Polymers/Properties

Type classification: this is a lesson resource.

Subject classification: this is a chemistry resource.

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

Isotactic	Syndiotactic	Atactic

Molecular mass

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

$M_{n}={\frac {\sum M_{i}N_{i}}{\sum N_{i}}},\quad M_{w}={\frac {\sum M_{i}^{2}N_{i}}{\sum M_{i}N_{i}}},\quad M.W.D.orPDi={\frac {M_{w}}{M_{n}}}$

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