Nanoparticle-Based and Organic-Phase-Based AGET ATRP PolyHIPE Synthesis within Pickering HIPEs and Surfactant-Stabilized HIPEs

Abstract

PolyHIPEs are porous polymers synthesized within high internal phase emulsions (HIPEs). Recent research has shown that the locus of conventional free radical initiation (at the oil–water interface or in the organic phase) can affect the polyHIPE’s structure and properties. This paper is the first investigation of polyHIPE synthesis using activators generated by electron transfer for atom-transfer radical polymerization (AGET ATRP). Two different types of initiators (organic-phase-based and nanoparticle-based) were used to synthesize polyHIPEs within both surfactant-stabilized HIPEs and nanoparticle-stabilized Pickering HIPEs. The type and locus of initiation affected the macromolecular structure for all the polyHIPEs. Furthermore, the initiator also affected both the porous structure and the wall structure of polyHIPEs synthesized within Pickering HIPEs. Depending upon the initiator, either a polyhedral void shape or a nanoparticle assembly at the interface could become “locked in” at the very beginning of the polymerization.

Osteoinductive PolyHIPE Foams as Injectable Bone Grafts

“…This is supported by the TEM images and a recent study demonstrating the efficient self-assembly of nanoparticles in the range of 5-10 nm at polyHIPE pore walls. 30,42 Recent scouting studies with smaller MgOH nanoparticles (5-20 nm) in these polyHIPEs have confirmed our hypothesis that smaller particles can selfassemble and pack at the pore surface. Notably for this work, alizarin red staining of calcium ions on polyHIPEs with ACP and HA illustrated the presence of these particles at the surface (Fig.…”

The Chemistry of Porous Polymers: The Holey Grail

“…Pickering HIPEs, HIPEs stabilized using either inorganic or polymeric amphiphilic nanoparticles (NPs), have also been developed. One advantage of Pickering HIPEs is the relatively high stabilization efficiencies exhibited at relatively low NP concentrations . Stabilizing NPs that are functionalized can also play critical roles in the polymerization reaction (the NPs can bear initiation sites) and in defining the macromolecular structure (the NPs can bear crosslinking sites).…”

“…2020, 60, 140 -150 is the relatively high stabilization efficiencies exhibited at relatively low NP concentrations. [66,[85][86][87][88][89][90] Stabilizing NPs that are functionalized can also play critical roles in the polymerization reaction (the NPs can bear initiation sites) and in defining the macromolecular structure (the NPs can bear crosslinking sites). The presence of an internal phase and the use of a stabilization system thus provide additional factors that can be used to enable the generation of novel porous polymer systems.…”

Achieving Interconnected Pore Architecture in Injectable PolyHIPEs for Bone Tissue Engineering

“…The effect of the locus of initiation on pore interconnectivity has been noted previously in the polyHIPE literature. [33][34][35][36] However, a mechanistic understanding of the process has yet to be discussed. A probable description of interconnect formation based on the forces generated during the conversion from PFDMA macromer to cross-linked polymer is illustrated in Figure 3.…”

“…Recently, the Silverstein group published studies describing the effect of the locus of initiation on pore architecture and properties. [33][34][35][36] The authors proposed that organic-phase initiation resulted in larger, spherical, interconnected pores and an increased loss modulus relative to aqueous-phase initiation. 34 However, a mechanistic description of the effect of locus of initiation on the resulting macromer densification forces and the corollary effect on interconnect formation was not described.…”