This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonNovel PVA hydrogel nanocomposites, symmetric three-dimension (3D) printed poly(vinyl) alcohol (PVA) hydrogels and asymmetric 3D printed PVA/poly(lactic) acid (PLA)-graphene (G) nanocomposites have been prepared and characterised in detail using Fourier transform IR (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy. The aim was to produce new nanomaterials in part by fused deposition modelling (FDM) and to evaluate them as:
(i) Personal sensors for sensing of (a) pollutants (e.g. NO/NO2, SO2, VOCs/PAHs and particulates) in the atmosphere that might adversely affect human health. With improved response time, sensitivity, selectivity, recovery time and stability and an improved low cost spatial and temporal resolution (b) oil that pollutes water and soil. (ii) Localised sensors for CO2 that could be fine-tuned by water and monoethanolamine (MEA) incorporation to provide feedback on process efficiency affecting global warming and breathing efficiency.
(iii) Coatings for improved adsorption-cooling of Al-clad building surfaces, lowering power consumption for air conditioning. (iv) Coatings for improved electrochromic displays. Practical applications of such materials are remote patient monitoring through real-time breath analysis, synthetic sweating surfaces for residential and industrial buildings, wearable sensors connected to the IoT and solar reactive glass. 0.045mmol of CO2 produced a conductance change in a hydrogel in 4s for a 3D printed PVA hydrogel with on-board H2O; 1-1.5s slower than a quadrupole mass spectrometer (RGA). It could be that hydrogel sensors form an inexpensive method for breathing analysis and remote patient monitoring; tailoring for SO2 or NO2 detection remains to be seen. 3D printed PLA/G is unlikely to compete with vapour-deposited metal electrodes for detection of oil-in-water. Infra-red thermography (IRT) showed that novel hydrogel coatings exhibited a larger cooling effect (-13K when H2O swollen, -10K when MEA swollen and -11.8K when H2O swollen asymmetric sample) than previously (SPIE) for over 4000s on a construction-type Al substrate and even a 2.6K cooling with PVA hydrogel/Al substrate over a 25h period. “Real-world” IRT was also conducted with PVA-MxOy nanocomposite hydrogels and revealed that the species of MxOy affects the thermal signature of the gel differently when viewed against a background. More importantly, reversible electrochromic responses in novel WO3/PVA hydrogels (with and without additional salt) seen in <1s, open the possibility of colour switchable cool coatings for buildings. Addition of various salts enabled initial tuning of colour to be achieved
