Characterization of Polyisobutylene by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry

Abstract

A novel method of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis of isobutylene homopolymers is reported in this paper. Because of the difficulty in attaching ions for such materials, the ionization for MALDI-TOF MS analysis is realized by sulfonating the olefin end groups to introduce a readily ionized moiety into the polymer. Polyisobutylene samples obtained from both living cationic polymerization and industral procedures are studied here. The number-average molecular weights and weight-average molecular weights of these materials were also measured by laser light scattering and vapor pressure osmometry. Results obtained from the three techniques agree closely with one another except for the fraction having the highest molecular weight. We postulate that this is due to the range of the molecular weight of this sample being too broad to be accurately measured by MALDI-TOF MS.

Comparison of literature models for volatile product formation from the pyrolysis of polyisobutylene at mild conditions: Data analysis, free-radical mechanistic considerations, and simulation of initial product-forming pathways

“…The first formulation [7c] had S as a radical small enough to be volatile, either directly or after transfer to generate a Hrich volatile SH. In a second formulation however, the authors suggested [7d,7f] that the required SH product resides not in the volatiles but in the ''semi-volatile'' fraction, a small amount [7f] of product that did not volatilize but constituted a distinct low-MW peak in GPC spectra of the residue [11]; experimentally, this material was removed by solvent fractionation before characterization of the residue but its functionality was not reported to determine whether it was indeed H-rich ( f t < 1), compared with the major residue with f t > 1. In this second formulation, S would be of moderate size and not volatile.…”

Dopant-assisted atmospheric pressure photoionization mass spectrometry of polyisobutylene derivatives initiated by mono- and bifunctional initiators

“…However, mass spectrometric analysis of highly nonpolar isobutylene with a fully saturated structure by MALDI and/or ESI fails due to the lack of appropriate ionization sites. It has also been shown that the introduction of aromatic moieties (e.g., using aromatic initiators for the isobutylene polymerization) and/or polar or readily ionizable groups into the polyisobutylene facilitates the ionization under MALDI and ESI conditions [12][13][14][15][16][17]. It is therefore evident that nonpolar polymers like polyisobutylenes are not amenable to MS analysis due to the lack of effective site for ionization.…”

Atmospheric pressure photoionization mass spectrometry of polyisobutylene derivatives

“…Recently, we have shown that MALDI-spectra of good quality can be obtained by introducing aromatic moieties (e.g., using aromatic initiators for initiation of the isobutylene polymerization) and/or polar groups into the polyisobutylene chain [15][16][17][18]. Good spectral quality in the negative ion mode under MALDI conditions can also be attained by modifying the olefin end-groups of polyisobutylene to ϪSO 3 H [19]. Low molecular weight polyisobutylenes with succinic anhydride end-groups were analyzed by ESI in the negative ion mode [20].…”