Tailoring polyolefin properties by metallocene catalysis

Abstract

This doctoral thesis deals with the syntheses of olefin homo- and copolymers using different kind of metallocene catalyst. Ethene, propene, 1-hexene, 1-hexadecene, vinylcyclohexane and phenylnorbornene were homo- or copolymerized with the catalysts. The unbridged benzyl substituted zirconium dichloride catalysts (1-4), ansa- bridged acenaphtyl substituted zirconium dichloride catalysts, ( 5, 6), rac- and meso-ethylene-bis(1-indenyl)zirconium dichlorides, (rac- and meso-8), rac-ethylene-bis(1-indenyl)hafnium dichloride, ( 12), bis(9-fluorenyl)hafnium dichloride (14 ) enantiomerically pure (R)- phenylethyl[(9-fluorenyl-1-indenyl)]ZrCl2, (11), 14 and asymmetric dimethylsilyl[(3-benzylindenyl-(2-methylbenzen[e]indenyl)] zirconium dichloride, (13), were prepared in our laboratory. Dimethylsilyl-bis(1-indenyl)zirconium dichloride, (9), isopropylidene(9-fluorenyl-cyclopentadienyl)zirconium dichloride, (10), and were obtained commercially. The solid-state structures of the catalysts rac- and meso-1 were determined by X-ray crystallography. Computational methods were used for the structure optimization of the catalyst rac- and meso-1 in order to compare the theoretical calculations with the experimental results. Polymerization experiments were conducted in a highly purified autoclave system using low pressures (< 5 bar) of gaseous monomers. The experiments were designed to attain the optimal catalytic activity and a uniform copolymer composition. The prepared homo- and copolymers were characterized by the gel permeation chromatography, GPC, differential scanning calorimetry, DSC, nuclear magnetic resonance, NMR, and Fourier transform infrared spectrometry, FTIR . Molar mass (Mw, Mn), molar mass distribution (Mw/Mn), tacticity, comonomer content, melting temperature, glass transition temperature, and end group structures and content were determined. A special attention was paid on the correlation of the polymer properties with the catalyst structures and polymerization conditions. An intramolecular phenyl coordination was found in phenyl substituted benzyl zirconocenes 1-3 explaining the decreased activity of the catalysts. Novel copolymers poly(propene-co-phenylnorbornene) and poly(propene co-vinylcyclohexane), were synthesized and high molar mass poly(ethene-co-1-hexene) and poly(ethene-co-1-hexadecene) copolymers with elastic properties were prepared. Activation of a hafnocene catalyst was studied with UV-Vis spectrometry and activation process for the synthesis of ultra high molar mass poly(1-hexene) was found out.

Väitöskirjatyössä tutkittiin polyolefiinimuovien, kuten polyeteenin ja polypropeenin, muokkausta katalyyttisellä polyolefiinisynteesillä. Katalyytit olivat organometallisia metalloseenikatalyyttejä, jotka aktivoitiin alumiinialkyyli tai boraatti kokatalyyteillä. Polymerointikokeissa syntetisoitujen polymeerien ominaisuudet tutkittiin polymeerien tutkimusmenetelmillä, kuten geelipermeaatio kromatografialla (GPC), ydinmagneettisella resonassi spektroskopialla (NMR),differentiaalisella pyyhkäisykalorimetrialla (DSC) ja Fourier-muunnos infrapunaspektroskopialla, (FTIR). Metalloseenikatalyyttien erilaisilla rakenteilla havaittiin olevan selkeitä vaikutuksia syntyneiden polymeerien ketjunpituuteen, komonomeerien pitoisuuteen ja polymeeriketjussa olevien monomeeriyksiköiden avaruudelliseen järjestymiseen.

Lisäksi havaittiin eräällä katalyyttiryhmällä, että katalyyttiin kiinnitetty aromaattinen fenyyliryhmä voi hidastaa polymeroitumista kiinnittymällä itse aktiiviseen katalyyttikeskukseen. Erään metalloseenikatalyytin suorituskyvyn huomattava paraneminen havaittiin käyttämällä boraatti-kokatalyyttiä. Työssä syntetisoitiin myös uusia polypropeenin kopolymeerejä.