The Dimensions of Polystyrene Near and Below the Theta Temperature

Slagowski, Eugene L.; Tsai, Benjamin K.; McIntyre, D.

doi:10.1021/ma60052a033

Cited by 60 publications

(24 citation statements)

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“…According to de Gennes Scaling theory R is reasonably independent of concentration is clearly identifiable. The cross-over from dilute to semi-dilute regime is called the overlap concentration, c * , and can be estimated using a number of different equations; two of which are described by Equations (10) and (11). In fact the SANS data suggest that c * is lower than that suggested by either of these equations which may in part relate to the polydispersity of the polymers.…”

Section: Sans Results As F(concentration) In D-squalanementioning

confidence: 99%

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Covitch¹,

Trickett²

2015

ACES

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One of the requirements of engine lubricating oil is that it must have a low enough viscosity at low temperatures to assist in cold starting and a high enough viscosity at high temperatures to maintain its load-bearing characteristics. Viscosity Index (VI) is one approach used widely in the lubricating field to assess the variation of viscosity with temperature. The VI of both mineral and synthetic base oils can be improved by the addition of polymeric viscosity modifiers (VMs). VI improvement by VMs is widely attributed to the polymer coil size expanding with increasing temperature. However, there is very little physical data supporting this generally accepted mechanism. To address this issue, intrinsic viscosity measurements and Small-Angle Neutron Scattering (SANS) have been used to study the variation of polymer coil size with changing temperature and concentration in a selection of solvents. The results will show that coil size expansion with temperature is not necessary to achieve significant elevation of viscosity index.

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Section: Sans Results As F(concentration) In D-squalanementioning

confidence: 99%

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Covitch¹,

Trickett²

2015

ACES

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“…We must have AT > 8/N 1 ~~ to reach a significant collapse [3]. The final state has been widely studied experimentally [4][5][6][7][8] and theoreticallystarting from an idea of Stockmayer [9]. Here we shall use the simplest (mean field) theoretical description [10,11] to describe the collapse.…”

Section: Aims and Toolsmentioning

confidence: 99%

Kinetics of collapse for a flexible coil

de Gennes

1985

J. Phyique Lett.

226

255

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2014 Si on transfère tout à coup une chaine flexible depuis le point 03B8 vers une situation de mauvais solvant (par exemple, par un changement de température 0394T) elle s'effrondre en un temps 03C4c. Nous proposons ici une loi d'échelle pour 03C4c, basée sur un modèle de « saucisse gonflée », et prenant en compte les interactions hydrodynamiques. Nous trouvons 03C4c ~ 03C4R 0394T/03B8 où 03C4R est le temps de Rouse de la chaîne au point 03B8 : le temps 03C4c croit avec la profondeur de la trempe. Abstract. 2014 If a polymer chain is transferred abruptly from 03B8 conditions to bad solvent conditions (e.g. by a shift of temperature 0394T) it collapses with a certain characteristic time 03C4c. We propose a scaling structure for 03C4c, based on an « expanding sausage model », and taking into account the hydrodynamic interactions. We find that 03C4c ~ 03C4R 0394T/03B8 where 03C4R is the Rouse time of the 03B8 chain : the time 03C4c increases with the depth of quench.

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“…5 and Slagowski et a/. 6 should compose a single rx,Z vs. x curve, since all these measurements refer to the same polymer + solvent system. Figure 4 shows that our data of rx, 2 Polymer J., Vol.…”

Section: Chain Dimensionsmentioning

confidence: 99%

Excluded-Volume Effects in Dilute Polymer Solutions. X. Polystyrene in Cyclohexane below the Theta Temperature

Miyaki

Fujita

1981

Polym J

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ABSTRACT:Mean-square radii of gyration and viscosities of polystyrene samples covering a broad range of molecular weight M in cyclohexane were measured at temperatures above and below the theta temperature () in order to see how the coil of a linear flexible polymer collapses to a globule as T is lowered. The data for either the radius expansion factor or the viscosity expansion factor as a function of T and M gave a composite curve when plotted against (Tie-I)M 1 1 2 or (l-eiT)M 1 1 2 In the range of the abscissa values studied, this curve did not reach the asymptote for globular behavior. Thus, the coil-to-globule transition of a linear flexible polymer should be a very gradual process.KEY WORDS Coil-Globule Transition I Polystyrene I Cyclohexane I Radius of Gyration I Intrinsic Viscosity I Much still remains te be investigated theoretically and experimentally in regard to the chain dimensions and flow properties of a linear flexible polymer in a poor so.lvent below the theta temperature e. Long ago Stockmayer 1 suggested that a random coil might eventually collapse to a globule as the temperature Tis lowered below e. This coilglobule transition should manifest itself as a change in molecular weight dependence of (S 2 ) from the type (S 2 )a;:Mto the type (S 2 )ocM 213 , where (S 2 ) is the mean-square radius of gyration at infinite dilution and M is the molecular weight of the polymer.By extending Flory's mean-field theory to include a term associated with the ternary cluster integral {J3 and assuming that the binary cluster integral {J 2 is proportional to r and {J3 is independent of T, de Gennes 2 showed that as a coil shrinks to a globule, the dependence of (S 2 ) on M and Tasymptotically approaches the form (1) where r is a reduced temperature defined by r=(T-e)je (2)

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The Dimensions of Polystyrene Near and Below the Theta Temperature

Cited by 60 publications

References 0 publications

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

Kinetics of collapse for a flexible coil

Excluded-Volume Effects in Dilute Polymer Solutions. X. Polystyrene in Cyclohexane below the Theta Temperature

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