Whisker Morphology Consisting of Hierarchically Self-assembled Polymer Helices

1 Whisker Morphology Consisting of Hierarchically Self-assembled Polymer Helices 

A polymer whisker is a spontaneously formed assembly with a higher-ordered structure and could be used as a single fiber for amplification of the intrinsic properties of the polymer. The whiskers of aromatic polyesters such as poly(para-oxybenzoyl) and poly(2-oxo-6-naphthoyl) have been intensively investigated [31, 32], while there have been only few reports on the whiskers of conjugated polymers such as poly(3-alkylthiophene) [33]. When a helical conjugated polymer with a whisker structure is designed, the intrachain and interchain interactions must be balanced by precisely controlling the van der Waals, rr-electron overlap, and electrostatic interactions. 

In this study, we designed and synthesized a series of novel PMP derivatives with chiral groups as side chains, (/f)-/(S)-Poly-l (Fig. 11.2) [10]. Poly-1 features a chiral side chain with either (/ )- or (S)-2-nonanol chiral alkyl groups linked via 

G glass state, Colh hexagonal columnar phase, I isotropic phase 

It is found that (R)-Poly-l forms whiskers when slowly cooled from the isotropic phase, as depicted in Fig. 11.3. The observed whiskers of (R)-Poly-l are 5-7 pm in diameter and approximately 100-200 pm in length. The size of the whisker depends not only on the polymer structure including the side chains but also on the cooling rate from the isotropic phase. A large area of the POM micrograph is dark, but the circularly polarized micrograph indicates that the dark area contains many whiskers (Fig. 11.3b). 

---