The influence of adding functionality to dispersant and particle core compositions in non-aqueous dispersion polymerization

Abstract

Nano-sized polyacrylate colloids (< 200 nm) at high solids level (~ 60 wt%) are prepared via non-aqueous dispersion (NAD) semibatch polymerization using n-butyl methacrylate (BMA)based macromer dispersants of varying chain lengths and levels of functionality provided by incorporation of 2-hydroxyethyl methacrylate (HEMA) comonomer. The effect of building the complexity of the core polymer recipe from methyl acrylate homopolymer to a five-monomer composition is systematically studied. While average particle size increased with the introduction of functional comonomers, the resulting NAD systems remained stable for all core compositions using both BMA macromers and a copolymer macromer containing 5 mol% HEMA. However, introduction of the HEMA functionality to the dispersant at levels of > 5 mol% led to destabilization of the dispersion. The polarity differences between the core compositions and dispersant polymers and the mixed continuous medium, as represented by Hansen solubility parameters, are qualitatively used to interpret the nucleation of particles and the effectiveness of the dispersants.

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

“…A second type of functionality added to the dispersant chains is hydroxyl groups, needed to crosslink the nonincorporated dispersant chains during the application of the coating. It was found that adding up to 10 mol% of 2‐hydroxyethyl methacrylate (HEMA) as a comonomer to the P(BMA) macromonomer destabilized the final dispersion, although particle size was not greatly affected . In this study, we show that this result can be attributed to the increased polarity that results from adding HEMA to the dispersant, upsetting the thermodynamic balance between solution, dispersant, and particle.…”

“…The semibatch system is very different, as it involves a continuous phase that contains low monomer concentrations (starved‐feed operation) in a nonpolar solvent mixture. Yang and Hutchinson first proposed the use of HSPs to interpret results for NADs produced with the same experimental procedure as used in this study. It was found that small changes in particle polarity introduced by varying copolymer composition (either by addition of less‐polar styrene or more‐polar functional monomers) did not correlate with the observed changes in particle size in the presence of P(BMA) macromonomer as the dispersant.…”

“…M n values were maintained between 6000 and 7000 Da, with M w between 10 000 and 12 000 Da. Terminal double‐bond functionality was verified by NMR, as previously documented …”

“…The fraction of dispersant chemically anchored and physically adsorbed to the NAD particles was quantified from the difference between the known mass of dispersant added to the reaction and the mass of the free dispersant that remained in the continuous phase in the final dispersion. The procedure to quantify the latter value was adopted from previous work, adding 2 g of the NAD mixture into a vial to which was added 3.4 g heptane. The mixture was centrifuged at 6000 rpm for 10 min to separate the phase into a clear upper solution and a dense particle rich phase.…”

Modeling the Synthesis of Butyl Methacrylate Macromonomer by Sequential ATRP‐CCTP

“…In catalytic chain transfer polymerization (CCTP), a small amount of cobalt chain transfer (CCT) agent is added to radical polymerization to produce polymers containing unsaturated end groups with the so‐called macromonomer used for further post‐reaction . As the chains are produced continuously during the reaction by decomposition of a thermal initiator, the macromonomers synthesized by CCTP chemistry have a dispersity (Ð) close to 2 …”