Surface Segregation of a Star-Shaped Polyhedral Oligomeric Silsesquioxane in a Polymer Matrix

Abstract

A simple way to control only the surface properties of polymer materials, without changing the bulk properties, has long been desired. The segregation behavior when a component with a tiny amount fed into the matrix is thermodynamically enriched at the surface is one of the candidate methods. This capability was examined herein by focusing on a star-shaped polyhedral oligomeric silsesquioxane (s-POSS), where the central POSS unit is tethered to eight isobutyl-substituted POSS cages as a surface modifier. X-ray photoelectron spectroscopy revealed that the surface of a film of poly(methyl methacrylate) (PMMA) was almost completely covered with POSS units by adding just 5 wt % s-POSS to it. The segregated POSS dramatically altered the physical properties such as molecular motion and the mechanical and dielectric responses at the surface of the PMMA film. These findings make it clear that s-POSS is an excellent surface modifier for glassy polymers.

SiO2/Ladder-Like Polysilsesquioxanes Nanocomposite Coatings: Playing with the Hybrid Interface for Tuning Thermal Properties and Wettability

“…POSS have been widely utilized for the fabrication of hydrophobic surfaces and coatings, by virtue of their versatile features and of the possibility to easily covalently link them to polymer backbones [41][42][43][44][45]. In particular, the polyhedral structure and the high number of tunable peripheral functionalities enable us to increase the surface roughness and decrease the surface energy, simultaneously [43][44][45][46][47][48][49]. The majority of the studies in the field rely on the synthesis and modification of POSS structures with low-surface energy substituents (e.g., fluoroalkyl, alkyl groups, etc.)…”

“…Concerning the possibility of tuning the roughness with POSS, a few examples can be identified in the literature [47][48][49]. As an example, Foorginezhad et al [48] prepared super-hydrophobic coatings by creating a two-layer topography via the spraying method using TiO 2 NPs sols, which impart the micro-roughness, and octavinyl-POSS in polydimethylsiloxane, which delivers nano-roughness and lowers the surface tension thanks to the hydrophobic organic terminations.…”

Phenyl-Substituted Cage Silsesquioxane-Based Star-Shaped Giant Molecular Clusters: Synthesis, Properties, and Surface Segregation Behavior

“…The star-shaped isobutyl-substituted POSS derivative with a propylene (C3) linker worked as an effective surface modifier for poly(methyl methacrylate) (PMMA) via surface segregation. 17 The star-shaped POSS exhibited a better surface modifier because it does not crystallize due to its amorphous character, in contrast to most POSS compounds, which can become crystallized at the surface, leading to a rough surface, which limits their long-term stability, durability, and scalability for industrial applications. Among various surface modification methods, the use of surface segregation of surface modifiers in a polymer matrix is the most convenient and low-cost method because special apparatus and procedures such as plasma, corona, and gamma ray treatments are not required.…”

Entropy-Driven Segregation of a Hydrophilic Cage Octasilicate for Improving Surface Hydrophilicity

“…31 A star-shaped POSS, where a central octasilicate core unit is tethered to eight isobutyl-substituted POSS cages, was found to be more effectively covered on the surface of PMMA due to non-crystallized character of the star-shaped architecture. 32 Recently, we reported that hybrid polyurethanes composed of isobutyl-substituted open-cage silsesquioxane in the main chains showed excellent optical transparency and surface hydrophobicity and applied them as surface modifiers in PMMA by surface segregation to create hydrophobic surfaces. 33 Compared to these hydrophobic POSS units as surface modifiers, no hydrophilic POSS derivatives are used as surface modifiers via surface segregation.…”

“…Enhancement of surface hydrophobicity was promoted in organic–inorganic hybrid polyurethanes with POSS as the pendent groups. , Terminal POSS units in poly­(methyl methacrylate) (PMMA) promoted surface segregation in a PMMA film . A star-shaped POSS, where a central octasilicate core unit is tethered to eight isobutyl-substituted POSS cages, was found to be more effectively covered on the surface of PMMA due to non-crystallized character of the star-shaped architecture . Recently, we reported that hybrid polyurethanes composed of isobutyl-substituted open-cage silsesquioxane in the main chains showed excellent optical transparency and surface hydrophobicity and applied them as surface modifiers in PMMA by surface segregation to create hydrophobic surfaces .…”