Smart polymers, also known as stimuli-responsive polymers or intelligent polymers, are a class of polymers that can change their properties in response to external stimuli such as temperature, pH, light, electric or magnetic fields, and chemical agents. These polymers have a wide range of applications, including drug delivery systems, sensors, actuators, and self-healing materials. In contrast, conventional polymers do not exhibit such responsive behavior.There are several methods used to synthesize smart polymers, including:1. Free Radical Polymerization: This is one of the most common methods for synthesizing smart polymers. It involves the use of a free radical initiator to start the polymerization reaction, which then propagates through the addition of monomers. The polymerization can be controlled by adjusting the reaction conditions, such as temperature, initiator concentration, and monomer concentration.2. Controlled Radical Polymerization CRP : CRP techniques, such as atom transfer radical polymerization ATRP , reversible addition-fragmentation chain transfer RAFT , and nitroxide-mediated polymerization NMP , allow for better control over the molecular weight, polydispersity, and architecture of the smart polymers. These methods involve the use of a reversible deactivation process to control the polymerization reaction.3. Ring-Opening Polymerization ROP : ROP is a method used to synthesize smart polymers with cyclic monomers. The ring-opening reaction is initiated by a catalyst or an initiator, which then propagates through the addition of monomers. This method allows for the synthesis of polymers with a well-defined structure and molecular weight.4. Condensation Polymerization: This method involves the reaction between monomers with reactive functional groups, such as carboxylic acids and amines, to form a polymer with the elimination of a small molecule, such as water or methanol. This method is commonly used to synthesize smart polymers with specific functional groups that can respond to external stimuli.5. Electrospinning: Electrospinning is a technique used to fabricate smart polymer nanofibers. A high voltage is applied to a polymer solution, which causes the solution to form a jet that is then collected on a grounded collector. The resulting nanofibers can exhibit stimuli-responsive behavior due to their high surface area and the presence of functional groups.6. Self-Assembly: Some smart polymers can self-assemble into well-defined structures, such as micelles, vesicles, or hydrogels, in response to external stimuli. This method involves the synthesis of block copolymers or amphiphilic polymers, which can self-assemble in specific conditions, such as changes in temperature or pH.In summary, smart polymers differ from conventional polymers in their ability to respond to external stimuli, leading to changes in their properties. Various synthesis methods, including free radical polymerization, controlled radical polymerization, ring-opening polymerization, condensation polymerization, electrospinning, and self-assembly, can be used to create these intelligent materials.