Top-Down Preparation of Self-Supporting Supramolecular Polymeric Membranes Using Highly Selective Photocyclic Aromatization of Cis–Cisoid Helical Poly(phenylacetylene)s in the Membrane State

Abstract

A novel, highly selective photocyclic aromatization (SCAT) of π-conjugated polymers from phenylacetylene having two hydroxyl groups to exclusively yield a 1,3,5-trisubstituted benzene derivative was developed, and its success was confirmed by (1)H NMR, GPC, and TOF-MS. The SCAT reaction has many unique characteristics. (1) It is a quantitative reaction: it gave only the corresponding cyclic trimer, i.e., a 1,3,5-trisubstituted benzene derivative, quantitatively (100%). No byproducts were produced under the best conditions. (2) It is an intramolecular reaction: it occurred between three adjacent monomer units in one macromolecule. (3) It is a stereospecific and topochemical or template reaction: the reactivity strongly depended on the configuration and conformation of the starting polymer substrates. (4) It is a photoreaction: high selectivity (100%) was observed only by the use of visible light irradiation, not by heating. (5) It is a solid-state reaction: high selectivity (100%) was observed only in the solid state, not in solution. In addition, (6) the resulting cyclic trimers could form a self-supporting membrane, despite their low molecular weights. This new approach resulted in a new class of supramolecular polymers consisting of a 1,3,5-trisubstituted benzene derivative, numbers of which were linearly linked by hydrogen bonds and stacked benzene derivatives. Since SCAT has such high selectivities and is useful for the preparation of a self-supporting supramolecular polymer membrane, many applications can be expected.

Synthesis of a Fluorine‐Containing Cis‐Cisoidal One‐Handed Helical Polyphenylacetylene and Application of Highly Selective Photocyclic Aromatization Product on Oxygen Permselective Membrane

“…This result indicates that the introduction of perfluorinated alkanes enhanced the reactivity of SCAT reaction. Since only acetylene polymers taking a cis‐cisoidal conformation showed SCAT activity, as we reported before, the SCAT active polymer P-F must take cis‐cisoidal conformation …”

“…One‐handed helical poly(phenylacetylene)s by helix‐sense‐selective polymerization (HSSP) of achiral phenylacetylenes having two hydroxyl groups and a hydrophobic alkyl group(i.e., M-H in Scheme ) with a chiral catalytic system consisting of [Rh(norbornadiene)Cl] 2 (norbornadiene = nbd) as an initiator and ( R )‐phenethylamine (( R )‐PEA) as a cocatalyst have been reported by some of our group(Zang and Aoki) . The resulting polymers adopted a tight cis‐cisoidal one‐handed helical conformation . However, the efficiency and ability of the chiral induction was not high, that is, many of the chiral sources were needed and the resulting polymers showed low intensity of the circular dichroism (CD) signals.…”

“…In this study, in order to enhance the efficiency and ability in the chiral induction during HSSP and obtain a polyphenylacetylene having cis‐cisoidal one‐handed helical conformation which shows SCAT activity, a novel fluorine‐containing achiral phenylacetylene monomer ( M-F , Scheme ) was synthesized and polymerized. In addition, a facile synthesis of a 2D surface modifier having three hydrophobic perfluoroalkyl arms by the SCAT reaction and enhancement of oxygen permselectivity of polymer membrane by surface modification using the 2D surface modifiers are reported.…”

Stimuli-Responsive Polyacetylenes and Dendronized Poly(phenylacetylene)s

“…67 This reaction possesses many unique features: (a) It is a quantitative reaction; it gives only the corresponding cyclotrimer, i.e., a 1,3,5-trisubstituted benzene, in the quantitative yield. (b) It is an intramolecular reaction; it takes place between three adjacent monomer units in one macromolecule.…”

Substituted Polyacetylenes: Synthesis, Properties, and Functions

“…64 Polymer 7 provides a cyclotrimer membrane by photo-induced degradation. 65 Poly(PA)s having various chiral groups including optically active amino acids have been synthesized and their helical structures have been studied. 66 …”