Cardo polymer

As such, the cyclic side group lies perpendicular to the plane of the extended (all trans conformation) polymer chain.

[1] Because of these physical effects, recent advances in membranes used for gas separation have used cardo polymers.

[1] However, the addition of a cardo group increases solubility because the bulky structure creates steric hindrance, preventing the polymer chain from packing tightly.

[3] This loose packing offers more surface area for the polymer to interact with the solvent, increasing the solubility.

However, the bulky, and often non-polar cardo monomers do offer some challenges, requiring unique synthetic tactics.

High molecular weight cardo aromatic polyesters can also be achieved via low temperature, acceptor catalytic polycondensation methods.

These reactions are done under basic conditions in aprotic solvents, often in the presence of an inorganic salt, such as calcium chloride, to increase solubility.

Alternatively, the synthesis can be carried out in one step in which chain grown and ring closure happen simultaneously.

This reaction occurs at high temperatures in organic solvents including cresol, nitrobenzene, benzonitrile, and sulfolane.

[2][3][4] In general, as the amount of free volume in a material increases, the higher the gas permeability.

[2] Cardo polymers have a great deal of free volume since their bulky structure prevents tight packing, and a rigid backbone since the rings restrict rotational motion.

Specifically, strong intermolecular attractions arising from hydrogen bonding greatly inhibit the mobility of segments of the polymer chains resulting in a rigid, densely packed structure relative to a cardo polymer with only minor intermolecular interactions.