Dynamic viscoelastic properties of poly(vinyl chloride)
(PVC)/bis(2-ethylhexyl) phthalate
(DOP) solutions and gels have been studied as a function of polymer
concentration and molecular weight.
All PVCs were linear polymers and had a similar distribution in
molecular weight. Increasing the polymer
concentration gradually from the liquid state to the solid state
allowed the rheological observation of the
sol−gel transition. The gel point c
g,
which depends on the polymer concentration, was accurately
determined by the frequency independence of loss tangent in the
vicinity of the sol−gel transition and
was found to be inversely proportional to the molecular weight as
expressed by c
g ∝
M
w
-1. The
scaling
exponent n obtained was constant (n = 0.75) and
independent of the molecular weight of PVC. The gel
strength S
g at the gel point decreased with
increasing PVC molecular weight. A constant gel
strength
(S
g/c
g = 1.27 ×
10-2 Pa s0.75
g-1 L) was obtained by normalizing the gel
strength S
g with c
g to
eliminate
the effects of M
w. These results suggest a
unique character and structure at the gel point of the
gelling
system.
We investigate the dispersion of polymer-grafted particles
suspended in a polymer matrix
by viscoelastic measurements and electron microscopy. We find
that, when the graft density is low, the
particle dispersion improves with an increase of the graft density,
while the particle dispersion becomes
worse when the graft density is too high; i.e., there is an optimum
graft density for dispersing the particles.
We explain the phenomena by showing that the grafted polymers
cause attraction for high graft density.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.