Mechanics versus Thermodynamics: Swelling in Multiple‐Temperature‐Sensitive Core–Shell Microgels

Abstract

The thermal transition of a thermoresponsive microgel of poly‐N‐isopropylacrylamide (PNIPAM; transition temperature=34 °C) is shifted to higher temperatures when it is embedded in a shell of temperature‐sensitive poly‐N‐isopropylmethacrylamide (PNIPMAM; transition temperature=44 °C). The magnitude of the shift depends on the shell/core mass ratio. A thick shell induces a third transition arising from strong mechanical forces exerted on the core.

Size-controlled synthesis of monodisperse core/shell nanogels

“…1, 2, 5, 7 Particles composed of poly(N-isopropylmethacrylamide) (pNIPMAm) behave in a similar manner, exhibiting an LCST around 44 °C, with the increased LCST arising from an increase in the rigidity of the pNIPMAm polymer, as is common for methacrylamides. [25][26][27][28][29] This behavior is important to this work due to the fact that our group has optimized core/shell nanogel synthesis techniques that utilize this LCST behavior to drive the controlled nucleation and growth of the particles.…”

Encapsulation and Growth of Gold Nanoparticles in Thermoresponsive Microgels

“…A common example is poly (Nisopropylacrylamide) (pNIPAM), a thermoresponsive polymer that undergoes a phase transition from a hydrophilic, water-swollen state to a hydrophobic, globular state when heated above its lower critical solution temperature (LCST), which is about 32-33 8C, in water. Addition of co-monomers has also been proposed, as a means to add responsiveness towards different stimuli such as temperature, [4] pH, [5] ionic strength, [6,7] or light. [8] Although several reports have been recently published on the synthesis of metal nanoparticles with a wide variety of morphologies, such us spheres, rods, cubes, prisms and other polygons, with a good control over their size, morphology, and polydispersity, proper encapsulation within microgel colloids has only been reported for spheres.…”

An l-proline based thermoresponsive and pH-switchable nanogel as a drug delivery vehicle

“…[1][2][3] Conventional approaches have shown the limitations of untriggered release, where Fickian diffusion drives non-specific cargo delivery. 4 A variety of intelligent materials have been engineered to respond to stimuli such as pH, 5 temperature, 6 light 7 and magnetic field, 8 with temperature being the most studied. 9 Thermoresponsive polymers undergo conformational changes at a specific temperature, known as the lower critical solution temperature (LCST).…”