Slippage approach

The clipping reaction used in [52, 53, 55] to synthesize tetralactam-based squaraine rotaxanes such as 14 and 15 afforded only moderate yields (ca. 28-35%) of the rotaxanes, possibly because of the unavoidable presence of nucleophiles that react with the chemically unstable squaraines during the reaction. The slippage approach [62] minimizes the squaraine dye s contact with nucleophiles during the rotaxane formation process and therefore can be used to efficiently encapsulate a squaraine dye such as 23 in a macrocycle such as 25 [63],... 

In a recent full paper [32], a molecular switch 116+, which can be driven either photochemically or electrochemically, has been described. Synthesized in a 59% yield from the corresponding dumbbell compound using the slippage approach, this [2]rotaxane contains (Fig. 16) two chemically distinct recognition sites around which the BPP34C10 macrocycle can reside. Of the two sites, the unsubstituted bipyridinium unit is the better electron acceptor, and so it is around this site that the macrocycle encircles itself preferentially. However, upon reduction of the bipyridinium site to its radical cation - either... 

Recently, a third process has been identified which constitutes an example of strict self-assembly.The so-called slippage approach to rotaxane synthesis Figure 5) is based upon size complementarity between the macrocyclic polyether, BPP34C10, containing two 7i-electron rich recognition sites and the stoppers comprised of suitable tetra-arylmethane groups at the ends of dumbbell-shaped molecules incorporating at least one 4,4 -bipyridinium unit. ... 

Whereas the total dynamic head developed by a centrifugal, mixed-flow, or axial-flow pump is uniquely determined for any given flow by the speed at whicdi it rotates, positive-displacement pumps and those which approach positive displacement will ideally produce whatever head is impressed upon them by the system restrictions to flow. Actually with slippage neglecTed, the maximum head attainable is determined by the power available in the drive and the strength of the pump parts. An automatic relief valve set to open at a safe pressure... 

The viscosity function of the natural gums is utilized in both oil in water and water in oil emulsions. Often the gums are referred to as emulsifying agents. They are considered not so much as emulsifiers, but rather as emulsion protectors or stabilizers. To a large extent, the function is to increase the viscosity of the aqueous phase so that it approaches, or slightly exceeds, that of the oil hence, there is less tendency for the two phases, once emulsified, to separate by mechanical slippage. 

A recently developed technology takes a different approach to solving the stress problem (14). Rather than chemically plasticizing the sulphur, non-reactive additives are used to holistically plasticize the sulphur concrete mix. In essence these additives are lubricants which operate at the sulphur/aggregate interface to allow slippage and stress relief without disruption and cracking. The apparent permanency of this plasticization approach has been demonstrated by extensive testing over a four year period. 

In the temperature range c, the molecular process is the creep of the fibrils in the only present CDCs, due to the easier chain slippage occurring when approaching Ta. 

The approach of using acetylated Cps has one limitation. If the C=0 group and an additional donator in, for example, the biomolecule can form a six-membered chelate, this mode of coordination is preferred and slippage from this if coordination to rf coordination on the Cp takes place, if ever, very slowly. 

The aging rate of flax decreased from a value of 0.66 at 25 °C to a value of 0.41 at 50 °C. Flax could not be tested at 75 °C because fiber slippage between the clamps could not be eliminated. However, the nonunity and decreasing aging rate values suggest that Tg is being more closely approached than it is with cotton. 

The main assumptions made in arriving at eq 10 were (1) no interaction between the globules and (2) no slippage at the particle-fluid interface. Most emulsions of practical interest exceed the concentration for which eq 10 is valid. With increasing concentration, the hydrodynamic interaction between the globules increases, and eventually mechanical interference occurs between the particles as packed-bed concentrations are approached. To take into account the increased hydrodynamic interaction, many investigators (30, 38-43) have expanded eq 10 into the polynomial form ... 

Harrison [4, 33, 34] and later, Schill and coworkers [38] had explored temperature-controlled slippage. Another approach was to control the size of the stoppers by complexation. Stoddart and coworkers [90] could thread macrocycle (27) onto dumbbells ended by aza crown ethers. The slippage process was inhibited by addition of an alkali cation. Conversely, complexation of the aza-crown after the slippage process inhibited unthreading. 

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