Putting the Squeeze on Polymers is easier at the Nanoscale

Posted on: 07 October 2008

New Discovery by  Scientists at Trinity College Dublin and University of Illinois on Polymer Physics has Major Significance for Nanotechnology Industry

A new discovery concerning polymer physics by scientists at Trinity College Dublin and the University of Illinois may have major implications for manufacturing processes in nanotechnology. The research which has just been published in Science Express,  the on-line version of the internationally renowned journal Science was led by Dr Graham Cross of the School of Physics and the CRANN nanoscience research institute at Trinity College Dublin and Professor  William King of the University of Illinois at Urbana-Champaign. The results   shed new light on the mechanism of polymer flow at the nanometre scale.

From buttons to storage bins, moulded materials made of polymers are commonplace and   the moulding of plastics is a major manufacturing process. While substances such as steel or window glass are made of simple materials, moulded materials are made from complex, long chain molecules called polymers. An understanding of the physics of polymer flow is required to develop this manufacturing.  The 1991 Nobel Prize in physics was awarded to Pierre de Gennes, in part for developing this understanding.  Now Trinity College Dublin scientists, jointly with scientists in Urbana-Champaign, Illinois, have made a new discovery about polymer flow at the smallest scales.

Commenting on the significance of the discovery, TCD’s Dr Graham Cross said: “We have discovered that polymer flow is different at the nanometre scale.  Contrary to accepted scientific models the flow of polymer molecules in small channels becomes easier when the polymer is larger than the channel itself.  This means that forming shapes in the nanoworld  should become a lot easier than it currently is for the plastics industry today”.  

According to Dr Cross, film thickness and molecular intertwining are crucial:  “You can think of polymer materials like cooked spaghetti, with long chains knitted together to form a tough substance.  However, when the polymer film is made thinner and thinner, the polymer chains lie-down on a plane instead of becoming tangled in three dimensional space.  The polymer chains begin to behave in isolation as they find it increasingly difficult to intertwine with each other.  Their viscosity is decreased and this increases the flow.”

To make the measurements, the University of Illinois researcher, Harry Rowland used a modified nanoscale indentation system located and developed at Trinity College Dublin by collaborators Dr Graham Cross and Professor John Pethica, which pressed a flat “punch” into very thin films of polystyrene. The punch, which was much wider than the thickness of the film, forced the polymer to flow around it. This lateral squeeze flow governs the dynamics of polymer movement during processes such as nanoimprint nano-manufacturing.

The research is a significant step forward in the understanding of polymer deformation that is directly related to nanoscale manufacturing.

In Ireland, the plastics industry spans different sectors of the manufacturing industry, including medical devices, electronics, packaging, construction and domestic appliance industries. There are also many related industries which are linked to the plastics processing sector such as plastics recycling, tool making, rapid prototyping/ design services and material and equipment suppliers*. 

The research was funded by Science Foundation Ireland, the US. Department of Energy, and the US.National Science Foundation through the University of Illinois’s Center for Nanoscale Chemical-Electrical-Mechanical Manufacturing Systems.

Notes to the editor:
CRANN, the Centre for Research on Adaptive Nanostructures and Nanodevices, is Ireland’s first purpose built nanoscience research centre, housed in TCD’s Naughton Institute.  CRANN’s mission is to deliver world class research and innovation in nanoscience and nanotechnology, of value both to its industry partners and to Ireland.

Dr Graham Cross
Dr Graham Cross received his PhD degree in condensed matter physics from McGill University in Montréal, Canada in 2000, where he performed fundamental research on the mechanics of materials at the nanometre scale.  From 1999 to 2001 he worked on novel data storage devices as an FCAR postdoctoral fellow at IBM Research in Zürich, Switzerland.  He joined SFI Nanoscience Laboratory in Trinity College Dublin in 2002 to work on nanostructure fabrication by imprint techniques.  In 2007 he was appointed Principal Investigator in CRANN, and Lecturer in the School of Physics.

The Plastics Industry in Ireland
There are approximately 8,300 people employed in the Irish plastics industry*(CSO Quarterly National Household Data of March 2004), excluding those employed in the medical device industry where in house moulding of medical products is carried out.  There are ~ 239 companies involved in the manufacture of plastic products in Ireland (CSO Census of Industrial Production produced 2001), approximately 80% are Irish owned operations.