Upper critical solution temperature-type thermosensitive hydrogel phase equilibrium of poly(2-hydroxyethyl methacrylate)/water/n-alkanol mixtures

2015

Soft Matter

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The influence of co-solvents on the swelling behavior of tunable thermosensitive core-shell nanoparticle gels was investigated. The poly(methyl methacrylate) (PMMA) core and poly(2-hydroxyethyl methacrylate) (PHEMA) shell network in 1-propanol reacted differently upon the addition of three co-solvents (cyclohexane (CHX), 1,3-propanediol (PDO), and water), resulting in highly controllable swelling properties of the core-shell gels. In particular, a strongly enhanced solvation effect, called the cosolvency phenomenon, occurred even with a very small amount of water (1-3 wt%). To examine the tunability, thermo-optical analysis (TOA) and photon correlation spectroscopy (PCS) were employed. The results show that a small addition of CHX, PDO, or water induced the "lower/upper," "even/upper," and "lower/lower" volume transition temperatures (VTTs) of the core-shell networks, respectively. For theoretical treatment, a multi-component lattice theory of mixing was combined with the Flory-Rehner (F-R) chain model to calculate the net free energy of mixing. The required interaction parameters were obtained from the binary and ternary phase diagrams of the linear polymer solutions and were applied directly to the swelling calculation of the cross-linked core-shell network solutions. The calculated results corresponded well with the experimental swelling data without further adjustment.

Section: Resultsmentioning

confidence: 99%

Section: Preparation Of Homo-polymer Nanoparticlesmentioning

confidence: 99%

A cosolvency effect on tunable thermosensitive core–shell nanoparticle gels

Lee

2015

Soft Matter

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“…Figure a displays the influence of temperature on the swelling behaviors of the PMMA/PHEMA core–shell nanoparticle gels and, for comparison, of the PMMA and the PHEMA homopolymer nanoparticle gels. Each homopolymer gel exhibits an abrupt volume transition when the temperature is increased above the UCSTs of each polymer (PMMA: 68 °C and PHEMA: 25 °C in 1-propanol).…”

Section: Resultsmentioning

confidence: 99%

“…A polymer with LCST-type thermal behavior in a certain solvent exhibits a swelling-to-collapsing volume transition upon heating when the polymer is cross-linked. For example, chemically cross-linked PNIPAM nanoparticle gels reveal a drastic particle size decrease upon heating in aqueous solution. − A reverse transition is observed in UCST-type polymer networks such as PMMA and PHEMA in aliphatic alcohols, exhibiting a collapsing-to-swelling volume transition upon heating. , …”

Section: Introductionmentioning

confidence: 99%

“…Zhi et al developed a molecular thermodynamic model for multisensitive hydrogels. Quesada-Pérez et al analyzed properties of gel networks through a simulation approach within a coarse-grained model. , Recently, Bae et al ,− proposed a systematic approach predicting various types of swelling behavior using the same interaction parameters obtained from non-cross-linked polymer solutions.…”

Section: Introductionmentioning

confidence: 99%

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Swelling Behaviors of Doubly Thermosensitive Core–Shell Nanoparticle Gels

Lee

2014

Macromolecules

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Novel UCST (upper critical solution temperature) type doubly thermosensitive core−shell nanoparticle gels were prepared in order to investigate swelling behaviors. The core−shell nanoparticle gels are synthesized via precipitation polymerization and are composed of a chemically cross-linked poly(methyl methacrylate) (PMMA) core and a poly(2-hydroxyethyl methacrylate) (PHEMA) shell. Both polymers exhibit a UCST phase transition in 1-propanol solution; the transition temperatures are 25 °C for PHEMA and 68 °C for PMMA. Photon correlation spectroscopy (PCS) measurements indicate that the large UCST gap between the shell-and core-forming polymers gives rise to a clear two-step swelling process upon heating. For theoretical analysis, a corrected modified-double-lattice (MDL) model with a new type of interaction parameter (εĩ j ), called the MDL-T model, is introduced to represent the optimized thermal behavior of the interchange energy and is combined with the Flory−Rehner (F− R) chain model to express the net free energy of mixing. Required model parameters are obtained from the experimental swelling data of homopolymer nanoparticle gel solutions and are directly applied to core−shell swelling calculations. The model is applied to two LCST (lower critical solution temperature) type doubly thermosensitive core−shell nanoparticle gels such as poly(Nisopropylacrylamide) (PNIPAM) core/poly(N-isopropylmethacrylamide) (PNIPMAM) shell in water and PNIPMAM core/ poly(N-n-propylacrylamide) (PNNPAM) shell in water. A comparative analysis of the MDL-T and other lattice based models is carried out, and a noticeable improvement is observed.

Thermodynamic analysis of phase equilibrium and surface tension of ternary polymer solutions

Yang

2019

AIChE Journal

The liquid–liquid equilibrium (LLE) and surface behavior of polymer solutions were investigated. Systems of poly vinyl methyl ether (PVME)/water and polystyrene (PS)/cyclohexane were chosen as model systems because they show different types of LLE and surface behavior. Ternary polymer solutions of PVME/water/alcohol and PS/cyclohexane/alcohol were also studied. The cloud points of given systems were determined by thermo‐optical analysis method. For surface tension measurements at the air/polymer solution interface, the well‐known plate method was utilized. The investigated polymer solutions exhibit various types of LLE and surface behavior depending on the type of solvent and temperature. The modified double lattice model with chain length dependence is used for description of the phase equilibrium. To improve the interpretation of the surface behavior of the polymer solution, we developed a new thermodynamic frame work based on density gradient theory. Thermodynamic analysis was also conducted using the proposed model to provide understanding of the surface behavior. The surface energy difference and interchange energy had an important role in the driving force of the surface behavior. Utilizing the predetermined model parameters from the phase equilibrium calculation, the proposed model provides satisfactory agreement with measured surface tension data, with less than 5% error.