## 5 Exploring the Potential of Multi-Arm Polymers as Nanocarriers  
The development of nanosized structures for drug delivery has strongly relied on linear amphiphilic block copolymers since the discovery of liposome nanoaggregates [134]. The last few decades have witnessed significant progress in the synthesis of these copolymers, and their self-assembling has been extensively studied, resulting in the creation of a library of functional groups that can be customized to improve drug solubility, loading, release, and bioavailability while reducing the required dosage [69]. Most of the current knowledge comes from studying their linear architectures. Detailed assessments of the behavior of self-assembled copolymers in aqueous environments have enabled the prediction of the resulting structure morphology. The hydrophilic/hydrophobic ratios in polymer compositions have been reported in the literature to be critical in producing assemblies with varying shapes and properties, such as star-like, crew-cut, and rod-shaped micelles, polymersomes, and lamellar structures [135; 136]. Moreover, many papers have investigated the properties of their ordered assemblies, as well as the controlling factors, such as the chemical composition and molecular weight of the polymer [137]. The recent years have been crucial for the synthesis of star polymers due to the advances in the synthesis and characterization methods which give more control and more complexity to the fabrication of multifunctional polymers, such as polymers with symmetrical and asymmetrical stars and \"Multi-arm\" polymers [43; 138]. The importance of branched copolymers in the nano-assemblies have encouraged many works to develop methodologies to obtain well-defined homo- or hetero-branched copolymers. For this, various radical polymerization methods have been employed, including atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization, stable free radical polymerization (SFRP), and ring-opening polymerization (ROP) [139]. These methodologies can be classified into three main approaches: core-first, arm-first, or grafting approaches [140]. The arm-first methodology involves using pre-synthesized polymer arms that are covalently linked to the core. \"Click\" reactions such as alkyne-azide and esterification have been particularly popular in this approach. In general, a combination of core-first and arm-first methodologies has resulted in the improved synthesis of amphiphilic polymers for self-assembly [141]. The increasing interest in branched copolymers as self-assembly nanocarriers has led to several studies focused on establishing a way to synthesize branched structures with the same composition as linear polymers [142]. To achieve this, varying the number of arms linked to the central core, along with controlling molecular weight, has been suggested as a means of providing flexible and less viscous branched copolymers [143; 144; 145]. Controlling the molecular weight becomes increasingly necessary for polymers that exhibit crystalline behavior, such as polycaprolactone (PCL), which exhibits an amorphous character as long as the polymeric chain is short, thereby enhancing hydrophobic interactions between the polymer and the encapsulated drug [146; 147]. Another advantage of using the multiarms of block copolymers instead of their linear counterparts is the smaller hydrodynamic diameters that can be obtained, which result from the unique core-shell structure formed during microphase separation [148; 149]. The use of a copolymer with multiarms provides a high number of functional groups incorporated in the structure, which diversifies the application area of such copolymers, including but not limited to drug carriers [150; 151], due to the unique physicochemical properties that enhance the efficacity of drugs, as well as thermoplastic elastomers [152], polyelectrolytes [153], hydrogels [154], and adsorption dye removal [155].