This award will support the research program of Prof. Rebecca Braslau at the University of California Santa Cruz in developing alternatives to phthalate plasticizers used in polyvinyl chloride (PVC) formulations. Professor Braslau and her students plan to develop simple and economic methods to covalently attach phthalate ester mimics to PVC, imparting plasticity to otherwise brittle PVC, while preventing migration of small molecules that can leach out and become metabolized into endocrine disrupting chemicals. Phthalates are currently utilized on the million-ton scale annually, yet are implicated in a number of health problems. A successful outcome of this project will provide a new strategy to replace phthalate plasticizers using methodology that is scalable to industrial applications, mitigating the buildup of endocrine disrupting phthalates in consumer products and in the environment. The attachment of the plasticizer to PVC by chemical bonds may also improve the lifetime of the consumer products using flexible PVC. In addition, this research will provide interdisciplinary training to graduate and undergraduate students in the fields of synthetic organic chemistry and materials science, educating them with the tools they will need to make significant contributions in the future. Both graduate and undergraduate students will be mentored by the PI to participate in professional activities, presenting their work at meetings, and taking an active part in the preparation of manuscripts stemming from their research findings.
This project entails a simple and economic method to covalently attach phthalate ester mimics to PVC, as a substitute for standard phthalate plasticizers. As phthalate esters are now used on the million-ton scale annually, a substitute is desirable that is chemically similar, but which shows no migratory ability from the PVC matrix. Small molecule phthalate plasticizers leach from PVC products, changing the properties of the PVC with time, and releasing potential endocrine disrupting chemicals into the environment. A simple Huisgen 1,3-dipolar cycloaddition of alkyl azides and dialkyl acetylenedicarboxylates at moderate temperatures in the absence of copper will be utilized to prepare 1,2,3-triazoles bearing ortho-esters containing a variety of alkoxy groups, to mimic phthalate esters plasticizers. These phthalate mimics will be covalently linked to PVC, either by modification of commercially prepared PVC, or by copolymerization of vinyl monomers bearing ortho-diester triazole phthalate mimics with vinyl chloride. In addition, copolymers of monomers bearing phthalate mimics will be prepared as polymeric plasticizers to be blended with PVC. The properties of the modified PVC materials will be extensively evaluated to assess plasticity as indicated by Tg depression, homogeneity as a function of time, migratory potential, polymer morphology, and elastomeric behavior. The polymeric plasticizers will be analyzed for miscibility with PVC. The stability of these materials upon subjecting them to hydrolysis and subsequent extraction will be tested according to ASTM standards. The thermal and photodecomposition of these polymer-bound triazoles will be studied.
