PMSE 333 |
| The Scanning Force Microscope (SFM) has become an important tool to build up polymeric supramolecular architectures, since single polymer molecules, such as dendronized polymers or double stranded DNA (ds-DNA), can be manipulated by an SFM tip on a solid surface. However, with this method only a point force can be exerted on the polymer. Here we report the application of a homogeneous force on the polymer. It is based on an SFM tip generating a 2D-pressure in an ultra-thin liquid film on the solid substrate, which then exerts a homogeneous force on topologically or covalently formed polymer loops embedded in that film. Consequently the polymer loops can be isotropically "blown" into circular "bubbles" during SFM tapping mode scanning. In particular, by this blowing supercoiled ds-DNA loops on surfaces have been unraveled, stretched, overstretched to 2.0 times of their B-form lengths and then torn apart in situ as shown in Fig. 1. Thus, the force needed to break a single ds-DNA molecule is estimated. In future work controllable blowing manipulation can be used to unravel or construct more complicated polymeric superstructures, and on the other hand to investigate mechanical properties of synthetic or natural polymers.
|
|
Joint PMSE/POLY Poster Session
6:00 PM-8:00 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster
Sci-Mix
Division of Polymeric Materials: Science & Engineering |
