3 research outputs found
Versatile Platform for Controlling Properties of Plant Oil-Based Latex Polymer Networks
A series
of latexes from acrylic monomers (made from olive, soybean,
linseed, and hydrogenated soybean oils), significantly different in
terms of fatty acid unsaturation, were synthesized using miniemulsion
copolymerization with styrene. The number-average molecular weight
and the glass transition temperature of the resulting copolymers with
high levels of biobased content (up to approximately 60 wt %) depend
essentially on the amount of unsaturation (the number of double bonds
in triglyceride fatty acid fragments of plant oil-based monomers)
in the reaction feed. When plant oil-based latex films are oxidatively
cured, the linear dependence of the cross-link density on reaction
feed unsaturation is observed. Dynamic mechanical and pendulum hardness
measurements indicate that the properties of the resulting plant oil-based
polymer network are mainly determined by cross-link density. On the
basis of the linear dependence of the cross-link density on monomer
feed unsaturation, it can be concluded that the latex network formation
and thermomechanical properties can be adjusted by simply combining
various plant oil-based monomers at certain ratios (“given”
unsaturations) in the reaction feed. Assuming a broad variety of plant/vegetable
oils available for new monomers synthesis, this can be considered
as a promising platform for controlling properties of plant oil-based
latex polymer networks
Plasticization of Polystyrene with Copolymers Based on High Oleic Soybean Acrylic Monomer
In
this work, high oleic soybean oil was used to synthesize
an
acrylic monomer (HOSBM), which was copolymerized with myrcene and
styrene at a 90:10 wt/wt feed ratio to obtain copolymers containing
myrcene (HOSBM-M) and styrene (HOSBM-S). These copolymers were employed
here as macromolecular plasticizers to modify the brittle nature of
polystyrene (PS). Specifically, the soy-based copolymers were added
to commodity polystyrene at 5–20 wt %, and the copolymer effect
on the polymer blends’ structure and behavior was studied.
We report on the blends’ morphology and thermal/mechanical
properties and employ thermodynamic and mechanical models to understand
the interactions between the PS matrix and the HOSBM copolymer dispersed
phase. Microscopy indicated that the mixed materials have a phase-separated
structure composed of the PS-based matrix and the copolymer-based
dispersed phase. Our thermodynamic estimations and measurement of
the thermal transitions showed that the blends are partially miscible,
where a fraction of PS chains migrated into the dispersed phase and
the copolymer was partially situated in the PS matrix. Therefore,
HOSBM-M and HOSBM-S plasticize the PS matrix, decreasing the glass
transition temperature and moduli. The mechanical properties of the
blends depicted a trade-off between the flexural modulus, strength,
and toughness. Although the PS/HOSBM-S blends showed decreased storage/flexural
moduli and strength compared to neat PS, the decline was significantly
lower than that demonstrated by the HOSBM-M blends. Moreover, adding
the HOSBM-S copolymer to PS at 10–15 wt % loading enhances
the material’s extensibility compared to pure PS. The trend
in the toughness values shows that the optimal HOSBM-S loading is
10 wt % to obtain materials with the best middle ground between flexural
modulus, strength, extensibility, and toughness
Free Radical Polymerization Behavior of the Vinyl Monomers from Plant Oil Triglycerides
A one-step
method of plant oil direct transesterification was used
to synthesize new vinyl monomers from sunflower (SFM), linseed (LSM),
soybean (SBM), and olive (OVM) oils. The degree of unsaturation in
plant oil fatty acids was used as a criterion to compare the free
radical polymerization behavior of new monomers. The number-average
molecular weight of plant oil-based homopolymers synthesized in toluene
in the presence of AIBN at 75 °C varies at 11 000–25 000
and decreases as follows: poly(OVM) > poly(SFM) > poly(SBM)
> poly(LSM),
corresponding to increasing degree of unsaturation in the monomers.
Rate of polymerization depends noticeably on the degree of unsaturation
in monomers. Due to the allylic termination, chain propagation coexists
with effective chain transfer during polymerization. The obtained
values of <i>C</i><sub>M</sub> (ratio of chain transfer
and propagation rate constants) depends on monomer structure as follows: <i>C</i><sub>M</sub>(LSM) > <i>C</i><sub>M</sub>(SBM)
> <i>C</i><sub>M</sub>(SFM) > <i>C</i><sub>M</sub>(OVM). <sup>1</sup>H NMR spectroscopy shows that the fraction
of
the reacting allylic atoms does not vary significantly for the synthesized
monomers (7–12%) and is determined entirely by plant oil degree
of unsaturation. The glass transition temperature of homopolymers
[<i>T</i><sub>g</sub> = 4.2 °C for poly(SFM), <i>T</i><sub>g</sub> = −6 °C for poly(SBM)] from new
monomers indicates that varying biobased fragments in copolymers might
considerably change the intermolecular interactions of macromolecules
and their physicochemical properties