Semibatch Terpolymerization of Ethylene, Propylene, and 5-Ethylidene-2-norbornene: Heterogeneous High-Ethylene EPDM Thermoplastic Elastomers

Abstract

Thermoplastic elastomers (TPEs) are materials combining the processability of thermoplastics and the elasticity of rubbers. The global value and demand of TPEs is expected to grow in coming years, and advancement in synthetic chemistry is the key driving force. This contribution provides a simple synthesis of high−ethylene EPDMs with high molecular weight, narrow molecular weight distribution (1.9 < M w /M n < 2.3), and properties which can be adjusted from soft thermoplastic to elastomer. EPDMs are prepared through the terpolymerization of ethylene with propylene and 5ethylidene-2-norbornene (ENB), where ethylene is continuously supplied to the reaction bath, while 2 propylene and ENB are added only at the beginning. Polymerizations are catalyzed by three known imido vanadium(IV), differing in the imido substituents and coligand, in combination with Et 2 AlCl and Cl 3 CCO 2 Et. The obtained EPDMs are a mixture of macromolecules each of them featuring a non random comonomer distribution, and non uniform composition. Each chain likely contains multiblocks where the comonomers are segmented, i.e., blocks with high ethylene content that may crystallize, and blocks with high propylene and ENB content that may not crystallize. This broad chemical composition distribution is due to time drift that occurs during the polymerization, which in turn depends on the experimental conditions and ligand set. Composition drift causes variation in the instantaneous feed comonomer ratio, and hence in the chemical composition of the terpolymer over the period of conversion. In proper experimental conditions, EPDMs behave as TPEs without the need of vulcanization, polymer blending, and reinforcement through the addition of fillers. They exhibit high elongation at break, strain hardening at large deformation, remarkable shape retention properties (up to 76% recovery after 10 cycles at 300%, and about 90% at 410% strain), and remelting processability with no fall in properties for recycle and reuse.atmosphere for 8 h, distilled, and stored over 5Å molecular sieves away from bright light. Ethyltrichloroacetate (ETA, Aldrich, 97%) was dried by stirring over CaH 2 for about 4 h, and then distilled under reduced pressure. Et 2 AlCl (Aldrich) was used as received. ENB (Aldrich, mixture of endo and exo, 99% pure), 1-hexene (Aldrich, 97% pure), and 1-octene (Aldrich, 98% pure) were dried by stirring over CaH 2 for about 4 h, then distilled under reduced pressure and, finally, stored under dry nitrogen and kept at -30 °C. The synthesis of imido V(IV) complexes, hereinafter referred as 1a, 2a and 2b, is reported in our previous work. 35,36 Polymerization Experiment. Polymerizations were carried out in a 100 mL roundbottomed Schlenk flask containing a stirring bar. Prior to starting polymerization, the reactor was heated to 110 °C under vacuum for 1 h, and backfilled with nitrogen. The typical reaction procedure for ethylene/propylene/ENB terpolymerization is as follows. Toluene, the appropriate amount of propylene (as a toluene solution), ENB, ...

Methods for Predicting Ethylene/Cyclic Olefin Copolymerization Rates Promoted by Single-Site Metallocene: Kinetics Is the Key

“…In E/VCH copolymerization, VCH tends to suppress the ethylene incorporation rate, especially during 120 s to 360 s, and to lower the copolymers’ molecular weight. Comparable findings were observed in earlier investigations [ 34 , 43 , 44 , 45 ] Additionally, the VCH endocyclic π bond may interact with the active species distantly, resulting in a smaller incorporating gap and quicker chain transfer. According to these conclusions, small changes in the architectures of comonomers and catalysts can alter polymer behavior and activity.…”

Rapid kinetic evaluation of homogeneous single-site metallocene catalysts and cyclic diene: how do the catalytic activity, molecular weight, and diene incorporation rate of olefins affect each other?

“…These results look to be closely related to the comonomer's bulkiness. 10,[43][44][45] The above-discussed reaction has been conrmed from the peaks of the vinyl groups in the assembled polymer chain (see the ESI, Fig. S2 †).…”

Vanadium-Catalyzed Terpolymerization of α,ω-Dienes with Ethylene and Cyclic Olefins: Ready Access to Polar-Functionalized Polyolefins

“…Compared with the E/HXD copolymer, T g of the resulting terpolymers significantly increases because the bulkier pendant cyclic olefins restrict rotational freedom to some extent. The terpolymers showed T g s ranging between −6 and −3 °C and some of them did not show melting events because the total amount of incorporated 1,5-hexadiene and cyclic olefin is higher than 20 mol %, a composition that usually prevents crystallization (Table , entry 5 and 6) …”

“…The terpolymers showed T g s ranging between −6 and −3 °C and some of them did not show melting events because the total amount of incorporated 1,5-hexadiene and cyclic olefin is higher than 20 mol %, a composition that usually prevents crystallization (Table 2, entry 5 and 6). 40 The microstructure of the resultant terpolymers was investigated by NMR. Peak assignment was carefully performed by comparison of the observed chemical shifts with those of entry 3 (Figure 3a and Table S5) and the previous data by some of us.…”

“…These include V­(acac) 3 in combination with Et 2 AlCl. , Previously, we reported a series of imido V­(IV) precatalysts, which promote the copolymerization of ethylene with α-olefins, and cyclic olefins to afford thermoplastics and polyolefin elastomers (Chart ). , Further investigations on these complexes revealed that changing the imido skeleton significantly affects the catalytic performance.…”