Choosing the Right Agitation for a Polymer Synthesis


Polymerization as a chemical transformation is often required when developing new cGMP polymers for drug delivery systems or medical devices.   More than any other process parameter, agitation can often have the greatest influence on the quality of the final product.  Here at PCI Synthesis, we have fine-tuned our approach and understand the specific factors that can influence outcomes when utilizing polymer chemistry as shown below.

In an emulsion or suspension polymerization, there are two heterogeneous phases: a continuous phase and a dispersed phase. Typically, the continuous phase transfers energy (heat) into the dispersed phase (where the reaction occurs). The polymerization reaction creates a particle that has the same size and shape as the parent droplet. The benefit of suspension or emulsion polymerizations is the ability to control the size and the shape of the resulting polymer particles. The size and shape of such particles are controlled through several factors: the amount of dispersed phase, the amount of surfactant and the agitation (shear rate) in the reactor.

After the desired polymer composition is selected, the size optimization process begins. The optimization begins with the choice of material to be used in the dispersion phase and the surfactant (the stabilizer which prevents or slows the separation of the two heterogeneous phases) to be employed. Optimization of these two parameters gives the developer the general particle size distribution for a series of reaction conditions.

The size control is fine-tuned by the choice of impeller blade and reactor geometry. The selection of impeller affects the amount of power delivered from the agitator to the solution. The amount of power delivered to the solution can have a significant effect on particle size and shape, even at the same rotation rate. When more power is delivered from the agitator, the shear is increased in the mixture, creating smaller droplets. When the power decreases, the droplet size increases.

When performing the optimization process, the impellers and reactor used should be proportional and consistent throughout scale-up. This is done in order to minimize the need for re-optimization as a process is transferred to different sized reactors.

Selecting the proper agitation system for a Polymer Synthesis is essential to ensure the right outcome is achieved. We continue to perfect our skills at PCI Synthesis and remain at the forefront of process innovation.  PCI is fortunate to have a kilo lab where we develop the important process parameters at a small scale (up to 100liters). Once the small scale development is completed, and the process parameters determined we can begin to transfer the process to larger scale manufacturing. The investment in time and effort at a small scale often pays off when we have a seamless transition to our manufacturing plant with minimal need for any additional development. Every project is different and requires a different approach each time. However, after developing dozens of polymerization reactions to support drug delivery and medical device technologies PCI understands the challenges involved and has the expertise to overcome them.