Online monitoring of emulsion polymerization

1. Surfactant-free emulsion polymerization

2. Emulsion polymerization with SDS

An original idea was put in practice: use ACOMP to simultaneously measure properties of the dispersed components (emulsions) and their contents (polymer and monomer). dilute one withdrawn reactor stream with aqueous solution to preserve the dispersed (emulsion) phase and measure its characteristics online and the other withdrawn stream with THF to solubilize polymer and monomer.

A number of features are captured by this process:

• multi-phase conversion,

• multimodal mass production,

• the correlation between monomer droplet disappearance and monomer conversion,

• the reaction time and large polymer masses produced.

RESULTS

Surfactant-free emulsion polymerization - from dilute regime to high solid contents (14%): Soap-free emulsion polymerization of butyl acrylate (BA)

a) Polymer side:

Left: Raw viscosity, light scattering (90) and UV (215nm) data. [BA]=1.11M; [I]=5.586mM. Right: The evolution of Mw with conversion. In the inset to figure, radius of gyration and monomer conversion, f are shown vs. time

b) Particle side:

Large monomer-containing droplets (microns) gradually cede their contents to a growing population of polymer- containing micelles of much smaller diameter (fractions of a micron

Left: The evolution of the specific surface area A (upper) for two BA polymerization reactions. The volume weighted mean diameter, D[4,3] for two modes in the particle size distribution (lower) for the 14% BA.  Right: Cryo-TEM image for BA surfactant–free polymerization reaction ([BA]=0.268M)

Emulsion polymerization with surfactant added (SDS) - from dilute regime to high solid contents (35%):

Soap-free emulsion polymerization of methy methacrylate (MMA) - polymer side

Kinetic and molar mass analysis show that free radical polymerization of MMA and BA in emulsion approximately resemble free radical polymerization in homogeneous phase, with some notable differences in details.

Left: The evolution of the fractional monomer conversion f, and the polymer mass, Mw during the polymerization reaction (0.45M). Discrete points are SEC results from manually withdrawn reaction aliquots.  Right: Weight average reduced viscosity, hr,w and Mw vs. monomer conversion.

 

Emulsion polymerization with surfactant added (SDS) - chain transfer effect:

Emulsion polymerization of MMA and BA, respectively (~15%)

Left: MMA polymerization reactions - Mw vs. conversion for reactions with and without chain transfer agent. In the inset , reduced viscosity hr,w as functions of conversion for the same reactions. Right: BA polymerization reactions - hr,w as functions of time for reactions with different amount of transfer agent.

Emulsion Copolymerization - computing concentration of each comonomer during the reaction allows composition drift and distribution to be determined