Selectivity- and Size-Induced Segregation of Molecular and Nanoscale Species in Microphase-Ordered Triblock Copolymers

Abstract

Microphase-ordered block copolymers serve as model systems to elucidate the potential of molecular self-assembly and organic templates to fabricate functionalized polymeric materials. Both aspects are related to the incorporation of secondary species such as low-molar-mass compounds or nanoparticles within the copolymer matrices. Since the resulting properties of such functionalized copolymers critically depend on the morphology of the blend or composite, the nonrandom distribution of such inclusions within the copolymer matrix must be understood. Using a self-consistent field theoretical approach, we quantitatively evaluate the segregation and interfacial excess of low-molar-mass and nanoscale species in ordered triblock copolymers as functions of block selectivity and inclusion size. The predictions are found to agree with the morphology observed in a model triblock copolymer/nanoparticle composite, thereby demonstrating the generality of this approach. Our results suggest a wide correspondence in the structure-forming effect of molecular and nanoscale inclusions that will have implications in the design and processing of functional nanostructured polymers.

Nanoparticle-regulated phase behavior of ordered block copolymers

“…As seen in Fig. 1c, large neutral nanoparticles aggregate at interfaces 14,16 to reduce interfacial tension by decreasing A/B contacts and the driving force for copolymer demixing so that T ODT decreases. If small nanoparticles are selective (Fig.…”

“…1a and 1b, wherein the nanoparticles are almost uniformly distributed throughout the matrix. Opposing this spreading tendency is the energetic tendency for neutral nanoparticles to localize along the interface 16 to relieve interfacial tension (Fig. 1a).…”

Position transitions of polymer-grafted nanoparticles in diblock-copolymer nanocomposites

“…Among them, self-consistent field theory (SCFT) has proven to be a powerful method for exploring complex morphologies of block copolymers and blends [28][29][30][31][32]. Small bare nanoparticles can be regarded as large solvent molecules, and their distribution in ordered triblock copolymers has been evaluated by using SCFT [33]. For large nanoparticles in block copolymers, the effect of excluded volume of particles should be taken into account by such methods as a combination of SCFT with density functional theory (DFT) [34][35][36] and hybrid particle-field method [37].…”

“…In this paper, therefore, we theoretically investigate the self-assembly behavior of polymergrafted nanoparticle/diblock copolymer blends and the spatial position of nanoparticles within lamellar copolymer phases by employing the self-consistent field theory. The grafted nanoparticles are assumed to be sufficiently small so that they can be approximated as solvent molecules in the system [33]. The interactions among the nanoparticles, grafted polymers and copolymer matrix are all taken into account in our simulations because of their important roles in the self-assembling progress.…”

Controlled Ordering of Block Copolymer Thin Films by the Addition of Hydrophilic Nanoparticles

“…[5][6][7] When d/L g 0.3, they predict that the particles are localized around the center of domain due to the chain stretching penalty, while the particles move outward to the interface when d/L becomes smaller. Several experimental approaches have been developed to confirm this prediction, [8][9][10] and more recent work has examined the effect of chemistry where the surface of nanoparticle is tuned to allow favorable interactions between nanoparticles and block copolymers, which in turn allows their location to be influenced. [11][12][13][14] In addition to controlling the location of the nanoparticles, it would be highly desirable if the nanoparticles could also play an "active" role in the self-assembly process, such as directing the morphology and orientation of microstructures.…”