A phenomenological order approach to the volume phase transition in microgel particles

Abstract

We proposed a model to describe the volume phase transition of microgel particles, based on constitutive relations that consider the mechano-chemical coupling of deformation and solvency processes, as well as the phenomenological cooperative effect of molecular orientation of solvatable segments in the particles. We regard a nematic-isotropic like transition and define a tensor order parameter allowing analysis of the collective behaviour of water solvation mechanisms based on the Landau-De Gennes theory for liquid crystal elastomers. A complementary approach to the energy balance density is obtained with the order parameter field considering the deformation by a continuum mechanics approximation; our approach aims to extend the comprehensive understanding of the elastic behaviour and water sorption related phenomena in microgel particles. With the proposed model, we reproduce the behaviour of swelling curves through a volume phase transition of thermosensitive microgel particles by assessing characteristic parameters belonging to particular physical properties. The parameters defined within the model such as elastic and solvency related constants and characteristic temperatures were obtained by fitting of a data set mimicking the experimentally observed swelling behaviour. The obtained values of the parameters were consistent with the discussed phenomenology which shows the importance of molecular ordering interpretation as a source to describe the volume phase transition in microgel particles.

Nanogels and Microgels: From Model Colloids to Applications, Recent Developments, and Future Trends

“…Theoretical and computer simulation studies of nano- and microgels have been rapidly developing during the past several years. A major aspect of these studies ,,− is to show how the chemical composition and various external stimuli (such as the solvent quality, , temperature, ,,,, pH, ,,,, ionic strength, , and light) affect the structure of single neutral ,,,, and charged ,− ,,, microgel particles.…”

“…The simulations can also provide the concept of new microgel systems, such as artificial swimmers based on a bilayer network and particles with sliding cross-links possessing an enhanced swelling ability and deformability, or discover the new features of the existing systems. It was found that in copolymer core/shell particles the core could reveal unusual swelling behavior: apart from the conventional core/shell conformation, one can observe an “inverted core” and “patchy surface” morphology. , Also, the obtained phase diagram allows the tuning of the internal morphology of the microgels by varying the shell volume fraction and interaction strength between polymer chains. In the case of IPN microgels it was shown that they can form classical core/corona structures, shell/corona structures, and core/shell/corona structures, depending on the subchain length and molecular mass of the system .…”

Macroporous temperature‐sensitive gels with fast response: Comparison of preparation methods

“…Another approach where phase separation in a TS gels was modeled within the Landau theory of phase transition was suggested in Refs. for neutral gels and Ref. for polyelectrolyte gels.…”

Dissipative particle dynamics simulations of end-cross-linked nanogels

“…According to their composition, microgels show a range of unique features, the most notable of which is the capacity to respond to external stimuli such as temperature [2], pH [3], salt concentration [4] and electric fields [5], amongst others. Moreover, nanogels are also very appealing from a fundamental point of view because of their dual colloidal and polymer nature [6], and they are currently investigated both theoretically [7,8,9] and experimentally [10,11,12,13].…”