CBET Award Achievements
Notable Accomplishments from CBET Awards

Liquid-Core Capsules via Interfacial Free Radical
Alternating Copolymerization

Carlos C. Co  -  University of Cincinnati Main Campus

Sub-micron polymer capsules having liquid-cores have wide-ranging applications in the high efficiency encapsulation and controlled delivery of drugs, enzymes, and DNA molecules for gene therapy.  Current approaches for forming liquid-core capsules rely on forming polymers around a sacrificial solid core that is subsequently leached out, and replaced with the material to be encapsulated.  Although innovative chemistries have been developed to facilitate the leaching process, this two-step encapsulation approach inevitably forces a compromise between the release characteristics of the capsules and ease with which they can be loaded.

The PIs have devised a new polymerization approach, similar to emulsion polymerization processes used to make latex paint, that allow direct formation of liquid-core capsules without the need for sacrificial solid cores.  The approach used for making these liquid core capsules is analogous to the step-growth of nylon polymer at oil/water interfaces, except that the underlying chain-growth mechanism allows superior control of the onset of reaction and capsule properties such as size and release characteristics.  The reaction scheme as shown in Figures 1 & 2, makes use of vinyl ether molecules, which partition in the aqueous phase, dimaleate molecules, which partition in the oil phase, and a special 'soap' molecule that resides at the interface and initiates the polymerization upon heating or exposure to UV light. Upon initiation, vinyl ethers and dimaleates do not react with themselves.  Instead they react only in an alternating fashion thereby 'zippering' the interface with a polymer shell.

Overall, this approach is flexible and allows functionalization of the capsules with chemical groups that enable them to respond 'smartly' to changes in their environment, e.g., faster release in the acidic conditions of the stomach or targeted lock-key binding to cancer cells.  It further promises broad impact from a commercial standpoint due to its low-cost and the ease with which it can be implemented on a large scale.

The work is notable because it is a novel polymerization methodology that may yield inexpensive new materials that have a wide range of potential uses in a number of fields, including for example health care.

The synthesis of these liquid-core capsules involves knowledge of chemistry, polymer science and chemical engineering.  The process, which involves a chemical transformation at an interface, involves pure chemical kinetics, mass transfer (chemical engineering) and an understanding of polymerization initiation, growth and termination to produce a precisely designed polymeric material.

Carlos C. Co Figure 1

Figure 1:
Schematic of the interfacial free radical alternating
copolymerization process that the principal investigator
has successfully used to make new materials for
capsules for use in drug delivery.

Credit:  Carlos C. Co, University of Cincinnati

Carlos C. Co Figure 2

Figure 2: The chemistry of the process.

Credit:  Carlos C. Co, University of Cincinnati

Program Officer:   Maria Burka
NSF Award Number:   0457453
Award Title:   Liquid-Core Capsules via Interfacial Free Radical Alternating Copolymerization
PI Name:   Carlos C. Co
Institution Name:   University of Cincinnati Main Campus
Program Element:   1403
CBET Nugget:   FY 2006

Top of Page

This Nugget was Updated on 24 September 2008.