Chem Soc Rev CRITICAL REVIEW

中国科技论文在线 http://www.paper.edu.cnView Online Chem Soc Rev Dynamic Article Links Cite this: Chem. Soc. Rev., 2011, 40, 2402–2416 www.rsc.org/csr CRITICAL REVIEW Anisotropic particles with patchy, multicompartment and Janus architectures: preparation and application Jianzhong Du*a and Rachel K. O’Reilly*b Received 17th December 2010 DOI: 10.1039/c0cs00216j Anisotropic particles, such as patchy, multicompartment and Janus particles, have attracted significant attention in recent years due to their novel morphologies and diverse potential applications. The non-centrosymmetric features of these particles make them a unique class of nano- or micro-colloidal materials. Patchy particles usually have different compositional patches in the corona, whereas multicompartment particles have a multi-phasic anisotropic architecture in the core domain. In contrast, Janus particles, named after the double-faced Roman god, have a strictlybiphasicgeometryofdistinct compositions and properties in the core and/or corona. The term Janus particles, multicompartment particles and patchy particles frequently appears in the literature, however, they are sometimes misused due to their structural similarity. Therefore, in this critical review we classify the key features of these different anisotropic colloidal particles and compare structural properties as well as discuss their preparation and application. This review brings together and highlights the significant advances in the last 2 to 3 years in the fabrication and application of these novel patchy, multicompartment and Janus particles (98 references). a School of Materials Science and Engineering, Tongji University, 1. Introduction 4800 Caoan Road, Shanghai, 201804, China. 1.1 Patchy, multicompartment and Janus particles E-mail: [email protected]; Fax: +86 (021) 6958 4723; Tel: +86 (021) 6958 0239 The past few years have seen an almost unbelievable revolution Downloaded by Tsinghua University on 20 April 2011 b Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK. E-mail: [email protected]; in materials science, especially in the preparation and design of Published on 08 March 2011 http://pubs.rsc.org | doi:10.1039/C0CS00216J Fax: +44 (0)247 652 4112; Tel: +44 (0)247 652 3236 nano- or micro-sized anisotropic particles such as patchy, Dr Jianzhong Du is an ‘Eastern Dr Rachel O’Reilly is an Scholar’ professor at Tongji EPSRC career acceleration University in Shanghai. He fellow in the Chemistry received his PhD in 2004 from Department at the University Institute of Chemistry, Chinese of Warwick. She graduated Academy of Sciences (CAS), from the University of under the supervision of Prof. Cambridge in 1999 and went Yongming Chen. His PhD on to complete her PhD at thesis was awarded ‘The Top Imperial College London in 50 PhD Dissertations in CAS’ 2003. She then moved to the in 2005 and ‘The Nominated US under the joint direction of National Top 100 PhD Professors Craig J. Hawker Dissertations in China’ in and Karen L. Wooley. In 2006. He was also an Alexander 2004 she was awarded a Jianzhong Du von Humboldt Fellow in 2006. Rachel K. O’Reilly research fellowship from the He immediately moved to Royal Commission for the Prof. Steve Armes group at the University of Sheffield as a Exhibition for 1851 and in 2005 she took up a Royal Society postdoctoral fellow in 2004. Then in 2008 he moved to Rachel Dorothy Hodgkin Fellowship at the University of Cambridge. In O’Reilly’s group at Cambridge. In 2009 he was appointed a 2009 she moved to her current position. Her research focuses on special appointment professorship at Shanghai institutions of bridging the interface between creative synthetic, polymer and higher learning based at Tongji University. His research interests catalysis chemistry, to allow for the development of materials include controlled radical polymerization and stimuli-responsive that are of significant importance in medical, materials and and functional polymeric materials such as polymer vesicles and nanoscience applications. micelles, and their biomedical applications. 2402 Chem. Soc. Rev., 2011, 40, 2402–2416 This journal is c The Royal Society of Chemistry 2011 转载中国科技论文在线 http://www.paper.edu.cnView Online developed for the fabrication of Janus particles such as surface coating by deposition of evaporated metal particles,11,16–19 pickering emulsion methods,20,21 layer-by-layer self-assembly,22,23 biphasic electrified jetting,24 photo-polymerization in a micro- fluidic channel,25–27 olefin metathesis,28 polymer self-assembly,29–31 protonation/deprotonation cycling,32 surface-initiated free- radical polymerization,33 and in situ ‘‘click chemistry’’.34 However, achieving perfect biphasic Janus character is still problematic and challenging for materials scientists. Thus, recent research focus has gradually shifted towards the applica- Fig. 1 Scanning electron microscopy images of pollen grains. The tions of Janus particles and the fabrication of asymmetric center in the left image is a pumpkin pollen grain which has a patchy colloidal structures without perfect biphasic architectures, such 1 structure. The right image is an Indian mallow pollen grain. as multicompartment particles and patchy particles.35 multicompartment and Janus particles. These anisotropic 1.2 Definition of patchy, multicompartment and Janus particles have attracted much attention, although real world particles applications of these materials appear to still be far from realiza- Patchy particles are defined as particles with precisely con- tion. In nature, there are a number of structural analogues to trolled patches of varying surface and interaction properties.36 the recently developed anisotropic particles in modern materials As schematically described in Fig. 2, Janus particles (Fig. 2A) science. For example, in 2009, Oeggerli presented scanning have equal phase-separated domains which can be located electron microscopy (SEM) images of pollen grains, which either in the core or in the corona (if present), whereas multi- have beautiful anisotropic patches, as shown in Fig. 1.1 It is compartment particles (Fig. 2B) can be generally defined as believed that these patches not only help the pollen cling to colloidal structures which are composed of multiple phase- bird feathers, but also may cause hay fever.1 A further example separated domains in the core. Particles with patches on the of a natural anisotropic structure is heme which is classified surface are called patchy particles (Fig. 2C), and have potential as Janus-like.2 Janus-like structures can also form in nature applications in electronics37 and targeted drug delivery.38 through self-assembly processes such as the assembly of Furthermore Janus or multicompartment particles with patches hydrophobin proteins through the characteristic eight cysteine on the surface can be called ‘‘patchy Janus particles’’ (Fig. 2D) residues in their primary sequence.3 Due to this pattern, or ‘‘patchy-multicompartment particles’’ (Fig. 2E), respectively. hydrophobins have a non-centrosymmetric arrangement of Through the self-assembly of amphiphiles to a number of hydrophilic and hydrophobic patches, which undergoes self- interesting nanostructure morphologies can be accessed including assembly in aqueous solution to form Janus-like structures, spherical micelles, vesicles, cylinders (amongst many others) which are important in several different tasks in the growth Downloaded by Tsinghua University on 20 April 2011 all of which have a phase separated core–corona structure.39–41 and development of filamentous fungi.4 For example, they can However, in recent years there has been great interest in the Published on 08 March 2011 http://pubs.rsc.org | doi:10.1039/C0CS00216J form coatings on spores, hyphae, and fruiting bodies and can synthesis of more complex morphologies such as toroids, have roles in the attachment of fungi to different surfaces.5 discs and also nanostructures with more complex domains They also play a role in breaking the surface tension of water such as multicomponent structures, Janus and patchy particles. to enable the formation of fungal aerial structures.6 This has become a rapidly advancing field and a number of Furthermore, in the biological cell, compartmentalization excellent reviews covering each of these particles have been plays an important role and enables an enormous number of published in recent years. Most notably in 2005, Lutz and reactions and transport processes to be executed in parallel.7 Laschewsky reviewed the area of multicompartment polymer Given the importance of compartmentalization in nature and micelles.42 In 2008, Walther and Mueller highlighted the recent the recent development of synthetic analogues there is great interest in exploring multicompartment particles for the transport of several compounds for a wide variety of processes such as controlled/targeted drug/gene delivery, cosmetics, imaging techno- logy, selective entrapment and release of dyes, pesticides, perfume, etc.8 Indeed it has been proposed that the different subdomains in a multicompartment particle’s core may cosolubilize and transport several different and immiscible molecules selectively, preventing any undesired interactions before delivery. Generally, Janus particles have a strict 50 : 50 distinct coverage in shape, composition, chemistry, polarity, functionality, electrical and other properties, making them suitable for applications in switchable display devices,9 interface stabilizers,10 self-motile micro-particles,11 controllable pores in lipid

Load more