Nanohybrids of Metal Nanoparticles and Block Copolymers. Control of Spatial Distribution of the Nanoparticles in Microdomain Space

Abstract

KEY WORDSPalladium N anoparticles / Reduction of Palladium Ions/ Poly(2-vinylpyridine)-blockpolyisoprene / Mixtures of Block Copolymers/ Lamella Microdomain / Self-Assembled Structure/ As one of interesting themes in physical science of block copolymers, some groups of researchers have been exploring methods and principles of 'nanoprocessing' of block copolymer microdomain structures. The nanoprocessing involves processings of the microdomains formed in the block copolymers (i) to create 'nanochannels'1 (holes created in one of the microdomain phase dispersed in the matrix of other microdomain phase) or 'nanotextures' 2 (created by selectively removing the matrix phase, while preserving the dispersed phase) and (ii) to create 'nanohybrids' by incorporating nanometal particles, organic or inorganic particles into desired parts of the microdomain space. 3~5 The nanochannels and nanotextures can be coated with metals. 1 The nanoprocessing may involve a processing to create an oriented single grain ofmicrodomain structures. 6 • 7 In this communication we present highlights of our work to create a nanohybrid composed of alternating lamellar microdomains of polyisoprene (PI) and poly(2-vinylpyridine) (P2VP) containing palladium nanoparticles (denoted hereafter by Pd for the sake of simplicity) of ca. 5 nm in diameter selectively in the P2VP lamellae. We will present a novel method to control a spatial distribution of Pd in the P2VP lamellae across the interface. This method, which has never been reported so far to our knowledge, involves firstly a preparation of Pd coordinated and stabilized by poly(2-vinylpyridine)-blockpolyisoprene (Pd-(P2VP-b-PI)) and secondly induces selfassembling of Pd-(P2VP-b-PI) and poly(2-vinylpyridine)-block-polyisoprene (P2VP-b-PI) forming the matrix phase for Pd via solvent casting with benzene. In our earlier report 8 we presented a method to prepare Pd-(P2VP-b-PI) of 4 to 6 nm in diameter. The self-assembly of Pd-(P2VP-b-PI) and P2VP-b-PI block copolymer with chloroform as a solvent was shown to create a nanohybrid in which Pd are selectively localized in the P2VP lamellae. However no methods have been so far proposed to control the location of Pd within the P2VP lamellae, e.g., a uniform distribution of the particles across the interface, or controlled alignment of the particles along the interface or in the middle of the P2VP lamellae etc. This is a point which we would like to address in this paper.A method similar to that described above was presented earlier by Schrock and his coworkers.4 They first prepared a block copolymer having a block which contains P(octyl) 2 side groups and CdSe nanoclusters stabilized by P(octyl)a or O=P(octyl)a. The block copolymers and the CdSe nanoclusters were then solution-cast into films. The CdSe nanoclusters are selectively coordinated in the microdomains comprised of the block chains with P(octylh side groups. However the controlled spatial arrangement of the particles within the microdomains was not reported at all.Here in this work we used t...

Hierarchical self-assembly of nanoparticles in polymer matrix and the nature of the interparticle interaction

“…[13][14][15][16][17][18][19][20] The NPs confined in one of the selected microdomains have been found to uniformly distribute in the domain space or be localized at the interface between different microdomains or in the middle of the domains. 21,22 In this work, the metal precursor is deliberately reduced in a homopolymer matrix rather than bcp matrices for exploring the intrinsic interparticle interaction and its consequences on the morphology of NP aggregates without the influence of spatial confinement involved by the bcp microdomains. Here, the metal precursor palladium acetylacetonate (Pd(acac) 2 ) was first mixed homogeneously with a poly(2-vinylpridine) homopolymer (P2VP) and benzyl alcohol which serves as both the reduction agent for the metal salt and solvent for P2VP.…”

Phase Behavior of Block Copolymer Nanocomposite Systems

“…In the case of block-copolymer/ nanoparticle mixtures, adding colloids can reduce the critical electric field needed to induce alignment of the domains with the external electric field [2]. Block copolymer (BCP) materials are strongly periodic, serving as perfect templates for controlled placement of colloids [3,4], resulting in highly ordered materials. In order to achieve a detailed control of the NP assembly within the BCP matrix it is necessary to be able to predict the phase behavior of the overall system once nanoparticles are added, as the distribution of nanoparticles critically depends on the morphology of the BCP, and the morphology itself is modified by the presence of NPs.…”

Fabrication of 3D‐Periodic Ordered Metallic Nanoparticles in a Block Copolymer Bulk Matrix via Oscillating Shear Flow

“…These nanostructures are usually based on inorganic materials as they are the basis for the special electric, optical and magnetic behavior present at the nanoscale. [1][2][3][4] Novel properties are usually achieved when nanostructures are hierarchically ordered in two and three-dimensional arrays. One approach in thin film uses Block Copolymers (BCPs) as templates to order inorganic nanoparticulates through electrodeposition and decoration techniques.…”

“…An attempt to explain the generation of the small nanoparticles with such a limited size and narrow distribution is as follows: the gold precursor is coordinated in stoichiometric amounts along the P4VP chains (one ion of AuCl 4 À per each pyridine group). Thus, the size and growth of the metallic gold clusters inside the P4VP block is limited.…”