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Modulating Shape of Polyester Based Polymersomes using Osmotic Pressure
Published on: April 21, 2021
Osmotic shrinkage in star/linear polymer mixtures
A Wilk1, S Huissmann, E Stiakakis
1Laboratory for Neutron Scattering, ETH Zurich & Paul Scherrer Institut, Villigen PSI, Switzerland.
The European Physical Journal. E, Soft Matter
|July 3, 2010
Summary
Adding smaller linear polymers to star polymers causes them to shrink due to depletion forces. Increasing the size ratio of linear to star polymers reduces this shrinkage effect.
Area of Science:
- Polymer science
- Soft matter physics
- Colloid science
Background:
- Multiarm star polymers act as model grafted colloidal particles with long "hairs".
- The depletion phenomenon, driven by osmotic forces from smaller added polymers, can alter particle size and melt colloidal glasses.
- Shrinkage of hairy particles is a known phenomenon affecting macroscopic properties and state transitions.
Purpose of the Study:
- To investigate the size variation of star polymers due to osmotic forces from added linear homopolymers.
- To study the effect of varying size ratios between star and linear polymers on star shrinkage.
- To develop and validate a theoretical model for star polymer shrinkage.
Main Methods:
- Small-angle neutron scattering (SANS) experiments were used to study star/linear polymer mixtures.
- Dynamic light scattering experiments and effective interactions analysis were previously used to study depletion potentials.
- A theoretical model incorporating Flory contributions and osmotic forces was developed.
Main Results:
- The study confirmed osmotic star shrinkage in star/linear polymer mixtures.
- Increased linear/star polymer size ratio reduced star shrinkage for a given effective linear volume fraction.
- Shrinkage onset was observed at higher linear polymer volume fractions as the size ratio increased.
- The theoretical model accurately predicted reduced star size with increasing linear polymer concentration.
Conclusions:
- Osmotic forces from smaller linear polymers cause star polymer shrinkage, consistent with the depletion phenomenon.
- The degree of star shrinkage is dependent on the size ratio between the interacting polymers.
- A parameter-free theoretical model successfully describes the observed star polymer size variations.
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