Abstract:The formation and melting of Pluronic F127 gels in the presence of polyethylene glycols (PEGs) has been studied. All the PEGs studied raised T1 and lowered T2 of 20% F127 gels; this effect was proportional to PEG concentration. At a certain critical "no-gel" concentration of PEG (Cng), F127 lost its ability to form gels. Cng was found to be inversely proportional to PEG molecular weight. An empirical relationship between Cng and PEG molecular weight was obtained which can be used to predict effects of PEGs of … Show more
“…In an attempt to solve these issues, we are reporting here an approach to finely tune P407 micelle interactions using poly(ethylene glycol) (PEG400, M w = 400 g mol –1 ) (Figure A). This additive was previously used in P407 formulations to trigger the salting-out mechanism ,− but not as a yield stress regulator.…”
Freeform reversible embedding of suspended hydrogel (FRESH) is an additive manufacturing technique enabling the 3D printing of soft materials with low or no yield stress. The printed material is embedded during the process until its solidification. From the literature, FRESH abilities are self-healing, reusability, suspending, thermal stability, and high-precision printing. This study proposes a new support hydrogel bath formulation for FRESH 3D printing. To do so, a poloxamer micellar thermoreversible hydrogel is tuned through the addition of poly(ethylene glycol) (PEG) to adapt rheological properties. PEG macromolecules interact with poly(ethylene oxide) blocks of poloxamer and favor micelle dehydration, and then decreasing the gelation temperature, the yield stress, and the viscosity. Parameters such as the Oldroyd number and the Rayleigh−Plateau instability, both dependent on yield stress, were studied to determine their impact on the FRESH 3D printing resolution and accuracy. It was found that print accuracy of embedded parts increases with increasing yield stress but then the self-healing property gets limited, leading to crevasse formation. The usefulness of this approach is distinctly demonstrated through a six-axis printing of a highly complex silicone anatomical model. Printing fidelity of 96.0 ± 3.58% (5−40 mm printed parts) is thus achieved using the newly formulated FRESH material, while only 56.0 ± 0.76% fidelity is obtained using the standard formulation. The present study thus showed that complex FRESH 3D printing of soft materials is possible in this tunable hydrogel and that parts can be manufactured on an industrial scale, thanks to the reusability of the support bath.
“…In an attempt to solve these issues, we are reporting here an approach to finely tune P407 micelle interactions using poly(ethylene glycol) (PEG400, M w = 400 g mol –1 ) (Figure A). This additive was previously used in P407 formulations to trigger the salting-out mechanism ,− but not as a yield stress regulator.…”
Freeform reversible embedding of suspended hydrogel (FRESH) is an additive manufacturing technique enabling the 3D printing of soft materials with low or no yield stress. The printed material is embedded during the process until its solidification. From the literature, FRESH abilities are self-healing, reusability, suspending, thermal stability, and high-precision printing. This study proposes a new support hydrogel bath formulation for FRESH 3D printing. To do so, a poloxamer micellar thermoreversible hydrogel is tuned through the addition of poly(ethylene glycol) (PEG) to adapt rheological properties. PEG macromolecules interact with poly(ethylene oxide) blocks of poloxamer and favor micelle dehydration, and then decreasing the gelation temperature, the yield stress, and the viscosity. Parameters such as the Oldroyd number and the Rayleigh−Plateau instability, both dependent on yield stress, were studied to determine their impact on the FRESH 3D printing resolution and accuracy. It was found that print accuracy of embedded parts increases with increasing yield stress but then the self-healing property gets limited, leading to crevasse formation. The usefulness of this approach is distinctly demonstrated through a six-axis printing of a highly complex silicone anatomical model. Printing fidelity of 96.0 ± 3.58% (5−40 mm printed parts) is thus achieved using the newly formulated FRESH material, while only 56.0 ± 0.76% fidelity is obtained using the standard formulation. The present study thus showed that complex FRESH 3D printing of soft materials is possible in this tunable hydrogel and that parts can be manufactured on an industrial scale, thanks to the reusability of the support bath.
“…Having higher values of viscoelastic moduli in the liquid state and lower gelation temperatures with increasing concentration of PEG 400, indicate possible hydrogen bonding between hydroxyl groups and ether groups among PEG 400 molecules or between PEG 400 and polyethylene groups in the Pluronics. Prior studies showed that the presence of short polyethylene glycol chains lowers the critical micellization temperature of Pluronic aqueous solutions 58,59 .Fig. 5Effect of cosurfactant PEG 400 concentration on rheological properties and gelation temperature T gel .…”
Thermoresponsive nanoemulsions find utility in applications ranging from food to pharmaceuticals to consumer products. Prior systems have found limited translation to applications due to cytotoxicity of the compositions and/or difficulties in scaling-up the process. Here, we report a route to thermally gel an oil-in-water nanoemulsion using a small amount of FDA-approved amphiphilic triblock Pluronic copolymers which act as gelling agents. At ambient temperature the suspension displays liquid-like behavior, and quickly becomes an elastic gel at elevated temperatures. We propose a gelation mechanism triggered by synergistic action of thermally-induced adsorption of Pluronic copolymers onto the droplet interface and an increased micelle concentration in the aqueous solution. We demonstrate that the system’s properties can be tuned via many factors and report their rheological properties. The nanoemulsions are prepared using a low-energy process which offers an efficient route to scale-up. The nanoemulsion formulations are well-suited for use in cosmetics and pharmaceutical applications.
“…PEG has been reported in the literature to reduce G' with the increase of PEG concentration, 25 and that higher molecular weights of PEG disrupt gel formation at lower concentrations. 59 This has been attributed to entropic effects and increases in osmotic pressure disfavouring micelle formation, particularly for larger molecular weight polymers which are sterically excluded from the micelle. 60 For L-PAA G' has reduced in another study from 16 to 14 kPa when increasing concentration from 0.1 to 0.15 % w/w, respectively.…”
This study investigated the effects of additives on the properties of poloxamer (P) 407 thermogels, employing a design-of-experiments (DoE) approach. P407 is a thermoresponsive triblock copolymer that exhibits a solution...
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