Small and Medium Amplitude Oscillatory Shear Rheology of Model Branched Polystyrene (PS) Melts.

Hyeong Yong Song,Suk-Kyun Ahn,Lorenz Faust,Seung Joon Park,Manfred Wilhelm,Kyu Hyun,Jinha Son,Mingeun Kim

doi:10.3390/polym12020365

Abstract

Linear and nonlinear rheological properties of model comb polystyrenes (PS) with loosely to densely grafted architectures were measured under small and medium amplitude oscillatory shear (SAOS and MAOS) flow. This comb PS set had the same length of backbone and branches but varied in the number of branches from 3 to 120 branches. Linear viscoelastic properties of the comb PS were compared with the hierarchical model predictions. The model underpredicted zero-shear viscosity and backbone plateau modulus of densely branched comb with 60 or 120 branches because the model does not include the effect of side chain crowding. First- and third-harmonic nonlinearities reflected the hierarchy in the relaxation motion of comb structures. Notably, the low-frequency plateau values of first-harmonic MAOS moduli scaled with (total molecular weight), reflecting dynamic tube dilution (DTD) by relaxed branches. Relative intrinsic nonlinearity Q0 exhibited the difference between comb and bottlebrush via no low-frequency Q0 peak of bottlebrush corresponding to backbone relaxation, which is probably related to the stretched backbone conformation in bottlebrush.

Highlights

Understanding the rheological properties of branched polymers is essential for all forms of production and processing in the polymer industry because the processability of polymers is highly affected by the degree of long-chain branches (LCB) [1]
The linear viscoelastic behavior of model comb PS used has already been analyzed by Abbasi, Faust, Riazi and Wilhelm [21]
We investigated linear and nonlinear oscillatory shear (SAOS and Medium amplitude oscillatory shear (MAOS)) rheology of model comb PS melts, where the number of branches along the backbone was controlled while the branch length was kept

Summary

Introduction

Understanding the rheological properties of branched polymers is essential for all forms of production and processing in the polymer industry because the processability of polymers is highly affected by the degree of long-chain branches (LCB) [1]. Many researches have used well-defined model branched polymers of star [8], pom-pom [9], comb [10] and dendritic structures [11]. Architectures of these polymers are a substructure of industrial polymers with LCB. Comb polymer is the simplest class of model branched polymer with multiple branch points

Methods

Results

Conclusion