Gelation Inside Block Copolymer Aggregates and Organic/Inorganic Nanohybrids Yongming Chen,* Jianzhong Du, Ming Xiong, Ke Zhang, Hui Zhu State Key Laboratory of Polymer Physics and Chemistry, Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, P. R. China E-mail: ymchen@iccas.ac.cn Received: February 22, 2006; Revised: March 13, 2006; Accepted: March 14, 2006; DOI: 10.1002/marc.200600128 Keywords: block copolymers; gelation; nanoparticles; polysiloxanes; self-organization Introduction When two unfavorable polymer segments are linked together by a covalent bond, so called block copolymers are produced. As a result of a balance of entropy and enthalpy, the self- assembly of block copolymers generates a tremendous well- defined structure on the nanoscale. This property has attracted unprecedented attentions of people working in both academia and industry. Since many books and review articles have summarized the general chemistry and properties of block copolymers, only the self-assembly of block copoly- mers in solution is introduced briefly. In a selective solvent for one segment, block copolymers can form polymer micelles by self-assembling. Depending upon the block copolymer architecture, composition, and conditions of self- organization, a variety of morphologies like star micelles, [1] vesicles, [2,3] worms, [4] tubules, [5] donut rings, [6,7] multi- compartment micelles, [8] and many other kinetically con- trolled structures have been obtained from the spontaneous self-assembly of amphiphilic block copolymers. [9] Owing to their unique structures, well-defined self- assemblies of block copolymers in solution are considered to be good candidates for applications in nanomaterial science and technology. However, the fact that block copolymer aggregates are composed of many polymer chains and are subject to structural damage when the temperature and solvents change has significantly limited their applications in situations where a morphological stability is needed. In addition, block copolymer aggregates generally are organic objects, for their precursors are organic structures: the poor temperature stability and mechanic stability of organic objects have also made them Summary: Like in many other cases, block copolymers bearing alkoxysilyl groups in one segment self-assemble into aggregates. However, they may allow one to study the sol-gel reaction by making use of the gelable groups located in the domains of the aggregates, therefore, the gelation process can be made in a selected domain of the nanoscale. As a result, the organic nanostructure is transformed into an organic/ inorganic hybrid. The process of using covalently grafted alkoxysilane groups along the block copolymer precursors is applicable not only to the aggregates formed in solution, but also to the other forms of aggregates in melts, thin films, and interfaces. In this feature article, this emerging field is introduced, mainly focusing on the gelation that occurs inside the preformed block copolymer aggregates in solution. The morphologically fixed hybrid nanoparticles, such as spheres, hollow particles, and complex hollow particles, are presented and discussed. This technology has great potentials in the fields of nanomaterials and nanotechnologies, since various organic/inorganic hybrid nanoparticles and nanostructures can be effectively generated using this process. Gelation in preformed block-copolymer aggregates generates controlled structures. Macromol. Rapid Commun. 2006, 27, 741–750 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Feature Article DOI: 10.1002/marc.200600128 741