Dilute solution properties and phase separation of branched low‐density polyethylene

Abstract

Viscosity, light scattering, and precipitation temperature measurements on dilute solutions of high‐density and low‐density polyethylene fractions have been carried out and a theory by Flory for phase equilibrium of linear polymers has been extended to branched polymer. From the results, it is shown that the entropy parameter ψ, depends on branching; a method for the determination of long‐chain branching in polymer fractions is proposed combining precipitation temperature and molecular weight measurements. The method has been applied to the evaluation of long‐chain branching in low‐density polyethylene.

A Semiempirical Formulation of the Effect of Random Branching on Intrinsic Viscosity

“…A less clear-cut result is arrived at with the LDPE fractions from ref 16 (Figure 6). The plots are linear, but three points with the lowest molecular weights deviate upwards.…”

“…Plot of l/go vs. M1''2 for LDPE. Data from ref 16 (samples A (O), B (9), and C (•)). Curves calculated for (¡>; X X 104): 1 and 2 (0.8; 1.15), 3 (0.8; 1.4).…”

Liquid-Liquid Phase Separation in Multicomponent Polymer Systems. 18. Effect of Short-Chain Branching

“…This suggested effect does not necessarily contradict Nakano's conclusion that the temperature is independent of long-chain branching. 6 Nakano's data are well represented for linear and branched polyethylenes alike by a single Shultz-Flory plot provided the usual abcissa (mw~1/2) is replaced by [j?]-1. It is hard to conceive a theoretical foundation for this, but the procedure evidently works well.…”

Entmischung in hochmolekularen Vielstoffsystemen, XVII. Eine Wechselwirkungsfunktion für Lösungen verzweigter Polymerer

“…Ensembles of "athermal" chains, i. e. the segments being of hard sphere type with no other interaction admitted. the chains consisting of 50 to 400 segments each, were produced on a five way cubic lattice using a procedure [4], which is based on the Monte Carlomethod developed by Metropolis et al [ 5 ] . Instead of the rotation of the smaller part of the chain around a bond picked out at random as in 1141 (the proper method of producing four way cubic lattice chains) here the orientation of this bond in space (together with that of the rest of the chain) was altered by 90 or 180", the choice of the new direction likewise being a random one.…”