Evaluation of the Tensile, Water Diffusion, and Water Hydrolysis Properties of Graphene Oxide/Polyamide-11 Composites and Their Synthesis

Graphene oxide (GO) is a nanoparticle derived from pristine graphene and shows increasing promise for applications as a reinforcement material for polymer composites. Pristine graphene forms the basal plane of graphite and is one of the strongest materials known to man and exhibits excellent gas barrier properties. Polyamide-11 (PA-11) is a specialty polymer of the Nylon class and is commonly used in offshore oil pipes due to its excellent mechanical properties and superior resistance to hydrolysis compared to other polyamides. However, degradation by hydrolysis of PA-11 in the aqueous environments of these pipes still poses significant safety and budget concerns. This paper explores the advantages in tensile, water diffusion, and water hydrolysis properties of GO/PA-11 composites. Two separate batches of composites were made by polymerizing GO/11-Aminoundecanoic Acid dispersions in-situ. The batch with a faster heating rate during polymerization showed superior tensile properties at low GO concentrations and a lower diffusion coefficient at higher GO concentrations. The batch with the slower heating rate showed an improved equilibrium molecular weight at low GO concentrations but the tensile properties showed no improvement compared to the neat system

Development of Methodologies Toward Phosgene-free Syntheses of Morphologically Tunable Polyurethanes and Investigation of a Solvatochromic carbonate

Polyurethanes (PUs) comprise an important class of polymers that are used for a multitude of industrial applications. However, the toxicity of certain metal-containing catalysts and diisocyanate reagents, as well as the non-renewability of many common multi-functional hydroxyl monomers, have led to the investigation of more environmentally-friendly and sustainable alternatives. Additionally, the use of non-biodegradable and non-recyclable polymers has led to astonishing accumulation of waste in the world’s oceans, prompting an increasing outcry from the public. The work presented in this dissertation focuses on replacing non-renewable starting materials such as metal-containing catalysts and multi-functional hydroxyl monomers with natural products or organically-derived reagents. A synthetic methodology was developed that allows for the incorporation of carbohydrate-based natural products into functional PUs under mild conditions, employing relatively benign reagents, and resulting in nearly quantitative macrocycle formation as extensively verified using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-TOF MS). This work involved screening of conditions for PU synthesis using hexamethylene-1,6-di(p-nitrophenyl)carbamate, a diazabicyclo[5.4.0]undec-7-ene (DBU) organobase, and the bio-sourced diol, methyl 4,6-O-benzylidene-α-(D)-glucopyranoside. Unlike many previous PU syntheses involving dicarbamates, this system achieved polymerization under relatively mild conditions, e.g., attaining a molar mass of up to ca. 9 kDa in 8 h at 40 °C at ambient pressure. This chemistry has potential applicability to a wide range of di(p-nitrophenyl)carbamates and diols that should create broad interest in the PU community for sustainability and hazard mitigation. Additionally, this dissertation examines the unusual selectivity for cyclization that the glucopyranoside dihydroxyl monomer imparts on the system using Raman spectroscopy and molecular modelling. A structural difference was indicated by Raman spectroscopy but its identity remains inconclusive by molecular modelling. Third, multiple synthetic schemes were attempted towards an antibiofouling polyurethane using a capsaicinoid molecule as a sensory deterrent for marine and microbial antibiofouling. The conjugation via the carbonate linkage appears most promising but all synthetic routes were complicated by several factors and thus remain incomplete. Lastly, a solvatochromic carbonate was realized, and molecular modeling indicates that it undergoes electron transfer in polar, heteroatom-containing solvents giving rise to a solvent-induced “redoxochromic” effect that has potential applicability in radical-mediated reactions and polymerizations