For the synthesis of double co-oligomerization, hexene-1 and 4-methylpentene were used as initial C₆-olefins. Their double cooligomers with dicyclopentadiene [13] and indene [14] had been synthesized.

The process was methodically carried out as follows. In a three-necked flask equipped with a mechanical stirrer, thermometer and dropping funnel, the calculated amount of solvent (hexane or heptane) and catalyst were loaded. The reaction mixture was stirred while being cooled to the desired temperature. Then a mixture of the C₆-olefins with dicyclopentadiene (or indene) was fed through a dropping funnel in a certain ratio.

The feed rate of the mixture is adjusted so that the temperature rise does not exceed 1 - 2˚C. The reaction mixture is stirred until the temperature rises. The catalyst is then decomposed by the 1% - 3% solution of NaOH. The reaction mass is washed with a mixture of water-isopropyl alcohol to neutral medium, filtered, the solvent and light fractions are distilled off under vacuum. After that, the yield of the co-oligomers, their kinematic viscosity and molecular weight are determined.

Co-oligomerization were carried out in the presence of catalyst AlCl₃ at −10˚C - 40˚C with dicyclopentadiene and at 20 - 40˚C with indene. At the catalyst concentration 0.1% - 0.3%, the yield of co-oligomer was insignificant. Increase of catalyst consumption to 0.5% - 0.8% resulted in the increase of the yield of the reaction product up to 80% - 93%. In this case, molecular mass value was not considerably changed; as ionic polymerization molecular mass value didn’t depend on catalyst concentration. Further increase of catalyst consumption to 1% - 2% did not change the yield and molecular mass of oligomer. It was therefore decided to keep consumption of aluminum chloride within the range of 0.8% - 1.0% for α-olefin used in oligomerization (Figure 1).

Oligomerization of 4-methylpentene-1 resulted in the obtaining of higher molecular products than oligomerization of its unbranched analogue―hexene-1

within similar conditions. It is explained by structural peculiarities of compounds. As a matter of fact, the activity towards cationic polymerization was raised by methyl groups, the strong electron-donors.

In case of hexene-1 methyl group was joined by third carbon atom with relation to double bound, while in 4-methyl-penthene-1 two methyl groups were joined by second carbon atom with relation to double bound that determines different behavior of indicated monomers during the reaction of oligomerization.

To enhance thermal stability of synthesized oligomers and to create an additional reaction centre for conducting chemical modification, parent α-olefins―hexene-1 or 4-methylpentene-1 were subjected to co-oligomerization with dicyclopentadiene and indene.

It was found that the insertion of the co-monomers into co-oligomerization with C₆-olefins led to the reduction of molecular mass value. And it means the involvement of cyclic co monomers in restricting the length of oligomeric chain at the expense of alkylation.

It should be pointed that both co-monomers of α-olefins are industrial products within reach that proves the reasonability of carried out investigations, since the interest to chemical product is strictly determined by the availability of raw material resources.

The obtained structures of the products were studied by IR- and PMR-spectroscopic methods. It was found out that links of 4-methylpentene-1 entered into oligomeric chain in rather isomerized form, like creating formation of co oligomer with hexene-1 and 4-methylpentene-1 links [3] :

Chemical bound between co-monomers’ links is absent, i.e. as a result, we have obtained a pure co-oligomer with alternated monomer links that determined physicochemical properties of synthesized compounds included into lubricant oils.

In general, the reaction co-oligomerization may be represented as follows:

The carried-out investigations have resulted in obtaining of co-oligomeric compounds with molecular mass about 700 - 2000 and outcome 87% - 93% depending on conditions of reaction and on the ratio of initial monomers.

Synthesized oligomers and cooligomers were examined as synthetic components of petroleum oils to improve their viscosity-temperature and anti-corrosive characteristics.

The effect of co-oligomers hexene-1 with dicyclopentadiene and 4-methylpentene-1 with and indene on viscosity-temperature characteristics of petroleum oil (M-6) is given (Table 1 and Figure 2). Viscosity-temperature properties of copolymers are determined in the thermostat of VIS-T-09-3 brand (Figure 3). This thermostat is designed to maintain the set temperature during measurements using glass viscometers in accordance with GOST 33, ASTM D445, IP 71, ISO 3104 and DIN 51366.

As indicated, co-oligomers at concentration 20% - 30% help to obtain basic oil (viscosity about 8 ± 0.5 mm²/sec at 100˚C) with high viscosity index.

Note that co-oligomers with both dicyclopentadiene and indene links have anti-corrosive properties as well; at concentration 40% - 50%, corrosiveness of M-6 oil were completely eliminated (table and Figure 4). The anticorrosive properties of M-6 oil with added co-oligomers are determined in the DK-NAMI type device in accordance with GOST 13371-67 (Figure 5). The device is designed for testing according to GOST 20502-75 of lubricating oils (method for determination of anti oxidation and anti corrosive properties).

As proved [1] , corrosiveness is the consequence of oxidation and is caused by oxidation products. Including carboxylic (dicyclopentadiene) and aromatic (indene) links into oligomeric chain causes chemical modification of the structure, and co-monemeric fragments impart anti-oxidative properties to the synthetic component. As a result of the above, the compound also acquires anti-corrosive properties.