A high temperature osmotic pressure technique has been used to obtain molecular weight data on fractions of polychlorotrifluoroethylene. Samples representing a range of molecular weight of 74,000 to 510,000 were studied. Intrinsic viscosity data were obtained on the samples at 130°C. using a dilution viscometer. The principal solvent used in these studies was 2,5‐dichlorobenzotrifluoride. The plot of π/C vs. C yields satisfactory linear relationships with a slope closely equal to zero. The log log plot of molecular weight and intrinsic viscosity gives the following relationship:
The value of the exponent 0.74 suggests a relatively rigid molecule. This is consistent with the results of x‐ray studies.
From the shape of the curves of scattered light intensity plotted against sin2 0/2 where 0 is the scattering angle, one may estimate the concentration interval where one surpasses the upper bounds of the dilute solution and enters into the semi-dilute solution region. This transition interval, approximating C*, is at a concentration where the large-angle part of the curve flattens out and does not yet show a concavity in the small angle part of the curve. This concavity appears in the semi-dilute region at C >C* and is shown to be strongly dependent on molecular aggregation at these concentrations. The aggregation effects were demonstrated by means of filtration through various pore sizes, and by mixing visible iodized polystyrene (PS) with invisible PS in bromoform.It is further shown that the apparent radiusofgyration (R,) obtained from dissymmetry measurements change as a function ofconcentration, passing through a minimum at a concentration C = C*. It is proposed that C* may be experimentally determined from either the flatness of the scattered light intensity curves, or from the minimum in the curves of apparent Rci as obtained from dissymmetry measurements.
ZUSAMMENFASSUNG:Aus der Kurve der gegen sin' 0/2 aufgetragenen Streulichtintensitat (0= Streuwinkel) kann man das Konzentrationsintervall ermitteln, bei welchem man die obere Grenze der verdunnten Losung iiberschreitet und in den Bereich der maRig verdiinnten Losungen iibergeht. Dieses Ubergangsintervallangenahert bei C* -liegt bei einer Konzentration, bei der im Weit-Winkel-Teil die Kurve abflacht und im Klein-Winkel-Bereich keine konkave Durchbiegung mehr vorliegt. Diese konkave Form erscheint im maRig verdiinnten Bereich bei C > C* und ist stark abhangig von der Molekulaggregation bei diesen Konzentrationen. Die Aggregationseffekte wurden mit Hilfe von Filtrationen durch Filter verschiedener PorengroRe aufgezeigt, sowie durch Mischung von sichtbarem Jodpolystyrol mit unsichtbarem Polystyrol in Bromoform.Es wurde ferner gezeigt, daR der aus Dissymrnetrie-Messungen erhaltene scheinbare Tragheitsradius (R,) von der Polymer-Konzentration abhangt, und zwar durchlauft er ein Minimum bei der Konzentration C = C*. Es wird vorgeschlagen, C* experimentell entweder aus dem Abflachen der Streuintensitatskurve oder aus dem Minimum der Rcj(.,pp) = f(C)-Kurve zu bestimmen.
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