Jaroslav Straka

High-resolution solid-state 119Sn NMR spectroscopy of some organotin(IV) oxinates and thiooxinates

Abstract Solid-state 119 Sn CP/MAS NMR spectra have been recorded for eleven triorganotin(IV) oxinates and thiooxinates and diorganotin(IV) dioxinates and dithiooxinates. The spectra of tri- and diorganotin(IV) oxinates and dioxinates reveal only one centre-band, in accord with their crystal structure determined by X-ray diffraction, whereas those of some analogous thiooxinates show two centre-bands. The 119 Sn CP/MAS NMR spectra of the isotopomers, with 14 N and 15 N, of triphenyltin(IV) 5-methyl-8-chinolinolate show three centre-bands as does the 15 N CP/MAS NMR spectrum of the isotopomer containing 15 N. In the 119 Sn NMR spectra of triorganotin(IV) oxinates and thiooxinates, the centre- and side-bands which are attributable to the Zeeman effect and to the interaction with the 14 N quadrupole nucleus are split unsymmetrically into “doublets” with an approximate integration ratio 1 : 2. The spectrum of the isotopomer containing 15 N, shows splitting into a symmetrical 1 : 1 doublet attributable only to the Zeeman effect. “Triplet” splittings with a 1 : 4 : 4 integration ratio in the spectra of diorganotin(IV) dioxinates and dithiooxinates is probable because of interaction with two equivalent 14 N quadrupole nuclei. The triorganotin(IV) oxinates and thiooxinates and diorganotin(IV) dioxinates and dithiooxinates crystallize as molecular chelate complexes, which retain their structure in solutions in non-coordinating solvents.

Study of thermal degradation of polybutadiene in inert atmosphere: 2. Characterization of thermal crosslinking in polybutadiene by high resolution solid state 13C and 1H magic angle spinning n.m.r. spectroscopy

Abstract The chemical structure of polybutadiene thermally crosslinked at temperatures up to 250°C was characterized by high resolution solid state 13C n.m.r. spectra in combination with high resolution 1H and 13C magic angle spinning n.m.r. spectra of the swollen gel. Crosslinking is shown to involve the reaction of a vinyl group with the methylene group in 1,4-cis 1,2 sequences.

Reactive polymers: 61. Reaction of macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) with phenol

Abstract A series of sorbents differing substantially in the content of phenyl groups were prepared by a base-catalysed reaction of poly(glycidyl methacrylate- co -ethylene dimethacrylate) with phenol. Methods are described for quantitative determination of the degree of substitution of epoxide groups by phenol, based on 13 C nuclear magnetic resonance and infra-red spectroscopy and on elemental analysis (C, H); the last method was found to be inappropriate, however, owing to the large error involved. Infra-red spectroscopy is the method of choice for determining the degree of substitution. By studying the local properties of the regression surface, a polynomial equation was derived for the dependence of the degree of substitution of epoxide groups by phenol on the mole ratios phenol/epoxide and sodium hydroxide/phenol. The time dependence of the extent of reaction was also studied. The maximum degree of substitution attained was 0.65.

Poly(ethylene dimethacrylate) particles with poly(glycidyl methacrylate) functionalities

Abstract Macroporous particles, prepared by the suspension polymerization of ethylene dimethacrylate (EDMA), possessing high specific surface areas (558 m2g−1) and pore volumes (6.9 ml g−1), contain unreacted double bonds which are accessible for free radical polymerization. The amount of unreacted double bonds was determined by 13C CP/MAS n.m.r. These bonds were used for the functionalization of poly(EDMA) particles by the solution grafting copolymerization of glycidyl methacrylate (GMA) into the pore structure of the particles. The poly(GMA) formed in this way is permanently attached to the particles. By this method composite particles, containing up to 77 wt% of oxirane groups (determined by i.r. spectroscopy), were obtained. However, the presence of grafted polymer in the pores leads to a decrease in both the pore volume and the specific surface area. The oxirane groups can be chemically modified, as evidenced by their reactions with hydrogen chloride and 2,2,6,6-tetramethyl-4-aminopiperidine.