Self-assembly process, polymer monolayer

Figure 7. Scheme of the self-assembly process that leads to a (polymer) monolayer at a solid substrate. 

The fnnctionality present on the MNP surface also greatly impacts their assembly behavior. In most cases, the surface of the MNPs is passivated by an organic monolayer that protects them from aggregation and provides solubility in solvents. The particle surface also represents the interface at which the particle and polymer interact within the composite assembly. Self-assembly processes require favorable interactions between the MNP building blocks and the polymer, such that stable equilibrium (or near equilibrium) structures are formed. The types of intermolecular noncovalent interactions include hydrogen bonding, metal coordination, electrostatic, dipole-dipole, and hydrophobic interactions, as well as van der Waals forces, between MNPs and polymers. The successful self-assembly of MNPs into well-defined nanostructures not only depends on the ability to control precisely their composition, shape, and size but also on the modification of the MNP surface with the desired functionahty that mediates interactions with the polymer. 

As biological systems have always been an inspiration for scientists, intracellular compartments (such as lysosomes or mitochondria) also have their artificial equivalents in polymer vesicles, called polymersomes. Polymersomes are spherical compartments with a bi- or monolayer membrane, generated by self-assembly of di- or triamphiphilic block copolymers in diluted aqueous conditions. To favor the formation of structures such as polymersomes, it is necessary to have a hydrophilic fraction of the copolymer mass of 25-40%, and polymer concentration above the critical micellar concentration. Other parameters that affect the self-assembly process, and therefore the final architecture of the polymer supramolecular assemblies, are the molecular weight of the copolymer (Af ), block lengths, solubility, and glass transition temperature (Tg) [21,22], The relative mass or volume fraction of each block is a key parameter in the formation of a self-assembled structure with a certain membrane curvature, and ultimately, with a specific architecture. The of the copolymer (and thus the block lengths) dictates the membrane thickness and polymersome properties, such as membrane fluidity, stabihty, and permeabihty [21,74],... 

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