Synthesis of Nano-Latex Particles of Optically Active Helical Substituted Polyacetylenes via Catalytic Microemulsion Polymerization in Aqueous Systems

Abstract

This article reports on the first catalytic microemulsion polymerizations of substituted acetylenes in aqueous medium, providing nanoscale particles exhibiting optical activities and consisting of helical polymers. Three types of substituted acetylenessone achiral N-propargylamide, two chiral N-propargylsulfamides, and chiral N-propaygylureaswere polymerized in the presence of hydrophobic Rh-based catalyst and with SDS as emulsifier and DMF as coemulsifier. Such microemulsion polymerizations led to nanoscale particles (70-110 nm in diameter) of polymers adopting helical conformations. The particles derived from the chiral monomers showed large specific rotations and intense circular dichroism (CD) signals. The obtained polymer dispersions demonstrated high stability. The thus-prepared polymers after removing the emulsifier and coemulsifier showed much stronger CD signals, and the helices were found to have higher thermal stability when compared with the corresponding polymers synthesized via catalytic polymerizations in organic solvents. The microemulsion polymerizations enable the polymers to form predominantly one-handed helical structures. The possible mechanisms were proposed for the formation of optically active polymer particles, for the formation of predominantly one-handed helices, and for the increased thermal stability of the helices formed in the polymers.

A Novel Type of Mono-Substituted Polyacetylene: Synthesis and Characterization of Poly(N-Propargylthiourea)s

“…In appearance, poly(4) itself (Fig. 6a) appeared pale yellowish, similar to the other substituted polyacetylenes synthesized in our earlier studies [25,36,37]. The color of the metal complexes gradually became deeper with increasing amounts of Fe 3+ ions.…”

Preparation of Optically Active Nanoparticles by Emulsification of Preformed Helical Polymers

“…The second approach (route B) has been explored systemically in our earlier investigations. [16,17] The number-average molecular weight (M n ) and its distribution of the four polymers are listed in Table 1. For all the four polymers, emulsions can be obtained readily via emulsification.…”

“…CD spectroscopy has been proven straightforward and efficient to identify the secondary structures of helical polymers and polymer emulsions based on helical polymers. [15][16][17][18] The CD and UVVis spectra of the emulsion from polymer 1 are illustrated in Figure 2. As can be seen from Figure 2A, CD signals tend to be stronger in intensity as the content of SDS was increased.…”

“…To circumvent the limitations and to prompt the relevant application research, we have prepared for the first time a unique category of nanoparticles consisting of helical substituted polyacetylenes. [15][16][17] Further, we succeeded in the preparation of core/shell nanoparticles where the core was based on helical polyacetylenes and the shell was constituted by vinyl polymers. [18] Such (core/shell) nanoparticles exhibited interesting optical activities due to the core-forming polyacetylenes adopting helical structures of preferential handedness.…”

Optically Active Hybrid Materials Constructed from Helically Substituted Polyacetylenes

“…So, in 2008, we began a new research topic regarding substituted polyacetylenes, that is, preparing polymeric nanoparticles (NPs) based on HSPAs. [11] The purposes of this research included three points: 1) to examine whether chirally substituted acetylenes, particularly those bearing bulky pendants, could undergo aqueous emulsion polymerizations; 2) to investigate whether the formation of particles could affect the helical conformations of substituted polyacetylenes; and 3) to elucidate whether the as-prepared polymeric particles showed some properties that were distinguishable from the usual nonspherical counterparts, that is, general substituted polyacetylene solutions. Based on the above hypotheses, a series of studies have been accomplished in our group, and some exciting achievements have been made accordingly.…”