Different architectures of pH-responsive polymers

The most common pH-sensitive polymer structures described in the literature are linear homopolymers or copolymers, amphiphilic block copolymers which form micelles, grafted copolymers, polymer brushes, star and dendritic polymers, NPs, vesicles or HGs (Fig. 3.4). Some of these examples are explained in this section. 

Block copolymers are promising candidates for preparing responsive soft materials due to their self-assembling properties. In solution, amphiphilic 

4 Different architectures of pH-responsive polymers. Source Reprinted and adapted from Reyes et al., 2013, copyright 2013, with permission fromThe American Society of Chemistry.) 

Cationic HGs swell and release a drug in the low pH environment of the stomach (Fig. 3.6). Risbud et al. (2000) prepared a pH-sensitive, chitosan/ poly(vinyl pyrrolidone) (CS/PVP)-based, controlled drug release HG using air-dried and freeze-dried amoxiciUm. Porous freeze-dried hydrogel exhibited superior pH-dependent swelling properties over non-porous air-dried HGs. Freeze-dried membranes released around 73% of the amoxicillin (33% by air-dried) in 3 h at pH 1.0, and thus had the better drug release properties. 

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