Actually, in literature, so many groups are concentrating on side chain liquid crystalline polymers than main chain LC polymers.
What are the main advantages of side chain LC and functional polymers, particularly compared with the same groups and LCs containing main chain polymers?
Molecular design of the side chain LCP is more convenient than the main chain LCP (for synthesis of a new LCP)
1. Side chains have greate influence of teriary structure
2. Side chain functional groups are more accessible and active than main chain.
3. Interactions with small and macromoleules go via side chains
4. side chains can be more toxic than main chain units.
Previous answers get directly at the key issue: availability of side chains vs. main chains. Availability translates into potential reactivity for functionalities, including hydrophobic interactions in aqueous systems.
Crosslinking is essentially a side chain issue, because of the availability/reactivity issue, but also because the remaining functionality is by definition a side chain.
The most common means of studying side chain interactions is by following changes in Tg and rubber region modulus. Prof. Adi Eisenberg of McGill University conducted considerable studies in inorganic polymers where such interactions had magnified effect on main chain behavior. Peak of his work was probably in the 70's and 80's.
Crystallinity has been largely a main chain issue in the literature because of such articles of commerce like high density linear polyethylene. But for people seeking to modify the mechanical properties of main chain polymers, they have focused first on copolymerization to alter the basic properties, and then on side chains to alter rubber region behavior without disturbing the parent chain properties below Tg.
So if you want to alter behavior in the glass region, main chain may be the way to go. But in the rubber region, side chains are the preferred approach. Sorry for the bold generalization, but you must first decide what you're interested in studying, and then choose your terrain.
But keep in mind that Tg itself can be significantly altered by changing either the main chain or side chains. The basis of your decision must be on which side of the Tg you wish to study or alter properties.
But keep in mind that Tg is the onset of main chain translational motion. Thus to promote interactions in the main chain, one must be above the Tg of the system to permit polymer mobility. This even includes polymers in solution! [little known fact]
My reason for dealing primarily with side chains during my career is that I was always dealing with conflicting demands. The best compromises always came from dialing in certain properties via choice of main chain, and then building up the various compromises by way of side chain interactions or reactions. And don't forget simple ionic interactions in otherwise hydrophobic polymers -- the whole field of ionomers exists because of these. Again, Eisenberg is a rich trove of published work in the field of ionomers.
But enough of the generalities. The better you can focus your question(s), the more relevant and useful our answers can become.
1st, it is easy to change side group, comparing with the main chain
2nd, when you change the side group, the free volume change and so chain dynamics change, which means you can control the glass transition temperature,and that is an important parameter for LCP.
The reactivity is different. The interaction is easy with side chains tan in the main chain and also it is easy the synthesis of the polymers.
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