Effective Design for Long-Range Polymer Ordering Using Triptycene-Containing Side Chains

Abstract

Spontaneous long-range structural ordering of polymers can lead to improvements in their physical properties and the emergence of functions that cannot be expected in their amorphous states. We have demonstrated a design strategy to achieve structuring of various polymers using a particular type of triptycene, capable of forming a two-dimensional assembly. In this study, we investigated what designs are effective for achieving long-range polymer ordering by incorporating this triptycene motif into the side chains of polymers. Using poly­(n-butyl acrylate) as a fundamental polymer, we synthesized three types of copolymers, i.e., random, diblock, and ABA-type triblock copolymers, through RAFT polymerization protocols and found that the presence of block segments is essential to achieve polymer ordering, which in turn results in dramatically improved mechanical properties. Here, we also show that poly­(N-isopropylacrylamide)-based copolymers with triptycene-containing side chains undergo an interesting anisotropic expansion and contraction microscopically in response to temperature.

Recent advances in structurally elaborate triptycenes, triptycene-containing polymers and assemblies: structures, functions and applications

“…By reacting these methoxy-substituted triptycenes with boron tribromide, we have shown that 1,8-dihydroxy and 1,8,13-trihydroxytriptycenes (166, 167) can be synthesized [11,77]. A wide variety of substituents can be introduced to these hydroxylated derivatives via ether linkages, and the resulting alkoxytriptycenes have been found to exhibit particular 2D assembly properties [11,[77][78][79][80][81]], which will be described in detail later. The various 1,8(,13)-substituted derivatives developed thus far include those with terminal olefin moieties (168, 171, 172) [77,80,81] and acryloyl groups (169) Recent advances in structurally elaborate triptycenes, triptycene-containing polymers and assemblies:.…”

“…8) and n-butyl acrylate (Fig. 23a) [78]. The thermal stability of these triptycene-containing copolymers is comparable (2% weight loss temperature: ca.…”

“…Figure 5 shows the synthetic pathway for accessing triptycenes with hydroxyl, carboxyl, carboxylic acid chloride, isocyanate, and amino groups as polymerizable substituents at the 9,10-positions. The 9,10-positions of unsubstituted anthracene (77) were chloromethylated (78) and converted to acetoxy groups via nucleophilic substitution (79), followed by a Diels-Alder reaction with benzyne generated from anthranilic acid (80) and amyl nitrite to yield 9,10-diacetoxymethyltriptycene (81). The acetyl group can then be deprotected to the 9,10-dihydroxymethyl trip-monomer (82) [14,15].…”

“…The solid-phase polymerization of the oriented film of 183 proceeded while retaining the surface nanoterraced structure. The incorporation of 1,8,(13)-substituted triptycenes into polymers induces long-range ordered structures through 2D assembly of the triptycene units, greatly enhancing the mechanical properties of the polymers [77][78][79][80]. Such specific 2D assembly can be achieved by incorporating the triptycene units at various sites of polymers, including at both ends [80,81], in the main chain [77], side chains [78] and at various branch points [79].…”

“…The incorporation of 1,8,(13)-substituted triptycenes into polymers induces long-range ordered structures through 2D assembly of the triptycene units, greatly enhancing the mechanical properties of the polymers [77][78][79][80]. Such specific 2D assembly can be achieved by incorporating the triptycene units at various sites of polymers, including at both ends [80,81], in the main chain [77], side chains [78] and at various branch points [79]. Figure 21a shows the chemical structures of dimethylsiloxane) (PDMS) derivatives (poly-38-poly-40) with 1,8(,13)-triptycene units both ends (poly-38 and poly-39) along with a 1,4-substituted derivative (poly-40).…”