Post-functionalization Of Disubstituted Polyacetylenes Via Click Chemistry

Functional polyacetylenes as an important branch of advanced materials have been widely applied in the field of light/electronic-emitting devices, liquid crystal, wrapping carbon nanotubes, fluorescence sensors, simulation of biological proteins etc., which hints its huge potential development. However, the polymerization of substituted polyacetylenes is rather difficult.To solve the problem, enthusiastic chemists pay much attention to explore the new catalyst systems to improve the polymerization dilemma. Experience accumulated is shown as follows:1) The reaction condition significantly affects the polymerization of the substituted acetylene.2) There is selectivity effect between the monomer and catalysts.3) Subtle difference in the structure of the acetylene monomer will cause the reselection of the catalysts, which means that if the monomer's functional groups are changed, the catalysts system and the reaction condition should be explored once again, and that is really time-consuming. For convenience, we try to synthesize polymers with potential reactivity groups in the side chains which could react with functional groups via efficient chemistry reaction, realizeing the post-funtionalization of the polymer precursor. This method cuts off the functional groups'influence on the polymerization, which means that once achieving the polymer precursor, it will be rather easy to obtain types of function polyacetylenes as long as the reactive groups in side chains can react with the functional groups.Based on the idea, we designed and synthesized a kind of monomer with two type internal alkyne bonds, and got the disubstituted polyacetylenes P1with large steric hindrance group TMS in the side chain through its selective polymerization. The desiliconization product P2with the reactive terminal alkyne bonds and the azide molecule undergo click chemistry reaction in the presence of catalyst Cu (I), yielding the target polymer P3-2. For simplifying the whole procedure, one-pot method was explored. In other words, we wanted to merge the desiliconization with the post-functionalization procedure to get the target product P3-1directly (distinguishing from P3-2). IR, NMR spectra shown that post-functionalization of disubstiuted polyacetylenes can be realized by the two methods described above.In classic click chemistry, trace level of cuprous catalyst residue will poison cell, which hampers its application in biology field. However, functional polyacetylenes as important biocompatible materials develop fast. To deal with this situation better, metal-free click chemistry here is introduced to replace the classic click chemistry, which would root out cuprous catalyst completely from the very beginning. Therefore, we designed and synthesized a kind of disubstituted polyacetylenes P with vinyl (C=C) in its side chains, with which the thiol-based function molecules could react via thiol-ene metal-free click chemistry. It's worth mentioning that the metal-free click reaction between polymer P and the thiol compound run smoothly without adding any evocating agent. The reaction condition is rather simple, including the two reactants, a small amount of solvent THF. and the ambient environment (room temperature and normal sunlight). Luckily, we still got the target product Ps. Compared with the classic metral-free click reaction initiated by chemical evocating agent, the separation and purification of the product in this method is much simpler. And it also provides the possibility of graft for biomolecules such as protein that is unbearable to high temperature or metal ions etc.