Investigation of Thermoresponsive Microgel Polymer Swelling Theory

Agbim, Kenechi A.; Schaefer, Laura

doi:10.1080/15583724.2019.1711392

Cited by 13 publications

(8 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For all the above reasons, it is legitimate to say that the volume phase transition occurring in pNIPAM microgels is one of the most studied phenomena in soft condensed matter. Despite the huge amount of experimental and theoretical work on this topic, that is witnessed by the large number of recent reviews [26][27][28][29][30][31][32][33] , there are still fundamental aspects of the VPT that remain poorly understood. In particular, pNIPAM microgels are often treated as neutral systems, since electrostatic interactions are usually thought not to play an important role in their behaviour, apart from the stabilization against aggregation given to the suspension.…”

Section: Introductionmentioning

confidence: 99%

Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels

Del Monte,

Truzzolillo,

Camerin

et al. 2021

Preprint

View full text Add to dashboard Cite

Thermoresponsive microgels are one of the most investigated class of soft colloids, thanks to their ability to undergo a Volume Phase Transition (VPT) close to ambient temperature. However, this fundamental phenomenon still lacks a detailed microscopic understanding, particularly regarding the presence and the role of charges in the deswelling process. Here we fill this gap by combining experiments and simulations to show that the microgel collapse does not happen in a homogeneous fashion, but through a two-step mechanism, entirely attributable to electrostatic effects. The signature of this phenomenon is the emergence of a minimum in the ratio between gyration and hydrodynamic radii at the VPT. Thanks to simulations of several microgels with different cross-linker concentrations, charge contents and charge distributions, we build a unifying master-curve able to predict the two-step deswelling. Our results have direct relevance on fundamental soft condensed matter science and on microgel applications ranging from materials to biomedical technologies.

show abstract

Section: Introductionmentioning

confidence: 99%

Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels

Del Monte,

Truzzolillo,

Camerin

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…First, the coefficients in Eqn (1) (these parameters are expressed in terms of the specific enthalpy and specific entropy of a polymer network) that ensure good fit of experimental data adopt unrealistic values. 29,30 Second, this concept implies that the shear modulus G evolves with the volume fraction of the polymer network ϕ n following the pattern…”

Section: Introductionmentioning

confidence: 99%

“…Although the models grounded on the Flory–Rehner concept reveal an acceptable agreement with observations in swelling tests (in particular, when higher order terms with respect to ϕ n are introduced into Eqn ) 28 ), they were criticized for two reasons. First, the coefficients in Eqn ) (these parameters are expressed in terms of the specific enthalpy and specific entropy of a polymer network) that ensure good fit of experimental data adopt unrealistic values 29,30 . Second, this concept implies that the shear modulus G evolves with the volume fraction of the polymer network ϕ n following the pattern

\frac{G ((), Φ_{n 1})}{G ((), Φ_{n 2})} = {(\frac{Φ_{n 2}}{Φ_{n 1}})}^{1 / 3}

where Φ n1 and Φ n2 are volume fractions of the polymer at temperatures T 1 and T 2 .…”

Section: Introductionmentioning

confidence: 99%

Mechanical response and equilibrium swelling of thermoresponsive copolymer hydrogels

Drozdov

Christiansen

2020

Polymer International

View full text Add to dashboard Cite

Covalently crosslinked thermoresponsive (TR) gels form a special class of hydrogels that swell noticeably below their volume phase transition temperature Tc and shrink above Tc. As the critical temperature is weakly affected by the preparation conditions and molar fractions of monomers and crosslinkers in the pre‐gel solution, a facile method to modulate Tc (which is required for biomedical applications of TR gels and their use as temperature‐triggered actuators) is to incorporate relatively small amounts of neutral monomers whose hydrophilicity differs from that of the basic monomers. Although observations on copolymer gels confirm the effectiveness of this method, the molar fractions of comonomers necessary for the tuning of Tc remain unknown. A model was developed for the mechanical response and equilibrium swelling of TR gels. Adjustable parameters in the governing relations were found by fitting equilibrium swelling diagrams for poly(N‐isopropylacrylamide) homopolymer and copolymer gels. Good agreement is demonstrated between the experimental data and the results of simulation. Based on the model, an analytical formula is derived that expresses the volume phase transition temperature in terms of the molar fraction of comonomers. Its ability to predict the critical temperature is confirmed by comparison with observations on several copolymer gels. © 2020 Society of Chemical Industry

show abstract

“…The model of Xin et al considers the double lattice theory to describe oriented interactions and a temperature-dependent interchange parameter. Recent reviews show that modeling investigation on thermoresponsive hydrogels is still an advancing field. , Particularly noteworthy are the recent model developments by Drozdov and Christiansen and Lee and Bae . Drozdov and Christiansen model the hydrogel system applying the Flory–Huggins theory, using the transition temperature to calculate the maximum value of the Flory–Huggins parameter, which was assumed to be a function of temperature alone.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Nonelectrolyte Hydrogel Swelling and Its Pressure Effects with Simple Equation of State and Mechanical Models Using Liquid–Liquid Equilibrium Data

Carvalhal

Costa

Embiruçu

2020

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

From the liquid−liquid equilibrium (LLE) data of a linear polymer, an investigation of the Sanchez and Lacombe equation of state (SL-EOS) is performed with the goal of describing the swelling of three hydrogels: poly(N-isopropylacrylamide), PNIPA; poly(N-vinyl caprolactam), PVCL; and poly(N-diethylacrylamide), PNDEA. The phantom theory is applied to describe the elastic contribution of the network structure. Using SL-EOS with its binary interaction parameter as a linear temperature function is sufficient to describe the lower critical solution temperature (LCST) of non-crosslinked polymers. The results demonstrate that this function is also suitable for modeling the swelling/shrinking and the transition temperature of the corresponding hydrogel. We demonstrate that a simple mechanical model and a simple EOS are sufficient to adequately describe nonelectrolyte hydrogel swelling using LLE data and only one piece of swelling data. In addition, the pressure effects on the hydrogel swelling are analyzed without the need for new parameter estimation, an analysis scarcely found in the literature.

show abstract

Investigation of Thermoresponsive Microgel Polymer Swelling Theory

Cited by 13 publications

References 73 publications

Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels

Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels

Mechanical response and equilibrium swelling of thermoresponsive copolymer hydrogels

Evaluation of Nonelectrolyte Hydrogel Swelling and Its Pressure Effects with Simple Equation of State and Mechanical Models Using Liquid–Liquid Equilibrium Data

Contact Info

Product

Resources

About