Self-assembly of an AeB diblock copolymer blended with a C homopolymer and a CeD diblock copolymer through hydrogen bonding interaction Wan-Chun Chen a , Shiao-Wei Kuo b, ** , Feng-Chih Chang a, * a Institute of Applied Chemistry, National Chiao Tung University, Hsin Chu, Taiwan b Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, Taiwan article info Article history: Received 20 December 2009 Received in revised form 2 June 2010 Accepted 4 July 2010 Available online 24 July 2010 Keywords: Block copolymer Hydrogen bonding Self-assembly abstract In this study, we investigated the miscibility, phase behavior, and self-assembled nanostructures formed from the immiscible crystalline-amorphous diblock copolymer poly(3-caprolactone-b-4-vinyl pyridine) (PCL-b-P4VP, AeB) when blended with the homopolymer poly(vinyl phenol) (PVPh, C) and the diblock copolymer poly(vinyl phenol-b-styrene) (PVPh-b-PS, CeD). Long-range-ordered microphase separation was difficult to achieve in the PCL-b-P4VP/PVPh (AeB/C) blend system because PVPh interacted with both the P4VP and PCL blocks simultaneously through hydrogen bonding interactions. In contrast, we observed sharp, multiple orders of diffraction in the SAXS profiles of the PCL-b-P4VP/PVPh-b-PS (AeB/ CeD) blend system, indicating that perfect microphase separation occurred because the incorporation of the PS block induced the PVPh block to hydrogen bond preferentially with the P4VP block. This simple AeB/CeD (PCL-b-P4VP/PVPh-b-PS) diblock copolymer mixture exhibited self-assembly behavior (a three-lamella phase) similar to that of a corresponding ABC triblock copolymer. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Because diblock copolymers (A-b-B) comprising incompatible components can self-assemble into various microphase-separated structures in the bulk state [1e4], they are attractive soft materials for the creation of nanoscale materials exhibiting various functions [5]. Self-assembly of block copolymers plays a key role in the design of new functional supramolecular materials for a wide range of applications such as pollution control and drug delivery. In addi- tion, blends of diblock copolymers and homopolymers often display unusual phase behavior [6e18]. Originally, most studies of diblock copolymer/homopolymer blends concentrated on mixtures of an immiscible A-b-B diblock copolymer with an A homopolymer (e.g., a styrenic block copolymer with a polystyrene homopolymer); these systems can exhibit three types of phase behavior (e.g., macro-phase separation, dry-brush, and wet-brush behavior) depending on the molecular weight ratio of the homopolymer A to the block copolymer A [19]. Recently, however, more attention has been placed on the phase behavior of blends of A-b-B diblock copolymers and C homopolymers that interact through hydrogen bonding [20e31]. For an A-b-B/C blend system, there are four possible outcomes when C is miscible with the A and/or B blocks, as we have discussed in detail previously [31,32]. In addition to diblock copolymer/homopolymer blends, more- complicated macromolecules, such as ABC triblock copolymers, have attracted interest in recent years because they can form more-complicated structures, including three-phase lamellae and core/shell cylinder structures [33]. Although the synthesis of ABC triblock copolymers is complicated, mixing A-b-B and C-b-D copolymers is a relatively simpler method for preparing such self- assembled morphologies [34,35]. Typically, for such systems, the B and C segments should be attracted through intermolecular interactions (e.g., hydrogen bonding [36e41], electrostatic inter- actions [42e44], or metaleligand coordination [45,46]) and the A and D block segments should be incompatible or immiscible. Nevertheless, to the best of our knowledge, very few reports describe the structures of AB/CD blend systems in the bulk state. For example, Mastishita et al. reported that the blending of poly (isoprene-b-4-vinyl pyridine) (PI-b-P4VP, A-b-B) with poly(vinyl phenol-b-styrene) (PVPh-b-PS, C-b-D) formed highly complex hierarchically ordered nanophases, such as lamellae in lamellae structures [34]. In this case, the hydroxyl (OH) groups of PVPh (C) interacted only with the pyridyl groups of P4VP (B) in the PVPh/ P4VP complex phase, with the PI (A) with PS (D) segments being * Corresponding author. Tel./fax: þ886 3 5131512. ** Corresponding author. Fax: þ886 7 5254099. E-mail addresses: kuosw@faculty.nsysu.edu.tw (S.-W. Kuo), changfc@mail.nctu. edu.tw (F.-C. Chang). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2010.07.006 Polymer 51 (2010) 4176e4184