1,4-D-Glucan block copolymers: synthesis and comprehensive structural characterization

Abstract

Multi-block glucans comprising permethylated and partially methylated blocks are compounds of interest. In order to monitor their formation by transglycosylation of corresponding starting glucans, a method has been developed and applied to model compounds. This method allows determining the average length of the blocks and the progress of incorporation of methyl blocks in partially methylated sequences with a random distribution. The method, comprising liquid chromatography mass spectrometry (LC-MS) and electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS n ) measurements of two types of peralkylated glucans representing derivatives of the target compounds, is comprehensively described and discussed. ESI-MS n allows looking into the sequences of oligomeric domains. In addition, transglycosylation is followed by attenuated total reflection FTIR and NMR spectroscopy.

Impact of instrumental settings in electrospray ionization ion trap mass spectrometry on the analysis of multi-CH3-/CD3-isotopologs in cellulose ether analysis: a quantitative evaluation

“…Thus, slight discrimination effects observed for the border cases can be neglected in the case of conventional MCs. However, they have to be considered in the case of bimodal [ 37 ] or block-like structures [ 5 ], i.e., in the case of main contributions of less similar constituents or even the extreme cases of a DP profile.…”

“…Completeness of alkylation was checked by the absence of OH absorption > 3000 cm −1 by ATR-IR spectroscopy. Unless complete alkylation was achieved, alkylation was repeated by a modified Hakomori method using Li-dimsyl in DMSO as base [ 5 , 22 ]. Li-dimsyl was prepared by addition of the required volume of methyllithium solution to the same volume of dry DMSO under nitrogen.…”

“…Since exact quantification of the molar ratios of the constituents contributing to the substituent pattern profiles in such diades, triades, tetrades, etc. is essential for any conclusions on their homo- or heterogeneity, bimodal or block-like structures [ 1 , 5 ], reliability of the MS results is of great importance.…”

“…The vapor pressures of deuterated alkanes show an inverse isotope effect, i.e., a larger vapor pressure of the heavier deuterated isotopolog [ 7 ]. The physicochemical differences of C-H and C-D are also clearly visible from the retention behavior in chromatography: In gas chromatography on common non-polar polysiloxane phases, deuteromethylated compounds are less retained than their methylated analogs [ 8 , 9 ], and the same is observed in reversed-phase liquid chromatography [ 5 ], while the behavior on normal-phase LC columns is the opposite. Thus, a highly deuteromethylated molecule shows less interaction with a non-polar phase than its methylated counterpart.…”

Debenzylation of Benzyl-Protected Methylcellulose

“…As part of a research project conducted in our lab, glucan ether multi-block-copolymers comprising of water-soluble blocks of methylcellulose (with a degree of substitution (DS) ~1.9, meaning that on average of about 1.9 of the available 3 substitution sites on each anhydroglucose unit are substituted with methyl groups), interrupted by hydrophobic blocks of permethylated anhydroglucose units (per-Me-AGU), were synthesized. This is performed by transglycosylation between Bn-protected MC (BnMC) and permethylated cellulose (per-MC) based on a similar strategy as introduced by Rother et al [34] and further investigated by Hashemi and Mischnick [35]. It is of crucial importance to outline that such products are not uniform, but instead show dispersity with respect to average molecular weight (M w ), average block length (BL), and the distribution of blocks along the polymer chains.…”