. The Bell System technical journal . \ k \ k \ ^ --. ^ ^^-> -^^ CONCENTRATION IN GRAMS PER 100 ML. OF SOLUTION Fig. 21—Inherent viscositv of ])olvisol)ut vlenc (.1/^ = X lO) in cyclo-hexane at 25°C. 346 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1952 50°C ^ 35°C • — - ( J ._-- 25°C ^ ;=—— CONCENTRATION IN GRAMS PER 100 ML. OF SOLUTION Fig. 22—Inherent viscosity of polyisobutylene (Af, = X 10) in benzene,at various temperatures. more flexible compositions are often produced with low compatibilityplasticizers—indeed, sometimes wit
. The Bell System technical journal . \ k \ k \ ^ --. ^ ^^-> -^^ CONCENTRATION IN GRAMS PER 100 ML. OF SOLUTION Fig. 21—Inherent viscositv of ])olvisol)ut vlenc (.1/^ = X lO) in cyclo-hexane at 25°C. 346 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1952 50°C ^ 35°C • — - ( J ._-- 25°C ^ ;=—— CONCENTRATION IN GRAMS PER 100 ML. OF SOLUTION Fig. 22—Inherent viscosity of polyisobutylene (Af, = X 10) in benzene,at various temperatures. more flexible compositions are often produced with low compatibilityplasticizers—indeed, sometimes with those on the verge of phase sepa-ration than with those with highly favorable heats of solution. Thiswould mean that the bad solvents would compress the chains so thatthey would be more easily strained than if they were in a free chamor even extended configuration. If single chain, visco-elastic stiffnessesare acting this way, the dynamic mb would then actually decline as heatof mixing become more positive. 2 1200. Fig. 23-20 kc. CONCENTRATION IN GRAMS PER 100 ML OF SOLUTION -Rigidity of polyisobutylenes in and benzene at 25°C and INTERACTION OF POLYMERS AND MECHANICAL WAVES 347 This seems to take place, as indicated by the lower compared to theupper curve on Fig. 23. Here, the /xs of the usual modified , at 20 kc, is plotted against c for the polyisobutylene of M, = X 10 . Also, the middle curve shows hb for a polymer of about atiiird of this molecular weight; while there is a small reduction in hbwith il/, in this range, it is much less than the reduction caused bytightening up the polymer coil. Tiie M« Nalues per average molecule, [fa], fall from 18 X 10~ dynecm in cyclohexane to 7 X 10 in benzene. (Of course, [Jb] for the inter-mediate molecular weight polymer in cyclohexane is only 5 X 10~ be-cause so many more molecules are present in solution.) The temperature dependence of
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