Simplified method measures polymer characteristics

They believe their discovery will provide a routine analytical tool that could be used by industries that rely on polymer science to produce innovative products, including drug-delivery gels and renewable bio-materials.

Prof Omar Saleh and graduate student Andrew Dittmore of the UCSB materials department said they have successfully measured the structure and other critical parameters of a long, string-like polymer molecule — polyethylene glycol, or PEG — by stretching it with magnetic tweezers.

‘We attach one end of the PEG molecule to a surface and the other to a tiny magnetic bead, then pull on the bead by applying a magnetic field,’ explained Saleh.

’The significance is that we’re able to perform the elastic measurements — force-versus-length measurement — to see aspects of polymer structure that are hard to see in any other way, and we can do it within minutes on a benchtop apparatus,’ he commented.

Their research to characterise this particular polymer could lay the groundwork for developing a screening tool that could be used by a number of industries, according to Saleh’s research team.

’Our measurements of PEG can be used as a baseline for comparison to other polymers, including biomolecules such as DNA, RNA and proteins, which display more complex physics,’ said Dittmore.

PEG is one of the most frequently used polymers in creams, cosmetics, adhesives and medicines. As a coating, PEG can shield against an unwanted immune response to give a medicine a so-called ’stealth-like’ quality.

‘Until now, the most general method to obtain comparable data is to use neutron or x-ray diffraction which involves expensive national facilities such as nuclear reactors or particle accelerators,’ commented Prof Philip Pincus, chair of biomolecular science and engineering at UCSB.

The research was made possible by support from the National Science Foundation and was carried out at the Materials Research Laboratory, an NSF MRSEC facility at UC Santa Barbara.