Topochemical crosslinking

Four main mechanisms of the photoalignment are known (i) reversible photochemical trans-cis isomerization in azo-dye-containing polymers, monolayers, and pure dye films (ii) pure photophysical reorientation of the azo-dye chro-mophore molecules (iii) topochemical crosslinking in cinnamoyl side-chain polymers (iv) photodegradation in polyimide materials. 

During the late 1960s, Wegner reported that single-crystalline diacetylenes could be topochemically polymerized to ene-yne polydiacetylenes [78], and several groups subsequently applied this chemistry to crosslinking polymerizations in 2-D confinement. For example, Leblanc synthesized the dendrimer-based amphiphile 34 in which sixteen 10,12-pentacosadiynoic acid chains were coimected to the periphery of a third-generation poly(amidoamine) (PAMAM) dendrimer [79]. A monolayer of this dendritic amphiphile was prepared at the air/water interface, in which the... 

The topochemical nature of the polymerization of diacetylene monomers into polydiacetylene is well known [612, 621-623]. Studies of these polymers revealed that they may undergo crosslinking ( crosspolymerization ) when neighboring chains are well aligned in crystalline or semi-crystalline domains... 

As indicated in Figure 8, the crosslinking of discotic monomers might lead to insulated wires. The crosslinking of diacetylene-functionalized mesogens via a topochemical polymerization in a columnar phase was reported, but no electronical charartetization was performed. ... 

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