PEG-Based Methacrylate Tetrablock Terpolymers: How Does the Architecture Control the Gelation?

Abstract

An ABCA tetrablock terpolymer with excellent thermogelling properties in aqueous solutions has been identified by tuning the architecture of ethylene glycol-based tetrablock terpolymers. Specifically, it gels at concentrations as low as 5 wt % at a wide range of temperatures, including body temperature. Nine tetrablock copolymers based on hydrophilic oligo­(ethylene glycol) methyl ether methacrylate with average molar mass (MM) 300 g mol–1 (OEGMA300, A), hydrophobic n-butyl methacrylate (BuMA, B), and hydrophilic and thermoresponsive di­(ethylene glycol) methyl ether methacrylate (DEGMA, C) were synthesized and screened. The MM and composition were kept constant, while the tetrablock architecture was systematically varied. Specifically, copolymers with (i) two OEGMA300 blocks (ABCA, ABAC, and ACAB), (ii) two BuMA blocks (BACB, BABC, and ABCB), and (iii) two DEGMA blocks (CABC, CACB, and ACBC) were fabricated. The self-assembly and thermoresponsive properties of their aqueous solutions were investigated with the polymer architecture governing their solubility, micellization, thermoresponsive, and rheological properties.

Thermoresponsive oligo(ethylene glycol) methyl ether methacrylate based copolymers: composition and comonomer effect

“…As shown in Table 1, the theoretical molar mass and composition was compared to the number average molar mass (M n ) given by GPC, and the composition given by NMR. From the GPC results, we found that the dispersity (Đ) of all the final products were smaller than 1.21, similar to previous reported studies on OEGMA based polymers, 26,[90][91][92][93] indicating a successful synthesis of well-defined polymers. The M n s of the final products were between 9400 g mol −1 and 11 800 g mol −1 , higher than the theoretical molar mass (8100 g mol −1 ).…”

“…The cloud points of the 1% w/w polymer solutions with various solvents given by the UV-VIS are listed in Table 2. The cloud point of a polymer can be influenced by the molar mass, 26 composition, 32,94–97 structure, 98–101 architecture, 62,91,102 and solvent. 103,104…”

Homopolymer and ABC Triblock Copolymer Mixtures for Thermoresponsive Gel Formulations

“…This is observed at high contents in P1, as the concentrated solutions (15 and 20 w/w%) of the triblock terpolymer in PBS only present gel syneresis upon temperature increase, with no precipitation being detected, i.e., the gel does not progressively exclude more solvent. This double crossover has been previously observed by our group on OEGMA300 x -b-BuMA y -b-DEGMA z -b-OEGMA300 x tetrablock terpolymer [58]. The MM of the OEGMA300 x homopolymers plays a critical role in the stability of the gels, as the higher the MM, the higher the maximum storage modulus of the gels (Figure 4 from black (OEGMA300 10 ) to red/green (OEGMA300 31 /OEGMA300 47 ) to blue (OEGMA300 75 )).…”

“…Our group has recently reported a novel combination of methacrylate repeated units, which produces thermoresponsive polymers with a sharp sol-gel transition [56][57][58]. More specifically, the polymers consist of (i) the hydrophilic oligo (ethylene glycol) methyl ether methacrylate with average MM 300 g mol −1 (OEGMA300, A unit), which is also thermoresponsive at approximately 70 • C, depending on the MM [59], (ii) the hydrophobic n-butyl methacrylate (BuMA, B unit), and (iii) the hydrophilic and thermoresponsive (CP approximately 30 • C) [59] di(ethylene glycol) methyl ether methacrylate (DEGMA, C unit).…”

“…More specifically, the polymers consist of (i) the hydrophilic oligo (ethylene glycol) methyl ether methacrylate with average MM 300 g mol −1 (OEGMA300, A unit), which is also thermoresponsive at approximately 70 • C, depending on the MM [59], (ii) the hydrophobic n-butyl methacrylate (BuMA, B unit), and (iii) the hydrophilic and thermoresponsive (CP approximately 30 • C) [59] di(ethylene glycol) methyl ether methacrylate (DEGMA, C unit). Both ABC triblock copolymers of varying compositions and tetrablock terpolymers of varying architecture were investigated [57,58], with an ABC triblock terpolymer with OEGMA300-BuMA-DEGMA content at 40/35/25 w/w% showing promising thermogelation properties, with the gels being formed at concentrations as low as 2 w/w% [57]. Therefore, it is valuable to investigate the impact of polymeric additives on the gelation properties of this novel polymer.…”