Polyisobutylene random scission

At each stage of degradation, the M /M for the polyisobutylene remained constant at 2.0 which is a classical example of random scission. (See Fig. 2.8, which is Fig. 5 of Scott [14a].) Figure 2.9, which is Fig. 2 of the same reference, illustrates the influence of the original molecular weight distribution on the random degradation process. 

Fig. 2.8 Ultrasonic irradiation of a concentrated polyisobutylene solution [39a] initial = 2. Relative changes of and are compared with the theoretical behavior for random scission of a most probable MWD [14a].

The polymer polyisobutylene (—C(CH3)2—C—) presents a case where G(cl) = 0. This polymer is entirely amorphous (except on stretching, when it crystallizes) and the linear increase of /My (D) with dose has been established over a wide range of initial molecular weights. From these results it has been concluded that the scissions take place at random positions. ... 

---