments were conducted for temperatures from 25 to 70°C and pressures up to 2200 psi in a high-pressure cell (Kiamos and Donohue, 1994). 

Figure 6. Conventional two-component phase behavior in poly disperse Flory-Huggins theory, shown in the (p, p0) plane for three values of % As in Fig. 5, the parent has Ln = 100 and Ly/ = 150 (hence a = 2). Along the y-axis, we plot L//p0 rather than p0 so that the dilution line p = LNp0, shown as the thick solid line in (a-c), is simply along the diagonal. With x considered as an additional variable, the dilution line constraint defines a plane (p, = L/vPq, x)- The last plot, (d), shows the cut by this plane through the phase behavior in (a-c) the solid line is the cloud point curve, and the dashed line is the spinodal stability condition.

Almgren, M., W. Brown, and S. Hvidt. 1995. Self-aggregation and phase behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers in aqueous solfflirthnid Polym. Sci. 

Zhou, Z. and B. Chu. 1994. Phase behavior and association properties of poly(oxypropylene)-poly(oxyethylene)-poly(oxypropylene) triblock copolymer in aqueous soluftdacromolecule 7 2025-2033. 

Real substances often deviate from the idealized models employed in simulation studies. For instance, many complex fluids, whether natural or synthetic in origin, comprise mixtures of similar rather than identical constituents. Similarly, crystalline phases usually exhibit a finite concentration of defects that disturb the otherwise perfect crystalline order. The presence of imperfections can significantly alter phase behavior with respect to the idealized case. If one is to realize the goal of obtaining quantitatively accurate simulation data for real substances, the effects of imperfections must be incorporated. In this section we consider the state-of-the-art in dealing with two kinds of imperfection, poly-dispersity and point defects in crystals. 

The experimental studies on phase behavior and pattern formation reviewed here have been done on substrate-supported films of cylinder-forming polystyrene- foc -polybutadiene diblock (SB) [36, 43, 51, 111-114] and triblock (SBS) [49, 62, 115-117] copolymers (Table 1), lamella-forming polystyrene- /ocfc-poly(2-vinyl pyridine) diblock copolymers (SV) [118, 119] and ABC block terpolymers of various compositions [53, 63, 120-131], In simulation studies, a spring and bid model of ABA Gaussian chains has been used (see Sect. 2) [36,42, 58, 59],... 

Massa, Voit, and coworkers1231 conducted a survey of the phase behavior of blends of these polyester hyperbranched polymers with linear polymers. Blend miscibility of a hydroxyl terminated polyester was comparable to that of poly(vinylphenol) indicating strong H-bonding interactions, whereas miscibility of an acetoxy terminated analog decreased relative to the hydroxy derivative. 

Rodriguez, C., Uddin, M.H., Watanabe, K., Furukawa, H., Harashima, A. and Kunieda, H. (2002) Self-organization, phase behavior, and microstructure of poly(oxyethylene) poly(dimethylsiloxane) surfactants in nonpolar oil. /. Phys. Chem. B, 106(1), 22-9. 

Homopolymer (A)/random copolymer (B) blends, poly(1)/poly(2-ran-3). Phase behavior may be discussed in terms of the interaction parameter XAB which is given in the mean-field approximation by [2, 3]... 

Before discussing theoretical approaches let us review some experimental results on the influence of flow on the phase behavior of polymer solutions and blends. Pioneering work on shear-induced phase changes in polymer solutions was carried out by Silberberg and Kuhn [108] on a polymer mixture of polystyrene (PS) and ethyl cellulose dissolved in benzene a system which displays UCST behavior. They observed shear-dependent depressions of the critical point of as much as 13 K under steady-state shear at rates up to 270 s Similar results on shear-induced homogenization were reported on a 50/50 blend solution of PS and poly(butadiene) (PB) with dioctyl phthalate (DOP) as a solvent under steady-state Couette flow [109, 110], A semi-dilute solution of the mixture containing 3 wt% of total polymer was prepared. The quiescent... 

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