Helix-Sense-Selective Polymerization of 3,5-bis(hydroxymethyl)phenylacetylene Rigidly Bearing Galvinoxyl Residues and Their Chiroptical Properties

Abstract

Four kinds of newly synthesized achiral phenylacetylenes bearing a phenylhydrogalvinoxyl residue at 4-position were polymerized by using a chiral rhodium catalyst system, [Rh(nbd)B(C6H5)4] or [Rh(nbd)Cl]2 catalysts in the presence of chiral (R)-(+)- or (S)-(–)-1-phenylethylamine ((R)- or (S)-PEA) cocatalysts. Poly(m-HGDHPA) and poly(m-HGTHPA) in THF showed Cotton signals at the absorption regions of the main chain and hydrogalvinoxyl in the circular dichroism (CD) spectra. It indicated that excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization (HSSP) under the asymmetric conditions despite the achiral monomer, and the hydrogalvinoxyl moieties were also arranged to form one-handed helical structure. However, there was no Cotton effect for poly(p-HGDHPA) and poly(p-HGTHPA) because the intramolecular hydrogen bonding did not act well to stabilize the helical conformation. The hydrogalvinoxyl units of poly(m-HGDHPA) and poly(m-HGTHPA) were converted to the corresponding galvinoxyl radicals after treatment with PbO2. In the CD spectra of the polyradicals, the Cotton effects decreased depending on their static stability of helical conformation, suggesting that reversal conformation of the polymer chain arose.

Preparation of poly(thiophene-alt-pyrrole) bearing chiral LC group

“…In other words, distance chirality of terminal optically active group in the mesogen induces main chain chirality. In the previous studies, main chain chirality of polymers was induced by chiral side chain located near position to the main chain, showing molecular functionalities [17][18][19][20][21][22][23]. The polymer prepared in this study is first founding in researches of aromatic LC conjugated polymers that the optically active group in the terminal induces main chain chirality from distance in molecular level.…”

Design of an n-type low glass transition temperature radical polymer

“…57 The intermediate was quenched by KOH followed by HCl to give 2,6-di-tert-butyl-4-((3,5-di-tertbutyl-4-hydroxyphenyl)(4-(hydroxymethyl) phenyl)methylene) cyclohexa-2,5-dien-1-one (5) in one pot. [57][58][59][60][61] Then, the alkene functional group was successfully introduced (i.e., to form 6) by a substitution reaction under basic conditions. 32,62,63 Next, this precursor molecule was bound to the polysiloxane backbone through a Karstedt reagentcatalyzed coupling reaction to form the PGMS-H. [64][65][66] These compounds were characterized by 1 H NMR spectroscopy and 13 C NMR spectroscopy (Fig.…”

Helix-Sense-Selective Permeation of Racemic Helical Oligoacetylenes through One-Handed Helical Channels in Polymer Membranes

“…There are mainly two methods of obtaining chiral polymers with high optical purity. One is enantioselective polymerization such as helix-sense-selective polymerization (HSSPolym) − where an achiral monomer gives a chiral polymer such as a one-handed helical polymer. The other is enantioselective separation, which is usually called optical resolution, , where a racemate (an equimolar mixture of right-handed and left-handed helical polymers) is separated into two enantiomers (one-handed helical polymers).…”

“…In order to obtain one-handed helical polyacetylenes, we developed the HSSPolym − of achiral acetylenes. But no helix-sense-selective separations of racemic helical polyacetylenes have been realized so far.…”