Laser light scattering has been used to study the solution
behavior in aqueous NaCl of
poly(acrylamide) (PAM), polymerized by using two different
polymerization processes: solution (S) and
microemulsion (M). Results show that poly(acrylamide) samples
polymerized from the microemulsion
polymerization process behave as branched flexible chains, but
poly(acrylamide) samples synthesized
from solution polymerization exhibit a fairly expanded flexible
coil−chain behavior. By combining the
static light scattering results with the characteristic linewidth
distribution, as determined by a Laplace
inversion of the intensity−intensity time correlation function, the
molecular weight distribution (MWD)
and the radius of gyration distribution (RGD) could be estimated.
The molecular weight dependence of
the z-average diffusion coefficient
(Dz
) was determined during this conversion, with
Dz
0 = (3.05 ×
10-4)
M
w
-0.585 cm2
s-1 and Dz
0 = (1.52
× 10-4) M
w
-0.518
cm2 s-1 for PAM(S) and PAM(M),
respectively, with the
weight average molecular weight M
w expressed in
g mol-1 and Dz
0 in
cm2 s-1. The superscript zero
denotes
the value at infinite dilution. The smaller αD value
of 0.52 for PAM(M) suggests that PAM(M) could
have a fairly compact, but still soluble, flexible coil−chain
structure, possibly arising as a result of
(apparent) branching. Two different models, polydisperse branched
chains and branched soft spheres,
were used to fit the particle scattering factor obtained from SLS
measurements. The results show that
the particle scattering factors of samples PAM(M) (but not of
PAM(S)) could be fitted satisfactorily by
either model. Concentration and angular dependence of the mean
characteristic linewidth, as well as
the molecular weight distribution derived by using the CONTIN analysis,
are presented. The origin of
the apparent branching in the microemulsion prepared
poly(acrylamide) is shown to be a noncovalent
aggregation in 1 M NaCl which is not manifest in formamide solutions of
the same polymer.
The polymerization and copolymerization with styrene of a series of unsymmetrically B‐p‐vinylphenyl‐N‐methyl and N‐phenyl borazines [R3(R2)2B3N3(R1)3; R1 = methyl, phenyl, R2 = methyl phenyl, R3 = p‐vinylphenyl] has been studied. The polymerization of these monomers yielded both tractable and crosslinked materials. The polymers obtained were characterized by 1H‐ and 13C‐NMR spectroscopy, elemental analysis, gel permeation chromatography, and thermogravimeteric analysis. The reactivity ratios for the copolymerization reaction were calculated by the Mortimer‐Tidwell method.
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