5‐Ethylidene‐2‐norbornene Polymerization by α‐Diimine Nickel Catalyst: A Revealing Insight into the Pivotal Function of Binuclear and Mononuclear Catalyst Structure in Tailoring Polymer Architecture

Abstract

The present investigation is undertaken to provide a deeper understanding of the 5‐ethylidene‐2‐norbornene (ENB) homopolymerization. To this end, binuclear and mononuclear nickel α‐diimine catalysts, as well as modified methylaluminoxane (MMAO) as a cocatalyst, are selected and utilized. Al/Ni ratio of 1000 coupled with a temperature 25 °C and a polymerization time 12 h are chosen as the optimal statistics. It is shown that the highest obtained activity for binuclear and mononuclear catalysts are 511 and 478 kg polymer/mol, respectively. Thereafter, the characterization of the obtained poly 5‐ethylidene‐2‐norbornene (PENB) is performed by fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Concerning the glass transition of cyclic polyolefin, DSC analysis reveals that catalyst structure is a determining factor (Tg binuclear: 176 °C and Tg mononuclear: 140 °C). As validated by dynamic mechanical thermal analysis (DMTA), it is realized that the alteration in the catalyst structure exerts a far‐reaching influence on the polymer architecture. Surprisingly unexpectedly, excluding addition polymerization, an in‐depth examination of polymer structure uncovers the potentially tenable participation of both cationic and ring‐opening polymerization, albeit, with a diversified degree of contribution. Lastly, PENB is functionalized with three functional groups, and then the successful grafting of polar functional groups into modified cyclic polyolefin backbone is confirmed by NMR and FTIR spectroscopy.

Shedding light on the poly(5‐ethylidene‐2‐norbornene) microstructural differences: Skeleton rearrangements during polymerization

“…It is also important to note that these distinctions originate primarily from various modes of monomer enchainment coupled with the skeleton rearrangements during polymerization. According to the 13 C NMR spectra of P(NB-M), and P(NB-B), our former studies proved that the Ni-based catalysts (BNC, MNC), by and large, perform polymerization of NB through vinyl-addition polymerization (2,3-enchainment). 14,44 Hence, it can be suggested that the presence of tethered exocyclic double bond exerts a far-reaching impact on the governing polymerization pathways.…”

“…23 The characteristic signals that are assignable to unsaturated moieties (2.4-2.8 and 5-6.2 ppm) for P(ENB-B) have been previously shown to disappear following the chemical functionalization. 13 According to spectroscopic data in this study, two probabilities, namely Scheme 6 and Scheme 7 can be proposed as probable structures of P(ENB) samples produced by BNC and MNC, respectively. Figure 8 displays the 1 H NMR spectra of ENB-NB copolymers (Table 1).…”

“…The 13 C NMR spectrum (Figure 5) of P(ENB-B) indicates that the observed peaks are not similar to the characteristic signals of vinylic P(ENB). 22 Yet these signals are comparable to the peaks of cationic P(ENB).…”

“…The preparation method of the ligands, catalysts, and some general characterizations (FTIR, elemental analysis, and 1 H NMR) are reported in the supporting information; see Figures S1-S12). [12][13][14] The structures of the respective catalysts are depicted in Scheme 2.…”

Ansa-metallocene Catalyst based on 3-phenyl and 4-methyl Substituted: Catalyst Evaluation in Conjugated and Non-conjugated Diene Polymerization

“…[ [1][2][3][4][5][6] Recent developments, metallocene-catalyzed chain-shuttling polymerizations, have facilitated expanding the range of metallocene versatility. However, only five metallocene catalysts have been kinetically studied in the literature, partly because there are no efficient methods or rapid kinetic models for obtaining necessary information, such as active site counts.…”