Other Interchain Links

Members of the trefoil factor family of small proteins are solid candidates to be mucin interchain cross-linkers (Otto and Thim 2005). For example, TFF1 is mainly expressed in the goblet cells of gastric mucosa, where it co-localizes with and binds to MUC5AC (Ruchaud-Sparagano et al. 2004). Yeast two-hybrid 

---

As a class the aliphatic polyalkenamers have low values due to a combination of low chain stiffness and low interchain attraction. The presence of double bonds has the effect of increasing the flexibility of adjacent single bonds (see Chapter 4) and overall this leads to a reduction in. Thus in the sequence from polydecenamer down to polypentenamer an increase in the double bond concentration leads to a lowering of Tg. On the other hand the Tg of polybutenamer, i.e. poly butadiene, is somewhat higher than that of polypentenamer, presumably because the proportion of stiff links, i.e. double bonds, becomes sufficiently high to override the flexibilising effect on adjacent chains. Consequently the polypentenamers have the lowest Tg values known for hydrocarbon polymers (cis- -114°C, trans- -97°C). 

It is reasonable to consider that in an ester group the in-chain ether link —C—O—C— increases the chain flexibility compared with a polymethylene chain to decrease the heat of fusion. At the same time there will be some increase in interchain attraction via the carbonyl group which will decrease the entropy of fusion. Since these two effects almost cancel each other out there is almost no change in melting point with change in ester group concentration. 

The Hg-0 distances within the chains is 2.03 A while the closest interchain distance is 2.82 A. If a Hg+ salt solution is treated with warm, aqueous NaOH for several hours, metastable crystals of HgO form that have the hexagonal cinnabar (HgS) sfructure. Again the basic building blocks are O-Hg-O chains but now they wrap in a helical fashion and are cross-linked to other chains by Hg-O bonds to form a highly distorted octahedron of oxygens about each mercury with the motif of 2 short linear Hg bonds being maintained. 

Other approaches have involved reduction of interchain interaction either by cross-linking the polymers using vinyl endgroups [ 71 ] or by attaching bulky groups, e.g., dendrimers [72,73] or silsesquioxanes [74,75], as end- or side-groups. There is evidence that reduction of fluorene by calcium cathodes is implicated in the formation of ketone defects during LED operation, and this can be suppressed by introduction of a buffer layer between the polymer and the cathode [76]. 

---