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Nanotextiles and Recent Developments
Published in Asis Patnaik, Sweta Patnaik, Fibres to Smart Textiles, 2019
Rajkishore Nayak, Asimananda Khandual
Self-assembly is a manufacturing method where small molecules are used as basic building blocks which add up to give nanofibres (Hartgerink et al. 2001). The small molecules are arranged in a concentric manner, which upon extension in a normal plane produces the longitudinal axis of nanofibres. In self-assembly, the final (desired) structure is ‘encoded’ in the shape from small blocks, when compared with traditional techniques (such as lithography), where the desired structure must be carved out from a large block of matter. Self-assembly is thus referred to as a ‘bottom-up’ manufacturing technique, whereas lithography is a ‘top-down’ technique. The synthesis of molecules for self-assembly often involves a chemical process called convergent synthesis. This process requires standard laboratory equipment and is limited to specific polymers.
Nanofibers: General Aspects and Applications
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Drug Delivery Approaches and Nanosystems, 2017
Raghavendra Ramalingam, Kantha Deivi Arunachalam
Self-assembly is a formulating method where small molecules are used as basic building blocks which add-up to give nanofibers (Hartgerink et al., 2001). Through this technique, very fine fibers (7–100 nm in diameter; hundreds of nanometers in length) are produced. Liu et al. (2014), Dhinakaran et al. (2014), Nalluri et al. (2014) have prepared nanofibers using self-assembly. In self-assembly the final (desired) structure is ‘encoded’ in the shape of the small blocks, thus referred to as ‘bottom-up’ manufacturing technique. The synthesis of molecules for self-assembly often involves a chemical process called convergent synthesis. Figure 8.4 is a simple schematic representation on self-assembly for obtaining nanofibers. The main mechanism for a generic self-assembly is the intermolecular forces that bring the smaller units together and the shape of the smaller subunits which determine the overall shape of the macromolecular nanofiber. The main advantages are easy processability, easy to get smaller fibers, reproducible but it’s a complex process, only lab scale production, inability to control dimensions of nanofibers, and difficult to maintain its porosity for longer duration of period (Endres et al., 2012).
Nanotheranostics: Implications of Nanotechnology in Simultaneous Diagnosis and Therapy
Published in Alok Dhawan, Sanjay Singh, Ashutosh Kumar, Rishi Shanker, Nanobiotechnology, 2018
Brahmeshwar Mishra, Ravi R. Patel
Dendrimers are polymer-based nanosized structures composed of highly branched polymers in a spherical manner. Nanomedicine-based dendrimers are of 10–100 nm in size and can be used for theranostic purposes (Fahmy et al. 2007). The basic architecture of dendrimers involves the repeated, covalently linked branching surrounding the core to form a three-dimensional geometrical pattern. Based on the number of layered structures, dendrimers are classified into different generations. As the layered structure increases, higher-generation dendrimers are obtained (Kaminskas et al. 2012). The functional properties and activities of the dendrimers are a result of their surface functional groups from the hyperbranched structures. During synthesis, branching units are added repetitively to the core to form dendrimers. They can be synthesized mainly by two strategies: divergent synthesis (i.e., synthesis begins from functional core to periphery) and convergent synthesis (i.e., synthesis begins from periphery to reactive core) (Oliveira et al. 2010). Poly(amidoamine) (PAMAM)- and polypropylenimine (PPI)-based dendrimers are synthesized by the divergent method, whereas poly(ether-imide)s dendrimers are synthesized by the convergent method (Esfand and Tomalia 2001, Leu et al. 2001). Dendrimers generally possess a positive surface charge, which might result in severe toxicity by perturbing the cellular membrane. The size, shape, molecular weight, surface chemistry, and chemical composition of dendrimers can be effectively harnessed by controlling the degree of polymerization. These properties confer monodispersity, longer blood circulation potential, and tunable biodistribution capability to the dendrimers, along with controlled drug release characteristics (Li et al. 2007).
A review of application of amine-terminated dendritic materials in textile engineering
Published in The Journal of The Textile Institute, 2019
Somaye Akbari, Ryszard Michal Kozłowski
In general, synthetic methods for the preparation of branched architectures rely on two similar procedures described as divergent and convergent. Both procedures usually rely on mutually compatible and complementary protection and deprotection sequences (Vögtle, Richardt, & Werner, 2009). In the divergent synthetic routes which have been firstly illustrated by Tomalia, Naylor, and Goddard (1990), dendrimer grows outwards from a multifunctional core molecule generation by generation. In contrast to divergent synthesis, the convergent synthetic routes introduced by Fréchet and Hawker (1990) is constructed stepwise, starting from the end groups and progressing inwards to attach to a multifunctional core molecule. The convergent growth method has several advantages; purification of the desired product is relatively easy and the occurrence of defects in the final structure is minimized. Although preparation of dendrimers requires a high degree of purity of the starting materials and high yields of the individual synthetic steps, synthesis of hyperbranched polymers proceeds in a single-stage process. Owing to their molecular structures and their properties, hyperbranched polymers represent a transition between linear polymers and highly branched dendrimers (Mekelburger et al., 1992; Zhu, Zhou, & Yan, 2011). Due to the stepwise synthesis of a dendrimer, the price of a dendrimer is high (Irfan & Seiler, 2010). As a result, for large-scale industrial use, hyperbranched polymers can be considered as an economic alternative for dendrimers which share many of the dendrimers' special properties.