Polymerization of Styrene in Cyclodextrin Channels: Can Confined Free‐Radical Polymerization Yield Stereoregular Polystyrene?

Abstract

Summary: Modeling of polystyrenes (PS) with various stereosequences in the narrow cylindrical channels corresponding to those found in γ‐cyclodextrin inclusion compounds (CD ICs) has been conducted. Based on the conformational modeling of stereoisomeric polystyrenes (PSs) in narrow channels, it was suggested that polystyrene with unusual microstructures might be produced by the constrained polymerization of styrene monomer in its γ‐CD‐IC crystals. The in‐situ polymerization of styrene inside the narrow channels of its γ‐CD‐IC crystals was performed in both organic and aqueous media. The 13C NMR spectrum of PS synthesized inside the γ‐CD channels in an aqueous medium shows some differences when compared to the 13C NMR spectrum of PS synthesized in toluene. These are presumably because of differences in their stereosequences. Here, we report our preliminary findings.Schematic of cyclodextrin inclusion compound (CD‐IC) channels with included polymer guests.magnified imageSchematic of cyclodextrin inclusion compound (CD‐IC) channels with included polymer guests.

Polymerization of styrene in γ-cyclodextrin channels: Lightly rotaxanated polystyrenes with altered stereosequences

“…Thus, based on the modeling of stereoisomeric polystyrenes (PSs) in narrow g-CD channels, it was suggested [9], and confirmed here, that polystyrene with unusual microstructures might be produced via constrained polymerization of styrene monomer in its g-CD-IC crystals, as was described in a preliminary report [4]. Consequently, here we present the details of the polymerizations of styrene monomer in its channel structure inclusion compound formed with g-CD, as well as the characterization of the resulting PSs.…”

“…1d). The first approach is a ''suspension'' method in which preformed [10] g-CD channel crystals containing only water of hydration are suspended into neat styrene to form the inclusion compound [4]. In the case of the suspension method, we have found that only the preformed g-CD channel crystals, and not as-received cage structure g-CD crystals, form styrene/g-CD channel -ICs when suspended in neat styrene.…”

“…In the case of solid monomer/CD complexes, the monomer resides in the CD cavities and can be polymerized either by solid-state polymerization or by suspending the crystals of monomer/CD inclusion compound in a solution where the inclusion compound is not soluble [4]. In order to obtain polymer, the CDs have to adopt continuous channel-type packing (Fig.…”

“…Solution or solid inclusion complexes of guest monomers, i.e., styrene [4,5], methyl methacrylate [4], pyrrole [6], bithiophene [7], aniline, [8] etc., with host CDs or modified CDs and their polymerization have been studied. In solution complexes, host CDs show the unique characteristic of complexing with water-insoluble hydrophobic guest monomers, which become water-soluble.…”

Why is Stereoregular Polyacrylonitrile Obtained by Polymerization in Urea Canals Isotactic?

“…It was suggested that the probability of producing isotactic stereosequences, with narrower diameters, and syndiotactic stereosequences, with larger diameters, might be small. [9] Solution 13 C NMR observations suggested that a new type of PS with altered stereosequences could be obtained inside the g-CD CS channels only by suspension of styrene-g-CD CS -IC crystals in aqueous polymerization medium. [10,11] The first detailed attempts to obtain a highly stereoregular polyacrylonitrile (PAN) were made by White [3] in 1960 and employed the urea canal complex of AN.…”