Chinese Journal of POLYMER SCIENCE ARTICLE https://doi.org/10.1007/s10118-018-2055-5 Chinese J. Polym. Sci. 2018, 36, 214−221 Synthesis of High Performance Cyclic Olefin Polymers Using Highly Efficient WCl6-based Catalyst System Yi-Ran Zhanga, Ji-Xing Yanga, Li Pana*, and Yue-Sheng Lia, b a Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China b Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China ◆EE ElectronicA Supplementary Information Abstract Cyclic olefin polymers (COPs) with high glass transition temperature, high transparency (higher than 80%) in the visible light range, excellent thermal stability and outstanding mechanical properties have been synthesized by effective ring opening metathesis polymerization (ROMP) of exo-1,4,4a,9,9a,10-hexahydro-9,10(1′,2′)-benzeno-l,4-methanoanthracene (HBM) and dicyclopentadiene (DCPD) or norbornene (NBE) using WCl6/i-Bu3Al/ethanol/1-hexene catalyst system, followed by hydrogenation of double bonds. 1-Hexene acted as a molecular weight controller in the polymerization reaction, tuning the number-average molecular weight (Mn) of P-HBM from 5.8 × 104 to 41.1 × 104. The monomer composition and thermal properties of the copolymers were characterized by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The saturated polymers exhibited high decomposition temperatures (Td) around 340 °C and glass transition temperatures (Tg) in the range from 117.5 °C to 219.7 °C. What is more, tensile tests indicated that the mechanical properties of the COPs could be effectively tuned in a wide range by introducing varying amount of small cyclic olefin such as DCPD or NBE. Keywords Ring-opening metathesis polymerization; Hydrogenation; Cyclic olefin polymers; Glass transition temperature; Mechanical properties Citation: Zhang, Y. R.; Yang, J. X.; Pan, L.; Li, Y. S. Synthesis of High Performance Cyclic Olefin Polymers Using Highly Efficient WCl6-based Catalyst System. Chinese J. Polym. Sci. 2018, 36(2), 214−221. [15, 16] INTRODUCTION service temperature range . The Tgs of the main-stream products are in the range of 130−160 °C. Besides, toughness Over the past years, cyclic olefin copolymers (COCs) and is another important parameter of COC or COP products. cyclic olefin polymers (COPs), as a kind of high value-added However, most of the commercial products with high Tg thermoplastic engineering plastics made by usually show very poor toughness. For example, commercial (co)polymerization of cyclic olefin, have attracted extensive ® TOPAS 6017 with high Tg of 180 °C has very low attention from both academic and industry researchers elongation (< 3%), whereas, the COPs of Zeones® such as because of their excellent properties such as excellent 480R with improved ductility (elongation = 40%) shows low transparency, low moisture absorption, low birefringence, Tg (140 °C). Therefore, there is a strong desire to synthesize low density, good chemical resistance, excellent thermal high-performance COCs and COPs with both improved stability and etc[1−4]. The promising COCs and COPs can be toughness and high Tg. For COCs, increasing the cycloolefin widely used in the field of drug packaging, digital cameras, content[17, 18] and employing bulkier cycloolefin[15, 19−21] are optical recordings and electrical insulation, and they are two effective ways to enhance the Tg value. However, high showing very good prospects. COCs and COPs are cycloolefin content always results in increased brittleness. synthesized in different ways. COCs are usually obtained by Taking copolymer of norbornene (NBE) and ethylene as a the addition copolymerization of cycloolefin with ethylene [5−10] typical example, its Tg can be enhanced from 40 °C to 150 °C or α-olefin , while COPs are synthesized by ring-opening when NBE content is increased from 23 mol% to 54 mol%[15]. metathesis polymerization (ROMP) of cycloolefin and [11−14] There is no doubt that with the increase of the fraction of rigid subsequent hydrogenation . Glass transition temperature chains, the chain entanglement density is also decreased, (Tg) is one of the most important parameters of COC and COP leading to much more brittleness of polymer materials. To products, because it directly determines their continuous solve this problem, using bulkier cycloolefin monomer instead of the relative small ones is proved to an effective * Corresponding author: E-mail [email protected] Invited paper for special issue of “Metal-Catalyzed Polymerization” approach. Recently, we prepared ethylene/exo-1,4,4a,9,9a,10- Received September 15, 2017; Accepted October 2, 2017; Published online hexahydro-9,10(1′,2′)-benzeno-l,4-methanoanthracene (HBM) November 21, 2017 copolymer showing high Tg of 207.0 °C with only 30.4 mol% © Chinese Chemical Society Institute of Chemistry, Chinese Academy of Sciences www.cjps.org Springer-Verlag GmbH Germany, part of Springer Nature 2018 link.springer.com Y.R. Zhang et al. / Chinese J. Polym. Sci. 2018, 36, 214−221 215 of HBM incorporation[22]. Improved toughness was also formation of gel. COPs with very high molecular weight (up 4 achieved because of the existence of higher level of soft to 48 × 10 ), tunable monomer ratio and high Tg value (up to polyethylene segment. Different from COCs, introducing 210 °C) were synthesized. The properties including thermal bulky comonomer seems to be the only way to improve Tg of properties, mechanical properties and transparency of the COPs[23]. Ring-opening metathesis polymerization is a very hydrogenated polymers have also been explored. effective polymerization method, which can achieve complete conversion of cyclic olefin monomers. Thus, the EXPERIMENTAL synthesized polymers are very easy to be purified. Therefore, ring-opening metathesis polymerization of a cycloolefin with Materials Anhydrous solvents used in this study were purified by bulky structure is expected to yield COP with high Tg. Recently, we have synthesized a series of COPs from bulky solvent purification system (Mbraun). Tetrachloroethane HBM via ring-opening metathesis polymerization and (98.5%), dicyclopentadiene (95%), norbornene (99%) and [24] subsequent hydrogenation . Efficient Grubbs first-generation 1-hexene (97%) were purchased from J&K and dried by CaH2 catalyst was chosen to promote the polymerization of HBM and distilled before use. Norbornadiene (97%) and anthracene with 5,6-trimethylene-2-norbornene (TDE), yielding a series (97%) were purchased from TCI and used without further purification. Tripropylamine (TPA, 98%), anhydrous ethanol of COPs with high Tg values in the region of 160−220 °C (99.5%), triisobutylaluminium (1.1 mol/L in toluene) and through adjusting the monomers feed ratio. Besides, the Tgs of the COPs were elevated linearly with the increase of HBM WCl6 (99.5%) were used as received from J&K. and the elongation was also slightly improved from 2.7% to 4-Methylbenzenesulfonhydrazide (TSH, 97%) was purchased from Acros. HBM was prepared according to the previous 4.9%. However, the TDE is not commercially available; [22−24, 28] besides, the cost of Grubbs catalyst is high, and these two reports . limit wider application of this route. Therefore, to prepare Characterizations COP with desired T and toughness via an economic approach g All work involving air- and/or moisture sensitive compounds is a great challenge. On the other hand, both were carried out in an Eteluxlab2000 glovebox or under a dicyclopentadiene (DCPD) and norbornene (NBE) are high nitrogen atmosphere using standard Schlenk technique. All reactive monomers toward ROMP, and they are also very 1H- and 13C-NMR spectra were recorded on a Bruker- cheap and readily available. Compared with Ru-based 1 400 MHz spectrometer (399.65 MHz for H, 100.40 MHz for catalyst, WCl /i-Bu Al/ethanol/1-hexene is commercially 13 6 3 C). The molecular weights (MWs) and the molecular weight available and industrially applicable catalyst system. What is distributions (MWDs) of the polymer samples were more, it exhibited high reactivity in the polymerization of determined at 35 °C by a waters 515 type gel permeation norbornene derivatives and complete conversion of monomer [25−27] chromatography. Trichloromethane was employed as the was accomplished . In this study, homopolymerization of elution solvent at a flow rate of 1.0 mL/min and the HBM and copolymerization of HBM with comonomers calibration was made by polystyrene standard Easi-Cal PS-1 (DCPD and NBE) promoted by WCl6-based catalyst system (Polymer Laboratories). Differential scanning calorimetry were studied (Scheme 1). By optimizing catalyst composition, (DSC) measurements were performed on a TA Q2000 DSC quantitive conversion of COP can be achieved without Scheme 1 The synthetic routes of HBM-based COPs in this study https://doi.org/10.1007/s10118-018-2055-5 216 Y.R. Zhang et al. / Chinese J. Polym. Sci. 2018, 36, 214−221 instrument under nitrogen atmosphere. The samples were RESULTS AND DISCUSSION heated at a rate of 10 K/min and cooled down at a rate of 10 K/min. Thermogravimetric analyses (TGA) were carried ROMP of HBM, HBM/DCPD and HBM/NBE out with a TA Q50 TGA instrument at a heating rate of The bulky monomer HBM could be obtained easily via Diels-Alder reaction of norbornadiene and anthracene. This 20 K/min in nitrogen. Tensile tests were conducted at room monomer played an important role in formation of polymer temperature using a cross-head rate of 5 mm/min according to with high T . DCPD and NBE, with less bulky steric the ASTM standard. The data reported were the mean and g hindrance, are highly active toward ring-opening metathesis standard deviation from at least five determinations. The polymerization. There are two types of double bonds in transparency of polymer film was recorded on a UV-3600 DCPD, one in the six-membered norbornene ring and another spectrophotometer. in the five-membered cyclopentene ring.