Phenolic Resin and Derived Carbon Hollow Spheres Mu Yang, 1 Jin Ma, 1 Shujiang Ding, 1 Zhaokai Meng, 1 Jinge Liu, 2 Tong Zhao, 2 Lanqun Mao, 3 Yi Shi, 1 Xigao Jin, 1 Yunfeng Lu,* 4 Zhenzhong Yang* 1 1 State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China Fax: (þ86) 10 6255 9373; E-mail: yangzz@iccas.ac.cn 2 Laboratory of High Technology Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China 3 Laboratory of Analytical Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China 4 Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Los Angeles 70118, USA E-mail: ylu@tulane.edu Received: June 5, 2006; Revised: July 13, 2006; Accepted: July 14, 2006; DOI: 10.1002/macp.200600273 Keywords: carbon; composites; gels; hollow spheres; phenolic formaldehyde resin Introduction Capsules and hollow spheres have spurred growing interest due to their potential applications in controlled delivery, artificial cells, thermal insulators, light-weight fillers, catalysts, and confined reactors. [1] Core–shell based template synthesis that is usually assisted by layer-by- layer (LBL) deposition, has been extensively utilized to prepare these structured spheres with varied shell compo- nents such as polyelectrolyte, inorganic, biological, metal- lic. [1c,d] However, the template cores have to be removed by diffusing through the shell during the synthesis of hollow spheres. As a result, the osmotic pressure associated with the molecular diffusion usually causes apertures or fragmentation in the shell. We have recently proposed to synthesize composite hollow spheres and double-shelled hollow sphere with intact shells using polymer hollow spheres as templates. [2] The gel shell can favorably absorb precursors and induce growth of materials therein. The gel can be derived by modification of the parent shell resulting in functional groups such as sulfonic acid (–SO 3  H þ ). [2b] Although a huge family of hollow spheres have been syn- thesized, such a polymer hollow sphere that is resistant to high temperature above 450 8C has been reported scarcely. This kind of polymer hollow spheres hold promise such as light-weight fillers and thermal insulators at high tem- perature. In this report, we extend the gel-induced favorable synthesis [2] to a representative high temperature resistant polymer, phenolic formaldehyde (PF) resin, to obtain PF and the correspondingly derived carbon hollow spheres. The sulfonated polystyrene gel shell of the hollow sphere template plays dual roles: (1) favorable absorption of PF resin, and (2) catalytic crosslinking of PF resin therein at low temperature within the gel shell. The gel can also act as a porogen to achieve porous carbon. Summary: Phenolic formaldehyde (PF) resins are attractive due to their excellent performances such as high temperature resistance, thermal abrasion, and high yield of carbon conversion. In this communication, PF resin-based compo- site hollow spheres were fabricated by in situ favorable absorption and catalytic crosslinking of PF resin within sulfonated polystyrene gel layers of the hollow sphere temp- lates at low temperature. The composite hollow spheres were achieved in one step, avoiding traditional removal of template cores. The intact shell was tuned from double-layered to single-layered. Carbon hollow spheres with porous shell were derived by carbonization of the PF composite hollow spheres. Metal/carbon composite hollow spheres were further synthe- sized by the incorporation of metal within the porous shell, which would be a promising material for catalysis. TEM image of carbon double-shelled hollow spheres after the PF composite spheres are calcined at 800 8C for 2 h in nitrogen. Macromol. Chem. Phys. 2006, 207, 1633–1639 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Full Paper DOI: 10.1002/macp.200600273 1633