Microstructure elucidation of polyflavonoid tannins by MALDI‐TOF‐CID

High molar mass wood tannin extracts are complex mixtures that are distributed in both molar mass and chemical composition. Condensed tannins from quebracho and mimosa woods were analyzed and compared with cacao tannins using matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry. Although MALDI‐TOF MS reveals the oligomer structure of the tannins, this method cannot distinguish between isomers with isobaric masses, and therefore, ambiguous structural assignments were made in a number of cases. To determine the actual microstructures present, MALDI‐TOF collision‐induced dissociation (CID) experiments were conducted. MALDI‐TOF‐CID enables monomer sequence determination, and positive assignments of isobaric structures can be made. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

MALDI‐TOF‐CID for the microstructure elucidation of polymeric hydrolysable tannins

High molar mass wood tannin extracts are complex mixtures that are distributed in both molar mass and chemical composition. Hydrolysable tannins from tara, Turkey gall, and chestnut woods were analyzed and compared using matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. Although MALDI‐TOF MS reveals the oligomer structure of the tannins, this method cannot distinguish between isomers with isobaric masses and, therefore, ambiguous structural assignments were made in a number of cases. To determine the actual microstructures present, MALDI‐TOF‐CID (collision induced dissociation) experiments were conducted. MALDI‐TOF‐CID enables monomer sequence determination and positive assignments of isobaric structures can be made. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of poly (γ‐benzyl‐L‐glutamate) with well‐defined terminal structures and its block polypeptides with alanine,leucine and phenylalanine

The ring‐opening polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (BLG‐NCA) was initiated by n‐hexylamine in N,N‐dimethyformamide under normal pressure at 0 °C. The products were characterizated by gel permeation chromatography, matrix‐assisted laser desorption/ionization time of flight mass spectroscopy (MALDI‐TOF MS), nuclear magnetic resonance etc. MALDI‐TOF MS gave direct evidence that the side reactions during the polymerization of BLG‐NCA could be greatly reduced by decreasing the reaction temperature, e.g. from room temperature to 0 °C. As a result, over 90% of the products were amino‐terminated poly(γ‐benzyl‐L ‐glutamate) (PBLG) with low polydispersity index when the polymerization was carried out at 0 °C, which could be used to re‐initiate the polymerization of other NCAs. Then several well‐defined PBLG‐containing block copolypeptides were successfully synthesized in a convenient way. Copyright © 2012 Society of Chemical Industry     

Characterization of the biocide polyhexamethylene biguanide by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry

The biocide polyhexamethylene biguanide (PHMB) has been characterized by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). Previously, no method has been able to provide a detailed structural characterization of PHMB. MALDI‐TOF MS was able to detect PHMB oligomers with n ≤ 6. Six different PHMB product types were identified, which possess combinations of amine, cyanoamine, guanidine, or cyanoguanidine end‐groups. Postsource decay (PSD) fragmentation was used to confirm the correct assignment of PHMB structure for the dominant PHMB molecular ion. MALDI‐TOF MS analysis of a ¹⁵N‐labeled PHMB confirmed the correct assignment of PHMB molecular ions, and also indicated the existence of a polymerization–depolymerization equilibrium during melt polymerization of the polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4928–4936, 2006     

Preparation and characterization of mono‐ and di‐d‐α‐tocopheryl polyethylene glycol 1000 succinate

Mono‐d‐α‐tocopheryl polyethylene glycol 1000 (TPGS 1000) and di‐TPGS 1000 were prepared from the synthesized TPGS 1000 mixture. The key separation step was performed by a Simulating Moving Bed chromatographic process. The chemical structures and molecular weight distrubution were characterized by ¹H‐NMR and MALDI‐TOF mass spectroscopy. NMR and MALDI‐TOF MS data confirmed the occurrence of di‐TPGS. Both NMR and MALDI‐TOF MS results showed the degree of polymerization of the two esters and the molecular mass. The melting temperatures of the two polymers were investigated by DSC and the thermal decomposition temperatures have been determined by TGA. The melting temperatures of the two esters were 33 and 15°C, separately. And the two separated TPGS esters exhibited different thermal decomposition courses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Matrix‐Assisted Laser Desorption/Ionization Mass Spectrometry of Synthetic Polymers, 5. Analysis of Poly(propylene oxide)s by Coupled Liquid Chromatography at the Critical Point of Adsorption and MALDI‐TOF Mass Spectrometry

Poly(propylene oxide)s can be analyzed efficiently with respect to functionality and molar mass by coupled liquid chromatography and MALDI‐TOF mass spectrometry. Both techniques are coupled via a robotic interface, where the matrix is coaxially added to the eluate and spotted dropwise onto the MALDI target. It is shown that size exclusion chromatography and liquid chromatography at critical conditions of adsorption coupled to MALDI‐TOF yield useful structural information on oligomer masses and chemical composition. In particular, the analysis of technical poly(propylene oxide) triols by LC‐CC/MALDI‐TOF reveals the presence of diols and monools in addition to the triols. The oligomer distributions of all functionality fractions are determined.     

One‐step synthesis and ring‐opening polymerization of novel macrocyclic(arylene multisulfide) oligomers

A series of macrocyclic(arylene multisulfide) oligomers were synthesized under high dilution conditions by reacting diphenyl ether/diphenyl/diphenyl disulfide/diphenyl methane with dichloro disulfide in the presence of a trace amount of iron powder by a one‐step reaction. From MALDI‐TOF mass spectra, it was established that the repeating units of the cyclization ranged from two to seven and the unit of macrocyclic(arylene multisulfide) oligomers had one to seven sulfur atoms. The macrocyclic oligomers readily underwent ring‐opening polymerization in the melt, resulting in linear, high molecular weight polymultisulfides. DSC thermograms demonstrated that the four polymultisulfides, derived from the macrocyclic(arylene multisulfide) oligomers, are amorphous in nature. The macrocyclic(arylene multisulfide) oligomers and polymers were analyzed by MALDI‐TOF‐MS, IR, HPLC, NMR, DSC, and TGA methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 735–741, 2004     

Characterization of polyamideamine‐epichlorohydrin (PAE) resin: Roles of azetidinium groups and molecular mass of PAE in wet strength development of paper prepared with PAE

Polyamideamine‐epichlorohydrin (PAE) resin is a crosslinked heteropolymer having cationic charges, and has been widely used as a wet strength agent of paper in the papermaking process. In this study, more accurate molecular mass values of PAE were determined by size exclusion chromatography attached with a multi angle laser light scattering detector (SEC‐MALS). The obtained weight average molecular mass (M_w) values of commercial and laboratory‐made PAE samples were 1,140,000 and 494,000, respectively, and these values were much higher than those reported so far. SEC‐MALS analysis also revealed that PAE molecules had highly crosslinked structures and extremely wide molecular mass distributions. Molecular mass values and content of 3‐hydroxy‐azetidinium (AZR) groups in PAE and PAE intermediates during the course of PAE synthesis were also determined by the SEC‐MALS and ¹H NMR methods, and the relationships between these values and the wet strength development of handsheets prepared with these PAE samples were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2249–2255, 2005     

Matrix‐assisted laser desorption/ionization mass spectrometry of synthetic polymers. VI. Analysis of phenol–urea–formaldehyde cocondensates

Phenolic resoles can be regarded as copolymers of phenol and formaldehyde that are distributed in the chain length and the number of methylol groups per molecule. While other spectroscopic methods like FTIR and NMR only give average structures, MALDI–TOF mass spectrometry is able to resolve the oligomer distribution of phenolic resoles. Using 2,5‐dihydroxybenzoic acid or 2,4,6‐trihydroxyacetophenone as matrices, MALDI–TOF spectra are obtained where each oligomer peak can be assigned to a particular chemical structure. Thus, the degree of polymerization and the number of reactive methylol groups can be determined. For urea‐modified resoles, in addition to phenol–formaldehyde and urea–formaldehyde structures, for the first time, phenol–urea–formaldehyde cocondensate structures can be identified directly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2540–2548, 2003     

Molar mass analysis of polyamides-11 and -12 by size exclusion chromatography in HFiP

The SEC analysis of polyamide-11 and polyamide-12 can be conducted free of association and aggregation phenomena when hexafluoroisopropanol + 0.05 mol/L potassium trifluoroacetate are used as the mobile phase. The calibration of the SEC system can be conducted in different ways. As stationary phases non-polar polystyrene and polar perfluoro silicagel were tested. The investigations showed that the polystyrene gel exhibits hydrophobic interactions with the polyamides while with the silicagel selective interactions were not found. Investigating different options for SEC calibration it was found that conventional PMMA calibration does not yield correct results. The universal calibration approach based on PMMA calibration did not work either. Correct molar masses were obtained when the PMMA calibration curve was corrected with data from polyamide blends using a simplex algorithm. Alternatively, calibration can be conducted with broadly distributed polyamides that were first fully characterized by SEC-MALLS. The resulting molar mass distributions for different sets of polyamides were compared with molar masses that were determined directly by SEC-MALLS and excellent correlation was obtained.     

Synthesis conditions and structure of low density polyethylene. II. Average molar mass and molar mass distribution

The first part of this publication dealt with the effect of synthesis conditions on short and long-chain branching of low density polyethylene; this second part reports on the effect on the molar mass, the molar mass distribution and the polydispersity that can be determined from these parameters. The average molar mass was measured with a membrane osmometer and the molar mass distribution by gel permeation chromatography, using the same samples as those used for the branching analysis. These samples were produced in continuously operating stirred autoclaves under widely differing polymerization conditions. The number-average molar mass falls as the polymerization temperature and the initiator concentration rises and the pressure decreases. When the polymerization temperature is high, the molar mass distribution is narrower and less asymmetrical. When the polymerization temperature is low, there are broader, more asymmetrical distributions with a larger higher molar mass fraction. The polydispersity calculated from the molar mass distribution falls accordingly as the polymerization temperature rises. The polyethylene samples produced in a squat stirred autoclave have a higher polydispersity than those produced in a narrow autoclave. These findings have been confirmed on commercial products produced in various types of reactors.     

Considerations on the macromolecular structure of chestnut ellagitannins by matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry

The rather novel picture of chestnut wood tannin, in situ in the wood, which emerges from matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) is that of a pervasive and extended random tridimensional macromolecular network, formed by pentagalloylglucose clusters linked to each other, to form chains and encrust the wood constituents matrix. Up to pentagalloylglucose trimers were identified in the MALDI‐TOF analysis of the commercial chestnut tannin extract, which were clearly degradation products of more extensive chains likely to be present in situ in the wood before extraction, in the network through polygallic/polyellagic chains or flavogallonic acid bridges. The hydrolyzable chestnut tannin network is capable of being extracted, to yield the commercial chestnut tannin extract exclusively by its degradation, a degradation that is possible only because of the susceptibility to hydrolysis of the ester bridges holding the network together. Internal rearrangements of the fragments formed by the extraction appear to occur readily and with ease, to yield a variety of structures characterized by the presence of ellagic acid residues, flavogallonic acid residues, and also, but less readily, nonahydroxytriphnoic acid residues. The other main constituents of the commercial tannin extract, castalagin and vescalagin, are shown to be simply the more stable degradation plus internal rearrangement products derived from the hydrolysis of polypentagalloylglucose chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 429–437, 2002     

Synthesis,structure, and characterization of glyoxal‐urea‐formaldehyde cocondensed resins

To decrease the formaldehyde emission of urea‐formaldehyde (UF) bonded products at source, monomethylol urea (MMU) was chosen to react with glyoxal (G), a nonvolatile and nontoxic aldehyde, to prepare a novel glyoxal‐urea‐formaldehyde (GUF) cocondensed resin. The GUF resins were synthesized with different MMU/G molar ratios, and the basic properties were tested. The GUF resins were characterized by ultraviolet‐visible spectroscopy, Fourier transform infrared spectroscopy, carbon‐13 nuclear magnetic resonance spectroscopy and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF‐MS). The results show that the synthesized GUF resins remain stable for at least 10 days at ambient temperature. Conjugated structures, and large amounts of ? OH, ? NH? , C? N, and C?O groups with different levels of substitution exist in the GUF resin. There are two repeating motives in the MALDI‐TOF‐MS spectrum of the GUF resin, one of 175 ±1 Da and a second one of 161 ± 1 Da. Moreover, the peaks due to the dehydration condensation reaction of MMU also appear in the spectra. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41009.     

Calibration of size-exclusion chromatography columns with polydisperse polymer standards. II. Applications

New methods for calibrating SEC columns by means of polydisperse polymer samples with known M_n and M_w have been tested with computer-generated chromatograms and with experimental data of high-performance SEC. Calculations with the artificial chromatograms show that accurate calibration dependences can be recovered even when polymers with broad and/or bimodal molecular weight distributions are used as standards. Polystyrene calibration calculated by the proposed method from chromatograms of five polydisperse polystyrenes follows closely the curve obtained in a conventional manner from nine narrow polystyrene standards. The dependence log M vs. ν for PMMA determined from chromatograms of six PMMA samples with moderately broad molecular weight distributions agrees well with the curve obtained by shifting the dependence for polystyrene using the universal calibration concept. The new method is particularly useful when SEC columns are to be calibrated for dextrans in water, where only a few standards having a rather broad molecular weight distribution are available, and can considerably improve the accuracy of molecular weight determination by SEC.     

Polymer structure of commercial hydrolyzable tannins by matrix‐assisted laser desorption/ionization‐time‐of‐flight mass spectrometry

The structures of six commercial hydrolyzable tannins, chestnut, oak, tara, sumach, chinese gall, and turkey gall tannins have been examined by matrix‐assisted laser desorption/ionization‐time‐of‐flight (MALDI‐TOF) mass spectrometry. Their oligomeric structures and structure distributions have been defined. Degradation products of rather different structure than what previously reported were present. Different galloyl glucose monomers were observed for chestnut and oak tannin extracts and in chinese gall gallotannin extract. Combination of positive‐ and negative‐mode MALDI‐TOF showed that most galloyl residues of the galloyl glucose chains were stripped from a skeletal glucose chain. Oligomers, in some cases up to 16 or 17 glucose units long, almost totally stripped of galloyl residues were observed. This indicated that a wide distribution up to very long gaIloylglucose chains exist in most commercial hydrolyzable tannin extracts. This indicated that these commercial tannin extracts are mainly composed of long galloyl glucose chains of mixed di‐, tri‐, and pentagalloyl glucose repeating units being present in the same chain. The presence of long glucose chains where most of the galloyl residues have been stripped indicates that their linkage may be sugar residue to sugar residue. Commercial tara and turkey gall tannins have been shown to be mainly polygallic oligomers of up to eight gallic acid residues linked to each other in a chain. Commercial sumach extract revealed itself a more complex mixture of glucose oligomers up to 13 repeating units. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Improved methods for evaluating the molar mass distributions of cellulose in kraft pulp

Multi‐angle laser light scattering (MALLS) was used to characterize birch kraft pulps with respect to their absolute molecular mass distributions (MMDs). The pulps were dissolved in lithium chloride/N,N‐dimethylacetamide and separated by size exclusion chromatography (SEC). The weight‐average and number‐average molecular masses of the cellulose fractions of the pulps obtained from the absolute MALLS measurements were compared with the molar masses obtained by direct‐standard‐calibration relative pullulan standards. Discrepancies between the two detection methods were found, and two ways of correlating the relative pullulan molar masses to the absolute molar masses were examined. In the first method, the correlation was made over a large range of molecular masses. The second method correlated the molecular masses of the standards to the molecular masses of samples by the calculation of fictitious, cellulose‐equivalent molar masses of the standards. With the preferred second method, a more correct MMD of kraft pulp samples could, therefore, be obtained from an SEC system calibrated with narrow standards. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1170–1179, 2003     

Characterization of paraffin oils and petrolatum using LDI‐TOF MS and principle component analysis

Laser desorption/ionization time‐of‐flight mass spectrometry (LDI‐TOF MS) followed by evaluation of the mass spectra with principal component analysis (PCA) was used for the in‐depth characterization of paraffin oils (mineral oils) and petrolatum (paraffin jelly) samples. These raw materials are liquid and semisolid mixtures of hydrocarbons obtained from petroleum. Mass spectrometric analysis was done using a solvent‐free sample preparation with silver trifluoroacetate. The analysis was carried out on a commercially available matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometer. Mass spectra were evaluated using parameters calculated from the areas of different alkane and cycloalkane species and by PCA. The ratios between specific peak areas were chosen as PCA‐input data instead of the less reproducible absolute peak areas. The principal components enable comparison of a large number of samples and can also be used for visualization of data. In this work, it is clearly demonstrated that combining LDI‐TOF MS and PCA provides a fast and efficient tool for the characterization of paraffin oils and petrolatum. Petrolatum and four different kinds of paraffin oil were analyzed and the results compared with other analytical methods.     

Effect of cationization reagents on the matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum of Chinese gallotannins

In this study, Chinese gallotannins were characterized by MALDI‐TOF MS, and effects of cationization reagents on the quality of spectra were investigated. The trideca‐ and tetradeca‐galloyl glucoses were observed in Chinese gallotannins, which could not be detected in earlier studies. When Cs⁺ was used as the cationization reagent, Chinese gallotannins gave a relatively simple MALDI‐TOF spectrum, three series of quasimolecular ions [M + Cs]⁺, [M + 2Cs–H]⁺, and [M + 3Cs–2H]⁺ and a series of metastable ion peaks with minimum abundance were detected. Selection of Na⁺ as the cationization reagent, additional three series of ion peaks including two patterns from the fragmentation and complex 2M adducts [2M + Na]⁺ can be distinguished. In the case of no deionization or addition of cationization reagent to the analyte/matrix, naturally abundant Na⁺ and K⁺ as the cationization reagent, [M + Na]⁺ and [M + K]⁺ molecular ions both appeared in the complicated spectrum. Therefore, we conclude that cationization reagents affect the MALDI‐TOF MS spectrum of Chinese gallotannins significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of perfluorohexyl‐terminated poly(ethylene oxide) using maghnite‐h as clay catalyst

Activated monomer cationic ring‐opening polymerization of ethylene oxide initiated with 1H,1H,2H, 2H‐perfluorooctan‐1‐ol, using acid exchanged montmorillonite clay called Maghnite‐H⁺ (Mag‐H⁺) as an effective catalyst, was carried out to obtain the corresponding homopolymers with narrow polydispersity ratios. The molecular weights of the obtained polymers could be controlled with the feed ratio of the monomer and initiator. The effect of amount of catalyst and time on the polymerization yield and viscosity of the polymers were studied. The structure was confirmed by ¹H‐NMR and MALDI‐TOF‐MS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010