Thin films of PS/PS-b-PNIPAM and PS/PNIPAM polymer blends with tunable wettability

TL;DR

This study develops and analyzes thin polymer blend films with tunable wettability, revealing how blend composition and polymer architecture influence surface morphology and thermoresponsive wetting behavior.

Contribution

It introduces a method to create and characterize PS/PNIPAM and PS/PS-b-PNIPAM thin films with controllable surface properties and thermoresponsive wettability.

Findings

PS/PNIPAM films show increased water contact angle above PNIPAM's LCST.

PNIPAM content ratio affects the temperature at which wettability changes.

Surface morphology depends on blend ratio and drying conditions.

Abstract

We develop thin films of blends of polystyrene (PS) with the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM) (PS/PNIPAM) and its diblock copolymer polystyrene-b-poly(N-isopropylacrylamide) (PS/PS-b-PNIPAM) in different blend ratios and we study their surface morphology and thermoresponsive wetting behaviour. The blends of PS/PNIPAM and PS/PS-b-PNIPAM are spin-casted on flat silicon surfaces with various drying conditions. The surface morphology of the films depends on the blend ratio and the drying conditions. The PS/PS-b-PNIPAM films do not show an increase of their water contact angles with temperature, as it is expected by the presence of the PNIPAM block. All PS/PNIPAM films show an increase in the water contact angle above the lower critical solution temperature of PNIPAM, which depends on the ratio of PNIPAM in the blend and is insensitive to the drying conditions of the films. The difference between the wetting behaviour of PS/PS-b-PNIPAM and PS/PNIPAM films is due to the arrangement of the PNIPAM chains in the film.