Synthesis and liquid crystalline properties of azobenzene‐containing poly(vinyl ether)s with narrow molar mass distribution

Abstract

A series of new liquid crystalline (LC) poly(viny1 ether)s with different molar masses was synthesized via a two-step procedure involving the preparation of functional matrices by living cationic polymerization of an o-chloroalkyl vinyl ether monomer followed by a grafting reaction of an azobenzene mesogenic unit onto them. By appropriately adjusting the experimental conditions, it was possible to predetermine the molar mass characteristics of the LC polymers. Each of the parent and modified poly(viny1 ether)s had a narrow molar mass distribution. The LC polymers were semicrystalline and formed a nematic mesophase, enantiotropic or monotropic in character. The transition temperatures increased with increasing molar mass up to a limiting value and then remained nearly constant. Accordingly, poly(viny1 ether)s with predetermined molar mass and narrow molar mass distribution could be prepared.

Photo‐responsive copolymers with azobenzene side groups synthesized by living cationic polymerization: Efficient amplification of photosensitivity in aqueous photo‐switching system

“…Azobenzene‐containing polymers are potentially useful for constructing photo‐responsive self‐assembling system using cis – trans isomerization 2. However, there are few examples of living polymerization of azobenzene‐containing momomers,3–6 although there have been numerous reports on the synthesis and properties of azo polymers 7. Especially, post‐polymerization reactions were required in cationic polymerization to prepare azo polymers with narrow molecular weight distribution (MWD) 6.…”

“…However, there are few examples of living polymerization of azobenzene‐containing momomers,3–6 although there have been numerous reports on the synthesis and properties of azo polymers 7. Especially, post‐polymerization reactions were required in cationic polymerization to prepare azo polymers with narrow molecular weight distribution (MWD) 6. Recently, we have reported the synthesis of well‐defined homo‐ and copolymers of azo‐containing vinyl ethers by living cationic polymerization in the presence of an added base 8, 9.…”

Molecular engineering of side-chain liquid crystalline polymers by living polymerizations

“…168 In addition to preventing spontaneous termination, increased stability of the metal center also minimizes chain transfer and other termination reactions. The elementary reactions 1Degree of polymerization (e.•) and polydispersity (0,0) of the precursor polymer resulting from the cationic polymerization of 6-chlorohexylvinyl ether (e,O) initiated by HI/1 2 in toluene at -40°C, and of the final poly { 6-[( 4' -n-ethoxy-4" -azobenzene )hexyl]vinyl ether}s prepared by polymer analogous reactions <•.D) 214.…”

Semicrystalline poly(vinyl ether)s with high and phototunable glass transition temperature: application for thermally stable and reworkable adhesives

“…On the other hand, some liquid crystalline PVEs with mesogenic side chains are solid and display relatively high T g 's. For example, Percec and Lee reported the synthesis of PVEs containing biphenyl side chains with corresponding T g 's of up to 61 °C, while Chiellini et al synthesized a semicrystalline PVE with azobenzene side groups exhibiting a high T m of 143 °C . Thus, azobenzene‐based PVEs are potential candidates for photoinduced phase transition materials with high thermal stability to broaden the application field of such materials.…”