Novel polymorphism behavior of poly(butylene adipate) in its nanocomposites with carbon nanofibers

Nanocomposites formed between poly(1,4-butylene adipate) (PBA) and carbon nanofibers (CNF) were prepared and characterized. The results showed that CNF had significant alpha-form crystal nucleating ability on PBA, and the alpha-form crystals could appear at rather low crystallization temperatures in PBA/CNF composites, for example 0 degrees C. Furthermore, a novel plateau content phenomenon of alpha-form crystals was discovered, and the value of the plateau content almost increased linearly with increasing CNF loading content. Microscopic morphology data suggested that PBA chains could wrap (or coat) around the nanofillers after the solution mixing process to form an interaction region. And in situ FTIR spectra proved the existence of multiple-weak CH-p interactions between CH2 groups on PBA chains and sp(2) structures on the surface of CNF in composites, which helped to induce some precursory structures in the interaction region containing a chain conformation close to that in alpha-form crystals. Thus, the wrapping (or coating) behavior and precursory structures are responsible to the formation of alpha-form crystals at low temperature and the appearance of a novel plateau content phenomenon of alpha-form crystals. The change of PBA polymorphism behavior in nanocomposites provides a pathway for evaluating the interaction between polymer chains and nanofillers more intuitively.