Interfacial conversion for poly(para‐phenylenevinylene) at a cholesteric liquid crystal surface

Abstract

A new approach for the preparation of poly (para-phenylenevinylene) (PPV) with an ordered structure is presented. PPV is synthesized by a precursor method using a cholesteric liquid crystal medium. The resultant PPV film is observed to have a cholesteric fingerprint-like texture, indicating replication of the cholesteric liquid crystal medium. Infrared absorption measurements confirm that the PPV has essentially the same molecular structure as normal PPV film. Ultraviolet-visible absorption measurements show that the absorption band due to p2p* transition of the conjugated main-chain is located at 402 nm. The conversion is found to occur at the interface with the cholesteric liquid crystal medium as a mechanical process.

Spectroscopic ellipsometry as a complementary tool for studying luminescent polymers: Poly(p-phenylenevinylene) as a particular case

“…These curves were separated into three regions for the sake of clarity, and where it can be seen how the IR bands vary with the conversion temperature, i.e., decreasing or increasing in intensity (see arrows). The band at 964 cm À1 , assignable to the out-of-plane bending of the trans-vinylene CeH of PPV [11,12], can be considered as one of the most important bands in the spectrum of PPV. During the conversion process, the bands at 964 cm À1 and 835 cm À1 gain intensity (see arrows in Fig.…”

Textile‐surface interfacial asymmetric polymerization

“…The polymers thus obtained show structural chirality because they lack a chiral center in the primary structure. Interfacial chiral conversion of optically inactive polyphenylenevinylene (PPV) precursor at the interface of cholesteric liquid crystals results in production of chiral PPV . Dissolution of optically inactive polymers forms helical structure in optically active limonene as a solvent, demonstrating noncovalent molecular chirality transfer leading to chiroptical activity in achiral polymers …”

Chirality in conjugated polymers: when two components meet

“…40 To induce polymerization, acetylene gas was guided through the reaction vessel with a N*-LC reaction medium and a Ziegler-Natta catalyst. 32,[41][42][43][44][45] This was quickly followed by other chiral conjugated polymers like poly(3,4-ethylenedioxythiophene) (PEDOT), [46][47][48] poly(bithiophene) (PBT), 49 poly(pyrrole) (PPy), 50 poly(para-phenylenevinylene) (PPE) 51 and copolymers of those [52][53][54][55][56] starting from achiral monomers. CD measurements of the resulting films and solutions all show a bisignate Cotton effect in the region of the p-p* transition (450 to 800 nm) of the conjugated backbone, and there is a mirror image relationship when the other enantiomer of the solvent is used (Fig.…”

“…40 To induce polymerization, acetylene gas was guided through the reaction vessel with a N*-LC reaction medium and a Ziegler-Natta catalyst. 32,[41][42][43][44][45] This was quickly followed by other chiral (PEDOT), 46-48 poly(bithiophene) (PBT), 49 poly(pyrrole) (PPy), 50 poly(para-phenylenevinylene) (PPE) 51 and copolymers of those [52][53][54][55][56] polymers, the helical structure is retained even after heating or washing with toluene. 41 Control experiments of the polymerization in the absence of a chiral dopant or liquid crystals in the solvent or polymerization above the N*-LC temperature all show a randomly oriented fibrillar morphology, rather than the 40 helical one for the resulting polymer.…”