Sebastiano Cesca

Copolymerization of isobutene with 2,4,6-octatriene and other triconjugated trienes

SummaryThe cationic homogeneous Copolymerization at low temperature of 2,4,6-octatriene (OT), 1,3,5-heptatriene (HPT), 2,5-dimethyl-1,3,5-hexatriene (DMH) and alloocimene (AO) with isobutene (I) was performed and the structure of the resulting copolymers examined spectroscopically. OT reacted mainly by 2,7-opening of the triene system yielding soluble copolymers with block character and containing a low amount of cyclized units. Soluble I-HPT copolymers containing 2–4 mol % of conjugated double bonds were obtained. DMH alway gave insoluble copolymers and only traces of conjugated unsaturations were found in I-AO copolymer.

Synthesis and modification of polymers containing a system of conjugated double bonds

Two broad classes of hydrocarbon copolymers containing a system of conjugated double bonds randomly distributed in the chains, i. e., (i) ethylene-propylene based terpolymers and (ii) triene-isobutene copolymers.

Cationic copolymerization of isobutene with 1,1,4,4-tetramethyl-1,3-butadiene

SummaryThe copolymerization of isobutene (I) and 1,1,4,4-tetramethyl-1,-3-butadiene (TMB) was carried out easily and for the first time at −30°C, in a homogeneuos medium and using EtAlCl2 as catalyst. The structure of TMB in the copolymer is exclusively trans-1,4 while the monomer distribution, studied by C-NMR, is random.Using the values of the dyad and triad (centered on I) fractions, the reactivity ratios of both the monomers were obtained according to a procedure previously described: rI=2.0 ±0.4 and rTMB=0.4±0.2.

Copolymerization of isobutene with trans-1,3,5-hexatriene

SummaryThe cationic copolymerization of isobutene (I) and trans-1,3,5-hexatriene (HT) at low temperature occurs randomly (rI=0.59, rHT=1.57). The prevalent 1,6-opening of the triconjugated system of HT was ascertained mainly by 1H- and 13C-NMR analysis. The formation of gelled products was avoided by working in a homogeneous medium and the cyclization of the triene units by copolymerizing I and HT in bulk.

On the Epimerization of endo-Dicyclopentadiene during Terpolymerization with Ethylene and Propylene

Abstract The isomerization of endo-DCP (I) to exo-DCP (II) during the synthesis of EPDM with several Ziegler-Natta catalysts has been investigated by means of IR spectroscopy and by reference to EPDM containing different levels of true exo-DCP. The I - II epimerization was absent for ail the catalysts examined. Only with the systems VC14-Et2AlCl was a trace of isomerization observed, and then only at the limit of sensitivity of the analytical method. No isomerization was detected via gas-chromatographic analysis in monomeric DCP recovered from the polymerization mixture. Ziegler-Natta catalysts having acidic character can homopolymerize I, but epimerization was observed only with the system voc13-Et3Al2Cl3. The results obtained have been interpreted in terms of a terpolymerization mechanism having a prevalent coordinated character. The poly functionality of Ziegler-Natta catalysts is sometimes responsible of the secondary isomerization process.

Synthesis and Properties of New Toughened Resins Based on Ethylene-Propylene Copolymers

Toughened resins (ACS) displaying interesting physical properties can be synthesized by grafting styrene and acrylonitrile (SAN) onto EPM provided that suitable reaction conditions are chosen. ACS resins exhibit better ageing behaviour than classical toughened plastics which contain unsaturations in the elastomeric back-bone. The mechanical properties are satisfactory owing to the network-like morphology of the rubbery phase and the level of graft achieved in the ACS resins studied.

Quaterpolymerization of Ethylene, Propylene, Dicyclopentadiene, and Methylcyclopentadienyl-5-endo-norborn-2-enyl-methane

Abstract The quaterpolymerization of methylcyclopentadienyl-5-endo-norborn-2-enyl-methane with ethylene, propylene, and either endo- or exo-dicyclopentadiene was studied by using the catalyst system VAcac3-Et2AlCl. The influence of catalyst and polyenes concentrations, catalyst modifiers, and other polymerization parameters on the general properties of quaterpolymers was investigated. The polymers obtained showed a random distribution of the comonomeric units and the ability to covulcanize with 1,4-cis-polyisoprene.