ORCID Profile
0000-0002-6182-739X
Current Organisation
University of Queensland
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Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SM02460A
Abstract: This study investigates the parameters that affect the dispersion of polymer grafted mesoscopic iron-oxide rods (FeMRs) in polymer matrices. FeMRs (212 nm long by 36 nm in diameter) are grafted with poly(methyl methacrylate) (PMMA) at three different brush molecular weights: 3.7 kg mol(-1), 32 kg mol(-1), and 160 kg mol(-1). Each FeMR s le was cast in a polymer thin film consisting of either PMMA or poly(ethylene oxide) (PEO) each at a molecular weight much higher or much lower than the brush molecular weight. We find that the FeMRs with 160 kg mol(-1) brush disperse in all matrices while the FeMRs with 32 kg mol(-1) and 3.7 kg mol(-1) brushes aggregate in all matrices. We perform simple free energy calculations, taking into account steric repulsion from the brush and van der Waals attraction between FeMRs. We find that there is a barrier for aggregation for the FeMRs with the largest brush, while there is no barrier for the other FeMRs. Therefore, for these mesoscopic particles, the brush size is the main factor that determines the dispersion state of FeMRs in polymer matrices with athermal or weakly attractive brush-matrix interactions. These studies provide new insight into the mechanisms that affect dispersion in polymer matrices of mesoscopic particles and therefore guide the design of composite films with well-dispersed mesoscopic particles.
Publisher: Springer Science and Business Media LLC
Date: 24-01-2014
Publisher: American Chemical Society (ACS)
Date: 07-07-2017
DOI: 10.1021/ACS.LANGMUIR.7B01449
Abstract: Here, we introduce a technique for the direct formation of semisoft colloidal crystals of hybrid particles in nonvolatile ionic liquid (IL) solvents. The hybrid particles are comprised of a silica core and a densely grafted polymer brush shell, which were synthesized by surface-initiated living radical polymerization. A phase transition of the suspensions from a disordered fluid to a crystallized system was observed within a narrow concentration range. Confocal laser scanning microscopy observation and ultraviolet-visible light (UV-vis) spectrometry confirmed the highly ordered structure of the hybrid particles in ionic liquids. The effect of the hybrid particle structure on the photonic band gap of the colloidal crystals was investigated, and the band gaps varied by changing graft chain lengths. In addition, the colloidal crystal suspensions were successfully immobilized in ILs.
Publisher: American Chemical Society (ACS)
Date: 09-01-2015
DOI: 10.1021/LA504429C
Abstract: We investigated the surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate (MMA) using monodisperse rod-type particles of iron oxide, β-FeOOH. The slow hydrolysis of iron(III) chloride yielded monodisperse β-FeOOH rods with an average length-to-width ratio, L/W, of 6 (L = 210 nm and W = 35 nm on average). The surfaces of the β-FeOOH rods were modified with a triethoxysilane derivative as an ATRP-initiating site, namely, (2-bromo-2-methyl)propionyloxypropyl triethoxysilane. The SI-ATRP of MMA, mediated by a copper complex, was performed using the initiator-coated β-FeOOH rods in the presence of a "sacrificial" free initiator. Well-defined poly(methyl methacrylate) (PMMA) brushes with molecular weights of up to 700,000 could be grafted on the β-FeOOH rods with a surface density as high as 0.3 chains/nm(2). The resultant polymer-brush-afforded hybrid rods exhibited high dispersibility in various solvents for PMMA without forming aggregates. Thin films were prepared by dip-coating from a suspension of the hybrid rods, and the rods were oriented in a specific direction in the films. The arrangement of the rods could be controlled by varying the chain length of the polymer brush and the withdrawal speed during the dip-coating process.
Publisher: American Chemical Society (ACS)
Date: 05-10-2010
DOI: 10.1021/MA1018389
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR06400G
Abstract: Monodisperse silica nanoparticles (SiNPs) grafted with well-defined and highly dense polystyrene brushes are used as building blocks for the formation of three-dimensional (3D) colloidal crystals.
Publisher: Springer Science and Business Media LLC
Date: 07-12-2013
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9PY00200F
Abstract: Spatially controlling self-assembly of block copolymer thin films through photoinduced molecular interactions that significantly impact on the glass transition temperature.
Publisher: American Chemical Society (ACS)
Date: 31-10-2011
DOI: 10.1021/MA202105Y
Publisher: American Chemical Society (ACS)
Date: 31-10-2016
Publisher: American Chemical Society (ACS)
Date: 17-06-2014
DOI: 10.1021/LA5011488
Abstract: An immobilization technique for semisoft colloidal crystals, which are ordered arrays of polymer-brush-afforded hybrid particles synthesized by surface-initiated living radical polymerization (SI-LRP), is reported. Silica particles were first grafted with well-defined block copolymers of poly(methyl methacrylate-co-hydroxyethyl methacrylate)-b-poly(methyl methacrylate), P(MMA-co-HEMA)-b-PMMA by SI-LRP, which gave a graft density as high as 0.7 chains/nm(2). The HEMA units reacted with 2-isocyanatoethyl methacrylate to introduce vinyl groups at the outer layer of the polymer-brush shell. The modified hybrid particles formed a colloidal crystal in a solution containing a small amount of free polymers with vinyl groups. The colloidal crystal was photoirradiated in the presence of a photoradical initiator to immobilize it through a cross-linking reaction among the vinyl groups. The structural analyses of the colloidal crystals before and after the photoirradiation were carried out by confocal laser scanning microscopy the results showed that the periodic structures of the crystals were maintained after immobilization.
Location: Australia
No related grants have been discovered for Yun Huang.