Related Experiment Video
Updated: Feb 16, 2026

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by π-π Stacking Interactions
Published on: October 10, 2016
Extensional Strain Hardening Induced by π-π Interactions in Barely Entangled Polymer Chains: The Curious Case of
Carlos R López-Barrón1, Huaxing Zhou2
1ExxonMobil Chemical Company, Baytown, Texas 77520, USA.
Abstract:
Aromatic π-π interactions between phenyl groups of adjacent chains in poly(4-vinylbiphenyl) (PVBP) have profound effects on the dynamics of this polymer. We report two unexpected nonlinear viscoelastic responses of PVBP when subjected to uniaxial flow. One is the unprecedented observation of extensional strain hardening (SH) in a barely entangled polymer melt. An even more intriguing finding is that SH of lightly (or even barely) entangled melts occurs at strain rates one order of magnitude below the coil-stretch transition predicted by Rouse theory (ϵ[over ˙]_{H}=0.5/τ_{R}).We postulate that this behavior is due to a molecular rearrangement mechanism (supported by x-ray diffraction measurements) that involves flow-induced π-π stacking of the phenyl groups, which results in an enhancement of the friction coefficient between polymer chains.
Related Concept Videos
π Molecular Orbitals of 1,3-Butadiene
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
π Electron Effects on Chemical Shift: Overview
π Molecular Orbitals of the Allyl Radical
The allyl systems have identical molecular orbitals but differ in the number of π electrons....
π Molecular Orbitals of the Allyl Cation and Anion
Hückel's Rule Diagram of π MOs: Frost Circle
A Frost circle is constructed by drawing a polygon whose number of edges is equal to the number of carbons of the given cyclic system, with one of the vertices pointing down. Then, a circle is drawn enclosing the polygon so that...
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

