Self-healable polymer gels with multi-responsiveness of gel–sol–gel transition and degradability

Abstract

P(NIPAM-co-FPA) contains an aldehyde group and a phenolic ester moiety is synthesized. The aldehyde group can form reversible covalent bonds with hydrazide to endow the polymer gels with self-healing properties. The self-healable polymer gel can be degraded in Na2CO3 solution based on cleavage of phenolic ester bond.

Elasticity‐Dependent Fast Underwater Adhesion Demonstrated by Macroscopic Supramolecular Assembly

“…[3,[30][31][32][33] Upon contacting,o nly al imited number of host/guest groups can reach the interactive distance for the molecular recognition because the random spatial distribution of interactive moieties and ahigh surface roughness hinder the simultaneous interactions of most surface molecules.A sar esult, if the surface is elastic enough for the flexible surface deformation, these minor local binding events will result in self-adaption of the surface morphology to induce "chain reactions" of drawing adjacent groups into the interactive distance and enabling more interaction events (i.e., multivalency), which increases the binding strength between macroscopic surfaces to realize MSA. Because the motility of the building block surface is intrinsically correlated with the elastic modulus regarding deformability, [34,35] the occurrence of multivalencyi sa ctually determined by the elastic modulus of building blocks.T he facts of the MSA probability decreasing with the increasing modulus of building blocks has revealed apotential designing rule regarding material rigidity:A bove ac ritical modulus of 2.5 MPa, no MSA will be observed in this CD/Azo system due to the decline or even loss of the deformability. Because the motility of the building block surface is intrinsically correlated with the elastic modulus regarding deformability, [34,35] the occurrence of multivalencyi sa ctually determined by the elastic modulus of building blocks.T he facts of the MSA probability decreasing with the increasing modulus of building blocks has revealed apotential designing rule regarding material rigidity:A bove ac ritical modulus of 2.5 MPa, no MSA will be observed in this CD/Azo system due to the decline or even loss of the deformability.…”

“…However,i ft he materials are too rigid to achieve surface deformation, then the multivalencycannot be realized and these few local binding events alone are not sufficient to associate two large building blocks,l eading to the failure of MSA. Because the motility of the building block surface is intrinsically correlated with the elastic modulus regarding deformability, [34,35] the occurrence of multivalencyi sa ctually determined by the elastic modulus of building blocks.T he facts of the MSA probability decreasing with the increasing modulus of building blocks has revealed apotential designing rule regarding material rigidity:A bove ac ritical modulus of 2.5 MPa, no MSA will be observed in this CD/Azo system due to the decline or even loss of the deformability.…”

Dynamic covalent polymer hydrogels and organogels crosslinked through acylhydrazone bonds: synthesis, characterization and applications

“…Extending their previous work, Qin and colleagues prepared randomly crosslinked dynamic covalent polymeric organogels by combining linear PEGs, of M n = 1000, 4000 and 10 000 g mol −1 and having terminal benzaacylhydrazide groups, with random copolymers of NIPAM and 4‐formylphenylacrylate (FPA) bearing a pendant benzaldehyde group . Thus, in this work, the benzaldehyde groups were in the NIPAM–FPA random copolymer, while the acylhydrazide groups were attached at the termini of the linear PEG.…”

“…Qin and co‐workers prepared several self‐healable, randomly crosslinked DCPNs by combining linear PEGs, end‐functionalized either with benzaldehyde or benzaacylhydrazide groups, with random copolymers of NIPAM or N , N ‐dimethylacrylamide (DMAAm) also containing monomer repeat units bearing acylhydrazide or carbonyl (from benzaldehyde or aliphatic ketone) side groups . The random copolymers were synthesized using reversible addition–fragmentation chain transfer copolymerization.…”

“…(a, b) Gel‐to‐sol transition and (b, c) sol‐to‐gel transition of randomly crosslinked organogel in DMF upon the consecutive addition of acid and base. Reproduced from Chang et al with permission from the Royal Society of Chemistry.…”