Dr. Tony Wallner
NMR of UV Stabilized PMMA
Poly(methyl methacrylate) (PMMA) is by far the most important of the methacrylic ester polymers industrially available. Compared to the other n-alkyl methacrylates, PMMA has a higher softening point and higher tensile strength which makes it very useful and a common plastics material in rigid applications. Some of the uses of PMMA include aircraft glazing, display signs, light fittings, dentures, and orthopedic appliances. As a copolymer, PMMA has been added to increase dyeability, solubility and processability of copolymers and to create transdermal drug delivery systems.
Our interest in PMMA is the study of surface coatings. One major use of PMMA as a surface coating agent is in the automobile industry. PMMA has also been used in solar applications and space environments. PMMA is relatively stable over time but cracking, color changes and loss of physical properties occur over time. In extreme conditions expected in solar and space applications, this degradation is quicker and more severe.
Our research interest is in the use of stabilizers to improve the performance of PMMA in these more extreme solar and space applications. Many stabilizing agents are generally dry blended into polymer surfaces industrially improving their physical characteristics. This physical mixing technique would cause evaporation of the stabilizer in the high vacuum environment of space applications without providing significant protection. We are interested in incorporating the stabilizers into the backbone of PMMA rather than being distributed upon its surface. This process should increase the lifetime of the polymer and expand its useful to solar and space applications.
We have used a variety of photostabilizers to protect the PMMA from degradation due to exposure to UV radiation. We have used NMR to determine the quantity of stabilizer incorporated into the polymer and to differentiate chemical incorporation from physical mixing of the stabilizer. The chemical shifts of the PMMA and stabilizer are vastly different so quantification based on peak area can be accomplished. We continue to work on unambiguous determination of chemical bonding of the stabilizer into the PMMA backbone.