A comparative study of 5-ethylidene-2-norbornene (ENB) or 5,7-dimethylocta-l,6diene (5,7-DMO) as diene termonomer in ethylene-propylene-diene (EPDM) terpolymer synthesis is presented. The reactivities of the cyclic and linear non-conjugated dienes are first compared in homopolymerization in the presence of two conventional Ziegler-Natta catalytic systems: TiCl,, 1/3A1C13, 14MgC1, associated to AIEt,, and VOCl, (or VCI,) associated to AlEt,Cl. ENB polymerization yields a branched poly(ENB) in agreement with a predominant cationic reaction, whereas polymerization of 5,7-DMO proceeds exclusively by a Ziegler-Natta mechanism. In terpolymerization, ENB is much more reactive than 5,7-DMO and is incorporated more easily in the terpolymer. However, the high sensitivity of ENB toward acidic species also results in cationic side reactions and therefore limits the utilization of ENB to a low concentration range. We have shown that the productivity of vanadium catalysts, which are mainly used in industrial EPDM synthesis, is drastically reduced in the presence of ENB an 5,7-DMO, due to the rapid reduction of vanadium involving the diene.

The carbonation of biosourced 1,2-diols is a sustainable avenue for the synthesis bis-five-membered cyclic carbonates (bis-5CCs), the precursors of a valuable class of polymers, for example, polyhydroxyurethanes (PHUs). In this work, we performed the direct carbonation of optically pure sugar-based butadiene tetraols, namely, (i) meso-erythritol and (ii) its (S,S) diastereoisomer, (L)-threitol. The corresponding vicinal bis-5CCs, erythritol dicarbonate (EDC) and threitol dicarbonate (TDC), respectively, retain the stereochemistry of the starting tetraols. The comprehensive study of their aminolysis reaction, in DMSO and at room temperature, indicates that the kinetics and the regio-orientation of the ring opening of the 5CC are very much dependent on their stereochemistry. The total aminolysis of EDC results in the formation of hydroxyurethanes with an excess of secondary hydroxyl groups, (OH) II , of about 85%, against 60% for TDC. Moreover, when considering the two consecutive aminolyses of EDC (and TDC, respectively), the kinetic rate constant of the first aminolysis k 1,EDC (and k 1,TDC , respectively) is 1 order of magnitude higher than that of the second aminolysis, k 2,EDC ∼ k 1,EDC /10 (and k 2,TDC ∼ k 1,TDC /10, respectively). We used this feature to develop a onepot, two-step polymerization procedure, offering sequence-controlled PHUs. All the experimental results are well supported by density functional theory calculations. In the end, the comparative study of these two diastereoisomers of simple sugar-based vicinal bis-5CCs provides a new family of PHUs with tunable sequence-and regioregularities.

The synthesis in the presence of the ruc-EtInd,ZrC1,/MAO catalytic system of new EPDM terpolymers based on linear non-conjugated dienes issued from biomass, 3,7-dimethylocta-l,6-diene (3,7-DMO) and 5,7-dimethylocta-1,6-diene (5,7-DMO), is described. 5,7-DMO can be readily incorporated in ethylene/propylene (ER) chains, while 3,7-DMO does not react in the presence of the metallocene catalyst. The reactivity of these linear dienes is compared with that of 2-ethylidenebicyclo[2.2.l]hept-5-ene (ENB), the preferred termonomer for the industrial synthesis of EPDMs. With the metallocene catalyst, the reactivity of 5,7-DMO is close to that of ENB, suggesting that 5,7-DMO is a good candidate for the synthesis of a new EPDM. A comparison with the conventional catalysis based on vanadium systems shows that the advantages of the metallocene catalysis consist in higher catalyst activities and higher incorporation rates of the termonomers in the polymer without any noticeable side reaction. The structural and physico-chemical characteristics of the various terpolymers, investigated by NMR, SEC and DSC, also underline that the use of metallocenes allows one to prepare EPDM based on linear dienes, with an homogeneous chemical composition and a controlled structure.

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