Molecular and Performance Properties of Poly(Amides & Imides) and the Use of Graphene Oxide Nano-Particles for Improvement

• Main Author: Hocker, John-andrew Samuel
• Format: Others
• Language: English
• Published: W&M ScholarWorks 2016
• Subjects: Physical Sciences and Mathematics
• Online Access: https://scholarworks.wm.edu/etd/1477068376; https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=1086&context=etd

Macroscopic properties of polymers, and in general all types of materials, are innately related to their molecular structure and intermolecular properties. This dissertation offers insight into how the molecular structure, chain properties, and inter-molecular chain interactions within PA11 can be used to explain and predict improved macro level performance properties; and how the addition of graphene oxide nanosheets enhances the performance properties of PA11 and polyimide(ODA-BTDA) through those same intermolecular interactions. Chapter 3 describes the unexpected result that weak small organic acids at low concentrations hydrolyze a polyamide at rates approximately twice that of a water HCl solution of the same pH at 100 ˚C and 120 ˚C under anaerobic conditions. Chapter 4 discusses how by varying the rate of Mm degradation with small organic acids the correlated effects of Mm and crystallinity upon the ultimate strain of PA11 were decoupled. The result demonstrates the need for both crystallinity and molecular weight knowledge to monitor and predict the ductile to brittle transition and when embrittlement occurs. Chapter 5 explores the elevated resistance to hydrolytic degradation and molecular properties that a graphene oxide (GO) loaded PA11 has compared with neat PA11 at 100 and 120 ˚C. The decreased rate of degradation and resulting 50 % increased equilibrium molecular weight of PA11 was attributed to the highly asymmetric planar GO nano-sheets that inhibited the molecular mobility of water and the polymer chain. The crystallinity of the polymer matrix was similarly affected by a reduction in chain mobility during annealing due to the GO nanoparticles’ chemistry and highly asymmetric nano-planar sheet structure. Chapter 6 extends the experimental work to effects on polyimides. GO and GO functionalized with 4-4’ oxydianiline (ODAGO) are incorporated at 0.01 to 0.10 wt% into a polyimide (PI) made from 3,3’-benzophenonetetracarboxylic dianhydride (BTDA) and 4-4’ oxydianiline (ODA). The performance properties of these two systems GOPI and ODAGO-PI at extremely low GO concentrations of 1 part per 10,000 are comparable to previous results citing concentrations 10 times higher and displayed significantly greater improvement than unfunctionalized GOPI films. The results suggest that the improved barrier properties are due a toruosity effect of the GO sheets and to a stabilizing effect of the flakes on the polymer matrix, where reduced mobility of the PI chain reduces diffusion through the polymer matrix. ATR-FTIR, WAXS, Raman and Tg results support this view.