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

Exploring the role of Muscovite in poly(alkyl methacrylate)-based ternary nanocomposite cryogels with selective functional groups: formation via cryogelling with the aid of inorganic clay

Easy fabrication of inorganic clay muscovite (MUS) embedded poly(2-acrylamido-2-methyl-1-propane sulfonic acid-co-diethylaminoethyl methacrylate-co-hydroxyethyl methacrylate) (PADH) nanocomposite cryogels with dual temperature/pH dependent catalytic potential was reported. Nanocomposite cryogels were fabricated by a method involving cryogelation and free radical crosslinking of aqueous systems containing MUS ranging from 0% to 1.50% (w/v). The changes in the properties of polybasic PADH networks were investigated to explain how the network parameters and gel properties were affected by the addition of clay, with the formation of a single terpolymer-MUS structure. The potential of the addition of different amounts of MUS to strengthen the prepared terpolymer matrix was investigated by uniaxial compression tests. By lowering the polymerization temperature or increasing the MUS content, the PADH/MUS nanocomposite cryogels became more elastic and compressible with stronger entanglement of terpolymer chains between the clay layers. With the addition of 1.50% (w/v) MUS, the swelling capacity was reduced by 50%, resulting in a two-fold increase in compression elasticity. The nanocomposite gels showed a strong pH-dependence, and when the pH of the swelling medium decreased from 9.8 to 2.1, there was a significant increase in the degree of swelling with increasing protonation of tertiary amine groups. Under an acidic environment, the swelling capacity of the nanocomposite gel containing 1.10% (w/v) MUS increased by 49.5%. In temperature dependent swelling between 15 and 75 °C, all ternary PADH/MUS-Ngels showed a tendency to swell at low and high swelling temperatures, by the predominance of DEAEM units at low temperatures and HEMA monomers at high temperatures, respectively. As the temperature was increased to 55 °C, the swelling decreased and reached a minimum, and then the nanocomposite gels tended to swell again. The obtained results provide an insight into the effect of MUS addition on the properties of poly(alkyl methacrylate)-based ternary nanocomposite gels and demonstrate a simple and efficient way to produce multiple response systems with enhanced elasticity.

A cosolvency effect on tunable thermosensitive core-shell nanoparticle gels

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.