Chemical Engineering Journal 165 (2010) 354–357 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Facile fabrication of colloidal particles based on the electrostatic aggregation of block copolymer micelles Jinkee Hong a,c , Sang Wook Kang b,∗ a School of Chemical & Biological Engineering, Seoul National University, Seoul 151-744, South Korea b Department of Chemistry, Sangmyung University, 7 Hongji-Dong, Jongno-Gu, Seoul 110-743, South Korea c Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA article info Article history: Received 27 May 2010 Received in revised form 27 July 2010 Accepted 16 August 2010 Keywords: Colloidal particle Block copolymer micelle Aggregation abstract Block copolymer assembled colloidal particles were successfully prepared through electrostatic interactions between cationic polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) in a one-pot process. The colloidal particles were pre- pared by simple mixing of complementary charged block copolymer micelle aqueous solution. This process presents the possibility of very simple and versatile method of mass production of BCM based colloidal particles. Both hairy and crew-cut types of block copolymer micelles (BCMs) showed different electrostatic assembly tendencies as confirmed by Field emission scanning electron microscopy (FE- SEM). These phenomena are mainly caused by the different degrees of electrostatic interdigitation and entanglement between the protonated and deprotonated corona block regions of the micelles. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Over the past few years, colloidal particles containing encapsu- lated drugs have attracted considerable attention for their potential applications in biomedical fields as vehicles for drug-delivery, as imaging and diagnostic agents, for catalysis, and as enzyme- immobilizing hosts. Efforts to prepare colloidal particles for the encapsulation of hydrophobic materials have mainly focused on hollow-shell structures, micro-emulsion droplets, interface assem- blies, and carbon materials [1–6]. Among various approaches for possible drug carriers, block copolymer micelles (BCMs) have been investigated because they have several advantages, including the capacity to solubilize hydrophobic molecules in aqueous solution in which they would otherwise be insoluble; the ability to shield hydrophobic functional molecules from environmental conditions; and BCM hydrophilic corona parts offer various opportunities for further applications such as targeting, sensing or diagnosis [7–12]. Recently, Irvine and coworkers reported the application of BCMs as carriers for hydrophilic drugs [13]. Furthermore, Zhang et al. and Hammond et al. have shown that BCMs could be used as drug carrier stacks inside a multilayer polymer film [14–16,19,20]. Further- more, we recently reported that the charge densities of BCMs could be easily controlled by simply changing the solution pH [17,18]. ∗ Corresponding author. Tel.: +82 2 2287 5362. E-mail address: swkang@smu.ac.kr (S.W. Kang). Here, we report a facile, one batch process for the synthe- sis of versatile colloidal particles which were assembled utilizing electrostatic interactions between positively charged polystyrene- block-poly(4-vinylpyridine) (PS-b-P4VP) and negatively charged polystyrene-block-poly(acrylic acid) (PS-b-PAA). This versatile and simple approach for the construction of colloidal particles that incorporate the various advantages of BCMs enlarges the range of functional materials that can be used as encapsulating polymer containers. 2. Materials and methods 2.1. Materials PS (Mw=18.6K) - b - P4VP (Mw=55.8K) (PS 18.6K - b - P4VP 55.8K ), PS 49.5K - b - P4VP 16.5K , PS 4.3K - b - PAA 19.5K , and PS 16K - b - PAA 4K block copolymers were purchased from Polymer Source. 2.2. Preparation of colloidal particles from BCMs BCMs were prepared using methods described in our previous reports [17,18]. After forming PS-b-P4VP micelles at pH 2, the pH of the PS-b-P4VP micelle solution was adjusted to pH 4 using 0.1 M NaOH. In contrast, PS-b-PAA (50 mg) in 2 mL DMF/THF was dis- solved in 48 mL water at pH 10 to prepare the anionic PS-b-PAA BCMs. The PS-b-PAA micelle solution was then adjusted to pH 5 using 0.1 M HCl. Subsequently, the pH-adjusted PS-b-P4VP micelle and PS-b-PAA micelle solutions (10 ml each) were mixed together 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.08.035