Forum für Wissenschaft, Industrie und Wirtschaft

Hauptsponsoren:     3M 


Polymer Membranes with Molecular-sized Channels That Assemble Themselves

Many futurists envision a world in which polymer membranes with molecular-sized channels are used to capture carbon, produce solar-based fuels, or desalinate sea water, among many other functions. This will require methods by which such membranes can be readily fabricated in bulk quantities. A technique representing a significant first step down that road has now been successfully demonstrated.

Researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have developed a solution-based method for inducing the self-assembly of flexible polymer membranes with highly aligned subnanometer channels. Fully compatible with commercial membrane-fabrication processes, this new technique is believed to be the first example of organic nanotubes fabricated into a functional membrane over macroscopic distances.

“We’ve used nanotube-forming cyclic peptides and block co-polymers to demonstrate a directed co-assembly technique for fabricating subnanometer porous membranes over macroscopic distances,” says Ting Xu, a polymer scientist who led this project. “This technique should enable us to generate porous thin films in the future where the size and shape of the channels can be tailored by the molecular structure of the organic nanotubes.”

Ting Xu holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley's Departments of Materials Sciences and Engineering, and Chemistry. (Photo by Roy Kaltschmidt, Berkeley Lab Public Affairs)

Xu, who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the University of California Berkeley’s Departments of Materials Sciences and Engineering, and Chemistry, is the lead author of a paper describing this work, which has been published in the journal ACS Nano. The paper is titled “Subnanometer Porous Thin Films by the Co-assembly of Nanotube Subunits and Block Copolymers.”

Co-authoring the paper with Xu were Nana Zhao, Feng Ren, Rami Hourani, Ming Tsang Lee, Jessica Shu, Samuel Mao, and Brett Helms, who is with the Molecular Foundry, a DOE nanoscience center hosted at Berkeley Lab.

Channeled membranes are one of nature’s most clever and important inventions. Membranes perforated with subnanometer channels line the exterior and interior of a biological cell, controlling – by virtue of size – the transport of essential molecules and ions into, through, and out of the cell. This same approach holds enormous potential for a wide range of human technologies, but the challenge has been finding a cost-effective means of orienting vertically-aligned subnanometer channels over macroscopic distances on flexible substrates.

“Obtaining molecular level control over the pore size, shape, and surface chemistry of channels in polymer membranes has been investigated across many disciplines but has remained a critical bottleneck,” Xu says. “Composite films have been fabricated using pre-formed carbon nanotubes and the field is making rapid progess, however, it still presents a challenge to orient pre-formed nanotubes normal to the film surface over macroscopic distances.”

Schematic drawing depicts process by which a polymer is tethered to cyclic peptides (8CP)then blended with block copolymers (BCPs) to make a membrane permeated with subnanometer channels in the form of organic nanotubes.

For their subnanometer channels, Xu and her research group used the organic nanotubes naturally formed by cyclic peptides – polypeptide protein chains that connect at either end to make a circle. Unlike pre-formed carbon nanotubes, these organic nanotubes are “reversible,” which means their size and orientation can be easily modified during the fabrication process. For the membrane, Xu and her collaborators used block copolymers – long sequences or “blocks” of one type of monomer molecule bound to blocks of another type of monomer molecule. Just as cyclic peptides self-assemble into nanotubes, block copolymers self-assemble into well-defined arrays of nanostructures over macroscopic distances. A polymer covalently linked to the cyclic peptide was used as a “mediator” to bind together these two self-assembling systems

“The polymer conjugate is the key,” Xu says. “It controls the interface between the cyclic peptides and the block copolymers and synchronizes their self-assembly. The result is that nanotube channels only grow within the framework of the polymer membrane. When you can make everything work together this way, the process really becomes very simple.”

Xu and her colleagues were able to fabricate subnanometer porous membranes measuring several centimeters across and featuring high-density arrays of channels. The channels were tested via gas transport measurements of carbon dioxide and neopentane. These tests confirmed that permeance was higher for the smaller carbon dioxide molecules than for the larger molecules of neopentane. The next step will be to use this technique to make thicker membranes.

“Theoretically, there are no size limitations for our technique so there should be no problem in making membranes over large area,” Xu says. “We’re excited because we believe this demonstrates the feasibility of synchronizing multiple self-assembly processes by tailoring secondary interactions between individual components. Our work opens a new avenue to achieving hierarchical structures in a multicomponent system simultaneously, which in turn should help overcome the bottleneck to achieving functional materials using a bottom-up approach.”

This research was supported by DOE’s Office of Science and by the U.S. Army Research Office. Measurements were carried out on beamlines at Berkeley Lab’s Advanced Light Source and at the Advanced Photon Source of Argonne National Laboratory.

Lawrence Berkeley National Laboratory is a U.S. Department of Energy (DOE) national laboratory managed by the University of California for the DOE Office of Science. Berkeley Lab provides solutions to the world’s most urgent scientific challenges including sustainable energy, climate change, human health, and a better understanding of matter and force in the universe. It is a world leader in improving our lives through team science, advanced computing, and innovative technology. Visit our at

Additional Information

For more information on the research of Ting Xu, visit her Website at

A copy of the paper in ACS Nano paper “Subnanometer Porous Thin Films by the Co-assembly of Nanotube Subunits and Block Copolymers” is available at

Lynn Yarris | EurekAlert!
Further information:

More articles from Materials Sciences:

nachricht Coming to a monitor near you: A defect-free, molecule-thick film
27.11.2015 | University of California - Berkeley

nachricht Controlling Electromagnetic Radiation by Graphene
27.11.2015 | Universität Augsburg

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tübinger Forscher entdecken neue Zelltypen im Gehirn

Untersuchung im Neocortex von Mäusen - Zusammenarbeit mit Wissenschaftlern aus Houston

Wissenschaftler aus Tübingen und Houston haben zahlreiche neue Zelltypen im Gehirn identifiziert. Im Neocortex von erwachsenen Mäusen führten sie erstmals eine...

Im Focus: Klimawandel: Forscher weisen dramatische Veränderung in den 1980er Jahren nach

Ende der 1980er Jahre erlebte die Erde eine dramatische Klimaveränderung. Sie umfasste die Tiefen der Ozeane ebenso wie die obere Atmosphäre und reichte vom Nord- bis zum Südpol. Ausgelöst durch den Ausbruch des Vulkans El Chichón in Mexico 1982 und verstärkt durch menschliches Handeln folgte daraus die größte Temperaturverschiebung der letzten 1.000 Jahre. Erstmals nachgewiesen hat dies ein internationales Forscherteam um Prof. Philip C. Reid von der Plymouth University und der Sir Alister Hardy Foundation for Ocean Science (UK). Die Ergebnisse wurden kürzlich in der Fachzeitschrift „Global Change Biology“ veröffentlicht.

Abrupte Klimaveränderungen haben oft dramatische Folgen für unseren Planeten. Dennoch sind sie in ihrer Art, ihrem Ausmaß und in ihrer Wirkungsweise meist nur...

Im Focus: Climate study finds evidence of global shift in the 1980s

Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fuelled by anthropogenic warming and a volcanic eruption, according to new research published this week.

Scientists say that a major step change, or ‘regime shift’, in the Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from...

Im Focus: Innovative Photovoltaik – vom Labor an die Fassade

Fraunhofer ISE demonstriert neue Zell- und Modultechnologien an der Außenfassade eines Laborgebäudes

Das Fraunhofer-Institut für Solare Energiesysteme ISE hat die Außenfassade eines seiner Laborgebäude mit 70 Photovoltaik-Modulen ausgerüstet. Die Module...

Im Focus: Innovative Photovoltaics – from the Lab to the Façade

Fraunhofer ISE Demonstrates New Cell and Module Technologies on its Outer Building Façade

The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...

Alle Focus-News des Innovations-reports >>>



im innovations-report
in Kooperation mit academics

Bürger treffen Experten: Gespräch zu Chancen und Risiken der Nanotechnologie am 30.11.2015

27.11.2015 | Veranstaltungen

Arbeit in Sozialen Dienstleistungen - Welche Zukunft hat die Branche?

27.11.2015 | Veranstaltungen

Konzepte nutzergerechter Fahrerarbeitsplatzgestaltung

26.11.2015 | Veranstaltungen

Weitere VideoLinks >>>
Aktuelle Beiträge

Künstliche Herzklappe nach dem Vorbild der Natur

27.11.2015 | Förderungen Preise

Siemens liefert 126 Megawatt Onshore-Windleistung nach Schottland

27.11.2015 | Unternehmensmeldung

Hauptkläranlage Wien wird mit Siemens zum Ökokraftwerk

27.11.2015 | Energie und Elektrotechnik