Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC−ESI−MS2) was employed for the characterization of three poly(n-butyl acrylate)s. These polymers were produced at high temperature using the same initiator, tert-butyl peroxy-3,5,5-trimethylhexanoate, but in different solvents, viz. pentyl propionate, xylene and butyl acetate. Exact mass experiments performed on these polymers in an Orbitrap instrument supplied valuable information on the end group structures. Study of the data allowed identification of many reactions during the polymerization such as beta-scission and chain transfer to solvent or radical transfer to solvent from the initiator. Different fragmentation pathways were observed from the same precursor mass on MS/MS experiments, indicating the presence of isomers. The comprehensive assignment of the peaks in the LC−MS data allowed us to describe the end group distribution in a semiquantitative way. The results clearly show that the relatively reactive solvents used for polymerization have strong influences on the polymer composition.
A comprehensive study using liquid chromatography electrospray ionization multistage mass spectrometry (LC-ESI MS n ) was performed to get detailed structural information on poly(butylene adipate-co-butylene terephthalate) co-polyester and its product of partial degradation. LC-MS and LC-MS n identified the existence of cyclic structures in the original samples that disappear completely during the degradation. The occurrence of methanol transesterification in the degradation process was confirmed. MS 2 on the first 13 C isotope peak helped to determine the elemental composition of the fragments and facilitated end group determination. The method can be used to provide an alternative for high mass accuracy MS 2 experiments. Sequence information was also revealed for certain copolymeric structures.
Synthetic polymers are produced in industry to serve a global market across a wide range of areas.[1a-c] Increasingly complex polymeric structures have been developed to provide desirable properties and functions.[1d] The performance of these products depends on many factors such as endgroup composition, molecular weight distribution (MWD), and 3D conformation.[1e,f] Various analytical methods have been developed to obtain information about these properties. Conventional analytical techniques to study polymer systems include gel-permeation chromatography (GPC), [2a] Fourier-transform IR (FTIR), [2b] NMR spectroscopy, [2c] and differential scanning calorimetry (DSC).[2d]The development of "soft" ionization methods such as elecrospray ionization (ESI) [3a,b] and matrix-assisted laser desorption/ionization (MALDI) [3c,d] allowed mass spectrometry (MS) to become one of the most promising analytical methods for the analysis of polymeric systems. MS has the ability to characterize a dispersed polymer containing oligomers with different structures such as isomers or isobaric molecular weights. The combination of liquid chromatography (LC) and MS reduces the effects of ion suppression that may occur in an infusion MS analysis and provides an extra dimension of separation.[4] However, a relatively long separation time (> 30 min for HPLC, around 10 min for UPLC) is needed and a complex elution system using a variety of solvents has to be developed to suit a specific polymeric system.The combination of ion mobility spectrometry (IMS) and ESI-MS has been developed to analyze biomolecules and biopolymers.[5] Ion mobility describes how fast an ion in the gas phase moves through a drift cell that is filled with a carrier buffer gas under the influence of an electric field. More compact ions with a smaller collision cross-section will drift more quickly than expanded ions. The time-scale for separations in IMS is 100 ms to 10 ms, which is ideally suited for interfacing with an MS instrument. The extra dimension of separation based on drift time (t D ) provided by IMS is also highly complementary to the information obtained by MS. Although some studies on IMS-MS measurements of blends of disperse macromolecules, for example, poly(ethylene glycol) (PEG), have been reported, studies using IMS-MS on complex synthetic polymer systems are still limited. [6] Here, we demonstrate the power of using high resolution IMS-MS to study a poly(methyl methacrylate) (PMMA) synthesized by radical polymerization using peroxide initiator (tert-butyl peroxy-3,5,5-trimethylhexanoate) in solvent. Comprehensive studies on acrylic polymer produced by radical polymerization using MS have been done in the past decade. [7] It has been proven that high-resolution MS can discriminate between the effects of various polymerization mechanisms such as b-scission, chain transfer to solvent, radical transfer to solvent from the initiator, etc.[7] A system with complex endgroup combinations is expected since various initiation and termination reactions may ...
Synthetic polymers are produced in industry to serve a global market across a wide range of areas. [1a-c] Increasingly complex polymeric structures have been developed to provide desirable properties and functions. [1d] The performance of these products depends on many factors such as endgroup composition, molecular weight distribution (MWD), and 3D conformation. [1e,f] Various analytical methods have been developed to obtain information about these properties. Conventional analytical techniques to study polymer systems include gel-permeation chromatography (GPC), [2a] Fourier-transform IR (FTIR), [2b] NMR spectroscopy, [2c] and differential scanning calorimetry (DSC). [2d] The development of "soft" ionization methods such as elecrospray ionization (ESI) [3a,b] and matrix-assisted laser desorption/ionization (MALDI) [3c,d] allowed mass spectrometry (MS) to become one of the most promising analytical methods for the analysis of polymeric systems. MS has the ability to characterize a dispersed polymer containing oligomers with different structures such as isomers or isobaric molecular weights. The combination of liquid chromatography (LC) and MS reduces the effects of ion suppression that may occur in an infusion MS analysis and provides an extra dimension of separation. [4] However, a relatively long separation time (> 30 min for HPLC, around 10 min for UPLC) is needed and a complex elution system using a variety of solvents has to be developed to suit a specific polymeric system.The combination of ion mobility spectrometry (IMS) and ESI-MS has been developed to analyze biomolecules and biopolymers. [5] Ion mobility describes how fast an ion in the gas phase moves through a drift cell that is filled with a carrier buffer gas under the influence of an electric field. More compact ions with a smaller collision cross-section will drift more quickly than expanded ions. The time-scale for separations in IMS is 100 ms to 10 ms, which is ideally suited for interfacing with an MS instrument. The extra dimension of separation based on drift time (t D ) provided by IMS is also highly complementary to the information obtained by MS. Although some studies on IMS-MS measurements of blends of disperse macromolecules, for example, poly(ethylene glycol) (PEG), have been reported, studies using IMS-MS on complex synthetic polymer systems are still limited. [6] Here, we demonstrate the power of using high resolution IMS-MS to study a poly(methyl methacrylate) (PMMA) synthesized by radical polymerization using peroxide initiator (tert-butyl peroxy-3,5,5-trimethylhexanoate) in solvent. Comprehensive studies on acrylic polymer produced by radical polymerization using MS have been done in the past decade. [7] It has been proven that high-resolution MS can discriminate between the effects of various polymerization mechanisms such as b-scission, chain transfer to solvent, radical transfer to solvent from the initiator, etc. [7] A system with complex endgroup combinations is expected since various initiation and termination ...
End-group analysis was achieved on poly(methyl methacrylate) and poly(methyl methacrylate-r-butyl acrylate) by liquid chromatographyelectrospray ionization-ion trap mass spectrometry (LC-ESI-IT MS) and electrospray ionization-Fourier transform ion cyclotron resonance tandem mass spectrometry (ESI-FTICR MS 2 ). The two polymers were produced by radical polymerization in butyl acetate at relatively high temperature using the same initiator, tert-butylperoxy-3,5,5-trimethylhexanoate. In both polymers, structures with different end-groups were successfully assigned using gradient elution LC-IT MS, with the aid of exact mass experiments in an FTICR MS instrument. Isobaric materials in PMMA were discriminated using accurate mass FTICR MS 2 . Isocratic LC-MS reduced the complexity of the data of P(MMA-r-BA), made the attribution of peaks easier, and shortened the experimental time compared to gradient elution LC-MS. The identification of end-groups in both the methacrylic homo-and copolymer demonstrated that β-scission and radical transfer to solvent play an important role in the polymerization.
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