# Interfacial Properties of Miktoarm Star Polymers with a Poly(divinylbenzene) Core

## TL;DR

This paper studies how miktoarm star polymers behave at oil-water interfaces, focusing on their adsorption and rheological properties.

## Contribution

The study reveals how the structure of miktoarm star polymers affects their interfacial behavior and rheological response.

## Key findings

- Adsorption from the oil phase is slower due to less facile desolvation of polymer arms.
- Interfacial rheology depends on arm lengths and shows frequency-dependent or independent responses.
- Longer hydrophilic arms lead to frequency-independent interfacial behavior due to interface pinning.

## Abstract

The interfacial properties of miktoarm star polymers
composed of
poly­(divinylbenzene) (PDVB) cores with poly­(ethylene oxide) (PEO)
hydrophilic arms and poly­(n-butyl acrylate) (PBA)
or poly­(lauryl acrylate) (PLA) hydrophobic arms at the oil/water interface
are reported. The kinetics of miktoarm star polymer adsorption from
the oil phase depended on the polymer concentration. This suggested
that the rate-determining step was the adsorption and penetration
of the polymer onto and through the interface. This was attributed
to the desolvation of the polymer arms from the oil phase being less
facile than that of similar star polymers with PEO arms alone from
the aqueous phase. PEO star polymers showed diffusion-controlled kinetics,
and as such, the adsorption and so forth were facile and rapid compared
to the rate of diffusion to the interface. The interfacial oscillatory
dilatational rheology of the polymers adsorbed at the interface was
dependent on the relative molecular weights or lengths of the arms.
In the case where both arms showed similar contour lengths, the interfacial
rheological response was strongly frequency dependent, suggesting
that the polymer adsorption/desorption was relatively facile on the
time scale of the oscillation. Polymers in which the hydrophilic arms
were longer than the hydrophobic arms showed a relatively frequency-independent
response. This was attributed to the hydrophobic arms effectively
increasing the size of the hydrophobic core in conjunction with the
penetration of the hydrophilic arms through the interface into the
aqueous phase, thus pinning the polymer at the interface.