| Abstract: | Poly(vinyl acetate) (PVAc) of M?w 750,000 M?w/Mn 3.85 and B?n (the number of long branches per molecule) 2.2 was subjected to chain scission by mechanical (high-speed stirring) as well as chemical (saponification and reacetylation) methods to investigate the effect of shear on the branching distribution. The extent of long branching was measured by gel permeation chromatography on-line with low-angle laser light scattering photometry. It was concluded that (i) the branches through the acetate group are long and are ruptured preferentially on shearing, (ii) the branches through the α- and β-carbons are not broken on shearing, (iii) the extent of long branching through the acetate group is about 67% of total branching, and (iv) the poly(vinyl alcohol) derived from branched PVAc contains a smaller but nevertheless significant amount of branching. |
