Effect of nanoparticle loading and magnetic field application on the thermodynamic, optical, and rheological behavior of thermoresponsive polymer solutions

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 fielddependent 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.

Multifunctional properties optimization and stimuli‐responsivity of shape memory polymeric nanoarchitectures and applications

“…Meanwhile, a versatile range of studies have been conducted on SMP and nanoarchitectures recently with versatile enhanced properties for multifunctional applications. [ 98–180 ]…”

Cosolvent incorporation modulates the thermal and structural response of PNIPAM/silyl methacrylate copolymers

“…Cloud point measurements were conducted on an instrument developed in house, 54,59 and are performed in a manner similar to our prior work. 32 Samples were prepared at 1 wt% polymer and filtered through a plug of glass wool prior to characterization.…”

The role of additives in rheology and processing

“…[ 14 ] Neal, Calabrese, et al studied magnetically and thermo‐responsive materials. [ 15 ] They describe the influences of application of magnetic field and/or incorporation of nanosilica on phase change behavior in the material systems. Finally, Soliman, et al characterize material systems made using combinations of two different antimicrobial agents (doxycycline and cephalexin) in three different rubber materials (natural rubber, styrene butadiene rubber, and ethylene propylene diene monomer), including properties like rheological, mechanical, antimicrobrial, and cytoxicity to humans.…”