Maria M. Marques

Polymerization with TMA‐protected polar vinyl comonomers. II. Catalyzed by nickel complexes containing α‐diimine‐type ligands

α-Diimine Ni complexes (7, 8) were used as catalyst precursors with MAO in co- and terpolymerization of ethylene/propylene/α-olefins with OH and COOH functional groups. Trimethylaluminium was used to protect the functional group of polar monomers. The presence of 5-hexen-1-ol seems to have no effect on the polymerization rate at all for the N,N′-bis(2,6-diisopropylphenyl) derivative 8 but caused activity decreases of about fivefold in copolymerization and around two times in terpolymerization for the N,N-dimesityl derivative 7. The effect levels off at higher polar comonomer concentration. This system, (7)/MAO, also incorporates well both 10-undecen-1-ol and 10-undecen-1-oic acid. The activities obtained with these α-diimine Ni complexes in co- and terpolymerization are three to twenty times higher than those obtained with group 4 Cp based complexes especially at concentrations of polar monomer in the feed higher than 80 mM.

Polymerization with TMA‐protected polar vinyl comonomers. I. Catalyzed by group 4 metal complexes with η5‐type ligands

This paper describes the use of several kinds of group IV Cp based catalyst systems, in the synthesis of co- and terpolymers of ethylene, propylene and α-olefins endowed with OH and COOH functional groups. The hydroxy monomers used were 5-hexen-1-ol (4) and 10-undecen-1-ol (5) and the carboxy monomer was 10-undecen-1-oic acid (6). The three catalyst systems used were the C 2 symmetric ansa-zirconocene (1) the in-site titanium complex (2) and the non-rigid zirconocene (3), all activated by methylaluminoxane. Trimethylaluminium was used to protect the functional group of polar monomers. The first two catalyst systems suffer similar activity loss in the presence of polar monomer whereas the third one exhibited better tolerance toward the hydroxyolefins. NMR and FTIR spectroscopies were used to characterize the polymerization products. All three catalyst systems afforded functionalized co- and terpolymers by direct polymerization of ethylene/propylene/hydroxy-a-olefins but only the catalyst system (1)/MAO displays appreciable activities for direct polymerization of ethylene, propylene and carboxy-α-olefins.

Polymerization of ethylene using metallocene and aluminoxane systems

This paper describes ethylene polymerization using a number of metallocene and aluminoxane catalyst systems, Cp 2 MR 2 and methylaluminoxane [M = Zr, W, Nb; R = Cl, CH 3 ]. Two types of methylaluminoxane, MAO (I) and MAO (2), were used as cocatalysts. The polymerization activities of the complexes Cp 2 WCl 2 and Cp 2 NbCl 2 were compared with that of Cp 2 ZrCl 2 . The Nb and W complexes were found to be less active than the Zr complex. Polyethylene characterization was also carried out by the following methods: gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR).

(R=alkyl or aryl) complexes as catalysts for ethylene polymerization

Abstract (R=alkyl or aryl) complexes in combination with methylaluminoxane were found to be highly efficient catalysts towards ethylene polymerization. The species with aromatic R groups display higher activity than those with aliphatic ones. This tendency could not be correlated with the electronic properties of the complexes that were evaluated by cyclic voltammetry. The polyethylenes obtained in the catalytic processes were characterized by 1 H NMR and DSC.

A KINETIC APPROACH TO HOMOGENEOUS ZIEGLER TYPE POLYMERIZATION. STEADY STATE

In this paper we present a kinetic approach to the analysis of steady-state homogeneous Ziegler-Natta polymerization activity data. The influence of the number of monomeric species that are coordinated to the active site on the apparent rate law is discussed and the equations are fitted to the experimental results.

THE ROLE OF THE ACUTE PHASE PROTEIN PTX3 IN THE VENTILATOR-INDUCED LUNG INJURY

The pentraxin 3 (PTX3) is an acute phase proinflammatory protein produced by fibroblasts and alveolar epithelial cells. We have previously demonstrated that PTX3 is a key modulator of inflammation. Mechanical ventilation (MV) is a life saving therapeutic approach for patients with acute lung injury that, nevertheless could lead to an inflammatory response and tissue injury (ventilator-induced lung injury: VILI), representing a major cause of iatrogenic lung damage in intensive units. Our objective was to investigate the role of PTX3 in VILI. PTX3 transgenic, knockout and Wt control mice (n = 12/group) were ventilated (45ml·kg−1) until respiratory system Elastance increased 50% (Ers150%), an indicator of VILI. Histological analysis demonstrated that using a Ers150% was appropriate for our analysis since identical degrees of inflammation were observed in Tg, KO and Wt mice as assessed by leukocyte infiltration, oedema, alveolar collapse and number of breaks in alveolar septa. However, Tg mice reached Ers150% faster than Wt controls (p = 0.0225). We also showed that the lack of PTX3 does not abolish the occurrence of VILI in KOs. Gene expression profile of PTX3, IL-1beta, IL-6, KC, IFNgamma, TGFbeta and PCIII were investigated by QPCR. MV drastically up modulated PTX3 as well as IL-1beta, IL-6, IFNgamma and KC. Alternatively, mice were ventilated for 20, 40 and 60 min. The faster kinetics of Tg mice to reach Ers150% was accompanied by an earlier augmentation of IL-1b and PTX3 expression. The kinetics of local PTX3 expression in the lungs of ventilated mice strongly suggests the involvement of this pentraxin in the pathogenesis of VILI.

Copolymerization of Ethylene/ω-Hydroxy α-Olefins

Two different homogenous catalyst systems, a C2 symmetric ansa-zirconocene (1) and a α-Diimine Ni complexes (2) activated by methylaluminoxane were used in copolymerization of ethylene /α-olefins with OH functional groups.The α-olefins with OH functional group used as co-monomer in the polymerisation reactions were 5- Hexen-l-ol (3) and 10-Undecen-1-ol (4).

A kinetic approach to homogeneous Ziegler type polymerization. Transient state

In this paper we present a kinetic approach to the analysis of transient-state homogenous Ziegler-Natta polymerization activity data. The main features of the experimental data are discussed and fitted to transient kinetic models.

Study of low catalytic activity systems (biscyclopentadienyl complexes–aluminoxane) on olefin polymerization

Olefin polymerization using low activity catalyst systems: Cp 2 WCl 2 -methylaluminoxane, [Cp2 Mo(CH 3 ) 2 ] [PF 6 ]-methylaluminoxane and Cp2Mo(CH 3 ) 2 -methylaluminoxane, is described. All these catalyst systems were studied in ethylene and propylene polymerization; however, they only showed catalytic activity for ethylene. Only one type of methylaluminoxane (MAO) was used, prepared in an Al/H 2 O ratio of 2. The kinetics of polymerization were examined and the experimental data (either presented here or in previous papers) were fitted to the kinetic models developed previously and now extended to account for the methylaluminoxane effect.

Heterogeneization of alpha diimines nickel catalysts for the polymerization of ethylene and methylmethacrylate

Abstract In this paper we present two different techniques for the preparation of single site heterogeneous catalyst. The first method consists in the impregnation of a solution of the organometallic compound in MCM41. The second method intends to establish the in situ synthesis of the complex within the solid’s pores by the reaction of the organic ligand with the metal cation previously introduced in the support. The direct deposition of the organometallic complex in the support resulted in an active catalyst which gives polyethylene with the same microstructure as the one obtained with the related homogeneous systems. The heterogeneous catalysts obtained by reaction of the ligand with the metal already present in the support showed a lower catalytic activity.