Synthesis of ultrahigh molecular weight polymers by homopolymerisation of higher α-olefins catalysed by aryloxo-modified half-titanocenes

Abstract

Polymerisation of 1-decene, 1-dodecene, 1-hexadecene, and 1-octadecene by Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1) – MAO catalysts yielded high molecular weight polymers with unimodal molecular weight distributions, and the M_n values in the resultant polymers were higher than those prepared by linked half-titanocene, [Me₂Si(C₅Me₄) (N^tBu)]TiCl₂ and ordinary zirconocenes (Cp₂ZrCl₂ etc.); Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) – [Ph₃C][B(C₆F₅)₄] catalyst showed higher catalytic activities, affording ultrahigh molecular weight polymers (M_n = >1.07 × 10⁶).

---

Introduction

Polyolefins produced by metal catalysed olefin polymerisation are important synthetic polymers in industry, and synthesis of new polymers with specified functions is an attractive research subject. Design of molecular catalysts has been considered to play an important role for synthesis of new polymers,^1,2 and the recent progress offers new possibilities.^1–6 In contrast to successful applications of isotactic polypropylene as a crystalline material, the use of amorphous poly(α-olefin)s (APAOs) has been shown less attention due to their inherent stickiness and softness. However, APAOs are used in hot melt applications due to their high melt flow rate with low density; these are known to improve adhesion on wood and PP, cohesion and even improve the free-flowing ability of the APAO granules.⁷

In general, as described below, polymerisation of α-olefin (1-hexene, 1-octene etc.) by ordinary metallocene catalysts gave oligomers (M_n = ca. 4000),⁸ and several examples^8–13 were known for synthesis of (ultra)high molecular weight poly(1-hexene)s by using [2,2-(O-4-Me-6-^tBu-C₆H₃)₂S]TiCl₂ (in the presence of specified modified MMAO),⁹ or (C₅HMe₄)₂HfCl₂ (under ultrahigh pressure);¹⁰ some examples by the others afforded rather high molecular weight polymers.¹⁴ It was reported by us that polymerisation of α-olefin (1-hexene, 1-octene) by Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1) – MAO catalyst afforded high molecular weight polymers¹¹ that were rather higher than those prepared by CpTiCl₂(N = ^tBu₂) – MAO catalyst,¹² and the others.¹⁴ Moreover, we reported that polymerisation of 1-hexene by Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) – borate catalyst afforded ultrahigh molecular weight poly(1-hexene)s (M_n = >1.0 to 1.9 × 10⁶);¹³ the polymerisation proceeded in a quasi-living manner under certain optimised conditions.^13b

In this paper, we thus report our explored results for polymerisation of higher α-olefins (1-dodecene, 1-hexadecene, 1-octadenece) using Cp*TiX₂(O-2,6-ⁱPr₂C₆H₃) (X = Cl, Me) – cocatalyst systems including comparison with those by [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂ (ordinary linked half-titanocene), Cp₂ZrCl₂ (ordinary metallocene).¹⁵ In particular, we wish to demonstrate that synthesis of ultrahigh molecular weight (brush like) polymers by polymerisation of 1-dodecene has been achieved especially by using Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) – borate catalyst Scheme 1.¹⁵

Scheme 1 Polymerisation of higher α-olefins (with long branching).

Results and discussion

Polymerisation of 1-decene (DC), 1-dodecene (DD), 1-hexadecene (HD), 1-octadecene (OD) by Cp*TiX₂(O-2,6-ⁱPr₂C₆H₃) (X = Cl, Me), [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂, Cp₂ZrCl₂

It turned out that, as reported previously (in the 1-hexene and 1-octene polymerization),¹¹ polymerisation of 1-decene (DC), 1-dodecene (DD) using Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1) – MAO catalyst proceeded with high catalytic activities affording high molecular weight polymers with uniform molecular weight distributions (M_n = 4.35 to 7.88 × 10⁵, M_w/M_n = 1.23–1.84, shown in Table S1 in the ESI†);^16,17 no significant effects of number of side chain (from 1-hexene to 1-dodecene) toward the M_n values were observed. The activity was affected by the Al/Ti molar ratios (shown in Table S1†),¹⁶ but significant differences in the M_n values were not observed by varying the Al/Ti molar ratios. The results could suggest that β-hydrogen elimination would be a major chain transfer rather than transfer to Al in this catalysis.

Polymerisations of 1-octene (OC), 1-decene (DC), 1-dodecene (DD), 1-hexadecene (HD), and 1-octadecene (OD) using 1, [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂ (2), Cp₂ZrCl₂ (3) were conducted in the presence of MAO (α-olefin 5.0 mL, 25 °C, 30 min), and the results are summarised in Table 1. It turned out that complex 1 showed higher catalytic activities than 2 in the polymerisations of OC, DC, DD under the same conditions (runs 1–5, 9–12). For example, the activity by 1 in DD polymerisation (TON 4120 after 30 min, run 5) was higher than that by 2 (2060, run 12), and the M_n value in the resultant polymer by 1 was higher than that by 2 [M_n = 5.25 × 10⁵ (by 1, run 5) vs. 3.51 × 10⁵ (by 2, run 12)]; the similar trend was observed in these polymerisations. Moreover, the observed activities by 1 in 1-octene and 1-decene polymerisations were higher than those previously reported by [2,2-(O-4-Me-6-^tBu-C₆H₃)₂S]TiCl₂ (activity 300 kg mol⁻¹-Ti h in OC polymerisation),^9c [O-2-^tBu-6-(PhN = CH)C₆H₃]TiCl₂ (activity ca. 1480 kg mol⁻¹-Ti h in DC polymerisation).⁸ The M_n values in the resultant poly(DC)s, poly(DD)s prepared by 1 were higher than those by 2. However, no significant difference in both the activity and the M_n values in the resultant polymers were observed in HD, OD polymerisation using 1,2 – MAO catalysts. In contrast, the reactions with Cp₂ZrCl₂ (3) afforded low molecular weight oligomers with high catalytic activities, as observed in the polymerisation by rac-[Et(indenyl)₂]ZrCl₂ – borate catalyst.⁸ The observed activities by 3 were higher than those reported previously by the bis(indenyl) analogue.⁸ It is thus clear that catalysts 1,2 are effective for synthesis of high molecular weight polymers with unimodal molecular weight distributions (by 1, M_n = 2.27 to 5.25 × 10⁵, M_w/M_n = 1.35–1.49, runs 5–8). The resultant polymers possessed atactic stero-regularity (and are amorphous materials),^18,19 which possess melting temperatures (T_m) in poly(DD), poly(HD) due to their longer side chains (side chain crystallization); the T_m value increased upon increasing number of the methylene units.¹⁸

Table 1 Polymerisation of 1-octene (OC), 1-decene (DC), 1-dodecene (DD), 1-hexadecene (HD), 1-octadecene (OD) using Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1), [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂ (2), Cp₂ZrCl₂ (3) – MAO catalysts^a

Run	Cat.	α-Olefin	Yield/mg	TON	Activity^b	Mn^c	Mw/Mn^c	Tm^d/°C
a Conditions: complex 1.0 μmol, α-olefin 5.0 mL, d-MAO (prepared by removing toluene and AlMe3 from ordinary MAO) 2.0 mmol, 25 °C, 30 min.b TON (turnover number) = (mmol of α-olefin reacted)/(mmol-Ti).c Activity = kg-polymer/mol-Ti h.d GPC data THF vs. polystyrene standards.
1	1	OC	1117	9950	2240	501 000	1.42
2	1	OC	1070	9530	2140	492 000	1.49
3	1	DC	922	6570	1840	574 000	1.84
4	1	DC	904	6450	1810	435 000	1.78
5	1	DD	694	4120	1390	525 000	1.35	−24
6	1	HD	234	1040	470	389 000	1.35	26
7	1	OD	289	1140	580	227 000	1.42	42
8	1	OD	285	1130	570	268 000	1.49
9	2	OC	540	4810	1080	292 000	1.64
10	2	DC	430	3070	860	301 000	1.47
11	2	DC	410	2920	820	231 000	1.82
12	2	DD	346	2060	690	351 000	1.33	−24
13	2	HD	258	1150	510	291 000	1.57	26
14	2	HD	254	1130	510	303 000	1.49
15	2	OD	215	852	430	245 000	1.70	42
16	3	OC	2395	21 300	4790	4100	1.55
17	3	DC	2432	17 300	4860	4400	1.56
18	3	DC	2646	18 900	5290	4000	1.62
19	3	DD	2594	15 400	5190	5000	1.57
20	3	HD	2501	11 100	5000	4700	1.35	26
21	3	OD	1105	4380	2210	6600	1.46	42

---

Polymerisation of 1-octene (OC), 1-dodecene (DD) using Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) (4) – AlⁱBu₃ – [Ph₃C][B(C₆F₅)₄] catalyst

It should be noted that Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) (4) – AlⁱBu₃ – [Ph₃C][B(C₆F₅)₄] catalyst afforded ultrahigh molecular weight polymers with uniform molecular weight distributions in 1-dodecene (DD) polymerisation at −30 °C (M_n = 9.46 to 14.5 × 10⁵, M_w/M_n = 1.62–1.99, runs 27–30, Table 2). The observed activities in the DD polymerisation (at −30 °C) by 4 – borate catalyst were higher than those by 1 – MAO catalyst (at 25 °C, shown in Table 1). Moreover, as exemplified in OC polymerisation (runs 22–26) as well as demonstrated by 1-hexene polymerisation under certain conditions,^13b the M_n values increase upon increasing the TON values (polymer yields, conversions). The resultant polymers possessed atactic stero-regularity [amorphous in poly(1-octene)s (glass transition temperature (T_g) = −62 °C) and only melting temperature (−26 °C) was observed in poly(1-dodecene), shown in ESI, Fig. S4†],¹⁸ as observed in the polymerisation using 1 – MAO catalyst. These results clearly indicate that the present catalyst (4 – borate catalyst) should be effective for synthesis of ultrahigh molecular weight polymers and would suggest a possibility of (quasi) living polymerisation (control of repeat units and synthesis of block copolymers) in this catalysis under certain optimised conditions.

Table 2 Polymerisation of 1-octene (OC), 1-dodecene (DD) using Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) (4) – AlⁱBu₃ – [Ph₃C][B(C₆F₅)₄] catalyst^a

Run	α-Olefin	Time	Yield/mg	TON^b	Activity^c	Mn^d × 10^−6	Mw/Mn^d
a Conditions: olefin 5.0 mL, cat. 0.25 μmol, −30 °C, Ti/[Ph3C][B(C6F5)4]/Al^iBu3 = 1.0/3.0/500.b TON (turnover number) = (mmol of α-olefin reacted)/(mmol-Ti).c Activity = kg-polymer/mol-Ti h.d GPC data in THF vs. polystyrene standards.
22	OC	3	70.2	2500	5620	1.18	1.54
23	OC	5	125.4	4470	6020	1.59	1.65
24	OC	10	160.3	5710	3850	2.00	1.89
25	OC	20	198.7	7080	2380	1.97	2.04
26	OC	30	237.7	8470	1900	2.45	1.90
27	DD	15	110.3	2620	1770	0.95	1.73
28	DD	15	111.7	2660	1790	1.07	1.62
29	DD	20	157.0	3730	1880	1.32	1.99
30	DD	20	145.0	3450	1740	1.45	1.84

---

We have shown that synthesis of ultrahigh molecular weight polymers by polymerisation of higher α-olefin have been achieved simply by 4 – borate catalyst. The fact would also introduce a possibility for synthesis of a new class of poly(α-olefin)s that possess highly branched (brush, cylindrical etc.) structure; further application by introduction of functionality into the side chain (for additional functionality, modification) would be thus highly expected.^20,21 We are now exploring a possibility of not only (quasi) living polymerisation under certain optimised conditions, but also for synthesis of block copolymers and/or star polymers based on polyolefin main chain by adopting a certain living polymerisation technique. We believe that these should introduce a new possibility as promising materials based on poly(α-olefin)s.

Experimental section

General procedure

All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox unless otherwise specified. All chemicals used were of reagent grade and were purified by the standard purification procedures. Anhydrous grade of toluene (Kanto Kagaku Co. Ltd) was transferred into a bottle containing molecular sieves (mixture of 3A and 4A 1/16, and 13X) in the drybox, and was used without further purification. Reagent grade 1-octene (TCI Co., Ltd.), 1-decene (TCI Co., Ltd.), 1-dodecene (Kanto Chemical Co., Inc.), 1-hexadecene (Mitsubishi Chemical Co.) and 1-octadecene (Mitsubishi Chemical Co.) were stored in bottles in the drybox and were passed through an alumina short column prior to use. Toluene and AlMe₃ from commercially available methylaluminoxane [TMAO, 9.5 wt% (Al) toluene solution, Tosoh Finechem Co.] were removed under reduced pressure (at ca. 50 °C for removing toluene and AlMe₃ and then heated at >100 °C for 1 h for completion) in the drybox to give white solids. Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1)²² and Cp*TiMe₂(O-2,6-ⁱPr₂C₆H₃) (4)¹⁶ were prepared according to the reported procedure. [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂ (2, MCAT GmbH) and Cp₂ZrCl₂ (3, Aldrich) were used as received.

All ¹H and ¹³C NMR spectra were recorded on a Bruker AV 500 spectrometer (500.13 MHz for ¹H; 125.77 MHz for ¹³C), and all chemical shifts are given in ppm and are referred to SiMe₄. ¹³C NMR spectra for the resultant polymers were recorded with proton decoupling, and the pulse interval was 5.2 s, the acquisition time was 0.8 s, the pulse angle was 90°, and the number of transients accumulated was about 6000. The polymer samples for analysis were prepared by dissolving the polymers in CDCl₃ solution, and the spectra was measured at 25 °C.

Molecular weights and the molecular weight distributions of the resultant polymers were measured by gel-permeation chromatography (GPC). HPLC grade THF was used for GPC and was degassed prior to use. GPC was performed at 40 °C on a Shimadzu SCL-10A using a RID-10A detector (Shimadzu Co. Ltd.) in THF (containing 0.03 wt% of 2,6-di-tert-butyl-p-cresol, flow rate 1.0 mL min⁻¹). GPC columns (ShimPAC GPC-806, 804 and 802, 30 cm × 8.0 mm diameter, spherical porous gel made of styrene/divinylbenzene copolymer, ranging from <10² to 2 × 10⁷ MW) were calibrated versus polystyrene standard samples. The molecular weight was calculated by a standard procedure based on the calibration with standard polystyrene samples.

Differential scanning calorimetric (DSC) data for the polymer were recorded by means of Hitachi DSC-7020 instrument under a nitrogen atmosphere [preheating: from 30 to 250 °C (20 °C min⁻¹), cooling to −100 °C under N₂, and measurement from −100 to 250 °C (10 °C min⁻¹) under N₂]. This heating and cooling was repeated two times. T_m values were determined from the middle point of the phase transition of the second heating scan.

Polymerisation of higher α-olefins

α-Olefin (1-octene, 1-decene, 1-dodecene, 1-hexadecene or 1-octadecene) polymerisations were conducted in a 10 mL scale vial in the drybox. A prescribed amount of MAO white solid, prepared by removing toluene and AlMe₃ from commercially available MAO (TMAO-S, Tosoh Finechem Co.) and α-olefin were charged into the vial in the drybox. After an addition of a toluene solution (1.0 mL) containing a prescribed amount of complex via a syringe, the reaction mixture was stirred magnetically for 30 min. After the above procedure, the mixture was then poured into ⁱPrOH (150 mL) containing HCl (10 mL). The resultant polymer was collected and was adequately washed with ⁱPrOH and then dried in vacuo.

The polymerisations in the presence of AlⁱBu₃ and [Ph₃C][B(C₆F₅)₄] were performed as follows: α-olefin (5.0 mL) and prescribed amount of AlⁱBu₃ were added into a 25 mL scale Schlenk flask under N₂ at −30 °C. A toluene solution containing a prescribed amount of complex [at −30 °C] was added into the above solution, and the polymerisation was then started by addition of borate compound dissolved in toluene (1.0 mL). The reaction mixture was stirred for prescribed time. After the above procedure, the mixture was then poured into ⁱPrOH (150 mL) containing HCl (10 mL). The resultant polymer was collected and was adequately washed with ⁱPrOH and then dried in vacuo.

Acknowledgements

The present research is partly supported by Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (JSPS, No. 15H03812). S. P. expresses her thanks to Tokyo metropolitan government (Asian Human Resources Fund) for pre-doctoral fellowship, and the project was partly supported by the advanced research program (Tokyo metropolitan government). The authors also express their thanks to Tosoh Finechem Co. for donating MAO (TMAO), and express their thanks to Profs. A. Inagaki, K. Tsutsumi, S. Komiya (TMU) for discussions.

Notes and references

1. Selected reviews/accounts in 1990's, see: (a) G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew. Chem., Int. Ed., 1999, 38, 428; (b) A. L. McKnight and R. M. Waymouth, Chem. Rev., 1998, 98, 2587; (c) J. Suhm, J. Heinemann, C. Wörner, P. Müller, F. Stricker, J. Kressler, J. Okuda and R. Mülhaupt, Macromol. Symp., 1998, 129, 1; (d) W. Kaminsky and M. Arndt, Adv. Polym. Sci., 1997, 127, 144; (e) M. Bochmann, J. Chem. Soc., Dalton Trans., 1996, 255; (f) T. J. Marks, Acc. Chem. Res., 1992, 25, 57; (g) R. F. Jordan, Adv. Organomet. Chem., 1991, 32, 325; (h) Metalorganic Catalysts for Synthesis and Polymerisation: Recent Results by Ziegler–Natta and Metallocene Investigations, ed. W. Kaminsky, Springer-Verlag, Berlin, 1999.
2. Selected reviews, accounts, books, see: (a) V. C. Gibson and S. K. Spitzmesser, Chem. Rev., 2003, 103, 283; (b) A. F. Mason and G. W. Coates, in Macromolecular Engineering, ed. K. Matyjaszewski, Y. Gnanou and L. Leibler, Wiley-VCH, Weinheim, Germany, 2007, vol. 1, p. 217; (c) Metal Catalysts in Olefin Polymerisation, ed. Z. Guan, Topics in Organometallic Chemistry 26, Springer-Verlag, Berlin, 2009; (d) K. Nomura and S. Zhang, Chem. Rev., 2011, 111, 2342; (e) H. Makio, H. Terao, A. Iwashita and T. Fujita, Chem. Rev., 2011, 111, 2363; (f) M. Delferro and T. J. Marks, Chem. Rev., 2011, 111, 2450; (g) C. Redshaw and Y. Tang, Chem. Soc. Rev., 2012, 41, 4484; (h) Orgaometallic Reactions and Polymerisation, ed. K. Osakada, The Lecture Notes in Chemistry 85, Springer-Verlag, Berlin, 2014; (i) J. P. McInnis, M. Delferro and T. J. Marks, Acc. Chem. Res., 2014, 47, 2545 . Metal–metal cooperative effects in olefin polymerisation.
3. Selected special issues: (a) Frontiers in Metal-Catalyzed Polymerisation (special issue); J. A. Gladysz, Chem. Rev., 2000, 100, 1167; (b) Metallocene complexes as catalysts for olefin polymerisation; H. G. Alt, Coord. Chem. Rev., 2006, 250, 1; (c) Metal-catalysed Polymerisation; B. Milani and C. Claver, Dalton Trans., 2009, 41, 8769; (d) Advances in Metal-Catalysed Polymerisation and Related Transformations; P. Mountford, Dalton Trans., 2013, 42, 8977.
4. Reviewing articles, accounts for half-metallocenes, see: (a) K. Nomura, J. Liu, S. Padmanabhan and B. Kitiyanan, J. Mol. Catal. A: Chem., 2007, 267, 1; (b) K. Nomura, Dalton Trans., 2009, 8811; (c) K. Nomura and J. Liu, Dalton Trans., 2011, 40, 7666.
5. Selected reviewing articles for living polymerisation, see: (a) G. W. Coates, P. D. Hustad and S. Reinartz, Angew. Chem., Int. Ed., 2002, 41, 2236; (b) G. J. Domski, J. M. Rose, G. W. Coates, A. D. Bolig and M. Brookhart, Prog. Polym. Sci., 2007, 32, 30; (c) K. Rhett, Chem.–Eur. J., 2007, 13, 2764; (d) L. R. Sita, Angew. Chem., Int. Ed., 2009, 48, 2464; (e) G. M. Miyake and E.-Y. X. Chen, Polym. Chem., 2011, 2, 2462; (f) A. Valente, A. Mortreux, M. Visseaux and P. Zinck, Chem. Rev., 2013, 113, 3836 . Coordinative chain transfer polymerisation (CCTP).
6. Recent review article, (a) The Chemistry of Catalyst Activation: The case of Group 4 Polymerisation Catalyst. M. Bochmann, Organometallics, 2010, 29, 4711. Related references are cited therein; (b) Discovery of Methylaluminoxane as Cocatalyst for Olefin Polymerisation. W. Kaminsky, Macromolecules, 2012, 4, 3289.
7. For example, Presentation by S. Babik, Advances in Polyolefins 2015, L29, Santa Rosa, California, 2015.
8. J. Saito, Y. Suzuki and T. Fujita, Chem. Lett., 2003, 32, 236.
9. Examples for syntheses of ultrahigh molecular weight poly(1-butene), poly(1-hexene) using thiobis(phenoxy)titanium dichloride in the presence of water-modified MMAO cocatalyst, (a) M. Fujita and T. Miyatake, US 6,288,192 B1, 2001; (b) M. Fujita, Y. Seki and T. Miyatake, Macromol. Chem. Phys., 2004, 205, 884; (c) M. Fujita, Y. Seki and T. Miyatake, J. Polym. Sci. PartA: Polym. Chem., 2004, 42, 1107.
10. Synthesis of ultrahigh molecular weight poly(1-hexene) by (C₅HMe₄)₂HfCl₂ – MAO catalyst under ultrahigh pressure (ex. 250 MPa), A. Fries, T. Mise, A. Matsumoto, H. Ohmori and Y. Wakatsuki, Chem. Commun., 1996, 783.
11. (a) K. Nomura, T. Komatsu and Y. Imanishi, J. Mol. Catal. A: Chem., 2000, 152, 249; (b) K. Nomura, T. Komatsu and Y. Imanishi, J. Mol. Catal. A: Chem., 2000, 159, 127.
12. K. Nomura, K. Fujita and M. Fujiki, Catal. Commun., 2004, 5, 413.
13. (a) K. Nomura, T. Komatsu, M. Nakamura and Y. Imanishi, J. Mol. Catal. A: Chem., 2000, 164, 131; (b) K. Nomura and A. Fudo, J. Mol. Catal. A: Chem., 2004, 209, 9.
14. For examples, see: (a) K. C. Jayaratne and L. R. Sita, J. Am. Chem. Soc., 2000, 122, 958; (b) E. T. Kiesewetter and R. M. Waymouth, Macromolecules, 2013, 46, 2569; (c) N. Nakata, T. Toda, T. Matsuo and A. Ishii, Macromolecules, 2013, 46, 6758; (d) G. J. Domski, E. B. Lobkovsky and G. W. Coates, Macromolecules, 2007, 40, 3510.
15. These results were partly presented at Advances in Polyolefins 2015, Santa Rosa, California, September, 2015; Asian Polyolefin Workshop 2015 (APO2015), Tokyo, November, 2015; Pacifichem 2015, Honolulu, Hawaii, December, 2015.
16. Data concerning effect of Al/Ti molar ratios in polymerisation of 1-decene, 1-dodecene using Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1) – MAO catalyst are shown in the ESI.†.
17. MAO white solids by removing toluene and AlMe₃ from commercially available MAO (methylaluminoxane; PMAO-S, Tosoh Finechem Co.) have been chosen as Al cocatalyst, because use of this MAO was effective in terms of catalytic activity and synthesis of high molecular weight polymers. K. Nomura, N. Naga, M. Miki and K. Yanagi, Macromolecules, 1998, 31, 7588.
18. Typical ¹H and ¹³C NMR spectra in the resultant polymers and their DSC thermograms are shown in the ESI.†.
19. Assignment for resonances in ¹³C NMR spectra for poly(α-olefin)s, see: T. Asakura, M. Demura and Y. Nishiyama, Macromolecules, 1994, 24, 2334.
20. For examples (introduction of reactive functionality in polyolefin), see: (a) T. C. Chung, Functionalization of Polyolefins, Academic Press, San Diego, 2002; (b) T. C. Chung, Prog. Polym. Sci., 2002, 27, 39; (c) K. Nomura and B. Kitiyanan, Curr. Org. Synth., 2008, 5, 217; (d) K. Nomura, J. Synth. Org. Chem., Jpn., 2010, 68, 1150; (e) T. C. Chung, Green Sustainable Chem., 2012, 2, 29; (f) W. Apisuk, K. Tsutsumi, H.-J. Kim, D.-H. Kim and K. Nomura, Green Sustainable Chem., 2014, 4, 133.
21. Example for an introduction of terminal olefinic double bonds by copolymerisation with 1,7-octadiene, (a) K. Nomura, J. Liu, M. Fujiki and A. Takemoto, J. Am. Chem. Soc., 2007, 129, 14170; (b) W. Apisuk and K. Nomura, Macromol. Chem. Phys., 2014, 215, 1785; (c) W. Zhao and K. Nomura, Macromolecules, 2016, 49, 59.
22. K. Nomura, N. Naga, M. Miki, K. Yanagi and A. Imai, Organometallics, 1998, 17, 2152.

---

Footnote

† Electronic supplementary information (ESI) available: Data concerning effect of Al/Ti molar ratios in polymerisation of 1-decene, 1-dodecene using Cp*TiCl₂(O-2,6-ⁱPr₂C₆H₃) (1) – MAO catalyst, selected NMR spectra and DSC thermograms for polymers. See DOI: 10.1039/c5ra27797c

---