Home > Press > Polymer membranes with molecular-sized channels assemble themselves
 |
| Image (a) is an AFM image of a polymer membrane whose dark core corresponds to organic nanotubes. (b) is a TEM showing a sub-channeled membrane with the organic nanotubes circled in red. Inset shows zoomed-in image of a single nanotube. Credit: Image from Ting Xu |
Abstract:
Many futurists envision a world in which polymer membranes with molecular-sized channels are used to capture carbon, produce solar-based fuels, or desalinating 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.
Polymer membranes with molecular-sized channels assemble themselves
Berkeley, CA | Posted on January 12th, 2011
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."
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."
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.
####
About Lawrence Berkeley 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 www.lbl.gov
For more information, please click here
Contacts:
Lynn Yarris
510-486-5375
Copyright © Lawrence Berkeley National Laboratory
If you have a comment, please
Contact us.
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Bookmark:
Thin films
3-D printing could lead to tiny medical implants, electronics, robots, more June 18th, 2013
Beneq’s comprehensive industrial Thin Film Coating Services shorten time to market June 18th, 2013
News and information
Pioneering breakthrough of chemical nanoengineering to design drugs controlled by light June 18th, 2013
Study Shows How the Nanog Protein Promotes Growth of Head and Neck Cancer June 18th, 2013
New Method to Synthesize Zinc Oxide Nanoparticles with High Catalytic Activity June 18th, 2013
Production of Polyaniline Biosensors Modified with Conductive Polymer Composites June 18th, 2013
Govt.-Legislation/Regulation/Funding/Policy
3-D printing could lead to tiny medical implants, electronics, robots, more June 18th, 2013
Working backward: Computer-aided design of zeolite templates: Rice scientists apply drug-design lessons to production of industrial minerals June 17th, 2013
An Innovative material for the Green Earth: Simple and inexpensive process to make a material for CO2 adsorption June 17th, 2013
Discovery of new material state counterintuitive to laws of physics June 14th, 2013
Possible Futures
Space Solar Power: Key to a Livable Planet Earth June 10th, 2013
Global Nanotechnology Drug Delivery Market 2012-2016 June 10th, 2013
Nanorobot tetanus treatment animation June 9th, 2013
New horizons to drive the future of Medicine: European Technology Platform on Nanomedicine intends to lead the domain June 8th, 2013
Academic/Education
CNSE Welcomes Record Number of Students, Majority of Whom are New Yorkers, for Prestigious Summer Internship Program June 12th, 2013
FEI and University of Oklahoma Begin Collaboration Research Agreement for Understanding and Developing Unconventional Oil and Gas Reservoirs: Collaboration effort will focus on new methods to classify shales in the economic assessment of “tight” resource plays June 7th, 2013
Johannes Gutenberg University Mainz obtains new Collaborative Research Center on "Nanodimensional polymer therapeutics for tumor therapy" June 2nd, 2013
Lorraine University uses Nanoparticle Tracking Analysis to characterize biomolecules for agrichemicals, pharmacology and cosmetics May 28th, 2013
Self Assembly
Filmmaking magic with polymers June 12th, 2013
New microfluidic method expands toolbox for nanoparticle manipulation June 5th, 2013
Organic polymers show sunny potential: Rice, Penn State labs lay groundwork for block copolymer solar cells May 30th, 2013
Scientists at Tokyo Tech have developed a new self-assembled nanostructure that can survive very hot or saline environments May 27th, 2013
Nanotubes/Buckyballs
Unzipped nanotubes unlock potential for batteries: Rice University lab combines graphene nanoribbons with tin oxide for improved anodes June 13th, 2013
The Diabetes ‘Breathalyzer’: Pitt chemists demonstrate sensor technology that could detect and monitor diabetes through breath analysis alone June 10th, 2013
Los Alamos catalyst could jumpstart e-cars, green energy: The new material has the highest oxygen reduction reaction (ORR) activity in alkaline media of any non-precious metal catalyst developed to date June 4th, 2013
Even with Defects, Graphene is Strongest Material in the World: New Study Reveals Strength of CVD Graphene May 31st, 2013
Announcements
Pioneering breakthrough of chemical nanoengineering to design drugs controlled by light June 18th, 2013
Study Shows How the Nanog Protein Promotes Growth of Head and Neck Cancer June 18th, 2013
New Method to Synthesize Zinc Oxide Nanoparticles with High Catalytic Activity June 18th, 2013
Production of Polyaniline Biosensors Modified with Conductive Polymer Composites June 18th, 2013
Environment
An Innovative material for the Green Earth: Simple and inexpensive process to make a material for CO2 adsorption June 17th, 2013
Discovery of new material state counterintuitive to laws of physics June 14th, 2013
Iran Applying Nanotechnology in Growing Number of Industries June 9th, 2013
Conference Scheduled June 5-7 on Safe Use of Nanotechnology in Environmental Remediation May 23rd, 2013
Water
AXEON Acquires Assets of Leading Reverse Osmosis Systems Manufacturer June 17th, 2013
Nanoparticle Opens the Door to Clean-Energy Alternatives June 14th, 2013
Discovery of new material state counterintuitive to laws of physics June 14th, 2013
Filmmaking magic with polymers June 12th, 2013
Solar/Photovoltaic
Polymer-coated catalyst protects "artificial leaf" June 17th, 2013
Further research on effects of nanomaterials: BASF participates in BMBF research project on safety of nanomaterials: Results allow easier and faster evaluation of nanoparticle behavior June 12th, 2013
Graphene and semiconductor technology together: smaller, cheaper, better June 12th, 2013
Space Solar Power: Key to a Livable Planet Earth June 10th, 2013