Branching in poly(butadiene‐co‐styrene). I. Branching determined by viscometry and ultracentrifugation

Abstract

A sample of poly(butadiene‐co‐styrene), SBR, was divided into twelve fractions by precipitation from a dilute benzene solution. The intrinsic viscosities [η] and weights of all the fractions were measured, and the sedimentation coefficients s0 were determined for the nine fractions of highest molecular weight. From the values of [η] and s0 the number of crosslinks per molecule m, was calculated for each fraction. The results indicated that only the four fractions of highest molecular weight contained crosslinked molecules. The number of crosslinks per weight‐average primary (prior to crosslinking) molecule for the entire sample, δ0, was obtained from the weights of the fractions and the values of m. By use of various theories, values of δ0 of 0.78, 0.56, and 0.38 were obtained. From the values obtained for [η] and s0 and the pycnometric partial specific volume of the polymer in benzene, the molecular weights M of the nine fractions of highest [η] were calculated. The molecular weights of the remaining fractions were calculated from the relation between M and [η] obtained by others. A molecular weight distribution curve was established and used to obtain δ0 ≤ 0.36.

Mechanical Activation of Butadiene–Acrylonitrile Rubber Skn-26

“…Data were given that indicated that the ratio of the number of units m in molecules of a given molecular weight M to this weight (m/M) increased monotonically from 0.8 × 10 -6 at M = 2 × 10 5 to (10-12) × 10 -6 at M = 1.5 × 10 6 . Increase in m/M with increasing M was also established in a series of studies by Blachford and Robertson [7] for butadiene-styrene rubber. A similar effect was found by Podalinskii [8] for butadiene-acrylonitrile rubber from data of sedimentation and viscometric analyses.…”

A novel parameter of polymer structure

“…Thirdly, it is important that the samples have the same intrinsic viscosities, within a few per cent, since the concentrated and intrinsic viscosities for linear fractions are related by eq. (6) :I1 log 7 s = K + @/a) log [71 (6) where K and B are constants for a given polymer-solvent system and temperature when the molecular weight is greater than the critical value. The relationship of eq.…”

Properties of Dilute Solutions of Polyurethanes. II. Branched Polymers

“…4,5) The methods used The molar ratios of PCL to the trifunctional component (TME) in the polymers were as follows:…”