Defect Engineering using Precision Polymers
Among the crystallizable materials, polymers hold a special place, because the unit cell of a polymer crystal does not contain the entire molecule, but only some of the monomer units. Moreover, the molecular architecture of a polymer imposes a further constraint on the crystallization process: the monomer units form a chain, and, to construct a crystal structure, these need to be placed sequentially as imposed by the chemical sequence of the monomers. This constraint has drastic consequences for the crystallization of a polymer. Chemical irregularities such as side chain branches or co‐monomers in an otherwise regular polymer influence its crystallization and accordingly the physical properties of the material. In most polymer systems, these chemical defects are randomly distributed along the chain and it is difficult to understand in detail their effect on crystallization.
In our studies we examine precision polymers prepared by acyclic diene metathesis (ADMET) polymerization. This synthesis ensures an exact, equidistant placement of the chain defects. Since the defects are placed exactly at equidistant positions, we can expect this regularity to be transferred from the molecular chain to the crystal. Depending on the size of the defects these are either included or excluded from the crystal. In the case of the exclusion type of polymer, this directly influences the maximum achievable lamellar thickness, which is defined by the number of CH2 units between two defects.
The aim of our research is to explore the possibilities to exploit the precise molecular architecture of the precision polymers in combination with its crystallization in order to achieve novel material properties and nanosized structures.