Self-Assembled Block Copolymer–Nanoparticle Hybrids: Interplay between Enthalpy and Entropy

Abstract

The dispersion of nanoparticles in ordered block copolymer nanostructures can provide control over particle location and orientation, and pave the way for engineered nanomaterials that have enhanced mechanical, electrical, or optical properties. Fundamental questions pertaining to the role of enthalpic and entropic particle-polymer interactions remain open and motivate the present work. We consider here a system of 10.6 nm silica nanoparticles (NPs) dispersed in ordered cylinders formed by hydrated poly(ethylene oxide)-poly(propylene oxide) block copolymers (Pluronic P105: EO(37)PO(56)EO(37)). Protonation of silica was used to vary the NP-polymer enthalpic interactions, while polar organic solvents (glycerol, DMSO, ethanol, and DMF) were used to modulate the NP-polymer entropic interactions. The introduction of deprotonated NPs in the place of an equal mass of water did not affect the lattice parameter of the PEO-PPO-PEO block copolymer hexagonal lyotropic liquid crystalline structures. However, the dispersion of protonated NPs led to an increase in the lattice parameter, which was attributed to stronger NP-polymer hydrogen bonding (enthalpic) interactions. Dispersion of protonated NPs into cylindrical structures formed by Pluronic P105 in 80/20 water/organic solvents does not influence the lattice parameter, different from the case of protonated NP in plain water. Organic solvents appear to screen the NP-polymer hydrogen bonding interactions.

Block copolymer–nanoparticle composites: Structure, functional properties, and processing

“…Several studies have shown that NP incorporation into a specific location of ordered BCPs caused order-to-order phase transitions [67,78,118,119,120,121]. In addition to inducing structural transitions, NP incorporation can also influence the characteristic size of the nanodomains [75,122]. Below we discuss the effect of NPs on the overall phase behavior / morphology and on the characteristic length-scales of BCP nanostructures.…”

“…A c c e p t e d M a n u s c r i p t 9 The location of NPs and the overall BCP-NP morphology are dictated by properties of the NPs (such as size, concentration, and surface chemistry), properties of the block copolymers (such as chemistry, conformation, and molecular weight), and the presence of small molecules [73][74][75].…”

“…A c c e p t e d M a n u s c r i p t 13 Additives can also modify NP-polymer interactions by modifying NP surfaces [75,109,110].…”

“…For example, certain organic solvents can hydrogen bond with protonated silica NPs and, as a result, these organic solvents screen NP-polymer hydrogen bonding interactions [75,109], that may provide further control over particle-polymer interactions and particle location. [112][113][114][115]) that changes the interfacial curvature.…”

Functionalization of POSS nanoparticles and fabrication of block copolymer nanocomposite membranes for CO2 separation

“…An efficient method of controlling the enthalpy interactions is the modification of the nanoparticle surface by grafting of organic ligands. These should be chemically compatible with one of the blocks of the block copolymer [25][26][27][28][29]. Quite recently we have reported the influence of PEG POSS Ò (poly (ethylene glycol) functionalized POSS) incorporation in two grades of the commercial poly(ether-block-amide) thermoplastic elastomer PEBAX Ò upon CO 2 separation performance [30,31].…”