Macromol. React. Eng. 9–10/2011

Design of Acrylic Dispersants for Nonaqueous Dispersion Polymerization: The Importance of Thermodynamics

“…The observed trends are the same as Cockburn et al reported for dispersion polymerization of MMA with increasing methanol fraction in a methanol/water mixture using poly( N ‐vinyl pyrrolidone) as the dispersant; in that work the result was attributed to the influence of solvency on monomer partitioning and an increased fraction of reaction occurring in the continuous phase due to the increased solubility of the growing polymer radicals. In our system, the important contribution of the reactive macromonomer dispersant complicates the interpretation of the results, as seen in the data for incorporated fraction of macromonomer ( W inc ).…”

“…The choice of the dispersant and solvent is very important for successfully controlling the polymer particle size and particle size distribution, as well as the viscosity of the dispersion. Numerous studies of dispersion processes examine the polymerization of nonpolar monomers conducted in water or in a mixture of water and short‐chain alcohols to produce a narrow particle size distribution (usually in the 1–10 µm range) at relatively low polymer content, <20 wt%. Fewer studies are concerned with the dispersion polymerization of more polar monomers in nonaqueous medium such as dodecane, hexane, and heptane, again usually at relatively low solids content in a batch process.…”

Investigating the Effectiveness of Reactive Dispersants in Non‐Aqueous Dispersion Polymerization

“…The solution is still clear at 20 min then turns translucent (40 min) to milky and opaque after 60 min. Nucleation of polymeric particles formed by dispersion polymerization in polar media occurs at the early stages of polymerization, and in batch systems the number of particles remains constant after nucleation, with newly generated small particles (or polymer chains) swept up by existing particles . Figure demonstrates that particle size remained relatively constant in the semibatch system after 120 min; unfortunately, it was difficult to obtain reliable data during the earlier nucleation stage of the reaction.…”

“…The polymeric dispersant is of critical importance, as it creates a reproducible polymerization system (unlike precipitation polymerization) by providing colloidal stability and helping to control average particle size and size distribution of the polymer produced . Solvent selection is also critical, with particle size and distribution greatly influenced by the composition …”

Sustainable Polymers from Biomass‐Derived α‐Methylene‐γ‐Butyrolactones

“…In 2011, Hutchinson and co-workers reported free-radical dispersion copolymerization of γ MMBL and MMA in a methanol/water mixture with 2-amino-2-methylbutyronitrile (Vazo 67) as an initiator and poly(vinyl pyrrolidone) as a stabilizer (71). The scanning electron microscopy micrographs of the copolymers derived from various fractions of γ MMBL showed that increasing the γ MMBL fraction from 25 to 50 to 75% leads to a decrease in the average particle size (ie, 1.6 μm for 25%, 1.3 μm for 50%, and 1 μm for 75%) of copolymer particles; the addition of γ MMBL to an MMA dispersion also decreases the rate of polymerization.…”