Answer to Question #116020 in Organic Chemistry for Jaweria Rana

Question

What is the effect of low molecular weight and high molecular weight polymers on glass transition temperature? Give answer in detail.

Answer 1

The glass transition temperature $T_g$

 increases with molecular weight and asymptotically approaches a maximum value.

The glass transition temperature is the temperature range in which a polymer changes from a rigid “glassy” state to a more pliable “rubbery” state.

In polymer chemistry, the Flory–Fox equation relates the number-average molecular mass $M_n$

 of a polymer to its glass transition temperature $T_g$

$$T_g=T_{g,\infin}-\frac{K}{M_n}$$

where

• $T_{g,∞}$  is the maximum value of Tg
•  that can be achieved at a theoretical infinite molecular mass
• $K$  is an empirical parameter that is related to the free volume present in the polymer sample