Over 50% of all plastics are produced via free radical methods, with half of these processes involving aqueous media. Most commercial aqueous polymerizations are emulsion or miniemulsion polymerizations, producing surfactant stabilized hydrophobic polymer particles in water. These latexes are extensively used for thin films, coatings, paints, etc.
All of these polymerizations are made with little or no control over the polymer structure. The advent of living radical polymerization (LRP) in the late 90s now allows for excellent control over polymer structure in radical polymerizations, and well-defined structures such as block copolymers can now be made. Recently, the PIs reported the first miniemulsion LRP in continuous reactors, paving a path for LRP to move closer to large-scale technical feasibility.
Water-soluble polymers (acrylic acid, acrylamides, etc.) can also be prepared in a controlled manner using LRP techniques. However, there are no reports of aqueous LRP in heterogeneous media (insoluble organic and aqueous phases). The PIs plan to develop the science and technology of LRP in inverse miniemulsions. Water-soluble monomers will be stabilized by surfactants in organic media and reversible fragmentation chain transfer (RAFT) methodologies will be used to polymerize the monomers in a controlled/living manner. Homopolymer of several important water-soluble monomers will be prepared.
The impact of reaction components (monomer, surfactant, initiator, RAFT agent etc.) and reaction conditions (pH, temperature, monomer droplet size, etc.) on the ability to produce welldefined polymer in oil latexes via LRP will be elucidated. Subsequently, block copolymers that include two water-soluble blocks or one water soluble and one water-insoluble block will be synthesized. The use of monomers that are responsive to external stimuli (pH or temperature) will be utilized to give diblock copolymers with triggerable solution behavior.
The new polymers (homopolymer, statistical copolymer and diblock copolymer oil-based latexes) could find applications as associative thickeners, as nuclei for nanoencapsulation, or as vesicles and micelles for drug delivery.
Broader Impacts.
This multidisciplinary project will broadly educate both graduate students and undergraduates students in several key technology areas including colloid and interface science, reaction engineering, polymer science and synthetic chemistry. The PIs will actively recruit underrepresented students to take part in this research. These efforts will include participation in the Dow Minority Mentoring Program and the SURE program, which focus on involvement of underrepresented minority students in research.
Finally, the results of this work will be broadly disseminated to both the Georgia Tech student body and the greater polymer reaction engineering community.
