Thermoplastic elastomers (TPEs) are multiphase materials consisting of an elastomeric continuous phase that provides rubber-like properties and dispersed hard domains that provide reinforcement and elastic recovery. They have been developed into a formidable array of materials since the 1960s, among which, multigraft copolymer superelastomers have attracted much interest in the last decade. This is due to their possessing superior mechanical properties, especially improved elongation at break and superior elastic recovery when compared to conventional linear triblock TPEs, which is obtained from having multiple tethering points along the rubbery backbone. Styrenic thermoplastic elastomers (S-TPEs) are one of the most commercially utilized TPEs. However, a critical issue that hinders the extensive applications of S-TPEs is the upper service temperature (UST). In this work, we use polybenzofulvene (PBF) as side chains to increase the UST of the TPE; meanwhile, incorporating the multigraft architecture in order to improve mechanical properties of S-TPEs. A class of new high temperature multigraft copolymers, polyisoprene-g-polybenzofulvene (PI-g-PBF), was synthesized by using a macromonomer approach. PBF macromonomers were randomly grafted through the polyisoprene backbone. Both macromonomers and multigraft copolymers were prepared by living radical and/or living anionic polymerization. More specifically, we investigated several living anionic synthetic methods towards PBF macromonomer and compare their performance. In the case of copolymerization, different macromonomer molecular weights and numbers of branch points per polymer chain were to gain insight into structure-properties relationships. The macromonomer chain end functionality was verified by applying MALDI-TOF MS. Thermal analyses were performed using DSC and TGA. Mechanical properties will be evaluated by DMA and tensile tests to correlate mechanical properties to molecular weight of macromonomers and number of branch points. Additionally, morphological characterization will be carried out with TEM and SAXS.

Synthesis and characterization of new high temperature multigraft copolymer superelastomer: Polyisoprene-graft-polybenzofulvene

253rd National Meeting (2017)

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