Modification of statistical threading in two-component pseudorotaxane melts using the amphiphilic approach and variations in the confinement geometry

Abstract

Recently we described a coarse-grained model of poly(ethylene oxide) and then employed that model to study the amount of spontaneous threading of cyclic molecules by linear chains in the melt [C. A. Helfer, G. Xu, W. L. Mattice, and C. Pugh, Macromolecules 36, 10071 (2003)]. Since the amount of statistical threading at equilibrium is small, there is interest in identifying physical changes in the system that will increase the threading. We now use that coarse-grained model to investigate the effect on threading of various hypothetical (but feasible) modifications to the two-component system of macrocycles and linear chains in the melt, and different confinement geometries, that can bring about correlations in the arrangement of the rings. Our work follows on the concept of an amphiphilic approach [C. Pugh, J.-Y. Bae, J. R. Scott, and C. L. Wilkins, Macromolecules 30, 8139 (1997)] for increasing the statistical threading in homopolyrotaxane melts. We investigate whether introducing such correlations in the macrocycles can increase the spontaneous threading. This paper shows that some of our modifications can yield more than double the amount of threading seen in purely statistical mixing.

Structure and Internal Dynamics of Poly(ethylene oxide) Catenanes in the Melt

“…Nevertheless, Pugh and co-workers have demonstrated that homopolyrotaxanes are accessible in the laboratory. [30][31][32] Simulations have supported the laboratory synthesis by providing guidance on the optimal size for the cyclic component 26 and influence of the solvent 27 and by providing independent support 28 for the utility of the amphiphilic approach originated by Pugh. 30 Here the simulation method employed for the investigation of the homopolyrotaxanes [26][27][28][29] is used for the study of melts of catenanes in which all components are constructed from PEO.…”

“…[30][31][32] Simulations have supported the laboratory synthesis by providing guidance on the optimal size for the cyclic component 26 and influence of the solvent 27 and by providing independent support 28 for the utility of the amphiphilic approach originated by Pugh. 30 Here the simulation method employed for the investigation of the homopolyrotaxanes [26][27][28][29] is used for the study of melts of catenanes in which all components are constructed from PEO. The results are compared with similar simulations of melts composed of individual rings that have the same mass as both rings in the catenanes.…”

“…Cyclodextrins, crown polyethers, and cyclophanes have been widely used in the synthesis of polyrotaxanes. Recently, we studied various aspects of the equilibrium and dynamic properties of homopolyrotaxanes, where both the ring and the linear chain are composed of poly(ethylene oxide) (PEO). − Homopolyrotaxanes are interesting from the theoretical point of view because their properties are controlled by the physical fact of their threaded nature, without additional complications arising because the thread and the ring are constructed from different monomer units with inherently different properties. The synthesis of homopolyrotaxanes is a challenge because it is not facilitated by a favorable enthalpic interaction of the ring and the thread.…”

Synthesis and Mass Spectrometry Studies of an Amphiphilic Polyether-Based Rotaxane That Lacks an Enthalpic Driving Force for Threading

“…This indicates that threading is favored by aggregation in a poor solvent. In addition, planar alignment can double the extent of threading (to 9% of the rings threaded) compared to the purely statistical threading in the melt, if the distance between cycles in two consecutive layers is confined to a distance approximately equal to the size of the rings 1 Amphiphilic Approach for Synthesizing Polyrotaxanes that Lack an Enthalpic Driving Force for Threading …”

“…5 If an added thread is also not soluble in the selective solvent, it will be forced into the interior of the micelle (Scheme 1), where the high concentration and alignment of the macrocycles should promote threading. Although we have not yet mimicked this three-component system using simulations, we have recently used Monte Carlo simulations to investigate both the effect of solvent quality 6 and the alignment 7 of the macrocycles on the extent of threading 42-crown-14 with CH 3 (OCH 2 CH 2 ) 13 -OCH 3 ; we previously found that 42-crown-14 is approximately the optimum ring size for maximum spontaneous threading by PEO with inconsequential multiple threading. 8 Compared to the melt (1.73 threading events ) 4.33% of the rings threaded), 8 the number of threading events decreases with solvent dilution since there are fewer rings present, and the percentage of rings threaded are lower in the good and Θ solvents than in the melt and poor solvent.…”