Order−Disorder and Order−Order Transitions in Mixtures of Highly Asymmetric Triblock Copolymer and Low Molecular Weight Homopolymers

2000 ◽  
Vol 33 (19) ◽  
pp. 7072-7083 ◽  
Author(s):  
Seung-Heon Lee ◽  
Kookheon Char ◽  
Ginam Kim
Keyword(s):  
Molecular Weight ◽  
Triblock Copolymer ◽  
Low Molecular Weight

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.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Low-molecular-weight heparin in the prevention and treatment of thromboembolic disorders

1998 ◽  
Vol 1 (5) ◽  
pp. 166-174 ◽  
Author(s):  
Evelyn R Hermes De Santis ◽  
Betsy S Laumeister ◽  
Vidhu Bansal ◽  
Vandana Kataria ◽  
Preeti Loomba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Molecular Weight ◽  
Prevention And Treatment
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