vinylidene allyl 4-methyl-3-pentenyl ETHENE-PROPENE COPOLYMERS WITH FLUORENYL-BASED METALLOCENE CATALYSTS M.Cornelio 1,2, P.Locatelli 1, G.Di Silvestro 2, L.Boggioni 1, I.Tritto 1. 1 Istituto per lo studio delle Macromolecole, Consiglio Nazionale delle Ricerche, Via Bassini, 15, 20133, Milano. 2 Dipartimento di Chimica Organica e Industriale, Università degli Studi di Milano, Via Venezian, 21, 20133, Milano Introduction The development of C s -symmetric catalysts has opened the possibility to synthesize syndiotactic polypropylene (sPP):  Thermoplastic materials;  High melting point;  High cristallinity. Adding low amount of ethylene to sPP (1-5 mol %) a better plastic material could be obtained:  Higher cristallinity;  Higher elasticity;  Lower Molecular Weight Fig. 1 C s - and the two C 1 -symmetric metallocene precursors: A: R substituent more hindered than in D J.A. Ewen, R.L. Jonas, A. Razavi. J. Am. Chem. Soc, 1988, 110, 6255; J. Voegele, C. Troll, B. Rieger. Macromol. Chem. Physics, 2002, 203, 1918 D. Wang, S. Tomasi, A. Razavi, T. Ziegler. Organometallics, 2008, 27, A.Carvill, I. Tritto, P. Locatelli, M. C. Sacchi. Macromol, 1997, 30, 7056 r Objectives The aim of the work is to study the influence of low amount of ethylene on the M w of sPP obtained using C 1 - and C s -symmetric metallocene precursors Methods  Propene homopolymers and propene-ethene copolymers have been synthesized ;  C 1 -symmetric (A and D) and the reference CpFlu metallocene precursors activated by MAO have been used;  The homo- and copolymers have been characterized by 1 H and 13 C-NMR and GPC to have an evaluation of the factors that affect the chain transfers and molar masses Chain termination mechanisms Chain propagation  -hydrogen transfer to metal vinylidene  -hydrogen transfer to monomer vinylidene Chain propagation vinylidene  -hydrogen transfer to monomer vinylidene Chain propagation  -hydrogen transfer to metal allyl  -hydrogen transfer to monomer allyl a) Left chain end groupsb) Right chain end groups ethyl n-butyl n-propyl Homopolymers  The more hindered R substituent in A leads to the highest activity;  All the catalysts give mainly syndiotactic polypropylene;  The rrrr percentage decrease when T is increased;  The M w decreases when the T is increased;  The more hindered R and R 1 substituents in C 1 –symmetric catalysts leads to an increase in M w with respect the reference CpFlu catalyst. Copolymers  The more hindered R and R’ substituents in A leads to the highest activity;  The D catalyst incorporates high amount of ethylene;  The amount of comonomer incorporated increases when the T is increased;  The more hindered R and R 1 substituent in C 1 –symmetric catalysts leads to an increase in M w with respect the reference CpFlu catalyst; in any cases the M w is influenced by theT and is lower than homopolymers. S  S  T  T  T  S  P  + P  +P  P = PP + ½ PE E = EE + ½ PE PP = S  PE  S  S  EE  ½  S  S   S   -hydrogen transfer to metal 1 H-NMR: left chain end groups 13 C-NMR: right chain end groups ethyl n-propyl n-butyl  Ethyl>n-propyl groups with both C s and C 1 - symmetric catalysts: chain transfer to ethylene is preferred;  High percentage of n-butyl groups with both catalysts: the reinitiation is preferred with an ethylene unit.  No terminal groups visible with A catalyst because of too high molecular weights. In Autoclave. Conditions: Solvent: 150 ml of Toluene; Al/Zr: 3000 m.r.; pressure: beetween 4-7 bars; ethylene: 0.5 mol% in feed. allyl  -CH 3 abstraction CsCs C 1 : A and D vinylidene allyl HomopolymersCopolymers D A Conclusions  In the presence of less hindered ethene molecules the rate of  -H transfer to ethene become kinetically competitive with respect the chain propagation pathway and this results in lower molecular weight.  The appropriate hindrance of the ligand in catalyst A allows to minimize this effect which has a strong negative effect on the production and properties of the final copolymer material.  Ethene molecules can lead to an increase in activity due to the possibility of E insertion at dormant sites. D Copolymer  Homopolymers: percentage of vinylidene groups higher than allyl groups both by using C s and C 1 - symmetric catalysts: the  -H transfer is preferred with respect the CH 3 - abstraction.  Copolymers: the very low percentage of allyl groups with respect the vinylidene groups: the termination is preferred after propylene unit insertions;  The more hindered R and R’ substituents in A leads to the highest activity and to highest molar masses of Copolymers