Adsorption-active polydisperse brush with tunable molecular mass distribution.

Area of Science:

• Polymer science
• Surface chemistry
• Materials science

Background:

• Responsive uncharged polymer brushes with substrate affinity exhibit microphase separation.
• A fraction of chains adsorbs to form a dense layer, while others form an outer brush with reduced grafting density.
• The effective grafting density is tunable via adsorption strength and environmental parameters.

Purpose of the Study:

• Investigate preferential adsorption in polydisperse polymer brushes using numerical self-consistent field calculations.
• Analyze the impact of chain length on adsorption and the resulting molecular mass distribution (MMD).
• Develop a method to assign chain conformations to different microphases.

Main Methods:

• Numerical self-consistent field (SCF) calculations.
• Analysis of tail length distributions to differentiate chain conformations.
• Study of polydisperse brushes with varying surface affinity parameters.

Main Results:

• Shorter polymer chains are preferentially adsorbed to the substrate, even when chemically identical.
• Increased surface affinity leads to a reduced grafting density in the outer brush and a narrower MMD.
• An initially bidisperse brush can transform into a nearly monodisperse brush composed of longer chains.

Conclusions:

• Preferential adsorption in polydisperse brushes arises from the spectrum of chemical potentials across different chain lengths.
• This effect is expected in polyelectrolyte brushes and influences coexistence with other condensed phases.
• Brush polydispersity fundamentally impacts adsorption behavior and microphase formation.