Marek Matlengiewicz

Sequence distribution of the methyl methacrylate-ethyl acrylate copolymer by 13C n.m.r. spectroscopy

Abstract A method for characterizing triad and pentad distribution by 13 C n.m.r. spectroscopy has been developed and applied for an acrylate-methacrylate copolymer for which the chemical shifts of the homopolymers were sufficiently separated to observe mixed sequences up to pentads. Calculation of the intensity was performed applying Markov-Bernoulli statistics while the chemical shift for each sequence was calculated by a separately developed incremental method. Based on these data, the carbonyl signal was simulated yielding very good agreement at the triad level and satisfactory agreement at the pentad level.

Analysis of β-CH2 signals in the 13C NMR spectra of the methyl methacrylate–ethyl acrylate copolymer as a tool for microstructure determination

The incremental method of the chemical shift calculation in the 13C NMR spectra of the methyl methacrylate–ethyl acrylate copolymer, PMMA/EA, has been applied to the β-CH2 carbons. A positive simulation of the DEPT sub-spectrum shows that it is possible to determine in this way the distribution of configurational-compositional tetrads providing a tool for microstructure analysis of acrylic copolymers.

Microstructure Study of Methyl Methacrylate/n-Butyl Acrylate Copolymer by 13C NMR Spectroscopy

Abstract Detailed analysis of carbonyl signal in the 100 MHz 13C NMR spectrum of methyl methacrylate/n-butyl acrylate copolymer samples, PMMA/nBA, of different compositions, prepared by free radical polymerization, provided information on distribution of configurational-compositional triads and pentads. Incremental calculation of chemical shifts of individual sequences permitted spectral simulation and verification of the signal attribution.

Computer aided analysis of carbon-13 nuclear magnetic resonance spectra of multicomponent mixtures. Part 2. Determination of the content of alkadienes in a light gasoline

A method for the computer aided analysis of 13C nuclear magnetic resonance spectra of multicomponent mixtures has been applied to determine the content of polymerizable compounds, especially alkadienes, in light gasolines derived from the steam cracking process of crude oil. The results obtained are in good agreement with those provided by gas chromatography–mass spectrometry.

Sequence Distribution of Poly(methyl acrylate) by Incremental Calculation

The carbonyl signal in the 100 MHz 13C NMR spectra of poly(methyl acrylate) (PMA) recorded in benzene-d6 exhibits configurational sensitivity up to pentads, and the signal of backbone β-CH2 carbons shows splitting up to configurational hexads with traces of octads. Assignment of the sequences to respective signals was confirmed by computer simulation of both carbonyl and methylene signals applying a method of incremental calculation of chemical shifts of individual sequences and second-order Markov statistics for sequence probabilities.

Incremental Calculation of Sequence Distribution of Poly(Butyl Acrylate)

Abstract The carbonyl signal in the 100 MHz 13C NMR spectra of both poly(n-butyl acrylate) and poly(t-butyl acrylate) exhibit configurational sensitivity up to pentads. Since the attribution of respective sequences cannot be performed in a straightforward manner, a method of incremental calculation of chemical shifts of individual sequences has been applied. The simulated spectrum for PnBA obtained in this way required only slight corrections to match the experimental carbonyl signal. This method can therefore be extended to determine the configurational sequences in acrylic copolymers containing n-butyl acrylate units.

Influence of Polar Modifiers on Microstructure of Polybutadiene Obtained by Anionic Polymerization. Part 2: Lewis Base (σ) Amine-Ether and Ether-Type Polar Modifiers

The influence of Lewis base (σ complex) amine-ether and ether-type polar modifiers on the microstructure of polybutadiene obtained by anionic polymerization was studied. Analysis of FT-IR-ATR, 1H, and 13C NMR spectral data for polybutadienes obtained in the presence of the complexing agents showed that increase of concentration of all tested polar modifiers very strongly promoted formation of 1,2 butadiene isomeric structures, especially increasing the content of vinyl–vinyl and vinyl–trans-1,4 diads.

Influence of Polar Modifiers on Microstructure of Polybutadiene Obtained by Anionic Polymerization. Part 1: Lewis Base (σ) Amine-Type Polar Modifiers

In order to understand the influence of various types of polar modifiers on the microstructure of polybutadiene obtained by anionic polymerization, four types of polar modifiers were selected for detailed studies: Lewis bases (σ complex), Lewis acids (μ complex), a mixture of Lewis bases and Lewis acids (σ + μ complex), and acid-base polar modifiers (σ-μ complex) where one molecule combined acid and base character. The influence of five different tertiary amines (Lewis base polar modifiers) was studied. Analysis of FT-IR-ATR, 1H, and 13C NMR data for polybutadienes obtained in the presence of these complexing agents showed that all tested tertiary amines enhanced 1,2 addition of 1,3-butadiene and preferred trans-1,4 addition.

Reactivity Ratios of Butyl Acrylates in Radical Copolymerization with Methacrylates

The reactivity ratios of four butyl acrylates versus methyl methacrylate and tert-butyl methacrylate were determined for their radical copolymerization in 2-butanone solution using the Jaacks method. The reactivity ratios values obtained were positively verified by substituting into the Alfrey-Goldfinger equation, yielding correct copolymer composition for a series of samples obtained from different initial mole fractions of the comonomers.

THIN-LAYER CHROMATOGRAPHIC EVIDENCE OF PROLINE PEPTIDIZATION IN SOLUTION AND ITS THIN-LAYER CHROMATOGRAPHIC ENANTIOSEPARATION

Direct enantioseparation of underivatized amino acids dissolved in the aqueous and nonaqueous solvents by means of the chiral TLC is a difficult analytical task. Most often such enantioseparations are carried out for the derivatized amino acids, or by means of the ion-exchange chromatography or electrophoresis. The main reasons of the aforementioned difficulty seem an ability of the chiral low molecular weight carboxylic acids (amino acids included) to undergo spontaneous condensation and spontaneous chiral conversion, as confirmed, for example, by the results of our earlier studies. In this study, we provide an experimental evidence of rapid peptidization of L-proline and DL-proline obtained by means of the two different TLC systems, additionally confirmed by LC/MS and 1H NMR spectroscopy. Additionally, a novel TLC system for the direct enantioseparation of DL-proline is proposed, which considerably outperforms earlier elaborated systems. Finally, relevant practical conclusions are drawn.