Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

Nanostructured soft materials open up new opportunities in material design and application, and block copolymer self-assembly is one particularly powerful phenomenon that can be exploited for their synthesis. The advent of controlled/living radical polymerisation (CLRP) has greatly simplified block copolymer synthesis, and versatility towards monomer types and polymer architectures across the different forms of CLRP has vastly expanded the range of functional materials accessible. CLRP-controlled synthesis of block copolymers has been applied in heterogeneous systems, motivated by the numerous process advantages and the position of emulsion polymerisation at the forefront of industrial latex synthesis. In addition to the inherent environmental advantages of heterogeneous routes, the incidence of block copolymer self-assembly within dispersed particles during polymerisation leads to novel nanostructured materials that offer enticing prospects for entirely new applications of block copolymers. Here, we review the range of block copolymers prepared by heterogeneous CLRP techniques, evaluate the methods applied to maximise purity of the products, and summarise the unique nanoscale morphologies resulting from in situ self-assembly, before discussing future opportunities within the field

The Effect of Modified AuNPs on the Morphology and Nanostructure Orientation of PPMA-b-PMMA Block Copolymer Thin Films

Block copolymer/inorganic nanoparticle hybrids draw great attention of scientists from various areas for their potential applications in diverse fields such as microelectronics, sensors, and solar cells. Inorganic nanoparticles (NPs) can be expected to be incorporated into block copolymers with order and selectivity by self-assembly of NPs and/or by synergistic self-assembly between NPs and block copolymers. The morphology and nanostructure order of block copolymers can be also adjusted and directed by incorporation of NPs. In this study, the effect of the size and modification of AuNPs on the morphology and nanostructure orientation of block copolymer PPMA-b-PMMA thin films were systematically investigated. The lateral BCP structure in thin films was improved by adding AuNPs. The controlled location of AuNPs in the BCP thin films depended on the particle size and stabilizing species. The re-orientation of cylindrical domains depended on the modification of AuNPs. PPMA-coated AuNPs, corresponding to the lower surface energy component of BCP, were powerful in directing the cylinders from parallel to perpendicular to the substrate. These results provide a general guide for other BCP/inorganic NP hybrid systems for desired morphology and nanostructure orientation

In situ Crosslinking of Nanostructured Block Copolymer Microparticles in Supercritical Carbon Dioxide

We report a novel and facile approach to “fix” the internal nanostructure of block copolymer (BCP) microparticles via in situ crosslinking copolymerisation in dispersion in supercritical CO2 (scCO2). By delaying the addition of the crosslinker and a portion of the second monomer, polymerisation induced microphase separation (PIMS) within the microparticles is well preserved, while the growing chains of precursor poly(methyl methacrylate)-block-poly(4-vinyl pyridine) (PMMA-b-P4VP) or poly(methyl methacrylate)-block-poly(benzyl methacrylate) (PMMA-b-PBzMA) microparticles are crosslinked. The unique structure of the as-synthesised crosslinked microparticles were fully characterised using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, the swelling and solubility behaviour of the crosslinked PMMA-b-P4VP microparticles was investigated. Notably, the porosity generated by swelling in ethanol can be well controlled by the quantity of crosslinker incorporated. Macropores > 100 nm – ~20 nm, sub-10 nm mesopores, and non-porous microparticles were all achieved by varying the crosslinker incorporation from 0, 0.5, 1, to 4 wt%, respectively. In situ AFM nanomapping of the crosslinked P4VP domains in 80% humidity revealed that microparticles with a high degree of crosslinking (8 wt% divinylbenzene) are highly resistant to swelling in humidity, by contrast to their non-crosslinked counterparts. This versatile approach further expands the available repertoire for fabricating porous BCP microparticles with tunable physico-chemical properties, morphologies and pore sizes, greatly broadening their application potential to more diverse fields

A facile route to bespoke macro- and mesoporous block copolymer microparticles

We report a facile and versatile strategy for the bespoke fabrication of macro- and mesoporous block copolymer microparticles. A clean synthetic route, RAFT dispersion polymerisation in supercritical carbon dioxide (scCO2), is used to generate block copolymer microparticles. Selective swelling/deswelling is then applied to induce controlled morphology transitions and to trap the resulting porous state. The pore sizes are controllable over a large size range (~20 – 200 nm) by varying the length of the swellable block. Through a systematic approach we then demonstrate that the shape of the pores can also be tailored from isolated spheres through to interconnected/bicontinuous channels by varying the ratio of the two blocks. This process is shown to be applicable to a range of poly(methyl methacrylate) (PMMA)based block copolymer systems, including PMMA-b-poly(4-vinyl pyridine), PMMAb-poly(dimethyl acrylamide) (DMA) and PMMA-bpoly(dimethylaminoethylmethacrylate) (DMAEMA). In each case, the second minority block (e.g. P4VP, etc.) was selectively swollen with an alcohol to induce an order-toorder morphology transition and then quenched rapidly by the non-solvent hexane. This not only takes place on the order of hours, but is also freely scalable for the production of grams of material and beyond in a single step following polymerisation

The Effect of Modified AuNPs on the Morphology and Nanostructure Orientation of PPMA-b-PMMA Block Copolymer Thin Films

Block copolymer/inorganic nanoparticle hybrids draw great attention of scientists from various areas for their potential applications in diverse fields such as microelectronics, sensors, and solar cells. Inorganic nanoparticles (NPs) can be expected to be incorporated into block copolymers with order and selectivity by self-assembly of NPs and/or by synergistic self-assembly between NPs and block copolymers. The morphology and nanostructure order of block copolymers can be also adjusted and directed by incorporation of NPs. In this study, the effect of the size and modification of AuNPs on the morphology and nanostructure orientation of block copolymer PPMA-b-PMMA thin films were systematically investigated. The lateral BCP structure in thin films was improved by adding AuNPs. The controlled location of AuNPs in the BCP thin films depended on the particle size and stabilizing species. The re-orientation of cylindrical domains depended on the modification of AuNPs. PPMA-coated AuNPs, corresponding to the lower surface energy component of BCP, were powerful in directing the cylinders from parallel to perpendicular to the substrate. These results provide a general guide for other BCP/inorganic NP hybrid systems for desired morphology and nanostructure orientation

The Effect of Modified AuNPs on the Morphology and Nanostructure Orientation of PPMA-b-PMMA Block Copolymer Thin Films

Block copolymer/inorganic nanoparticle hybrids draw great attention of scientists from various areas for their potential applications in diverse fields such as microelectronics, sensors, and solar cells. Inorganic nanoparticles (NPs) can be expected to be incorporated into block copolymers with order and selectivity by self-assembly of NPs and/or by synergistic self-assembly between NPs and block copolymers. The morphology and nanostructure order of block copolymers can be also adjusted and directed by incorporation of NPs. In this study, the effect of the size and modification of AuNPs on the morphology and nanostructure orientation of block copolymer PPMA-b-PMMA thin films were systematically investigated. The lateral BCP structure in thin films was improved by adding AuNPs. The controlled location of AuNPs in the BCP thin films depended on the particle size and stabilizing species. The re-orientation of cylindrical domains depended on the modification of AuNPs. PPMA-coated AuNPs, corresponding to the lower surface energy component of BCP, were powerful in directing the cylinders from parallel to perpendicular to the substrate. These results provide a general guide for other BCP/inorganic NP hybrid systems for desired morphology and nanostructure orientation

Photochemical Preparation of Selenium-rGO Composite for Application in Photocatalytic Degradation

Abstract Se-rGO composite photocatalyst was prepared by photochemical method and improved Hummers method. The morphology and structure of the photocatalyst were characterized by SEM and XRD. The photocatalytic properties of the composite were studied by degrading RhB under UV light. The results showed that the composite retained the original mophorlogy of selenium and graphene oxide after compounding, where a large number of spherical Se particles are clustered and loaded on the surface of GO layers; hexagonal phase is observed in the pattern of pure Se, and the crystalline structure remains unchanged after compounding GO. The photocatalytic activity of the composite is more than twice as high as that of the pure Se. Moreover, the photocatalytic activity of the photochemical prepared Se-rGO composite is much higher than that of the mechanically mixed Se/GO. Se-rGO composite has good photocatalytic performance and the degradation process conforms well to the first-order reaction kinetics. The degradation rate of RhB solution can reach 76.8% after 120 minutes of UV irradiation.</jats:p