New polymer architectures: Recent results with polyrotaxanes

Abstract

Recent results from our laboratory have shown that the formation of polyester and polyurethane rotaxanes by polymerization in the presence of crown ethers is driven by hydrogen bonding of the OH groups with the oxygen atoms of the macrocycles. Here we summarize these findings. Then we describe the application of this type of self assembly for the production of polyrotaxanes by threading preformed macromolecules and for the controlled synthesis of branched and crosslinked systems. These latter protocols comprise a new and novel way to prepare mechanically linked, elastomeric materials. Rheological properties of main chain polyrotaxanes are compared to simple linear backbones; the rotaxanes display higher intrinsic viscosities and lower melt viscosities, reflecting larger hydrodynamic volumes and less entanglement, respectively; these are potentially useful aspects in terms of processability of this new class of polymeric materials.

The Effect of Urea on Wool Fibres

“…However, it seems likely that accelerated dyeing in the presence of urea is due to a combination of factors, such as swelling and dye disaggregation inside the fibre, rather than to a single effect. Undoubtedly, the 40% increase in the fibre volume due to the addition of sodium bisulphite to pad-batch dyeing liquors must contribute substantially to the enhanced dyeing rates obtained in that case [18]. In agreement with Blagrove's findings, there was no evidence that urea was absorbed by wool any more or less readily than water or that the surface of wool fibres behaved as an impermeable membrane or preferential adsorption surface towards urea.…”

Controlling Polymeric Topology by Polymerization Conditions: Mechanically Linked Network and Branched Poly(urethane rotaxane)s with Controllable Polydispersity

“…For the preparation of polyester rotaxanes, we proposed that H-bonding of the crown ethers with −OH groups provides the driving force for threading . Therefore, macrocyclic moieties described as structure 13 , macrocyclic diol 5 initially and in-chain macrocyclic units during the polymerization, are expected to form various intermediates simplified as structure 15 by H-bonding with −OH groups of 14 , another macrocyclic diol 5 , or glycol 6 at the start and the terminal −OH groups of polymeric chains during the polymerization (Scheme ).…”

“…Polyrotaxanes, in which rotaxane units (cyclics threaded by linear species) are incorporated into macromolecules, also have received world-wide attention. − Numerous main chain polyrotaxanes have been prepared with crown ethers as cyclic components. ,− Recently, hydrogen bonding between hy-droxy groups and the crown ether was proposed as a driving force for the threading. − Therefore, a crown ether bearing a hydroxy functional group brings about a driving force for the formation of a self-complexed structure ( 1 ), which can lead to a novel rotaxane structure ( 3 ) by an endo esterification with a poly(acid chloride) (Scheme ), as we demonstrated by the formation of a branched and/or cross-linked polymer ( 4 ) . In the present work, this concept is extended and used as a novel strategy to overcome the limitations of classical methods for the preparation of branched and network polymers, demonstrated by the syntheses of mechanically linked branched and network polyurethanes.…”

Polyrotaxanes

“…The details of these examples are described in our recent review (30). The groups of Gibson, Stoddart, and Takata actively synthesized these polyrotaxanes (27,(113)(114)(115).…”