MALDI-ToF mass spectrometry detection of intramolecular composition gradient in copolymers

Compositional Distribution of Binary Living Copolymers and Their End Sequences

“…The relations derived for copolymers with fixed PD were tested on the compositional distribution of Br-ended copolymers with PD 18 extracted from the experimental mass spectra. These are compared in Figure 2 with the theoretical prediction from Equation ( 16) with copolymerization parameters determined previously during the polymerization of BA-MMA-H. [29] An additional parameter required is the initial composition of the mixture of activated monomers, which is not known; therefore, the value P 1A = 0.69, corresponding to the composition of produced copolymer, was used. To demonstrate that actual value has a minute effect for copolymers with PD = 18, the dependence of the average composition on the PD is plotted in Figure 3 for P 1A = 0, 0.69, and 1.…”

“…The experimental distributions show that this is not the case. Using copolymerization parameters determined previously, [29] the composition of the initial monomeric fragments was calculated from the composition of initiated monomers and used in calculation of the composition of initial dimeric fragments. Even though the quantitative agreement between the calculated and experimental composition is rather poor, especially for the parent ion 1811, Equation (23) predicts the correct order of initial-dimer abundances in the majority of cases.…”

“…Previously, we reported on two low‐molecular‐weight copolymers of BA and MMA prepared by ATRP with low (BA‐MMA‐L) and high conversion (BA‐MMA‐H), the degree of conversion being 0.33 and 0.84, respectively, and analyzed by MALDI‐TOF mass spectrometry (MALDI‐TOF MS). [ 29 ] These samples are used for testing the theoretical predictions derived here.…”

“…[28] Therefore, the use of the bivariate distribution shape for determination of copolymer microstructure has been disputed and imperfect, prematurely terminated copolymers were recognized as a sort of "time capsule" carrying information on polymerization history. [29] The comparison of probabilities calculated from the initial and terminating sequence distributions may provide the information on the sequence arrangement along the copolymer chain and help to distinguish not only between statistical and di-block copolymers but also between statistical and gradient ones. NMR spectroscopy or pyrolysis followed by gas chromatography with mass detection (Py-GC/MS) seem to be suitable tools for the determination of the end-sequence distributions.…”

“…[ 28 ] Therefore, the use of the bivariate distribution shape for determination of copolymer microstructure has been disputed and imperfect, prematurely terminated copolymers were recognized as a sort of “time capsule” carrying information on polymerization history. [ 29 ]…”