*Selection and Role of Polymers for Designing of a Drug Carrier DOI: http://dx.doi.org/10.5772/intechopen.103125*

programmable drug release pattern. Furthermore, greater appropriate therapy might be provided by combination treatment, which involves the simultaneous administration of 2 or more medicaments/diagnostics substances [22–24]. In reaction to a modest external/internal stimulation, a stimuli-reactive or smart polymer changes its physical characteristics abruptly. Although minor changes take place in subjected to external/internal stimuli stimulus until a crucial limit is found, and they have the potential to revert to their original form when the stimulus is withdrawn, those polymers are indeed known as smart polymers [25–27]. The uniqueness of these polymers resides in their unpredictable reaction, which is initiated by a really tiny stimulus and results in enormous structural changes. Different triggers responsible for modulating the release of the drug using innovative polymeric drug delivery compositions are depicted in **Figure 1**. Modifications in physical state, structure, solubility, solvent interactions, aqueous soluble and lipid soluble equilibrium, and conductance are all reversible transitions. The introduction of oppositely charged polymers or a pH change to neutralize charged groups, as well as variations in the water-loving/ lipid-loving balance or hydrogen bonding owing to temperature differences, are the driving factors underlying such transitions. Fewer dosage periodicities, simplicity of preparation, preservation of optimal therapeutic level at a single dose, longer delivery of integrated medication, decreased adverse effects, and increased stability are all advantages of innovative polymer-based medicaments delivery systems [28–30].

**Figure 1.** *Stimuli and materials that respond to them.*

A dynamic polymeric material can respond in a variety of ways. The breakdown and development of numerous secondary interactions such as hydrogen bonding, van der Waals forces, hydrophobic forces, and electrostatic interaction [31, 32] restrict the responsiveness of such a polymeric solution induced by physicochemical stimuli. Fundamental processes including acid-base reaction, reduction, oxidation, and hydrolysis of components linked to the polymer chain are examples of chemical processes. Destruction of a polymeric structure owing to irreversible bond breaking in response to external stimuli is one example of the significant conformational shift in the polymer backbone. Biodegradability and biocompatibility; sustained-release characteristics; drug-loading potential; the dearth of deleterious characteristics including systemic toxicity, carcinogenic effects, immunogenicity, and reproductive toxicity; as well as outstanding stability characteristics are all important characteristics of a smart polymer.
