Stimuli-responsive gels as reaction vessels and reusable catalysts

Abstract

As part of a continuing scientific challenge, a substantial effort during the past few decades has been devoted towards altering the selectivity of chemical transformations by arranging the potential reactants in a number of organized and confining media. Such systems, having features significantly different from those of isotropic solutions, include, for example, micelles, microemulsions, molecular aggregates, liquid crystals, and zeolites. Among these materials, stimuli-response gels constitute another important class of nanostructured and dynamic systems with high active surface areas and remarkable diffusion properties. Within this group, polymer gels have been traditionally used to obtain catalytic and reactive soft materials. Moreover, gels made of low-molecular-weight compounds represent a major novelty in this area as potential soft-vessels to carry out chemical reactions with control on product selectivity. In addition, the possibility of integrating switchable catalytic functions in both organo- and hydrogels shall accelerate the development of robust platforms for the 'bottom-up' tailor-fabrication of more sophisticated functional materials. The present critical review reports on the most important results published during the last decade regarding the use of 'smart' gels that has displayed promising properties as selective soft-nanoreactors and/or heterogeneous recyclable catalysts (152 references).

Role of mechanical factors in applications of stimuli-responsive polymer gels – Status and prospects

“…The current development of SRGs as catalyst support media has been recently reviewed by Diaz Diaz and co-authors [66]. Here we summarize just a few achievements.…”

Stimuli-responsive electrospun fibers and their applications

“…1,2 The simplicity of the procedure, the possible large scale production and wide variety in usable polymers, make electrospinning attractive for a wide range of biomedical applications such as tissue engineering, wound dressing, drug delivery and more. 3 In polymer research, much progress is being made in the area of so-called stimuliresponsive polymers [4][5][6][7] which can alter one or more properties such as e.g. morphology, strength or color upon exposure to external signals, such as pH, ionic strength or light.…”

Triazolyl‐Based Molecular Gels as Ligands for Autocatalytic ‘Click’ Reactions

“…This organizationo fm ultiple catalytic sites at the surface of the fibers could provide additional catalytic features, such as multivalent interactions, neighboring effects and cooperativity. [17][18][19] Several studies mentioning supramolecular gels as active mediaf or catalysis have been reported. Between them, the use of Pd II metallogelsc ontainingp yridine-based ligands as catalysts for the aerobic oxidationo fb enzoyl alcohol to benzaldehyde,a sw ell as the application of bolaamphiphilic l-proline derived low-molecular-weightg elators as basic catalysts for the Henry nitro-aldolr eaction, are two clear examples of success regardingthe use of catalytic gels both in metallo-and or-ganocatalysis, respectively.…”