Introduction to Block Copolymer Self-Assembly

A remarkable property of polymer melts is their ability to self-assemble, driven by thermodynamic incompatibilities of the different monomers. A brief introduction to the thermodynamic theory of macrophase separation in homopolymer blends and microphase separation in diblock copolymer melts is given. In particular, the effect of controllable parameters, including the monomer interactions, the block composition. 

Parts of this chapter were previously published [1]. 

Scherer, Double-Gyroid-Stnictured Functional Materials, Springer Theses, DOf 10.1007/978-3-319-00354-2 4, 

4 Voided Double-Gyroid Thin Film Templates 

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Controlling the spontaneous formation of ordered domains in soft materials such as block copolymers [189] may lead to the development of stimuli-responsive materials for applications such as actuators [190] and photonics [191] due to the reversible nature of order formation. However, the stimuli that are typically used to control the morphology of block copolymers are e.g., temperature, pressure, solvent type and concentration... Pioneering work by Abbott and co-workers used the chemical oxidation approach to control the self-assembly of small-molecule amphiphiles containing ferrocene [192]. Rabin and co-workers have shown that the introduction of dissociated charges on one of the blocks of a diblock copolymer leads to stabilization of the disordered phase [193]. They also quantified the increase in x at the order-disorder transition (ODT), xodt, due to the entropic contribution of the dissociated counterions. The Flory-Huggins parameter,x, that is used to quantify interactions between polymer chains is assumed to be proportional to the difference in the polarizibility of the blocks [194]. The polarizibility of polyferrocenyldimethylsilane, which is larger than that of either polystyrene or polyisoprene [195], must increase upon oxidation due to the presence of the NO ions. 

Integrating block copolymer-directed nanostmcture control of hybrid materials with other stmcture formation processes is one future direction that this research will most likely take. A more fundamental direction is the transition from AB or ABA diblock copolymers to ABC terblock copolymers or even higher-order multiblock copolymers as stmcture-directing agents for inorganic materials. The introduction of a third block in ABC terblock copolymer self-assembly leads to a... 

Fig. 17 Top illustration of the reversible Mb oxygenation inside the PICsome self-assembled from a pair of oppositely charged block copolymers. Bottom change in the absorbance at 434 nm of the Mb-PICsome by the alternating introduction of 02/Ar gas to the solution. Reprinted with permission from [58], copyright (2007) Wiley...

The introduction of functional handles to direct the encapsulation of small molecules can be readily achieved using the self-assembly of polymer di- or tii block copolymers, given the facile introduction of reactive handles into the copolymerization strategy. One advantage of this method is that the loading of the nanoparticle can be readily tailored by the designed synthesis of the parent particle. 

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