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This document discusses the shaping and structuring of polymer gels and their applications in various fields. The document highlights the fabrication of gels with well-defined shapes and spatially controlled structures, as well as the measurement and analysis of their properties. It also explores the practical applications of these advancements in biomedical and food technology. The contributions in the document cover topics such as the creation of muscle tissue, the fabrication of collagen tube gels, the use of hydrogels for drug delivery, and the formation of supramolecular gels. The document emphasizes the potential for diverse applications and the alignment of these advancements with biological and biomedical objectives. [Extracted from the article]

Gel growth induced by contact of polymer solutions with crosslinker solutions yields an emerging class of anisotropic materials with many potential applications. Here, we report the case of a study on the dynamics in forming anisotropic gels using this approach with an enzyme as a trigger of gelation and gelatin as the polymer. Unlike the previously studied cases of gelation, the isotropic gelation was followed by gel polymer orientation after a lag time. The isotropic gelation dynamics did not depend on concentrations of the polymer turning into gel and of the enzyme inducing gelation, whereas, for the anisotropic gelation, the square of the gel thickness was a linear function of the elapsed time, and the slope increased with polymer concentration. The gelation dynamics of the present system was explained by a combination of diffusion-limited gelation followed by free-energy-limited orientation of polymer molecules. [ABSTRACT FROM AUTHOR]

The molecular weight and solvent dependences of the characteristic time of chain collapse were studied for poly(methyl methacrylate) (PMMA) of the molecular weight Mw=6.4×106 and 1.14×107 in pure acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol %). The size of PMMA chains was measured as a function of the time after the quench by static light scattering and the chain collapse processes were expressed by the plot of the expansion factor α2 vs ln t. The chain collapse in the mixed solvent AcN+water (10 vol %) was found to occur much faster than that in pure AcN, though the measurement of the former collapse process required several hours. In order to make a comparison between the rates of chain collapses, the fast chain collapse process was superposed on the slow one by scaling the time of the fast process as γt. The scale factor γ was determined by comparing the chain collapse processes of nearly the same equilibrium expansion factor with each other. Accordingly, the superposition of the collapse for Mw=6.4×106 on that for Mw=1.14×107 yielded γm=4.0±0.6 for the process in AcN+water and 5.5±0.6 in AcN. The superposition of the chain collapse process in AcN+water on that in AcN yielded γs=9.5±1.4 for Mw=6.4×106 and 12.0±1.8 for Mw=1.14×107. This analysis suggests that γm and γs are constant independent of each other. Thus, by assuming the molecular weight dependence of γm∼Mz, the characteristic time τexp of chain collapse was conjectured as τexp∼κMz, where κ reflects the nature of solvent species. The ratio of κ for PMMA in AcN to that in AcN+water is given by γs. The exponent was estimated to be z=2.4±0.7 for AcN+water and 3.0±0.7 for AcN. These values are compatible with the theoretical prediction z=3 based on a phenomenological model, though the observed characteristic times are longer by several orders of magnitude than those of the theoretical prediction. [ABSTRACT FROM AUTHOR]

Studies the tricritical phase equilibrium properties for the ternary solution of two polystyrene homologs in methylcyclohexane by numerical analysis of the generalized Flory-Huggins equation with an empirical interaction parameter and by experimental measurements. Calculated phase behavior near the tricritical point; Coexistence curve measurement.

The effect of pressure on the tricritical point (TCP) of a ternary system, polystyrene (PS) I+PS II+methylcyclohexane, was studied by numerical analysis of the generalized Flory--Huggins equation for the Gibbs free energy. For the ternary system, the molecular weight of PS II M[SUB2t], total volume fraction of PS φ[SUBst], volume fraction of PS II with respect to total volume of PS &xi[SUB2t], and temperature T[SUBt] at TCP were calculated for various values of the molecular weight of PS I M[SUB1] in the pressure range from 0 to 100 MPa. As M[SUB1] increases, the ratio r[SUBt] = M[SUB2t]/M[SUB1] and φ[SUBst] decrease, while T[SUBt] and ξ[SUB2t] increase monotonically irrespective of p. The curves of r[SUBt] and φ[SUBst] vs p have a maximum, while the curves of T[SUBt] and ξ[SUB2t] vs p have a minimum, irrespective of M[SUB1]. For small M[SUB1] these curves are nearly flat and roughly symmetrical with respect to the extrema. From these calculated results it is predicted that the tricritical solution at atmospheric pressure remains very near the tricritical state along the cloud-point curve in the temperature vs pressure diagram. [ABSTRACT FROM AUTHOR]

In order to examine the crossover from the Ising behavior to the renormalized Ising behavior, we have measured the coexistence curves of the ternary system, polystyrene I+ polystyrene II+ methylcyclohexane, by varying the molecular weight ratio r of polystyrene II to polystyrene I and volume fraction ξ2 of polystyrene II in total polystyrene. The observed critical exponent βt for the concentration difference between two coexisting phases varies from 0.33 to 0.38 with the increase of parameter k=ξ2r(r-1)2. This result is consistent with the theory of Broseta and Leibler [J. Chem. Phys. 90, 6652 (1989)]. The exponent for the diameter μt was found in the range from 0.81 to 0.92. The average of μt=0.86 is close to the exponent μ for binary systems. [ABSTRACT FROM AUTHOR]

Tricritical two-phase behavior of bimodal polystyrene (PS) in methylcyclohexane (MCH) was studied by using the Flory–Huggins theory combined with an empirically determined interaction parameter. In the ternary system PSI+PSII+MCH with the molecular weight M1=1.73×104 for PSI, the tricritical system was obtained for PSII with M2=2.24×105, which yielded a coincidence of the upper and lower critical end points. For the tricritical mixture the two-phase coexistence curve was calculated in the temperature range 0.01

Three-phase equilibria have been studied for the ternary system polystyrene (Mw=1.73×104)+polystyrene (Mw=7.19×105)+methylcyclohexane by numerical analyses of Gibbs free energy and experimental measurements. The calculation showed that the three-phase equilibrium appears at the temperature range from 21.4 to 23.4 °C. At these two temperatures two phases of the three coexisting phases coalesce into one phase and phase equilibria are represented by a tie line with one end being a critical point. The intersection of the two tie lines gives compositions the solution of which can give rise to the entire three-phase coexistence curve. The coexistence curve measurements were made for two solutions with different compositions near the calculated intersection. By a refractive index method coexistence curves were obtained in a temperature-total polymer composition diagram. The three-phase region was observed in a very narrow temperature range from 24.1 to 24.7 °C. The two solutions could give rise to almost entire three-phase coexistence curve and two critical points were predicted to be just above and below the three-phase region from strong opalescence. The mechanism of the three-phase separation was explained as due to the heterogeneous double plait point. [ABSTRACT FROM AUTHOR]

The three-phase coexistence curve for the ternary system polystyrene (Mw=1.73×104)+polystyrene (Mw=7.19×105)+methylcyclohexane was analyzed from the viewpoint of the critical phenomena. The critical exponent at the upper critical end point was determined as βf=0.381±0.012, which is close to 0.384±0.004 at the plait point for the same ternary system and compared with the fully renormalized critical exponent. The critical exponent at the lower critical end point was found to be smaller as βf=0.342±0.031. According to the numerical analyses of the empirical Gibbs free energy, this small value was ascribed to an improper behavior of the tie lines in a composition triangle. The tie lines near the upper critical end point were parallel with each other and contained the critical end point. The observed three-phase coexistence curve in a temperature-total polystyrene volume fraction diagram was much more symmetrical than the calculated one and suggested a tricritical phenomenon. [ABSTRACT FROM AUTHOR]

Cloud-point measurements were made for binary systems of polystyrene (PS) +methylcyclohexane (MCH) with three PS samples in the pressure range up to 90 MPa. On a temperature (T)–pressure (p) plane, observed cloud-point curves, which were determined at various compositions for the molecular weight Mw=1.61×104 and at the critical composition for Mw=1.02×104 and 3.49×104, decrease first, reach a minimum and increase with increasing pressure. For Mw=1.61×104 the coexistence surface was investigated in a T–p–[lowercase_phi_synonym] space, where [lowercase_phi_synonym] denotes the volume fraction of PS. On a T–[lowercase_phi_synonym] plane the coexistence curves give a critical composition independent of pressure. On a p–[lowercase_phi_synonym] plane one phase region appears between two coexistence curves. The top and the bottom of the coexistence curves give an upper critical solution pressure (UCSP) and a lower critical solution pressure (LCSP), respectively. The two critical points coincide forming a critical double point (CDP) at T=19.28 °C, p=48.6 MPa, and [lowercase_phi_synonym]=0.1719. The shape of the coexistence curves near the CDP is very sensitive to temperature and is characterized by the critical exponent 2β. The Gibbs free energy of the present system was evaluated as a function of T, p, and [lowercase_phi_synonym] from the molecular weight dependence of the observed critical lines. [ABSTRACT FROM AUTHOR]