Polymers/Properties

Tacticity (stereochemistry) can change the properties of the polymer.

Isotactic	Syndiotactic	Atactic

Molecular mass

Number average (M_n) and weight average (M_w).

$M_n=\frac{\sum M_i{N}_i}{\sum N_i},M_w=\frac{\sum M_i^2{N}_i}{\sum M_i{N}_i},M.W.D.orPDi=\frac{M_w}{M_n}$

Glass transition (T_g) and melting temperature (T_m)

• T_m: crystalline regions, first order transition
• T_g: amorphous regions, second order transition

• hydrogen bonding increases T_g
• longer side chains lowers T_g
• at or below T_g, the ratio of free volume to total volume of polymer is constant