Branching in polybutadiene

Abstract

A detailed study has been made of the intrinsic viscosity‐molecular weight relationship for a polybutadiene prepared at 50°C. and one prepared at 5°C. Original fractions were at least twice refractionated from very dilute solutions in an attempt to obtain fairly sharp distributions. Fox‐Flory K constants are observed to decrease with increasing molecular weight in each case, and the intrinsic viscosity‐molecular weight plots show a curvature. This is interpreted to be a result of branching. A method of plotting the data is proposed which simultaneously yields the K for unbranched material and an estimate of the degree of branching. It is estimated that, in polybutadiene prepared at 50°C., one out of 6500 monomer units is involved in a branch, and that in 5°C. polybutadiene, one out of 10,000.

Near Infrared and Nuclear Magnetic Resonance Spectrometry in Analysis of Butadiene Polymers.

“…The general problem of diene polymerization is of great importance as the physical properties of a polybutadiene depend to a large extent on the distribution of the monomer units. The distribution of The ratios of 1,4 to 1,2 and that of tram to cis in a given polymer are dependent on the type of polymerization catalysts and reaction conditions used (1, [15][16][17][18].…”

“…For this work commercial and laboratory preparations of polymers (11) were used as received or after fractionation according to standard methods (18).…”

Stereochemistry of Polymerization

“…1,3-Butadiene exists predominately in the transoid or s-trans conformation (ILa) as opposed to the cisoid or s-cis conformation (ILb). This is probably also the situation for a Data from Condon [1953], Richardson [1954], Pollock et al [1955]. b Data from Coleman and Brame [1978], Coleman et al [1977], Ebdon [1978].…”

General and physical chemistry

“…Intrinsic-viscosity and molecularweight studies indicate that in the polymerisation of butadiene at 50" one in 6,500 monomer units is involved in branching; at 5" only one in 10,000 units is involved. 438 Light-scattering studies suggest that there is also a decrease in branching as the temperature is lowered in the polymerisation of vinyl acetate. 439 Polymers made from deuterated styrene have the same solution properties as ordinary polystyrene, although it would have been expected that deuteration would make transfer, and hence branching, more difficult ; 440 presumably branching is only slight in the polymerisation of styrene.…”