Abstract: In the production of "inside-out" star polymers where a first polymer lithium chain is formed, coupled and thereafter additional monomer is introduced to produce the "out" polymer chains, improved control over the second polymerization is obtained by coupling with a mixture of a monoalkenyl-substituted aromatic compound and a polyalkenyl-substituted aromatic compound. For example, a mixture of divinylbenzene and styrene can be used. In another embodiment, an ether is introduced after completion of the first polymer chain formation. The presence of the ether also improves the second stage chain formation. Utilization of both the mixed coupling agents and the ether, preferably a diether such as 1,2-diethoxyethane gives the greatest control over the uniformity of the second stage polymerization, making possible the production of narrower molecular weight distribution polymer having no indication of bimodal distribution. The narrow molecular weight distribution is advantageous in many applications.

Abstract: An improved VI improver and a fluid composition comprising the VI improver. The VI improver is an asymmetric radial polymer comprising a plurality of arms having at least two distinctly different peak molecular weights, which arms are chemically the same. The weight ratio of a longest set of arms and a first set of shorter arms will vary within the range from about 1.2:1 to about 8.0:1. If more than one set of shorter arms is used the ratio of adjacent arms molecular weights will vary within the same range. While the arm might be essentially any polymer, polymers of conjugated diolefins and copolymers of at least one monoalkenyl aromatic hydrocarbon and at least one conjugated diolefin are preferred. Conjugated diolefin homopolymers are preferred and polyisoprene is most preferred.

Abstract: A method for preparing asymmetric radial polymers wherein the different polymeric arms are contacted sequentially with a nonpolymerizable coupling agent. Contacting of the final step in the process, which frequently but not necessarily always will be the second step in the process, will be carried out in the presence of a polar compound suitable for increasing the amount of vinyl content in a conjugated diolefin polymer during polymerization thereof. The method used narrows the relative arm distribution of the several asymmetric radial polymers produced and significantly increases the amount of total product having the desired ratio of polymeric arms and accomplishes this objective in relatively short reaction time.

Abstract: A star-shaped polymer useful as a polymeric VI improver comprising at least one arm which is a block copolymer containing a cunjugated diolefin block and a monoalkenyl aromatic hydrocarbon block and a plurality of arms which are either a homopolymer of a conjugated diolefin or a copolymer of two or more conjugated diolefin or a copolymer of two or more conjugated diolefins. Oil compositions comprising star-shaped VI improvers of this type exhibit relativelylow HTHSR viscosities, and hence, improved fuel efficients when used in automotive applications. Oil compositions comprising star-shaped VI improvers of this type also exhibit improved low temperature pumpability.

Abstract: A star-shaped polymer useful as a polymeric VI improver comprising at least one arm which is a block copolymer containing a conjugated diolefin block and a monoalkenyl aromatic hydrocarbon block and a plurality of arms which are either a homopolymer of a conjugated diolefin or a copolymer of tow or more conjugated diolefin or a copolymer of two or more conjugated diolefins. Oil compositions comprising star-shaped VI improvers of this type exhibit relatively low HTHSR viscosities, and hence, improved fuel efficiencies when used in automotive applications. Oil compositions comprising star-shaped VI improvers of this type also exhibit improved low temperature pumpability.

Abstract: This invention provides an improvement in anionic polymerization processes which comprise both a batch polymerization step to form and partially grow living polymer chains and a subsequent continuous or semi-continuous step in which growth of the chains is continued. For purposes of this improvement, the transition to the continuous or semi-continuous step takes place before the molar concentration of monomer in the batch polymerization step is depleted to a level below that of the living chains. Anionic polymerization processes are recognized as particularly useful for the production of polymers having narrow molecular weight distributions. Practice under the invention is found to enhance the narrow distribution of the polymer product by controlling thermal die-out of chains which has occurred in conventional processes during the transition from batch to continuous or semi-continuous polymerization steps.

Abstract: Random monoalkenyl arene-conjugated diene copolymers are produced by controlling the continuous rate of addition of the conjugated diene monomer to a reactor containing the monoalkenyl arene monomer, organolithium initiator and solvent, the rate being adjusted in response to the photometer measured presence of an active chromophore comprising a lithium ion directly associated with a poly(monoalkenyl arene) carbanion.

Abstract: Lithium metal-terminated polymers of one or more alkadienes and of one or more monoalkenyl arenes are coupled by reaction with a mixture of two different coupling agents having different functionality.

Abstract: An improved process for the preparation of branched polymers is provided wherein the individual branches may be selected at will comprising the formation of an anionic polymer of a polymerizable monomer, coupling with a polyvinyl aromatic hydrocarbon and block polymerizing this coupled product with an anionically active polymerizable monomer.