The theory described in the preceding paper is extended to include intramolecular reactions in A-A+ B-B type polymerisations. The extension is described in a general way and a limiting form is applied to previously published data giving total ring fractions during the formation of linear polyurethanes. The interpretations afforded by the present approach and by previous analyses of the data are discussed and compared.
Eingegangen a m 6. Mai 1971) S U M M A R Y :The numbers of rings formed in the reactions of hexamethytenc diisocyanate with two polyethylene glycols have been determined as a function of dilution and ratios of reactants. I n this work the cryoscopic apparatus developed in the preceding paper has been utilised. It is found that more rings are formed (a) in dilute solutions, (b) with reactants of lower molecular weight, and (c) in reactions at equimolar concentrations. Some of the results may be interpreted approximately by means of JACOBSON and STOCKMAYER'S theory. Values of the FLORY-I~UGCINS' interaction parameter x have been determined from the cryoscopic data. They show a very marked dependence on the density of hydroxyl groups in the chain. Z U S AMM E N F A S S U N G : Die Anzahl der sich bci Reaktionen von I-iexamethylendiisocyanat rnit zwei Polyathylenglykolen bildenden Ringe wurde als Funktion der Verdiinnung und der Verhiiltnisse der Rcaktionspartncr bestimmt. Die im vorhcgehenden Bericht beschriebene Kryoskopie-Apparatur wurde bci dieser Arbeit benutzt. Es wird gefunden, daO sich mehr Ringe bilden: (a) bei verdunnten Losungen, (b) bei Reaktiouspartnern niedrigeren Molekulargewichts, (c) bei Reaktionen mit iiquimolaren Konzentrationen. Einige dieser Rcsultate konnen mit Hilfe der Theorie von J A C O~S O N und STOCKMAYER anniihernd interpretiert werden. Werte fur die hoRY-HuccINsschen Interaktionsparameter x wurden mit IIilfe der kryoskopischenDaten berechnet. Sie wcisen eine sehr deutliche Abhiingigkeit von der Dichte der Hydroxylgruppen in der Kette auf.
The thermodynamics of the polymerization of acetone through the carbonyl group has been investigated in an attempt to find the limiting experimental conditions for producing high molecular weight polymer. Approximate values for the entropy and enthalpy of polymerization were estimated empirically from data published on polyolefins and polyacetals. A low negative heat of polymerization (ΔHp = −2.4 kcal mole.−t) rather than a high negative entropy (Δ Sp = −45 cal mole−1 (deg K)−1) was considered to be the controlling influence in the polymerization. From these values, a ceiling temperature of –220°C was calculated for the reaction of gaseous acetone to form amorphous polyacetone.
The development and use of a cryoscopic apparatus are described. Temperatures are simply measured by means of a thermistor and WHEATSTONE bridge. However, the thermal conditions within the cryoscopic cell during freezing were closely controlled with the result that a quick and accurate method for determining a series of freezing points without supercooling was made possible. The apparatus and method have been tested using solutes of molecular weights up to 2000.
ZUSAMMENFASSUNG:Die Entwicklung und Anwendung einer kryoskopischen Apparatur werden beschrieben. Die Temperaturen werden auf eine einfache Weise mittels eines Thermistors und einer V(iJ3EATsToNE-~riicke gemessen. Die thermischen Zustande innerhalb der kryoskopischen Zelle wahrend des Gefriervorganges werden streng kontrolliert. So wird es moglich, eine Serie von Gefrierpunkten ohne Unterkiihlung schnell und genau zu bestimmen. Die Apparatur und die beschriebene Methode wurden an Substanzen mit Molekulargewichten bis zu 2000 gepriift.
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