142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

44 B. Charleux, R. Faust
Scheme 8
3.1.2.4
Poly(styrene) and poly(a-methylstyrene) Branches
EPDM graft terpolymers with PS or poly(a-MeS) branches were prepared from
chlorinated commercial EPDM polymer (7.7% 5-ethylidene-2-norbornene as
diene, M n=50,000 g mol –1 ) in conjunction with Et 2AlCl, using the “grafting
from” technique [66]. Grafting could only be achieved in the presence of 10–20%
polar solvent, e.g., CH 3 Cl or CH 2 Cl 2 ; in pure heptane no graft copolymer could
be isolated. The grafting reaction was carried out at –30 °C, below this temperature
the EPDM polymer was not soluble in the mixed heptane/polar solvent
used. The grafting efficiencies were determined by selective solvent extraction
and found to be quite low, in the range of 10–20%. The tensile strength and ultimate
elongation were also determined and found to be quite low when the
amount of PS was 50 wt%, although at the expense of the elastomeric
properties (increased modulus and decreased ultimate elongation).
3.2
“Grafting Onto” Technique
In the “grafting onto” technique, the macromolecular branches are linked to the
main chain by specific reaction between their a or w end group and reactive
functional groups in the backbone.