Janus Cages of Bilayered Polymer-Inorganic Composites Ying Chen, Haili Yang, Chengliang Zhang, Qian Wang, Xiaozhong Qu, Jiaoli Li, Fuxin Liang,* and Zhenzhong Yang* State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China * S Supporting Information ABSTRACT: Janus cages with a bilayer polymer-inorganic composite shell are synthesized by an emulsion interfacial self- organized sol-gel process followed by a polymer grafting onto the interior surface containing a vinyl group. Binary surfactants experience a phase separation to create transverse channels across the shell. The Janus cages can be functionalized by either growing responsive polymers or integrating with functional nanoparticles. They are promising in controlled loading and triggered release of desired materials under guidance. 1. INTRODUCTION Janus objects with two different compositions compartmental- ized have gained growing academic and industrial interests due to their diversified performances. 1,2 Currently, those non- centrosymmetric Janus materials have been extensively reported with varied shapes including particle, 3 rod, 4 and disk. 5 Two different compositions are compartmentalized onto the same surface. Recently, centrosymmetric hollow spheres but with an asymmetric shell are becoming a key concern. 6 Such hollow spheres are recognized as Janus to mimic micellar structures. They can serve as specific containers, and desired compounds can be selectively captured thereby from their surroundings due to different affinity. The performance is promising in controlled loading and release and confined catalytic reaction. 7 Organic Janus hollow spheres have been extensively synthesized based on either self-assembly from amphiphilic molecules or seed emulsion polymerization. Their shells are rather weak that are easily swollen and weakening in the presence of solvents even after they are strengthened by polymerization or cross-linking. In the absence of transverse channels, mass transportation through the shell is restricted. 7b Robust inorganic shell is a rational alternative. Recently, we have reported a Janus silica hollow microsphere by an emulsion interfacial self-assembled sol-gel process, whose interior surface is hydrophobic and the exterior surface is hydrophilic. 6 One large window hole is resulted after dissolving the interior core, providing a window for hydrophobic materials being selectively captured inside the cavity from a hydrophilic environment. 6 However, the irregular window lacks of control in both shape and size. Moreover, the interior surface terminated with the pedant group from the silane lacks of responsive performance. It is required to create tunable transverse channels to enhance selective mass transfer forming Janus cages. It will be more interesting if the Janus cages are responsive. Herein, we extend our previous interfacial materialization synthesis of inorganic Janus hollow spheres to large scale fabricate Janus porous hollow spheres with a bilayered polymer-inorganic composite shell as illustrated in Scheme 1. Self-organized sol-gel process of silicon precursors proceeds at the emulsion interface to form inorganic Janus cages first; polymer-inorganic composite Janus cages were achieved by subsequently grafting polymer onto the interior face of the inorganic Janus ones. It is key to employ binary surfactants to create transverse pores across the shell after a phase separation at the emulsion interface during the sol-gel process. 8 The interior polymeric layer gives a tunable hydrophobic cavity to selectively collect oil, while the hydrophilic silica exterior layer ensures a good dispersibility of the microspheres in water. Received: March 26, 2013 Revised: April 30, 2013 Published: May 8, 2013 Article pubs.acs.org/Macromolecules © 2013 American Chemical Society 4126 dx.doi.org/10.1021/ma4006236 | Macromolecules 2013, 46, 4126-4130