Synthesis and Characterization of Poly[1,4-isoprene-b-(ethylene oxide)] and Poly[ethylene-co-propylene-b-(ethylene oxide)] Block Copolymers

Allgaier, Jürgen; Poppe, A.; Willner, Lutz; Richter, D.

doi:10.1021/ma961311q

Cited by 116 publications

(122 citation statements)

References 19 publications

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“…Two stock solutions for high and low refractive index layers were then prepared separately. For T3:1, 1.31 ml sol was mixed with 0.1 g of a isoprene-ethylene oxide block-copolymer (PI-b-PEO) (molecular weight Mn = 34.4 kg mol − 1, 28 wt% PEO) 19 in tetrahydrofuran (THF, 7 ml). The solution was then poured into a petri dish at 50…”

Section: Methodsmentioning

confidence: 99%

Tunable Mesoporous Bragg Reflectors Based on Block‐Copolymer Self‐Assembly

et al. 2011

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Distributed Bragg reflectors (DBRs) consist of periodically alternating layers of high and low refractive index materials, also known as one-dimensional photonic crystals. Interference of light reflected at the interfaces of the dielectric layers leads to strong reflection in a well defined wavelength range resulting in pronounced structural colouration. The spectral response can be finely tuned by varying the refractive index, the thickness, and the number of the alternating layers.1 Simple configurations are realized by sequential coating of thin solid films of alternating refractive index. Direct access to a 1D dielectric lattice via solution processing has been achieved by the self-assembly of block copolymers into a lamellar morphology. 2, 3A interesting recent area of research is the development of mesoporous DBRs (MDBRs) which access new fields of applications due to their porosity on the sub-optical length scale. MDBRs are promising as sensing materials. The adsorption and desorption of gas phase molecules in the pores leads to reversible changes in the refractive index and thereby in the photonic properties of the stack.4-7 Bonifacio et al. introduced the concept of a MDBR-based "photonic nose".8 Other applications include the use of MDBRs as environmentally responsive resonance cavities 10, 11 and their coupling to mesoporous surface layers.12 MDBRs also have great potential in optoelectronic devices. When infiltrated with light emitting polymers, MDBRs have exhibited distributed feedback lasing.13 Efficiency enhancements have been demonstrated by integrating a MDBR into a dye-sensitized solar cell.14 Recently, the coupling of plasmonic particles to MDBR-based resonant cavities has been shown. 15Typically, the refractive index contrast is realized by the alternating deposition of mesoporous layers of TiO 2 and SiO 2 . This concept was first introduced by Ozin and coworkers, who manufactured a TiO 2 /SiO 2 stack with ordered mesoporous morphologies, following a block copolymer directed sol-gel route.4 While the MDBRs exhibited an interconnected pore network, the stack fabrication was extremely time consuming with fabrication times of 4 days or more for each consecutive layer.4, 5 A less complex alternative is the sequential deposition of nanoparticle-based solutions to form mesoporous films. The group of Cohen introduced this concept for a homopolymer mediated nanoparticle approach following numerous dip-coating cycles.9 Miguez et al. subsequently presented

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Section: Methodsmentioning

confidence: 99%

Tunable Mesoporous Bragg Reflectors Based on Block‐Copolymer Self‐Assembly

et al. 2011

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“…Details of the two-step procedure can be found in an earlier publication (Allgaier et al 1997). The Pb-Peo block copolymer was characterized by size exclusion chromatography (SEC) using a mixture of tetrahydrofuran/dimethylacetamide 90/10 v/v as eluant.…”

Section: Methodsmentioning

confidence: 99%

Dynamic response of block copolymer wormlike micelles to shear flow

Lonetti

Kohlbrecher

Willner

et al. 2008

J. Phys.: Condens. Matter

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The linear and nonlinear dynamic response to an oscillatory shear flow of giant wormlike micelles consisting of Pb-Peo block copolymers is studied by means of Fourier transform rheology. Experiments are performed in the vicinity of the isotropic-nematic phase transition concentration, where the location of isotropic-nematic phase transition lines is determined independently. Strong shear-thinning behaviour is observed due to critical slowing down of orientational diffusion as a result of the vicinity of the isotropic-nematic spinodal. This severe shear-thinning behaviour is shown to result in gradient shear banding. Time-resolved small-angle neutron scattering experiments are used to obtain an insight into the microscopic phenomena that underlie the observed rheological response. An equation of motion for the order parameter tensor and an expression of the stress tensor in terms of the order parameter tensor are used to interpret the experimental data, both in the linear and nonlinear regimes. Scaling of the dynamic behaviour of the orientational order parameter and the stress is found when critical slowing down due to the vicinity of the isotropic-nematic spinodal is accounted for.

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“…Two different poly(isoprene-b-ethylene oxide) (PI-b-PEO) amphiphilic diblock copolymers synthesized via anionic polymerization techniques were used in this study. 22 Gel permeation chromatography (GPC) was employed to determine the precursor (polyisoprene) molecular weight and the dispersity of the block copolymers. 1 H NMR was used to determine the relative volume fractions of individual blocks and the microstructure of the PI blocks.…”

Section: Experimental Methodsmentioning

confidence: 99%

Flow-Induced Alignment of Block Copolymer−Sol Nanoparticle Coassemblies toward Oriented Bulk Polymer−Silica Hybrids

et al. 2005

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Macroscopically oriented bulk organic-inorganic hybrid materials were cast from solutions subjected to hydrodynamic flow by utilizing a simple flow device. The hybrids were prepared from an amphiphilic diblock copolymer, poly(isoprene-block-ethylene oxide) (PI-b-PEO), used as a structure directing agent for organically modified ceramic precursors, (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and aluminum sec-butoxide (Al(O s Bu)3), prehydrolyzed into sol nanoparticles. Varying amounts of these ceramic precursors (sol) were used to obtain different mesoscale structures, i.e., lamellae, and the regular and inverse hexagonal mesophases. To align the microstructure, flow fields were applied during microstructure setting. To this end, a custom-built device operated in a Bü chi evaporator subjected solutions of the polymer and ceramic precursors to a steady flow while the solvent evaporated. The flow induced a shearing force causing macroscopic alignment of the mesoscale structures. Small-angle X-ray scattering (SAXS) was used to characterize the oriented hybrids. From these data order parameters were calculated to quantify the degree of alignment in the hybrids in different directions. Order parameters as high as 0.77 were obtained for hybrids with lamellae lying parallel to the substrate. Alignment could also be evidenced in the hexagonal and inverse hexagonal samples with cylinder orientations along the flow direction. The results suggest the efficacy of this relatively simple flow technique in providing bulk polymer-inorganic hybrids with macroscopic alignment needed for realization of their true application potential.

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Synthesis and Characterization of Poly[1,4-isoprene-b-(ethylene oxide)] and Poly[ethylene-co-propylene-b-(ethylene oxide)] Block Copolymers

Cited by 116 publications

References 19 publications

Tunable Mesoporous Bragg Reflectors Based on Block‐Copolymer Self‐Assembly

Tunable Mesoporous Bragg Reflectors Based on Block‐Copolymer Self‐Assembly

Dynamic response of block copolymer wormlike micelles to shear flow

Flow-Induced Alignment of Block Copolymer−Sol Nanoparticle Coassemblies toward Oriented Bulk Polymer−Silica Hybrids

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