Abstract: Branched low-pressure polyethylenes are prepared by oligomerization of ethylene on a nickel-containing catalyst and polymerization of the oligomers obtained, if appropriate in the presence of ethylene, on a chromium-containing catalyst.

Abstract: Highly effective polarizers are described having a degree of polarization P of at least 95% and a dichroic ratio Q.sub.E =quotient of the extinction in the blocked position to the extinction in the transmission position, over almost the entire wavelength range of visible light, between 400 and 800 nm, of 10 or greater, the said polarizers comprising polyacetylene-containing polymer products with a matrix of pure polyvinyl alcohol (PVA). They are used in the form of films with a stretch ratio ##EQU1## (1=length after stretching, 1.sub.0 =length prior to stretching) of more than 300%. They can be prepared by polymerizing acetylene in a solution of pure PVA in the presence of a nickel catalyst.

Abstract: New light-polarizing articles (preferably in film form) are based on a polymer matrix which polarizers based on a polymer matrix which is constructed from polar or nonpolar monomer units or mixtures thereof, characterized in that polyacetylene is included as light-polarizing substance, said polyacetylene being obtained by polymerizing acetylene in solutions of said polymer matrix and thereafter processing the resultant polyacetylene/polymer solutions into polarizers.