Perpendicularly Aligned, Size-and Spacing-Controlled Nanocylinders by Molecular-Weight Adjustment of a Homopolymer Blended in an Asymmetric Triblock Copolymer

2006 ◽  
Vol 16 (15) ◽  
pp. 1950-1958 ◽  
Author(s):  
D. U. Ahn ◽  
E. Sancaktar
Keyword(s):  
Molecular Weight ◽  
Triblock Copolymer

scholarly journals Hydrophilic Dual Layer Hollow Fiber Membranes for Ultrafiltration

Membranes ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 143
Author(s):  
Lara Grünig ◽  
Ulrich A. Handge ◽  
Joachim Koll ◽  
Oliver Gronwald ◽  
Martin Weber ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hollow Fiber ◽  
Triblock Copolymer ◽  
Pure Water ◽  
Vinyl Pyrrolidone ◽  
Scattering Data ◽  
Coupling Mechanism ◽  
Additive Concentration ◽  
Hollow Fiber Membranes ◽  
Fiber Membranes

In this study, a triblock copolymer was used as additive to fabricate new dual layer hollow fiber membranes with a hydrophilic active inner surface in order to improve their fouling resistance. The polymeric components of the solutions for membrane fabrication were poly(ether sulfone), poly(N-vinyl pyrrolidone), and the triblock copolymer. The additive consists of three blocks: a middle hydrophobic poly(ether sulfone) block and two outer hydrophilic alkyl poly(ethylene glycol) blocks. By varying the additive concentration in the solutions, it was possible to fabricate dual layer hollow fiber membranes that are characterized by a hydrophilic inner layer, a pure water permeance of over 1800 L/(m2 bar h) and a molecular weight cut-off of 100 kDa similar to commercial membranes. Contact angle and composition determination by XPS measurements revealed the hydrophilic character of the membranes, which improved with increasing additive concentration. Rheological, dynamic light scattering, transmission, and cloud point experiments elucidated the molecular interaction, precipitation, and spinning behavior of the solutions. The low-molecular weight additive reduces the solution viscosity and thus the average relaxation time. On the contrary, slow processes appear with increasing additive concentration in the scattering data. Furthermore, phase separation occurred at a lower non-solvent concentration and the precipitation time increased with increasing additive content. These effects revealed a coupling mechanism of the triblock copolymer with poly(N-vinyl pyrrolidone) in solution. The chosen process parameters as well as the additive solutions provide an easy and inexpensive way to create an antifouling protection layer in situ with established recipes of poly(ether sulfone) hollow fiber membranes. Therefore, the membranes are promising candidates for fast integration in the membrane industry.

Direct Imaging of Non-Classical Triblock Copolymer Blend and Gel Morphologies in the Dilute Regime

1996 ◽  
Vol 54 ◽  
pp. 188-189
Author(s):  
Jonathan H. Laurer ◽  
Richard J. Spontak ◽  
Steven D. Smith ◽  
Rudy Bukovnik
Keyword(s):  
Molecular Weight ◽  
Self Assembly ◽  
Triblock Copolymer ◽  
Morphological Changes ◽  
Low Molecular Weight ◽  
Conformationally Constrained ◽  
Morphological Studies ◽  
Homopolymer Blends ◽  
Copolymer Blend ◽  
Copolymer Micelles

Incorporation of a low-molecular-weight, midblock-selective homopolymer into the microstructure of a microphase-ordered triblock copolymer results in preferential midblock swelling or a morphological transition, depending on the blend concentration and the size of the homopolymer chain relative to that of the host block. Since the blend properties are strongly dependent on the existing microstructure, morphological changes induced by variation in blend composition have attracted considerable interest. Recent efforts have sought to discern the phase stability of both copolymer-rich (concentrated) blends, in which parent homopolymer molecules are contained within their preferred microphase, and homo-polymer-rich (dilute) blends, in which the copolymer molecules micellize to reduce repulsive interactions in a parent homopolymer matrix. Since dilute blends typically consist of spherical copolymer micelles, most morphological studies have focused on concentrated copolymer/homopolymer blends in order to (i) tailor the blend microstructure, and properties, at the molecular level and (ii) examine macromolecular mixing in conformationally constrained nanoscale environments. In this work, we return to the dilute copolymer/homopolymer blend regime and examine the self-assembly of triblock copolymer molecules in the presence of low-molecular-weight parent and nonparent homopolymers and, in some cases, an oil.

Interface-Induced Morphology Transition in Triblock Copolymer Films Swollen with Low-Molecular-Weight Homopolymer†

Langmuir ◽  
2009 ◽  
Vol 25 (7) ◽  
pp. 4235-4242 ◽  
Author(s):  
P. Müller-Buschbaum ◽  
L. Schulz ◽  
E. Metwalli ◽  
J.-F. Moulin ◽  
R. Cubitt
Keyword(s):  
Molecular Weight ◽  
Triblock Copolymer ◽  
Low Molecular Weight ◽  
Morphology Transition ◽  
Copolymer Films

Phase Behavior of Triblock Copolymers upon Incorporation of Non-Parent, Midblock-Associating Additives

1996 ◽  
Vol 461 ◽  
Author(s):  
J. H. Laurer ◽  
J. F. Mulling ◽  
R. Bukovnik ◽  
R. J. Spontak
Keyword(s):  
Molecular Weight ◽  
Block Copolymer ◽  
Phase Behavior ◽  
Triblock Copolymer ◽  
Triblock Copolymers ◽  
Thermoplastic Elastomer ◽  
Low Molecular Weight ◽  
Repulsive Interactions

ABSTRACTAddition of a block-selective homopolymer to a microphase-ordered block copolymer is known to result in preferential swelling of the chemically compatible microdomain. In this work, we examine the miscibility between a triblock copolymer and a relatively low-molecular-weight, chemically dissimilar, midblock-associating homopolymer and demonstrate that the homopolymer molecules residing in the swollen midblock matrix self-assemble to avoid repulsive interactions with neighboring microdomains. We extend this investigation to include systems composed of a very low-molecular-weight, midblock-associating additive (an oil). At high oil concentrations, the glassy copolymer endblocks micellize, resulting in the formation of a thermoplastic elastomer gel.

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