Anionic Synthesis,Hydrogenation Of Myrcene/Isoprene Oligomers And Their Rheological Behavior

Liquid rubber as a low molecular weight functional polymer has broad application prospects in plastic and rubber processing.The viscosity of liquid rubber is an important parameter to characterize the fluidity,which directly affects the processing method and application performance,and the viscosity mainly depends on the molecular structure.Therefore,the structural design of liquid molecules with different structures and the study of rheological properties have important guiding significance for the development of liquid rubber.In this paper,based on the designable molecular structure of active anionic polymerization,isoprene with short branched chain and myrcene with long branched chain were copolymerized,and liquid rubbers with different topological structures were designed and synthesized,and they were hydrogenated to obtain saturated oligomers,thereby establishing the relationship between structure and rheology.The research achievement shows that:Based on the characteristics of active anionic polymerization,liquid rubber with different molecular structures was designed and synthesized by using myrcene and isoprene monomers in cyclohexane solvent.The molecular weight was controlled in the range of 500-6000g/mol,and the minimum polydispersity was 1.10.The microstructure of linear polyisoprene liquid rubber(L-PI)increased from 6.49%to 70.50%,and that of linear polymyrcene liquid rubber(L-PMy)increased from 5.83%to 54.35%.The microstructure of star polymyrcene liquid rubber(S-PMy)was controlled by tetrahydrofuran,and the content of 3,4-PMy structure increased from 1.98%to 34.02%.The linear myrcene/isoprene copolymer(L-PIMy)has different monomer composition,and the content of myrcene increases from 30%to 70%.Compared with linear L-PMy,KV of star S-PMy increases and VI decreases.The rheological behavior of the above series of liquid rubbers was studied.The higher the molecular weight,the higher the kinematic viscosity(KV)and the higher the viscosity index(VI).For L-PI,the higher the content of 3,4-PI microstructure,the higher the KV,the smaller the VI.For L-PMy,the higher the microstructure content of 3,4-PMy,the higher the KV and the lower the VI.For L-PIMy,the higher the content of myrcene,the lower the KV and the higher the VI.Compared with short side chains,the introduction of long side chains significantly improves the rheological properties of liquid rubber.The content of myrcene increased from 30%to 70%,the KV40 of liquid rubber decreased from 220.4 mm2/s to 131.4 mm2/s,the KV100 decreased from 28.35 mm2/s to 20.02 mm2/s,and VI increased from 166 to 175.Compared with linear L-PMy,the star structure S-PMy has an increase in KV and a decrease in VI.Part of the synthetic liquid rubber was hydrogenated.The maximum hydrogenation degrees of hydrogenated products HPI,HPMy and HPIMy were 99.9%,95.03%and 97.3%,respectively.The rheological behavior of the liquid rubber was studied.Compared with the liquid rubber before hydrogenation,the KV of the hydrogenated product increased,and the higher the degree of hydrogenation,the more obvious the increase of KV.Before the hydrogenation of PI,the KV40 was 754.6 mm2/s,the KV40 of 56%hydrogenation HPI was 1350 mm2/s,and the KV40 of 98.7%hydrogenation HPI was 3460 mm2/s.For the change in viscosity index of the hydrogenated products,the longer the side chain,the more obvious the decrease in viscosity index.HPI decreased from 172 to 163,HPMy decreased from 157 to 128,and HPIMy decreased from 171 to 154.