Research On Synthesis Of End Functionalized Miktoarm Star-Shaped Solution Polymerized Styrene-Butadiene Rubber

With the development of high-performance rubber, coupling,modification of molecular chain end, and multi-block integration process, etc.have emerged successively in the synthesis of tire rubber. Some progress hasbeen made separately in the three dominant performances of tread rubber, highabrasion resistance, high resistance to wet, and low rolling resistance.However, it’s the direction of the development of high-performance tires stillthat to roll these three advantages up into one. Coupling, modification andintegration combined in a relatively simple process, a variety of structuraladvantages are gathered in order to maximize the balance of the contradictoryrelationship between the various performances.A modified initiator1,1-diphenyl hexyllithium (DPHL) was preparedand investigated in this article, and used further in the synthesis of activepolybutadiene (PB-Li~+) and active butadiene-styrene copolymer (SBR-Li~+).The coupling agent of SnCl4was used to synthesize A and B type endfunctionalized miktoarm star-shaped rubber through one-step process andtwo-step process respectively. And analytical methods of overall couplingefficiency and coupling efficiency of each arm were established. The results showed that: the preparation reaction of DPHL in non-polar solvent at40℃needs more than70hours to complete. When a small amount of polar solventTHF added, the reaction speed is greatly accelerated, but the the initiator got islikely to lose initiation activity. The PB chain coupling efficiency of thestar-shaped rubber got in one-step coupling process are mainly25%to40%.But the number can reach70%to80%in two-step coupling process duing toa special feeding mode applied, while the overall coupling efficiency oftwo-step coupling process can be above55%comparably. Study on theproperties of vulcanizates indicates that, to increase the relative molecularweight of the PB arm and SBR arm of the star-shaped molecules, to maximizethe overall coupling efficiency and PB chain coupling efficiency, the use ofmodified initiator, and to increase styrene content are conducive to theperformance of rubber, and to the dynamic mechanical properties especially.The end-modified miktoarm star-shaped rubber designed combining thesestructural factors, compared to raditional PB/star SBR blended rubber,achieved significant improvement at wear loss,(-25℃)tanδ,(0℃)tanδ and (60℃)tanδ at the same time, maximizing the balance of the contradictoryrelationship of the three driving performance of tread: high wear resistance,high wet skid resistance, and low rolling resistance.