Bulk properties of poly(macromonomer)s of increased backbone and branch lengths

We measured dynamic shear moduli of poly(macromonomer)s of an increased bac kbone chain length and those bearing branch chains of increased branch leng th up to the critical molecular weight for the intermolecular chain entangl ement, M-c, of a linear polystyrene as functions of frequency and temperatu re using a parallel-plate rheometer. The poly(macromonomer)s were prepared from omega -methacryloyloxyethyl polystyrene macromonomers (MA-PSt)s or ome ga -vinylbenzyl polystyrene macromonomers (VB-PSt)s. It was revealed that a great increase in the backbone length caused the poly(macromonomer)s to sh ow a weak rubbery plateau region in the master curves of the storage modulu s G', where the molecular weights of the branch chains were smaller than M- c. The plateau modulus was much lower than that observed for the linear pol ystyrenes. On the other hand, the poly(macromonomer)s with polystyrene bran ches are nearly equal to the M-c, and a very short backbone chain showed a clear rubbery plateau region. The glass transition temperature of poly(macr omonomer)s in the region without the chain entanglement decreased with decr easing branch length but remained almost constant over the wide range of th e backbone length.