Structure of Two-Compartment Hydrogels from Thermoresponsive ABC Triblock Terpolymers

Abstract

Aqueous dispersions of a poly(ethylene-alt-propylene)-bpoly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PON) triblock terpolymer with block molecular weights of 3 000−25 000−10 000 and polymer concentrations ranging from 1 to 5 wt % were investigated at several temperatures from 25 to 55°C using cryogenic scanning electron microscopy (cryo-SEM), cryogenic transmission electron microscopy (cryo-TEM), and small-angle neutron scattering (SANS). The cryo-SEM and cryo-TEM micrographs revealed that PON triblock terpolymer selfassembled into spherical micelles with PEP cores and PEO−PNIPAm coronae at room temperature and subsequently formed a twocompartment micellar network consisting of distinct spherical PEP and PNIPAm cores upon heating above the critical gelation temperature (42°C). The formation of two discrete spherical PEP and PNIPAm hydrophobic domains was supported by detailed SANS analysis of the PON triblock samples in D 2 O, as the resulting intensity profiles can be successfully fitted using a scattering equation based on the two-compartment network structure. The two-compartment structure was further confirmed using contrast-matching SANS experiments on a PON d7 triblock sample with similar block molecular weights and a partially deuterated PNIPAm block. An important result of the SANS profiles in the gel state was the emergence of two distinct scattering peaks, which could be accounted for by considering spatial correlations between PEP and PNIPAm micellar cores. This study confirms the hypothesis that the formation of two-compartment networks in ABC terpolymer hydrogels results in better gelation properties, in comparison to other physically associated hydrogels, and can further guide the design and development of advanced hydrogel systems with enhanced performance.

A new thermoresponsive polymer of poly(N-acryloylsarcosine methyl ester) with a tunable LCST

“…Compared with the T cp s of the reference homopolymers of PNIPAM 68 and PNASME 170 under similar conditions, the T cp of the PNIPAM 63 block is higher than that of the PNIPAM 68 homopolymer and the T cp of the PNASME 170 block is close to that of the PNASME 170 homopolymer, respectively. Similar results have also been found, [72][73][74][75][76] and the reason that the T cp of the PNIPAM 63 block higher than the PNIPAM 68 homopolymer is due to the PNASME 170 block, which is hydrophilic at the temperature of the T cp of the PNIPAM 63 block and therefore increases the solubility of the PNIPAM 63 block. In aqueous phenol solution, both the T cp s of the PNIPAM 63 and PNASME 170 blocks decrease, and ∆T is firstly at 6.5 o C at case of 20 mM aqueous phenol solution and then at 0 o C at case of 40 mM aqueous phenol solution.…”

Thermoreversible and Injectable ABC Polypeptoid Hydrogels: Controlling the Hydrogel Properties through Molecular Design

“…29,31,33 As the three blocks are mutually immiscible, the C block is hydrophobic and the B and A blocks are water-soluble below the sol–gel transition temperature, the triblock copolymers are expected to form core–shell–corona micelles below T gel . Upon temperature increases, the corona blocks (A) undergo cloud point transition and become dehydrated to form hydrophobic domains.…”

“…With the formation of separate A and C domains, the intramolecular association of the end blocks to form loop configurations is significantly suppressed, thereby giving rise to a rapid and sharp thermoreversible sol–gel transition at low concentration (≤ 5 wt %) upon a temperature increase. 29,31 …”

ABC triblock bottlebrush copolymer-based injectable hydrogels: design, synthesis, and application to expanding the therapeutic index of cancer immunochemotherapy

“…Here again, materials derived from ABC triblock copolymers were more mechanically robust than analogous ABA and CBC gels, presumably due to a reduction of primary loops. 38,39 Duvall and coworkers demonstrated the utility of linear ABC triblock copolymers with tunable degradation properties for controlled drug delivery applications. 40,41 Recently, Sheiko and coworkers reported on the development of linear-bottlebrush-linear "ABA" triblock copolymer elastomers where the central bottlebrush domain imbued the materials with strain stiffening behaviors analogous to biological tissues ( Fig.…”