Solution properties of high molecular weight polystyrene

Abstract

AbstractA series of polystyrenes with weight‐average molecular weight M̄w up to 1.3 × 107 was prepared by anionic polymerization in tetrahydrofuran (THF). Each sample was characterized by gel‐permeation chromatography, light scattering, and viscometry. It was found that each sample had an almost symmetrical and very narrow molecular weight distribution (M̄w/M̄n < 1.07). The mean‐square unperturbed radius of gyration 〈S2〉0 was determined in trans‐decalin at 20.4°C as 〈S2〉0 = 7.86 × 10−18M̄w (cm2). The particle scattering factor was well represented by the Debye equation irrespective of solvent in the range of M̄w < 4 × 106, and only a small deviation was observed in benzene at higher molecular weights. The penetration function Ψ ≡ A2M2/4π3/2NA〈S〉23/2 was found to approach a relatively low asymptotic value of 0.21–0.23 at molecular weights above 2 × 106 in benzene at 30°C, where A2 is the second virial coefficient and NA is Avogrado's number. It was also found that the theta temperature in trans‐decalin was affected by the nature of polymer samples. A difference of about 3°C in the theta temperature was observed between two series of anionic polystyrenes, one prepared in THF and the other in benzene, but there was practically no difference in unperturbed chain dimension.