Linear versus Dendritic Molecular Binders for Hydrogel Network Formation with Clay Nanosheets: Studies with ABA Triblock Copolyethers Carrying Guanidinium Ion Pendants

Abstract

ABA-triblock copolyethers 1a-1c as linear polymeric binders, in combination with clay nanosheets (CNSs), afford high-water-content moldable supramolecular hydrogels with excellent mechanical properties by constructing a well-developed crosslinked network in water. The linear binders carry in their terminal A blocks guanidinium ion (Gu(+)) pendants for adhesion to the CNS surface, while their central B block comprises poly(ethylene oxide) (PEO) that serves as a flexible linker for adhered CNSs. Although previously reported dendritic binder 2 requires multistep synthesis and purification, the linear binders can be obtained in sizable quantities from readily available starting materials by controlled polymerization. Together with dendritic reference 2, the modular nature of compounds 1a-1c with different numbers of Gu(+) pendants and PEO linker lengths allowed for investigating how their structural parameters affect the gel network formation and hydrogel properties. The newly obtained hydrogels are mechanically as tough as that with 2, although the hydrogelation takes place more slowly. Irrespective of which binder is used, the supramolecular gel network has a shape memory feature upon drying followed by rewetting, and the gelling water can be freely replaced with ionic liquids and organic fluids, affording novel clay-reinforced iono- and organogels, respectively.

Molecular glues for manipulating enzymes: trypsin inhibition by benzamidine-conjugated molecular glues

“…, noncovalent manipulation of enzymes. Recently, we confirmed that non-dendritic, linear polymers bearing side-chain Gu + pendants 17 are readily accessible alternatives to our prototype dendritic molecular glues. Hence, in the present study, we designed linear Glue n –BA with short ( n = 10) and long ( n = 29) glue moieties (Fig.…”

Supramolecular Polymer Networks: Preparation, Properties, and Potential

“…Addition of CB [8] to a colorless solution of the two copolymers leads to transformation into a highly viscous, colored supramolecular hydrogel with a cross-linking density that can be controlled by the amount of CB [8]. The hydrogels exhibit solidlike mechanical properties at 5 wt% in water, with plateau moduli of 350-600 Pa at a cross-linking density in the range of 2.5-10 %, which is complementary to other supramolecular hydrogels that exhibit higher mechanical strength [236,237]. In a following work, Sherman and coworkers reported on ultrahigh water content hydrogels (up to 99.75 % of water) based on the same host-guest complexation but derived from renewable cellulose derivatives [238,239].…”

“…The hydrogels exhibit an exceptional mechanical strength (G 0 up to 10 6 Pa) as well as rapid self-healing. In a follow-up study, the same group was able to prepare similar hydrogels by using linear ABA triblock copolyethers carrying guanidinium groups in their end blocks [237]. These hydrogels are as tough as the dendrimer-based gels, but the linear binders can be obtained by much less elaborate syntheses from starting materials that are readily available.…”

Recent advances in clay mineral-containing nanocomposite hydrogels

“…Based on such methodology, well-designed linear macromolecules with proper surface functional groups can also crosslink with CNPs through a salt-bridge to form nanocomposite hydrogels. For example, Tamesue et al 79 mixed a linear macromolecule with LAPONITE s XLG NPs, which were pre-dispersed in water with a minute amount of sodium polyacrylate. In this way, a supramolecular nanocomposite hydrogel composed of linear macromolecule and LAPONITE s XLG NPs was successfully obtained.…”