End-Functionalized Polymers. 2. Quantification of Functionalization by Time-of-Flight Secondary Ion Mass Spectrometry

Abstract

The applicability of time-of-flight secondary ion mass spectrometry (TOF-SIMS) for quantification of functionalization is demonstrated using five 1.0 X103 g/mol polystyrene samples which were synthesized by living anionic polymerization. The polymerizations were functionally terminated to various extents (0,25,50,75, and 100%) by using sequential termination techniques with chlorodimethylphenylsilane and methanol. Two distinct molecular weight distributions of intact oligomer signals are resolved in the TOF-SIMS spectra resulting from the functionalized and unfunctionalized (protonated) oligomer species in each sample. Through direct comparison of the signal intensities of the two types of oligomers, the extent of functionalization is determined at each degree of polymerization and agrees well with expected values. The results are substantiated using physical mixtures of dimethylphenylsilyl (100% functionalized) and proton (0% functionalized) terminated polymers. The relative oligomer intensities for the physical mixture of polymers corresponds well to the ratio in which they were initially combined. Sputter yield, extent of fragmentation, and ionization and detection probabilities are determined to be very similar for the protonand dimethylphenylsilyl-functionalized oligomers. Thus, quantification of endgroups can be achieved without standards calibration. Analysis by gel permeation chromatography (GPC) shows a systematic shift to higher (Md) values as the extent of functionalization of the polystyrene samples is increased from 0 to 100%. (M") values calculated from TOF-SIMS analysis for the oligomers agree well with GPC results. The <Af") values for the functionalized and unfunctionalized components in each sample can also be determined by TOF-SIMS and are distinct for each oligomer type.

Evidence of simple intramolecular rearrangement at polymer end groups in secondary ion mass spectrometry

“…It can be directly observed that [C 7 H 5 O] (7d) is absent in 8 but present in 9. Thus, it seems that ionic bonds (8) do not allow the formation of fragments 7d but they are observed for covalent bonds (end groups 7 and 9). Several explanations can be proposed.…”

“…Finally, with SIMS, it is also possible to desorb oligomers and then to obtain the molecular weight distribution similar to MALDI. 8,9 Oligomer desorption is generally restricted to masses below 10 000 (100 000 with MALDI). For this purpose, polymers have to be prepared as very thin films on a metallic substrate (most often silver).…”

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D3)

“…Secondly, we wanted to determine whether the relative peak intensities at each degree of polymerization in the mass spectra were true representations of the siloxanolate initiator populations. The earlier mass spectral studies did not establish this [13][14][15]. The third issue addressed in this study was to evaluate the changes in peak intensities as a function of reaction conditions such as the polymerization time, initiator concentration, and the reaction temperature.…”

“…A new approach for studying these systems was introduced by Hunt et al [13,14] where time of flight secondary ion mass spectrometry (TOF-SIMS) was used to determine the relative amounts of initiator species (Scheme 2: s-1, -2, and -3) from the sec-butyllithium initiated ring-opening polymerization of D 3 . Unlike the earlier studies that were restricted to analyzing low molecular weight oligomers, Hunt and coworkers analyzed the higher mass final polymer product.…”

Cationization of dendritic macromolecule adsorbates on metals studied by time‐of‐flight secondary ion mass spectrometry

“…All spectra contain a peak at m/z 943.30 corresponding to the dendron cationized by adventitious sodium Na C ion. 44 Here, we illustrate that this sensitivity can be used to give information about the dendron end-functionality provided that molecular or quasimolecular ions are collected.…”