The Bowers Group - University of California at Santa Barbara






		PMMA - Ion Mobility Results (obtained using the MALDI-Sector Instrument)

		Typical arrival time distributions (ATDs) obtained for the PMMA 3-mer, 6-mer, and 9-mer cationized by Na⁺ (Na⁺PMMAn) at a drift cell temperature of 300 K are shown at right. The average drift time increases with n, consistent with an increase in size and cross-section. Single peaks are observed for all M⁺PMMAn oligomers at all temperatures (80-600 K), strongly indicating that the oligomers have single conformations. From these ATDs, the collision cross-sections of the M⁺PMMAn ions can be determined and are given above right (at 300 K). The temperature dependence of the experimental collision cross-sections measured for the PMMA 5-mer, 7-mer, and 9-mer cationized by Na⁺ is shown below. The increase in cross-section below 200 K is due to the nature of the ion - He interaction potential (see Theory) and is not a conformational change. Unlike the polyglycols (PEG, PPG, PTMEG), which unraveled at higher temperatures, the cross-sections of Na⁺PMMAn do not increase at high temperature indicating that the PMMA oligomers tend to keep their original shape.