Anomalous behavior, polymer

A similar anomalous behavior has been detected also in 3d polymer melts but only for rather short chains [41] for longer chains, several regimes occur because of the onset of entanglement (reptation ) effects. In two dimensions, of course, the topological constraints experienced by a chain from... 

As a result of the dependence of universal calibration on column elution behavior (i.e., anomalous behavior due to adsorption or exclusion), the contribution of the polymer core and shell components (33,34) to hydrodynamic behavior must be fully understood if competent analysis of block copolymers and branched heteropolymers is to be made. It is hoped that with the advent of appropriate MW, composition, and branched polymer standards, the limits of fit of universal calibration to biopolymers such as lignin can be judged. 

R. Johnston Chain transfer to a mixture of agents The anomalous behavior of the acrylonitrile-dimethylformamide-water system. J. Polymer Sci. 39, 81-86 (1959). 

These assumptions are continuity of stress and velocity across the interfaces since stress discontinuities owing to high interfacial tensions increase the viscosity (3), to explain the unexpected low viscosities we must doubt the validity of the velocity condition at the interfaces. This is supported by the fact that the two polymers are incompatible, which implies a relatively low concentration or even complete absence of entanglements at the interface. A very thin layer of solute-free solvent around the droplets would result. Such a low viscosity layer might be the cause of the anomalous behavior. 

With high shear mixing equipment such as the Banbury or continuous mixer, the use of block polymers with a number average molecular weight (Mw) below 150,000 did not give the expected improvement in impact over polystyrene. This anomalous behavior occurred because the particle size of the discrete rubber phase averaged less than 0.2 pm compared with an average of 1 pm for blends with optimum impact obtained in the solution blends. 

Tg—TJ and change with the size of the molecular segment involved in yield a single value corresponding to the Y of polycarbonate at 300 K is indicated on Fig. 20. For polymers with Ve above about 5 x 10 m" shear yield should oceur in preference to crazing. Because of individual variations in Y from polymer to polymer, in isolated instances crazing may be favored over shear even above this value this may be the reason for the anomalous behavior of PMMA. 

Thermotropic LCPs have high melt elasticity, but exhibit little extrudate swell. The latter has been attributed to a yield stress and to long relaxation times (60). The relaxation times for LCPs are normally much longer than for conventional polymers. Anomalous behavior such as negative first normal stress differences, shear-thickening behavior and time-dependent effects have also been observed in the. rheology of LCPs (56). Several of these phenomena are discussed for poly(benzylglutamate) solutions in the chapter by Moldenaers et al. 

The results presented here on pectate solutions containing calcium or copper ions bring interesting evidence for an anomalous behavior of pectate properties in the range of ion to polymer ratio below that corresponding to the massive phase separation. The possibility that a conformational change proceeds along with the interaction with divalent ions is examined and discussed in comparison with the case of the proton-induced conformational transition. 

N. A. Halliwell and A. K. Lewkowicz, Investigation into the Anomalous Behavior of Pilot Tubes in Dilute Polymer Solutions, Phys. Fluids (18) 1617,1975. 

This paper, the third in a rheotechnics series, reports on rheological studies performed at y higher than 10 1 sec-1. In two-phase polymer systems, Rosen and Rodriquez (3) hypothesized anomalous behavior (yield shear stress) at y = 10 1. Recently, Zosel (9) verified this hypothesis experimentally for ABS systems. A study of the rheological behavior of ABS resins at very low y is now in progress at our laboratories. The correlation between rheological behavior and moldability will be discussed in detail in a subsequent paper. 

Complications such as these extend also to the case of polytetra-fluoroethylene. The large difference in estimated solid-vacuum tensions between this polymer and polyethylene is not imexpected, since a proportionately large difference exists for the liquid surface tensions of hydrocarbons and fluorocarbons having five to eight carbon atoms [58]. The underlying cause of this difference is, however, more obscure. The inter molecular forces for fluorocarbons apparently have features wuich lead to anomalous behavior, at least from the point of view of solubility parameter theory [59]. Thus, theoretical calculations of the surface tension for the bare solid in the case of polytetrafluoroethylene would face a number of difficulties not encountered with paraffin crystals. 

When the respective component glass transition temperatures are close, the blend Tg is not a useful measure of blend homogeneity. In fact, excess mixing volumes and specific interactions can cause anomalous behavior. The Tg of such a blend can be lower (as seen in polychloroprene/epoxidized polyisoprene blends (McGrath and Roland, 1994)) or higher (as seen in polylepichlorohydrin/polyvinylmethylether blends (Alegria et al., 1995)), than Tg of either neat component. In blends of polymers having nearly equivalent... 

Anomalous behavior is noted among some of the solution properties since polymers are not always well-defined. Crystalline-state properties ... 

In a more recent study, Muller-Plathe, Rogers, and van Gunsteren have pointed out a case of anomalous diffusion in polyisobutylene near room temperature [48], in harmony with the findings by TSA for gas motion in dense polymers [56]. For He in PIB, anomalous behavior could be clearly shown, and the transition to normal diffusion at around 0.1 ns could be captured. The log-log plot that shows this crossover, is reproduced in Fig. 6. For the much slower diffusing O2, the mean-square displacement data were not accurate enough to determine unambiguously if the curve represented diffusive behavior... 

Low Frequency Observations for Amorphous Polymers. Many amorphous materials studied by Raman exhibit an extremely broad band in the low frequency region. This is true for polycarbonate, poly(methyl methacrylate), and polystyrene (58). Low frequency Raman bands can potentially provide much information regarding the density of states (directly related to the intensity distribution of the broad Raman active band) as well as anomalous behavior observed for the specific heat (58). Often the separation of main-chain and side-chain bands is important in modeling of specific heat, making careful band assignment extremely meaningful (136,137). This separation is analogous to inclusion of optical... 

Although the overall low-frequenspectral response of all metallic conducting polymers, such as PANI-CSA, PPy-PF6, and PEDOT-PFg, can be attributed to free-carrier intraband excitations, their o like behavior below 0.2 eV [1160-1165]. The anomalous behavior of a(o)) and ei(oj) in the low energies (typically below 0.2-0.4 eV) can be attributed to disorder-induced localization, and can be analyzed in terms of the localization-modified Drude (LMD) model [1160-1165], This LMD model, originally proposed by Mott and co-workers [1125, 1156, 1157], has been modified by Lee et al. [1160] and successfully introduced into the analysis of optical spectra of metallic conducting polymers [1160-1165]. This model is a first-order correction of the Drude model in the regime of weak localization, as given by [1160]... 

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