Structure and Properties of Thermoresponsive Diblock Copolymers Embedded with Metal Oxide Nanoparticles

TL;DR

This study explores the structure and magnetic properties of thermoresponsive diblock copolymer films embedded with iron oxide nanoparticles, demonstrating temperature-controlled structural tuning and superparamagnetic behavior relevant for sensor and biomedical applications.

Contribution

It introduces a method to precisely control the block structure of PS-b-PNIPAM copolymers using temperature and humidity, and investigates their magnetic properties with embedded iron oxide nanoparticles.

Findings

Temperature and humidity can tune the copolymer structure.

The hybrid films exhibit superparamagnetic behavior.

In-situ SAXS and GISAXS effectively characterize structural changes.

Abstract

Nanostructured polymer-metal oxide composites are a current research area of great importance due to its highlight applications in sensors, optics, catalysts and drug delivery. Particularly the use of thermoresponsive polymers gives more flexibilities and possibilities in the design and construction of polymer templates. In the present investigation, the structure and magnetic properties of hybrid metal oxide/DBC films composed of two kinds of polystyrene-block-poly (N-isopropylacrylamide)(PS-b-PNIPAM) diblock copolymers (DBCs) with PS and PNIPAM as the major polymer domains respectively, and iron oxide were investigated. The thermoresponsive PNIPAM has a lower critical solution temperature (LCST) in aqueous solution at 32{\deg}C, which enables the controllable volume ratio of PS and PNIPAM in the structure of PS-b-PNIPAM diblock copolymers (DBCs). Thus, a temperature and humidity controlling cell was designed and built for precisely tuning the block structure of PS-b-PNIPAM DBCs, which was investigated by in-situ small-angle X-ray scattering (SAXS) and grazing-incidence small-angle X-ray scattering (GISAXS) measurements. The superparamagnetic behavior of the heat-treated hybrid iron oxide/PS-b-PNIPAM DBC films was investigated using a superconducting quantum interference device (SQUID) magnetometer.