Hydrogels physical cross-links

Keywords Aerogels Cellulose Derivatives Graft copolymers Hydrogels Physical cross-linking Supramolecular interactions... 

Liu B, Lewis AK, Shen W (2009) Physical hydrogels photo-cross-linked from self- assembled macromers for potential use in tissue engineering. Biomacromolecules 10 3182-3187 Vandermeulen GWM, Tziatzios C, Duncan R et al (2005) Peg-based hybrid block copolymers containing alpha-helical coiled coil peptide sequences control of self- assembly and preliminary biological evaluation. Macromolecules 38 761-769... 

Gel—A chemically or physically cross-linked polymer that is highly swollen with solvent. Called a hydrogel if the solvent is water (e.g., gelatin). 

Whether nascent or swollen, all of our PVA and PVA/y-CD hydrogels were found to be soluble in D2O indicating an absence of the formation of chemical crosslinks produced by the scission of PVA chains during their F-T preparation, which had been reported previously [98], It is clear that the elasticities of the PVA and PVA/y-CD hydrogels studied here are a result of the physical cross-linking of PVA chains. 

PEO-PPO-PEO triblock copolymers (Pluronics or Poloxamers) form reversible physically cross-linked hydrogels under certain concentration range and temperature. The use of this system in tissue engineering is scarce because of its inability to degrade. Di- or tri-block copolymers of PEG with PLA have been developed to overcome this problem. Multiple blocks of PEG and PLA, synthesized by condensation reaction of L-lactic acid in the presence of succinic acid. 

Fig. 1 Representative methods of hydrogel formation. (A) Chemically cross-linked hydrogels are prepared from monomers, oligomers, or polymers in the presence of cross-linking agents. The chemical cross-linking proceeds via radical polymerization or polycondensation reaction. (B) Physically cross-linked hydrogels can be formed by ionic interactions, hydrophobic interaction, or hydrogen bonding.

Fig. 4 Self-assembled hydrogel nanoparticles of hydrophobically modified polysaccharides. Note that nanoparticles have multiple inner cores which physically cross-link the hydrophilic polysaccharide chain. (Modified from Ref...

Stoy and co-workers (2) reported an approach that used alternative materials and involved the partial hydrolysis of poly(acrylonitrile) to form a complex structure that was presumed to involve sequences of unhydrolyzed poly(acrylonitrile) interspersed with acrylamide and acrylic acid sequences that resulted from hydrolyzed nitrile groups. Crystallites of unhydrolyzed poly(acrylonitrile) provided the physical cross-link domains within a matrix of the water-swellable portions of the structure. The tensile properties for such materials were considerably enhanced in comparison to the conventional covalently cross-linked hydrogels, and the absence of cross-links allowed processing under certain conditions. 

Recently, Song and coworkers reported a very simple new method for fabricating tough hydrogels that are physically cross-linked by cooperative hydrogen... 

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