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Uptake kinetics and photocrosslinking of poly(ethylene glycol) diacrylate in the nanostructure of a self-assembled sulfonated pentablock polymer

Abstract:

Self-assembly of charged ABCBA pentablock polymers that behave as thermoplastic elastomers with an anionic C block and spontaneously form highly ordered nanostructures makes them perfectly suited for a broad range of specialized applications. One strategy to exploit the inherent polymer morphology and simultaneously improve the properties of such multifunctional polymers is through the creation of mesoblends, wherein one polymer dissolved in a selective solvent is imbibed into a nanostructured one in the solid state. In the present case, mesoblends are prepared by using water to introduce poly(ethylene glycol) diacrylate (PEGda) into a self-assembled ABCBA polymer exhibiting different as-cast morphologies. This work explores the fundamental colloid science governing these systems, focusing on how the pre-existing morphological framework of the host polymer and the molecular characteristics of the secondary polymer dictate the resulting interfacial and transport properties. We first examine factors regulating the absorption kinetics of PEGda differing in molecular weight in the block polymer at several temperatures to extract diffusion coefficients and solubility limits. By doing so, we demonstrate that, while the solubility limits remain relatively invariant (38–54 wt% PEGda) and the PEGda molecular weight over the range examined is inconsequential, the absorption kinetics and diffusion characteristics PEGda are strongly related to the initial solvent-templated polymer morphology. Inclusion of a photoinitiator permits photocrosslinking of the PEGda under UV radiation to generate a PEGda network within the hydrophilic C-microdomains of the polymer. Morphological characteristics of the resultant mesoblends, along with their corresponding swelling and dissolution properties, are analyzed by transmission electron microscopy and small-angle X-Ray scattering. The ability to precisely produce chemically dissimilar networks within nanostructured block polymers not only expands the functionality and technological potential of these multicomponent materials but also highlights the effectiveness of mesoblends as colloidal templates for engineering complex soft materials for specialized applications.