We
present the synthesis and characterization of a new class of
high temperature thermoplastic elastomers composed of polybenzofulvene–polyisoprene–polybenzofulvene
(FIF) triblock copolymers. All copolymers were prepared by living
anionic polymerization in benzene at room temperature. Homopolymerization
and effects of additives on the glass transition temperature (T
g) of polybenzofulvene (PBF) were also investigated.
Among all triblock copolymers studied, FIF with 14 vol % of PBF exhibited
a maximum stress of 14.3 ± 1.3 MPa and strain at break of 1390
± 66% from tensile tests. The stress–strain curves of
FIF-10 and 14 were analyzed by a statistical molecular approach using
a nonaffine tube model to estimate the thermoplastic elastomer behavior.
Dynamic mechanical analysis showed that the softening temperature
of PBF in FIF was 145 °C, much higher than that of thermoplastic
elastomers with polystyrene hard blocks. Microphase separation of
FIF triblock copolymers was observed by small-angle X-ray scattering,
even though long-range order was not achieved under the annealing
conditions employed. In addition, the microphase separation of the
resulting triblock copolymers was examined by atomic force microscopy.