Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solution. The influence of relative block size

Mortensen, K.; Brown, Wyn

doi:10.1021/ma00068a010

Cited by 293 publications

(307 citation statements)

References 15 publications

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“…4,5 For an A-B-A type triblock copolymer, in a solvent selective for the A block, the association of the B blocks yields the brushlike core-shell micelles. [6][7][8] Recently, we have proposed a simple scaling for such formed nanostructures. 9 On the other hand, if the A block is insoluble, the association of the A blocks could be either an interchain or intrachain one, which makes the problem more complicated.…”

Section: Introductionmentioning

confidence: 99%

Self-Assembly of Poly(caprolactone-b-ethylene oxide-b-caprolactone) via a Microphase Inversion in Water

et al. 2001

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Triblock copolymer poly(caprolactone-b-ethylene oxide-b-caprolactone) (PCL-PEO-PCL) could self-assemble into narrowly distributed flowerlike "core-shell" micelles when its tetrahydrofuran solution was added dropwise into an excess of water. The core was formed via the aggregation of insoluble hydrophobic PCL blocks, while the shell was made of many hydrophilic PEO loops. The formation and stabilization of such micelles were examined by a combination of static and dynamic laser light scattering. The average hydrodynamic size decreased as the dispersion temperature increased, but there was no change in the average radius of gyration, indicating that the temperature dependence of 〈R h 〉 during heating or cooling was attributed to the conformation change of the PEO block. The composition dependent study revealed that using two short PCL blocks and a long PEO block unexpectedly lead to smaller micelles. The study of their biodegradation in the presence of enzyme Lipase PS shows possible biomedical applications of such formed polymeric micelles.

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Section: Introductionmentioning

confidence: 99%

Self-Assembly of Poly(caprolactone-b-ethylene oxide-b-caprolactone) via a Microphase Inversion in Water

et al. 2001

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“…During the micelle formation process there are three temperature regions of importance: the unimer region (where the surfactants are not aggregated), the transition region, and the micelle region [84,85].…”

Section: Temperature Dependencementioning

confidence: 99%

“…Above the CMT the spherical micelles increase in size with increasing temperature until the micellar core reaches the radius of a completely stretched PPO chain. At this point the structure of the micelles changes from spheres to cylinders [85]. Figure 9.…”

Section: Temperature Dependencementioning

confidence: 99%

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

Björk¹

2013

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On the cover, the structure of SBA-15 is illustrated. Inside the pores SEM micrographs have been inserted showing (clockwise from the top): rods, fibers, a film consisting of rods grown on a substrate, a film consisting of platelets grafted on a substrate, short rods, and platelets. In the center the sheet morphology is presented.© Emma Björk, unless otherwise stated.ISBN: 978-91-7519-516-2 ISSN: 0345-7524 Printed by LiU-tryck, Linköping, Sweden, 2013 Research is formalized curiosity. It is poking and prying with a purposeZora Neale Hurston (1903Hurston ( -1960 i ABSTRACTCatalyst supports, drug delivery systems, hosts for nanoparticles, and solar cells are just some examples of the wide range of exciting applications for mesoporous silica. In order to optimize the performance of a specific application, controlling the material's morphology and pore size is crucial. For example, short and separated particles are beneficial for drug delivery systems, while for molecular sieves, the pore size is the key parameter.In this thesis, mesoporous silica building blocks, crystallites, with hexagonally ordered cylindrical pores were synthesized, with the aim to understand how the synthesis parameters affect the particle morphology and pore size. The synthesis of the particles is performed using a sol-gel process, and in order to increase the pore size, a combination of low temperature, and additions of heptane and NH 4 F was used. By variations in the amounts of reagents, as well as other synthesis conditions, the particle morphology and pore size could be altered. Separated particles were also grown on or attached to substrates to form films. Also, a material with spherical pore structure was synthesized, for the first time using this method.It was found that a variation in the heptane concentration, in combination with a long stirring time, yields a transition between fiber and sheet morphologies. Both morphologies consist of crystallites, which for the fibers are joined end to end, while for the sheets they are attached side by side such that the pores are accessible from the sheet surface. The crystallites can be separated to a rod morphology by decreasing the stirring time and tuning the HCl concentration, and it was seen that these rods are formed within 5 min of static time, even though the pore size and unit cell parameters were evolving for another 30 min. Further studies of the effects of heptane showed that the shape and mesoscopic parameters of the rods are affected by the heptane concentration, up to a value where the micelles are fully saturated with heptane. It was also observed that the particle width increases with decreasing NH 4 F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH 4 F, and the growth mechanism for platelets was further studied. The pore sizes for various morphologies were altered by e.g. variations in the hydrothermal treatment conditions, or the method for removing the surfactants.ii T...

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“…The thermodynamics, phase behavior, and thermoreversible gelation of this set of block copolymers are well known [3][4][5][6][7][8][9][10][11][12]. At temperatures below about 15 °C both blocks are soluble in water.…”

Section: Open Accessmentioning

confidence: 99%

Structural and Mechanical Hysteresis at the Order-Order Transition of Block Copolymer Micellar Crystals

LaFollette

Walker

2011

Polymers

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Concentrated solutions of a water-soluble block copolymer (PEO) 20 -(PPO) 70 -(PEO) 20 show a thermoreversible transition from a liquid to a gel. Over a range of concentration there also exists an order-order transition (OOT) between cubically-packed spherical micelles and hexagonally-packed cylindrical micelles. This OOT displays a hysteresis between the heating and cooling transitions that is observed at both the macroscale through rheology and nanoscale through small angle neutron scattering (SANS). The hysteresis is caused by the persistence of the cubically-packed spherical micelle phase into the hexagonally-packed cylindrical micelle phase likely due to the hindered realignment of the spherical micelles into cylindrical micelles and then packing of the cylindrical micelles into a hexagonally-packed cylindrical micelle phase. This type of hysteresis must be fully characterized, and possibly avoided, for these block copolymer systems to be used as templates in nanocomposites.

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Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers in aqueous solution. The influence of relative block size

Cited by 293 publications

References 15 publications

Self-Assembly of Poly(caprolactone-b-ethylene oxide-b-caprolactone) via a Microphase Inversion in Water

Self-Assembly of Poly(caprolactone-b-ethylene oxide-b-caprolactone) via a Microphase Inversion in Water

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

Structural and Mechanical Hysteresis at the Order-Order Transition of Block Copolymer Micellar Crystals

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