Effect of Nanoparticle Loading and Magnetic Field Application on the Thermodynamic, Optical, and Rheological Behavior of Thermoresponsive Polymer Solutions

Authors

Christopher A P Neal
Grace V Kresge
Michelle C Quan
Valeria León
Nondumiso O Chibambo
Michelle A Calabrese

Publication Date

7-1-2023

Journal

Journal of Vinyl & Additive Technology

Abstract

Although processing via external stimuli is a promising technique to tune the structure and properties of polymeric materials, the impact of magnetic fields on phase transitions in thermoresponsive polymer solutions is not well-understood. As nanoparticle (NP) addition is also known to impact these thermodynamic and optical properties, synergistic effects from combining magnetic fields with NP incorporation provide a novel route for tuning material properties. Here, the thermodynamic, optical, and rheological properties of aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions are examined in the presence of hydrophilic silica NPs and magnetic fields, individually and jointly, via Fourier-transform infrared spectroscopy (FTIR), magneto-turbidimetry, differential scanning calorimetry (DSC), and magneto-rheology. While NPs and magnetic fields both reduce the phase separation energy barrier and lower optical transition temperatures by altering hydrogen bonding (H-bonding), infrared spectra demonstrate that the mechanism by which these changes occur is distinct. Magnetic fields primarily alter solvent polarization while NPs provide PNIPAM-NP H-bonding sites. Combining NP addition with field application uniquely alters the solution environment and results in field-dependent rheological behavior that is unseen in polymer-only solutions. These investigations provide fundamental understanding on the interplay of magnetic fields and NP addition on PNIPAM thermoresponsivity which can be harnessed for increasingly complex stimuli-responsive materials.

Comments

Supplementary Materials

PMID: 37546292