Ueber kinetische Flockungsmesser,I.

Ohne Zusammenfassung     

Singlet oxygen and polymer photooxidations. I. Sensitizers,quenchers, and reactants

A study designed to ascertain the role of singlet molecular oxygen in the photodegradation of plastics established that most classes of dye chromophores are sensitizers in polymer films, absorbing light and transferring the absorbed energy to ambient triplet ground state molecular oxygen, generating metastable reactive singlet molecular oxygen. Unsaturated polymers containing polybutadiene, polyisoprene, etc. are highly reactive to singlet oxygen produced through photosensitization, generating hydroxylic and carbonyl derivatives and losing their rubbery properties as consequences of such reactions. Many types of transition metal chelates are singlet oxygen quenchers. The relationships of the structures and spectroscopic properties of these chelates to their efficiency in quenching singlet oxygen are examined and discussed.     

Homooxacalixarenes: I. Structure,Synthesis, and Chemical Reactions

Data published on the structure, preparation, and chemical reactions of homooxacalixarenes with various number of aromatic fragments and dihomooxabridges in macrocycles were analysed and summarized.     

Vanadium oxide monolayer catalysts. I. Preparation,characterization, and thermal stability

Vanadium oxide catalysts of the monolayer type have been prepared by means of chemisorption of vanadate(V)-anions from aqueous solutions and by chemisorption of gaseous V₂O₃(OH)₄. Using Al₂O₃, Cr₂O₃, TiO₂, CeO₂ and ZrO₂, catalysts with an approximately complete monomolecular layer of vanadium(V) oxide on the carrier oxides can be prepared, if temperature is not too high. Divalent metal oxides like CdO and ZnO may already form threedimensional surface vanadates at moderate temperature. The thermal stability of a monolayer catalyst is related to the parameter z/a, i. e. the ratio of the carrier cation charge to the sum of ionic radii of carrier cation and oxide anion. Thus, monolayer catalysts will be thermally stable only under the condition that z/a is not too high (aggregated catalyst) nor too small (ternary compound formation).     

Photocrosslinking of polyethylene. I. Photoinitiators,crosslinking agent,and reaction kinetics

High density polyethylene has been photocrosslinked in the melt by using 4-chlorobenzophenone (4-CBP) as photoinitiator and triallylcyanurate (TAC) as crosslinking agent. Various factors affecting the crosslinking process (photoinitiator used and its concentration, irradiation temperature and time, atmosphere, UV light source, light intensity) were examined. By optimizing the irradiation conditions, it was found that samples up to 2 mm thick could readily be crosslinked to high gel content (≈ 90%) with satisfactory homogeneity within very short irradiation times (≈ 15 s). The kinetic analysis of the crosslinking process showed a linear relation between log S and log t (S is the sol fraction t is the irradiation time). An induction period was observed, the length of which decreased with increasing concentration of 4-CBP and increasing light intensity. An upper limit of gel content was also found for long irradiation times at a level depending on the concentration of 4-CBP. The crosslinking rate was proportional to the second order of light intensity at lower intensity and changed to first order at higher light intensity. A mechanism based on the recombination of chain radicals through both allyl and alkyl type radicals of TAC was proposed.     

Absolute raman intensities of CH3I,CH2DI,CHD2I and CD3I. Experimental results

The absolute Raman intensities of methyl iodide and deuterated derivatives have been measured in the gas phase, with an experimental accuracy of ten percent. We report the frecuency independent scattering coefficients and depolarization ratios, as well as the Raman tensor invariants, squared mean polarizability and anisotropy, derived from them.     

s-Triazines. I. Linear,sulfur bridged-s-triazine oligomers

A number of new thioether and disulfide oligomers of s-triazine have been prepared and identified. The reactions between 2,4-diphenyl-s-triazine-6-thiol and chloro substituted-s-triazines are described. A suggested mechanism for the formation of 2,2′-thiobis-(4,6-diphenyl-s-triazine) from 2,4-diphenyl-s-triazine-6-thiol is discussed.     

Zur Kenntnis der Adsorption,I.

Ohne Zusammenfassung     

Perfluoroalkylene-linked aromatic polyimides. I. Synthesis,structure, and some general physical characteristics

This paper describes the preparation of a series of novel perfluoroalkylene- and ether-linked aromatic polyimides. Depending on the nature of the precursor diamine, the polyimides were prepared by either melt or solution techniques, the latter via the corresponding poly(amic acids). The polymers were characterized by a variety of methods, and their structure is discussed.     

1,2-Dinitrile polymers. I. Hompolymers and copolymers of fumaronitrile,maleonitrile, and succinonitrile

Homopolymers and copolymers of fumaronitrile, maleonitrile, and succinonitrile have been prepared by using medium high temperature free-radical initiators. Black, nonfusible but soluble polymers were obtained. The spectroscopic and chemical evidence indicated a structure containing α-pyrrolenine rings and no free nitrile groups in the fumaronitrile and maleonitrile polymers and 1-pyrroline rings and free nitrile groups in the succinonitrile polymers. The polymers possessed good thermal stability, free spin concentration of 10¹⁷–10¹⁸ spins/g, and an ac conductivity at room temperature in nitrogen of 10^?6 to 10^?8 ohm^?1 cm^?1.