Surface Block Identity Controls Transport of Symmetric Diblock Copolymer Through Nanopores

TL;DR

This study reveals that the surface orientation of symmetric diblock copolymers at nanopore entrances critically influences their infiltration kinetics, with implications for nanostructure design and membrane applications.

Contribution

It demonstrates how surface block identity controls polymer transport through nanopores, combining experimental and simulation insights into the underlying mechanisms.

Findings

Infiltration is faster when P2VP is the top layer contacting silica.

Surface affinity and nanostructure dictate infiltration pathways and rates.

Disruption of pathways occurs when surface affinity is neutralized or above transition.

Abstract

Understanding how polymer architecture governs transport through nanopores is essential for nanocomposite fabrication, membrane design, and polymer upcycling. However, the effect of the nanoscale structure of copolymers on chain transport through nanoporous media remains poorly understood. In this study, we demonstrate that simply inverting the surface orientation of lamellar poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) diblock copolymers, composed of two monomers with strongly contrasting affinities for SiO2, at the entrance of nanoporous silica significantly alters the kinetics of capillary rise infiltration. Using in situ spectroscopic ellipsometry, we find that infiltration of symmetric PS-b-P2VP into silica nanoparticle (SiO2 NP) packings is significantly faster when the P2VP domain is the top layer of the film and first contacts the nanoparticles, compared to when the PS domain is the top layer. Coarse-grained molecular dynamics simulations reveal that this difference originates from block-specific adsorption pathways that reorganize the nanophase structure around nanoparticles: P2VP-first infiltration forms thin adsorbed layers that drive PS into the pore interiors, generating continuous interfacial pathways that enable rapid, interface-mediated transport. In contrast, PS-first infiltration produces thicker P2VP layers that isolate PS domains and disrupt pathway connectivity, forcing chains to rely on a slower, connectivity-limited transport mechanism through P2VP-rich interstitial regions. Above the order-disorder transition, or upon silanizing nanoparticles to neutralize surface affinity, the rate difference disappears. These findings demonstrate how the interplay between nanoscale domain configuration and polymer-surface affinity governs infiltration dynamics, providing mechanistic insight into tuning transport in nanostructured block copolymers.