Comparison of methods for the fabrication and the characterization of polymer self-assemblies: what are the important parameters?

Abstract

The ability to self-assemble was evaluated for a large variety of amphiphilic block copolymers, including poly(ethyleneoxide-b-ε-caprolactone), poly(ethyleneoxide-b-d,l-lactide), poly(ethyleneoxide-b-styrene), poly(ethyleneoxide-b-butadiene) and poly(ethyleneoxide-b-methylmethacrylate). Different methods of formation are discussed, such as cosolvent addition, film hydration or electroformation. The influence of experimental parameters and macromolecular structures on the size and morphology of the final self-assembled structures is investigated and critically compared with the literature. The same process is carried out regarding the characterization of these structures. This analysis demonstrates the great care that should be taken when dealing with such polymeric assemblies. If the morphology of such assemblies can be predicted to some extent by macromolecular parameters like the hydrophilic/hydrophobic balance, those parameters cannot be considered as universal. In addition, external experimental parameters (methods of preparation, use of co-solvent, …) appeared as critical key parameters to obtain a good control over the final structure of such objects, which are very often not at thermodynamic equilibrium but kinetically frozen. A principal component analysis is also proposed, in order to examine the important parameters for forming the self-assemblies. Here again, the hydrophilic/hydrophobic fraction is identified as an important parameter.

Facile assembly and loading of theranostic polymersomes via multi-impingement flash nanoprecipitation

“…The glass transition (Tg) of the amphiphile’s hydrophobic block influences chain flexibility and as a result the timescale of aggregate shape transformations, which can range from hours for glassy high Tg polymers to milliseconds for low Tg polymers [18–20]. Thus, the rapid mixing followed by an immediate increase in water content within the reservoir during FNP effectively minimizes the chain mobility of the hydrophobic copolymer blocks to stably lock the molecular orientation of the assembly, and this is particularly effective for high Tg polymers like polystyrene [6, 8, 15, 21, 22]. It was determined that the organic solvent must be removed from the assembly quickly to prevent nanoparticle instability and ripening, which can be achieved via flash solvent evaporation or using aqueous reservoirs with large volumes to decrease the solvent concentration [23, 24].…”

Polymer brushes based on PLLA-b-PEO colloids for the preparation of protein resistant PLA surfaces

“…The hydrophilic weight fraction f PEO reached the values 0.42, 0.56, and 0.68 for the 7/5, 7/10, and 7/15 PLLA-b-PEO copolymers indicating formation of micelle morphology according to Dionzu's work. 34 The formation of such self-assemblies is shown in Fig. 1A.…”

“…16,33 The character of selfassemblies of a wide range of PEO-based amphiphilic block copolymers was investigated in a comparative study by Dionzu et al 34 The hydrophilic/hydrophobic fraction was shown to be a significant factor for prediction of the morphology of emerging nano-objects, which are not usually in equilibrium, but kinetically frozen. However, besides molecular parameters, the threshold between micelles and vesicles also depends on details such as (co)solvent system and preparation method.…”

Polimerossomos versus lipossomos: a evolução da "Bala Mágica"

“…89 Assim, auto-agregados supramoleculares podem responder a estímulos externos (por exemplo, pH, temperatura, campos magnéticos, luz, processos redox). 90 Na Tabela 4 são apresentadas as modificações mais comuns em PL de maneira a funcionalizá-los.…”