Block copolymer phase separation basics, thermodynamics, and applications in thermoplastic elastomers

Block copolymers are an important class of polymeric materials having versatile applications such as information storage, drug delivery, photonic crystals, nanopatterned templates for nanofabrications, nanostructured electrodes, as thermoplastic elastomers. Based on the total volume of block copolymer production, control on the synthesis and the cost compared to commodity polymers, the applications of the block copolymer are limited. However, the fascinating properties like phase segregation in bulk or in selective solvents at a temperature higher than the glass temperature of constituting blocks can lead to the formation of nanostructured morphologies, which can find applications in specialized sectors. An exemplary control on molecular weight, chemical structure, molecular architecture, and composition of constituting blocks, the size scale, the type of ordering, and the characteristics of the targeted nanostructures can be manipulated. The phase separation behavior is also controlled by thermodynamic factors, the volume fraction of each block, interaction parameters and the total degree of polymerization. Besides the specialized applications, elastomers based on block copolymers like segmented polyurethanes, and styrenic triblock copolymers (ABA types), where a soft elastomeric segment is anchored between two hard blocks, are nowadays widely explored. These classes of materials are called thermoplastic elastomers. They can be processed as thermoplastics but behave elastomeric upon solidification. This chapter, therefore, discusses the fundamentals of block copolymer morphologies, tuning of morphological characteristics by altering molecular and annealing parameters, different methodologies to understand the state of nanostructured morphologies, thermodynamic point of view of phase separation, and applications of a wide variety of block copolymer with a strong emphasis of thermoplastic elastomers.