J. Štokr

Conformational structure of poly(ethylene terephthalate). Infra-red, Raman and n.m.r. spectra

Abstract Infra-red and Raman spectra of unoriented samples of poly(ethylene terephthalate) in the crystalline and amorphous states and in solution were measured. The dissolved polymer was also studied by n.m.r. spectra. Digital separation of the vibrational spectra of amorphous and crystalline components made possible the detection of some new bands, the interpretation of which is presented. By comparison with the vibrational spectra of model compounds combined with analysis of n.m.r. spectra, the conformational forms present in the amorphous and liquid states of poly(ethylene terephthalate) were characterized and their populations were determined. Bands in vibrational spectra which are characteristic of various conformational forms were defined.

Stretching and deformation vibrations of CH2, C(CH3) and O(CH3) groups of poly(methyl methacrylate)

Abstract Infrared and Raman spectra of atactic PMMA and infrared spectra of stereoregular PMMA and of its four deuterated derivatives , were measured. They were used to assign the bands of stretching and deformation vibrations of CH 2 , CCH 3 and OCH 3 groups in the infrared and Raman spectra and to discuss the effect of stereoregularity on these bands in the infrared spectra.

Vibrational spectra and structure of stereoregular poly(methyl methacrylates) and of the stereocomplex

Abstract Infra-red and Raman spectra of films and solutions of syndiotactic and isotactic poly(methyl methacrylate) (PMMA) and of the stereocomplex of PMMA were measured. Vibrational bands sensitive to conformational transitions were determined. Differences of band intensities in spectra of stereoregular PMMA and of the stereocomplex indicate changes of populations of conformational forms of polymer chains accompanying stereocomplex formation. For syndiotactic PMMA in the stereocomplex, the extended chain conformation predominates.

The structure of low conversion polymers of ethylene dimethacrylate

Abstract Results of study of the pregel chain polymerization of ethylene dimethacrylate in the presence of various amounts of diluent suggest the formation of compact microgel-like particles even at the very beginning of polymerization, as a consequence of predominant cyclization. This view is based on following experimental findings. The fraction of units with pendant vinyls (70 mol %) is independent of conversion and depends only slightly on dilution; critical conversion at gelation is displaced by a factor of about 10 2 ; molecular weights at the beginning correspond approximately to molecular weights of poly(methyl methacrylate) obtained under the same conditions; intrinsic viscosities are very low and much lower than those of strongly branched poly(methyl methacrylates).

Conformational structure and vibrational and NMR spectra of simple mono-alkylbenzenes

Abstract Infrared spectra of oriented crystals of toluene, ethylbenzene, cumene, tert -butylbenzene, 2-phenylbutane and 3-phenylpentane, and NMR spectra of 2-phenylbutane and 3-phenylpentane have been measured. From these measurements, conformers present in the liquid and crystalline state have been determined. In all these compounds, only forms with a C α -C β or C α -H bond coplanar with the benzene ring have been found.

Study of thermal degradation of polybutadiene in inert atmosphere: 1. Evidence of temperature and time of heating in i.r. and n.m.r. spectra

Abstract The degradation of polybutadiene by heating in inert atmosphere at various temperatures for different time intervals was characterized by i.r. and 1H n.m.r. methods. It was established that by i.r. analysis it is possible to assess both the temperature and the duration of the heating to which the sample had been subjected.

Determination of the activation energy of chlorocyclohexane conformational transitions by infrared spectra

Abstract Chlorocyclohexane is used to demonstrate that it is possible to determine the height of the barrier between conformational isomers by following the kinetics of conformational transitions by infrared spectra. For this, crystallization of the sample has to be prevented by a suitable solvent.

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.

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.

Preparation and properties of polypyromellitimides prepared from 1,n-bis(4-aminophenoxy)alkanes

Abstract Polyamic acids, polyimides and polyisoimides have been prepared from pyromellitic acid dianhydride and 1,n-bis(4-aminophenoxyalkanes). The synthesized polymers were characterized by physical and physico-chemical methods. The prepared polyimides and polyisoimides were found to be insoluble in common solvents and can only be dissolved in sulphuric acid. Compared with highly aromatic polyimides, their thermal stability is lower by 120–140°.