Linker effects

As discussed before, Winsor s premise that the quality of the system maybe improved by increasing the size of both the hydrophilic and lipophilic groups of the surfactant while 

The same concept was transferred to the water side and the respective molecules were called hydrophilic linker [47, 48]. However, since the shape of the water molecules and their interactions are quite different from those of oils, hydrophilic linkers are no elongated molecules like the lipophilic linkers. Up to now the hydrophilic linker concept has been tested with alkyl naphtalene sulphonates only. Non-alkylated naphtalene sulphonate is a 

Another improvement of the solubilisation has been accomplished by adding short amphiphilic block copolymers in low concentration (see Section 4.2 for details). Briefly, these polymers have a polyethylene-propylene hydrophobic block and a polyethylene oxide head group and are thus similar to the ethoxylated non-ionic surfactants to which these are added. The main difference is that the two blocks of the amphiphilic polymer are several times larger than the corresponding low molecular weight surfactant. The role of these polymers is to increase the reach of the amphiphilic layer such that it extends deeper into both the oil and the aqueous phase in accordance with Winsor s premise. As a consequence, they are found to notably increase solubilisation [50]. As seen in Fig. 3.9(c), these additives could be called amphiphilic linkers since they act upon both sides of the interface. 

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Cross-linked xanthan gums have also been used to reduce the permeabiUty of thief 2ones. Trivalent chromium is the preferred cross-linker (54). Cross-linker effectiveness is less at high salinity. However, Cr(III) has been used ia the field at salinities as great as 166,000 ppm total dissolved soHds (55). 

Song, Y. Tian, T. Wang, P. He, H. Liu, W. Zhou, X. Cao, X. Zhang, X.-L. Zhou, X. Phenol quaternary ammonium derivatives charge and linker effect on their DNA photoinducible cross-linking abilities. Org. Biomol. Chem. 2006, 4, 3358-3366. 

W. Wang, J. Xu, Y.-H. Lai, and F.Wang, Alternating aromatic and transannular chromophores with and without linker effect of transannular tt-tt interaction on the optical property of dithia-paracyclophane-based copolymers, Macromolecules, 37 3546-3553, 2004. 

The promethazine imprinted MIP particles were used as the recognition element to fabricate a relevant potentiometric chemosensor [200], These particles, prepared with the vinylbenzene functional monomer and the divinylbenzene cross-linker, effectively bound promethazine as compared to the MIP particles prepared with the MAA or vinylbenzene monomer and the EGDMA cross-linker. The MIP particles were embedded in a PVC membrane attached to one end of a glass tube, which was filled with 1 mM promethazine. The chemosensor was able to detect promethazine potentiometrically with LOD as low as 1.0 x 10-7 M and the dynamic linear concentration range from 5.0 x 10-7 to 1.0 x 10-1 M. With this chemosensor, promethazine concentration can be determined in syrup samples and biological fluids with a response time of 50 s. 

Matsushita M, Hoffman TZ, Ashley JA, Zhou B, Wirsching P, Janda KD. Cocaine catalytic antibodies the primary importance of linker effects. Bioorg. Med. Chem. Lett. 2001 ll(2) 87-90. 

Peptide Microassay possible, saving expensive Linker effect in situ synthesis not... 

One-bead On-bead Highly efficient synthesis and Linker effect nnpredictable nntil tested ... 

Post-synthetic modification (PSM) also can tune the pore size. Generally, it decreases the pore size in the framework since the pore can be blocked by functional groups or hybrid units. Akin to the pre-modification method, a change in length or width of the organic linker effects porosity and the nature of the framework. However, the influence made by modification is not limited to tuning the pore size of the framework. 

Four decades ago. Hush made a prediction that, when redox-active moieties were bound onto an electrode surface by conjugated linkers, effective interfa-cial intervalence transfer might occur." These studies are believed to be the first experimental verification to directly support such a hypothesis, which is anticipated to open a new chapter in electrochanical study of intervalence transfer. 

In some cases, long-chain alcohols have been found to behave as polar oils, with a tendency to place themselves not in the oil phase bulk but near the interface [60]. This means that the oil phase which is in contact with the interfacial C layer is richer in alcohol than the overall oil phase, with a consequence on the interactions. This alcohol role has been called a lipophilic linker effect because the alcohol molecules that are located near the interface are not randomly oriented like oil molecules in the bulk, but with their OH group pointing toward the interface (i.e., perpendicular to the interface), a conformation that produces an additional ordering in the oil molecules that ends up in a better interaction [83,84]. 

At the light of this new approach, it is worth asking how it could be possible to increase the reach of the surfactant tail into the oil phase even more, without falling into the penalty of low solubility and precipitation. Very recently, it was proposed to insert an intermediate polarity segment in between the hydrophilic and lipophilic groups of the surfactant, so that it would be longer. In order to mimic the lipophilic linker effect, the intermediate chain was selected as polypropylene oxide, which is mostly water insoluble but somehow polar, and also has a branched chain that would help prevent the formation of liquid dystals, as known from the behavior of EO-PO block copolymers. 

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