Environment–Stimuli Response of Chitosan-Based Hydrogels - Chitosan Based Hydrogels: Functions and Applications - page 231

5
Environment-Stimuli Response of
Chitosan- Based Hydrogels
Junjie Li and Fanglian Yao
CoNTENTS
5.1 Introduction ........................................................................................................................ 235
5.2 pH Response....................................................................................................................... 236
5.2.1 Physical Cross-Linking of Chitosan-Based Hydrogels .................................... 237
5.2.1.1 Chitosan-Derivative-Based Hydrogels ................................................ 237
5.2.1.2 Chitosan-Polyanion Polymer Polyelectrolyte Complex .................... 239
5.2.2 Chemical Cross-Linking of Chitosan-Based Hydrogels .................................. 240
5.2.2.1 Amphoteric Cross-Linking Hydrogels ................................................ 240
5.2.2.2 Chitosan-Based Semi-IPN Hydrogels .................................................. 241
5.2.2.3 Chitosan-Based HPN Hydrogels .......................................................... 244
5.3 Temperature Response...................................................................................................... 244
5.3.1 Chitosan/Polyol Thermosensitive Hydrogels ................................................... 246
5.3.1.1 Hydroxybutyl Chitosan Derivative Thermosensitive Hydrogels .... 246
5.3.1.2 Chitosan/PEG Thermosensitive Hydrogels........................................ 246
5.3.1.3 Chitosan/PVA Thermosensitive Hydrogels ....................................... 248
5.3.1.4 Chitosan/Polyol Salt Thermosensitivity Hydrogels .......................... 249
5.3.2 Chitosan/Amphiphilic Polymer Thermosensitive Hydrogels ........................ 251
5.3.2.1 Chitosan/Pluronic Hydrogels............................................................... 251
5.3.2.2 Chitosan/PNIPAAm Hydrogels ........................................................... 251
5.3.2.3 Chitosan/PNVCL Hydrogels ................................................................ 254
5.4 Ionic Response.................................................................................................................... 255
5.5 Electro-Response................................................................................................................ 255
5.6 Summary............................................................................................................................. 257
References..................................................................................................................................... 257
5.1 Introduction
Hydrogels can exhibit dramatic changes in their swelling behaviors, network structure,
permeability, or mechanical strength in response to different stimuli (such as temperature,
pH, ionic strength, chemicals, and fields), both internal and external to the body [1].
Chitosan-based hydrogels are “smart” or “intelligent” in the sense that they can perceive
the prevailing stimuli and respond by showing changes in their physical or chemical
behavior. Moreover, some systems have been developed to combine two or more stimuli-
response mechanisms into one polymer system. For example, pH-sensitive chitosan-based
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