Packing of Polymer Chains

It is evident that efficient packing of polymer chains containing aromatic rings and carborane units requires significant longitudinal displacement of adjacent chains, unlike the situation for all-aromatic systems where little or no such displacement is observed.9... 

Figure 2.7 Model of the packing of polymer chains in the crystal structure of polyethylene in which a = 7.41 A, b - 4.94 A, and successive pendant atoms are 2.55 A apart along the chain axis.

Chemical properties The bulky shape of the MMA group ensures an amorphous structure because it prevents close packing of polymer chains. PMMA has extremely good weathering resistance. Acrylics are dissolved or stress crazed on contact with ketones, esters, hydrocarbons, acids and alkalis. ... 

The packing of polymer chains into the unit cell normally follows two basic rules ... 

The flux increases while the separation factor decreases rapidly with an increase in benzene concentration. This is the effect of the membrane swelling at the higher benzene concentration. The effect of the incorporation of chitosan-wrapped CNT is presumably two fold (1) tuning the packing of polymer chains in the vicinity of... 

Whereas dense packing of polymer chains may appear to be a distressing task, a thorough examination of the problem leads to the firm conclusion that macromolecular chains whose structures offer sufficient flexibility are capable of meeting the challenge without departure or deviation from their Intrinsic proclivities. 

A quinodial type of resonance structure necessitates that a coplanar orientation of rings be readily accessible in order for a small band gap and high conductivity to be achieved [24]. If high energy constraints prevent the coplanar arrangement from being formed, then a low conductivity will result. In the solid state, dense packing of polymer chains can allow for overlap to occur in three dimensions. This 3-D electronic connectivity creates low resistivity pathways for electrons (or holes) to... 

Betulin, extracted from birch bark, has been used as a difunctional monomer to undergo polycondensations with acid chlorides, resulting in hyperbranched (networks) or linear polyesters (Scheme 12). The stiff sfructure of betulin and the geometric positioning of the OH groups prevent close packing of polymer chains to yield a microporous structure, making these polycondensates candidates for gas separation membranes [112]. 

---