Jiří Spěváček

NMR-study of structure and dynamics of associates of syndiotactic poly(methyl methacrylate) in toluene

SummaryHigh-resolution 1H NMR spectra (1H HR-NMR) of solutions of isotactic (i) and syndiotactic (s) poly(methyl methacrylate) (PMMA) in toluene-d8 were measured in the concentration range 0.2 to 10% w/v; for solutions of s-PMMA (10% w/v), 1H NMR spectra with magic angle rotation (MAR-NMR) at various temperatures and 13C NMR spectra with strong proton decoupling were also measured. It was found that even in very dilute solutions of s-PMMA in toluene-d8 a considerable portion (76%) of polymer segments are associated: association is of intramolecular origin and is due to interaction of long syndiotactic sequences. Prom NMR spectra the motion of associated segments appears as isotropic with and effective correlation frequency 106 – 107 Hz. A globular structure of the associates of s-PMMA is proposed.

Solvent induced crystallization of syndiotactic poly(methyl methacrylate) relation to the formation of polymer aggregates in solution

SummarySolutions of syndiotactic (s) poly (methyl methacrylate) (PMMA) and samples of solid s-PMMA prepared from these solutions were studied by NMR and infrared (IR) spectroscopy and by wide-angle X-ray scattering (WAXS). IR spectra of s-PMMA films obtained from o-dichlorobenzene solutions by evaporation of solvent at room temperature have shown that the ordering of polymer chains which exists in aggregates of s-PMMA in o-dichlorobenzene is preserved in the solid state. s-PMMA prepared in this way is characterized as partly crystalline by WAXS. When o-dichlorobenzene is evaporated at elevated temperatures at which the aggregates of s-PMMA are decomposed, or if solid s-PMMA is obtained from solutions in which aggregation does not take place, the obtained solid polymer is amorphous.

1H-NMR study of association in segmented polyurethane solutions

Abstract Samples of segmented polyurethanes were synthesized from polymethylenebutyleneadipatediol, of average molecular weight 2000 or 4000, a mixture of 2,4- and 2,6-toluenediisocyanate and diethyleneglycol. The values of the associated polyurethane fraction in solutions were determined by 1 H-NMR spectroscopy. It was found that the formation of associated structures depends on solvent, content of hard segments and molecular weight of soft segments. The associates, most probably formed by hydrogen bonding, were completely decomposed at 60°. The values of the association fraction are practically independent of solution concentration in the range 2–10% way.

Copolymerization of polyurethane macromer with 2-hydroxyethyl methacrylate: NMR kinetic study

SummaryThe copolymerization kinetics of Polyurethane containing a vinylic bond with 2-hydroxyethyl methacrylate in solution was investigated. The reaction was studied using a JEOL-PS-100 spectrometer at various temperatures and concentration conditions. The a and b exponents in the equation for the overall polymerization rate, Rp=const[M]a[I]b were determined. The reaction products were analyzed by means of 1H-NMR and turbidimetric titration.

1H-NMR study of interactions in the systems methyl methacrylate-dimethylformamide and methyl methacrylate-poly(methyl methacrylate-dimethylformamide

Abstract The temperature dependence of chemical shifts in 1 H-NMR spectra of solutions of methyl methacrylate (MMA) in various solvents revealed specific interaction of MMA molecules with dimethylformamide (DMF). In the system MMA-poly (methyl methacrylate) (PMMA)-DMF, PMMA acts as a further component interacting with MMA. This interaction is independent of the stereoregularity of PMMA and can be detected also in cases where PMMA is present in the form of an ordered structure, the so-called stereocomplex. In systems containing instead of MMA the dimethyl ester of 2,2,4,4-tetramethylglutaric acid, similar interactions have not been observed. The interactions in the system MMA-PMMA-DMF are discussed from the point of view of replica polymerization of MMA.

Isobutylene polymerization in the presence of t-BuCl/SnCl4

SummaryThe effect of tert-butyl chloride in the polymerizations of isobutylene carried out in the presence of SnCl4 in dichloromethane at temperatures-20°C and-78°C was investigated. Synthesized polyisobutylene samples showed a bimodal molecular weight distribution (MWD) and it was found that the weight content of the lowermolecular weight (LMW) fraction increased with increasing t-BuCl concentration in the polymerization mixture. The effect of ageing of the initiation mixture t-BuCl/SnCl4 in CH2Cl2 prepared in advance on MWD of the PIB samples was also studied. Ageing of the initiation system supports the formation of the LMW fraction and this oily PIB is the only product of the polymerization at-20°C,

Characterization of the conformational structure of t-butyl acrylate oligomers and polymers by infrared and NMR spectroscopy and computational methods

\bar M_n \sim 500,\bar M_w /\bar M_n \leqslant 1.4

HR-NMR study of formation and structure of the stereocomplex of poly(methyl methacrylate) in solution

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