1. SPE International Polyolefins Conference
Highly Branched Polyethylene Oligomers via Group 4-Catalyzed Polymerization in Very Nonpolar Media
Yanshan Gao
Research Assistant Professor
February 25, 2019
Houston TX

2. Background
A total value of 183 billion USD for HDPE, LLDPE, and LDPE, in HBPE, highly branched polyethylene; global synthetic lubricant market is 3.8 MT, 18 billion USD, in MT: million tons
Potential lubricant base oil alternatives (current synthetic lubricant base oils are PAO from expensive 1-decene)
Polymers can be functionalized and/or further polymerized to make block copolymers.
M. A.-A. AlMa'adeed, I. Krupa, Polyolefin Compounds and Materials: Fundamentals and Industrial Applications. (Springer, 2015)

3. HBPE: Current Synthetic Methodologies
Extremely low activity
Solid side-product (high Mn polyolefin)
A. Sen et al., JACS, 2000, 1867; 1998, 1932
Complex manipulations
Branch density increase → Mn increase
J. Klosin et al., WO
Low activity
Predominantly short branches (Me, Et, Pr)
Catalyst decomposition at elevated temperatures
M. Brookhart et al., JACS, 1995, 6414; Z. Guan et al., Science, 1999, 2059; Chem. Asian J. 2010, 1058; S. Mecking et al., JACS, 2014, 2078; ACIEE, 2004, 869

4. Background This Work Early Transition Metal Catalysis CGCZr + B1, H
Low molecular weight polyolefin with short and long chain branches
Low activity
Branch density relatively low: <15 total branches/1000C
CGCZr + B1, H
Solvent: toluene/DFB
Marks et al., J. Am. Chem. Soc. 2002, 124, 12725; Macromolecules 2005, 38, 9015
This Work
B1, H: insoluble in MeCy
B1, n-octyl: good solubility even in aliphatic solvent such as MeCy
Remarkable solvent effects on activity and branch density
Hyperbranched polyolefins from highly active early transition metal catalysis in MeCy

5. Table 1. Ethylene Homopolymerization and Ethylene + 1-Hexene Copolymerization Data for HBPEs.
entry
monomer
solvent
T/oC
t/min
polymer
yield (g)
actb Mn
(g/mol)c
ρbrd
ethyl
branches
/%e
n-butyl
LCB/% e 1 E
Tol 25 30
3.96
790
430 43 18 39 2f
MeCy - 3
12.57
2516
700 61 45 4 20
9.24
2773
630 59 44 26 5 10
4.74
2842
650 52 40 24 36 6
10.29
2058
850 60 34 7
7.75
1549
1140 51 33 23 8 80
5.59
1118
1020 38 27 19 54
Conditions: catalyst, CGCZr, 10 µmol; cocatalyst, B1, n-octyl, 10 µmol; ethylene, 1 atm; T, temperature of bath surrounding reactor; homopolymerization: toluene, or MeCy, 50 mL; ethylene (E)/1-hexene (H) copolymerization: toluene, or MeCy, 45 mL; 1-hexene, 5.0 mL; b Kg·(mol of metal)-1·h-1·atm-1. c Calculated from 1H NMR intensity ratio of unsaturated end groups vs overall integral.11 d Branch density (branches/1000 C) calculated from 1H NMR intensity ratio of methyl groups vs overall integral.11 e Percentages of various branches calculated from 13C NMR spectra.33 LCB, Long chain branch = n-hexyl and longer branches. f Ph3C+B(C6F5)4ˉ (B1, H) cocatalyst. Negligible activity presumed due to cocatalyst insolubility in MeCy.
See next for analysis

6. Dramatic Solvent Effects on Activity and Branch Contents in Ethylene Polymerizations
Figure 2. Trends in CGCZr + B1, n-octyl catalyzed ethylene polymerizations: A) Solvent effects on activity and branch densities. B) and C) Relationship between branch densities, polyolefin Mn, polyolefin yield, and reaction time in MeCy.
Switching solvent from toluene to PhCl and MeCy:
Higher activity (3.2x)
Higher branch densities (2.5x)
Time-insensitive branch density and Mn.

7. End Group Analysis Internal double bond<4%, thus no chain walking
Entry
Solvent
Tp/oC
t/min
Vinyl/%
Vinylidene/%
Internal/% 1
Tol 25 30 80 16 4 2
MeCy - 3 18 81 20 26 73 5 10 35 64 6 40 19 79 7 60 14 84 8 39
Internal double bond<4%, thus no chain walking

8. Oligomer/p roduct yieldc
GC-MS analysis of ethylene homopolymerization reaction mixtures
entry
rxn temp.
/oC t/
min
HBPE yield (g)
Oligomer, gc
Oligomer/p roduct yieldc
α-olefin, gc
α-olefin/
product yieldc
C6=
wt%d
C8=
C10=
C12=
C14= 1 25 30
12.57
1.298
10.3%
0.459
3.7% 16 11 22 23 27 2 80
5.59
0.150
2.7%
0.115
2.1% 18 20 24 3 6
2.26
0.018
0.8%
0.012
0.5% 14 19 17
entry
a1 in C10= %
a2 in C10=
a3 in C10=
b1 in C12=
b2 in C12=
b3 in C12=
p1 in C14=
p2 in C14=
p3 in C14=
p4 in C14= 1 23 68 9 30 41 29 18 48 14 20 2 71 21 8 16 3 72 10 4 33 47 83 17 62 5 7
a Conditions: catalyst, CGCZrMe2, 10 µmol; cocatalyst, B1,n-octyl, 10 µmol; ethylene, 1 atm; rxn temp., temperature of bath surrounding reactor; MeCy, 50 mL; b Kg·(mol of metal)-1·h-1·atm-1. c Yield of volatile C6= to C14= oligomers. Oligomer qualitative and quantitative analysis by GC-MS using n-heptane as internal standard. Includes hexenes (C6=), octenes (C8=), decenes (C10=), dodecenes (C12=) and tetradecenes (C14=). d wt% of each oligomer class, analyzed by GC-MS. e isomeric decenes, dodecenes, and tetradecenes are analyzed respectively.
10.3 wt% of volatile oligomers are produced
Only 0.5 wt% of volatile α-olefins is detected in the 6 min reaction
Besides α-olefins, there are non-negligible quantities of branched olefin isomers

9. Enhanced 1-hexene enchainment at the expense of LCB
Table 1. Ethylene Homopolymerization and Ethylene + 1-Hexene Copolymerization Data for HBPEs.
entry
monomer
solvent
T/oC
t/min
polymer
yield (g)
actb Mn
(g/mol)c
ρbrd
ethyl
branches
/%e
n-butyl
LCB/% e 1
E+H
Tol 25 20
3.30
987
460 48 11 49 40 2
MeCy 4
3.09
4627
470 87 16 64 3 8
5.52
4132
480 93 62 22
11.54
3461
600 79 19 44 37
Conditions: catalyst, CGCZr, 10 µmol; cocatalyst, B1, n-octyl, 10 µmol; ethylene, 1 atm; T, temperature of bath surrounding reactor; homopolymerization: toluene, or MeCy, 50 mL; ethylene (E)/1-hexene (H) copolymerization: toluene, or MeCy, 45 mL; 1-hexene, 5.0 mL; b Kg·(mol of metal)-1·h-1·atm-1. c Calculated from 1H NMR intensity ratio of unsaturated end groups vs overall integral.11 d Branch density (branches/1000 C) calculated from 1H NMR intensity ratio of methyl groups vs overall integral.11 e Percentages of various branches calculated from 13C NMR spectra.33 LCB, Long chain branch = n-hexyl and longer branches. f Ph3C+B(C6F5)4ˉ (B1, H) cocatalyst. Negligible activity presumed due to cocatalyst insolubility in MeCy.
Enhanced 1-hexene enchainment at the expense of LCB
Branch pattern/densities effectively adjusted by introducing α-olefin

10. Proposed Branch Formation Mechanism
The competitions between β-H transfer and chain propagation, monomer and solvent coordination determines Mn, branch density and patterns (Et, Bu, LCB)

11. Ion Aggregation Effects?
Unprecedented Non-Polar Solvent Effects in Enhancing Activity and Branch Formation Capacity
Ion Aggregation Effects?
Cationic Zr more electrophilic, thus higher activity.
Cationic Zr less crowded, facilitating α-olefin enchainment.
In situ generated α-olefins are more likely to be trapped/captured in ion pair higher aggregates/clusters than non-aggregated/less-aggregated catalyst ion pairs.
Pulsed Field-Gradient Spin-Echo (PGSE) NMR Shows No Ion Pair Aggregation at Polymerization Concentrations
Macchioni, Bochmann et al, Organometallics 2008, 27, 5474–5487; J. Am. Chem. Soc. 2007, 129,

12. Proposed Ion-Pairing Scenario in Different Solvents

13. In MeCy, predominant olefin monomers coordination
Thermodynamic data associated to the SSIP to MonSIP equilibrium. Gibbs free energies are in kcal/mol
In MeCy, predominant olefin monomers coordination
In toluene, olefin monomers compete with predominant toluene coordination
In collaboration with Alessandro Motta (Italy)

14. Viscosity tests and comparison with commercial oils
Fig. 3. a Viscosity and viscosity index to compare with commercial lubricant oils. Kinematic viscosity (KV) of the samples at 40 oC and 100 oC were determined as per ASTM D2270. Viscosity index was calculated from KV at 40 oC and 100 oC. a
Oligomers with a range of viscosity and viscosity index could be obtained by introducing different quantities of α-olefin comonomers.
In collaboration with David Pickens, Prof. Jane Q. Wang (Mechanical Engineer Department) and Yip-Wah Chung (Materials Science and Engineer Department)

15. Lubricant Tribology Test vs. Commercial PAO4
Pin-on-Disk Test
Saturated HBPE vs. PAO4:
Lower friction, better base oil!
Greater film formation characteristics
Tested by David Pickens (ME, NU), in collaboration with Prof. Jane Q. Wang (ME) and Yip-Wah Chung (MSE, NU) groups

16. Lubricant Tribology Test vs. Commercial PAO4
EHD (Elastohydrodynamic, Ultra Thin Film Measurement System)
Saturated HBPE vs. PAO4:
Lower friction, better base oil!
Greater film formation characteristics
Tested by David Pickens (ME, NU), in collaboration with Prof. Jane Q. Wang (ME) and Yip-Wah Chung (MSE, NU) groups

17. Conclusion
The first example of highly branched polyethylenes produced using group 4 transition metal catalyzed ethylene polymerization
Unprecedented activity and branch-directing selectivity reflect heretofore unrecognized aspects of the cationic catalyst-counteranion pairing in such non-polar/non-coordinating media
The products are rheologically and tribologically promising alternative candidates to expensive synthetic lubricants.
Tobin J. Marks; Yanshan Gao; Tracy L. Lohr. U.S. Provisional Patent Application. 2018, 62/626,879; Tobin J. Marks; Yanshan Gao; Tracy L. Lohr; Matthew Christianson; Jerzy Klosin; Edmund M. Carnahan; Andrew Young. U.S. Provisional Patent Application. 2018, 62/650,462; Yanshan Gao , Jiazhen Chen , Yang Wang , David Pickens , Alessandro Motta , Q. Jane Wang , Yip-Wah Chung , Tracy Lohr and Tobin J. Marks. Nature Catalysis, 2019, DOI : /s

18. Team Organization for Lubricant Projects
Tribology
Surface Analysis
Chemistry
Additive Design, Synthesis and Structural Characterization:
Prof. Tobin Marks
Dr. Yanshan Gao
Tribological and Rheological Properties, Model-Assisted Molecular Design:
Prof. Q. Jane Wang
David Pickens
Additive-Surface Interactions and Tribochemistry:
Prof. Yip-Wah Chung
Close collaboration between all different sectors drives design and development of next-generations of synthetic lubricant and lubricant additives

19. Organometallics and Catalysis
A Team
Organometallics and Catalysis
Hydro-elementation
Olefin Polymerization
Catalysis
Supported Organometallics
Atomic Layer Deposition
Chemical Tribology

20. Acknowledgement Tribology Tests Prof. Q. Jane Wang Prof. Yip-Wah Chung
David Pickens
DFT Calculations
Dr. Allesandro Motta
Prof. Tobin J. Marks
Tracy L. Lohr
Yang Wang
Jiazhen Chen
A-team
Marks group
Dr. Jerzy Klosin
Dr. Matthew Christianson
Dr. Edmund Carnahan
Dr. Andrew Young
Funding: Dow Chemical

21. Thanks for your attention!
Questions?

22. Tobin J. Marks; Yanshan Gao; Tracy L. Lohr. U. S
Tobin J. Marks; Yanshan Gao; Tracy L. Lohr. U.S. Provisional Patent Application. 2018, 62/626,879; Tobin J. Marks; Yanshan Gao; Tracy L. Lohr; Matthew Christianson; Jerzy Klosin; Edmund M. Carnahan; Andrew Young. U.S. Provisional Patent Application. 2018, 62/650,462; Yanshan Gao , Jiazhen Chen , Yang Wang , David Pickens , Alessandro Motta , Q. Jane Wang , Yip-Wah Chung , Tracy Lohr and Tobin J. Marks. Nature Catalysis, 2019, DOI : /s