Polymer hydrogel films change their properties in response to environmental change. This remarkable phenomenon results in many potential applications of polymer hydrogel films. In this thesis colored thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel film was prepared by firstly synthesizing polymer latex and secondarily crosslinking the nanoparticles and casting the polymers onto glass. The shape-memory effect has been observed when changing the environmental temperature. The temperature-dependent of turbidity of polymer hydrogel film was measured by HP UVVisible spectrophotometer. This intelligent hydrogel might be used in chemomechanical systems and separation devices as well as sensors. Polymer adsorption plays an important role in many products and processes. In this thesis, surfactant-free three-dimensional polystyrene (PS) nanoparticle network has been prepared. The infrared spectroscopy and solubility experiment are performed to prove the crosslinking mechanism, also the BET method was used to measure the adsorption and desorption of polystyrene network. The BET constant (C) is calculated (C=6.32). The chemically bonded polymer nanoparticle network might have potential applications as catalyst or used for chromatographic columns.

The thermally responsive hydroxypropyl cellulose (HPC) hydrogel nanoparticles have been synthesized and characterized. The HPC particles were obtained by chemically crosslinking collapsed HPC polymer chains in water-surfactant (dodecyltrimethylammonium bromide) dispersion above the lower critical solution temperature (LCST) of the HPC. The size distributions of microgel particles, measured by dynamic light scattering, have been correlated with synthesis conditions including surfactant concentration, polymer concentration, and reaction temperature. The swelling and phase transition properties of resultant HPC microgels have been analyzed using both static and dynamic light scattering techniques. By first making gel nanoparticles and then covalently bonding them together, we have engineered a new class of gels with two levels of structural hierarchy: the primary network is crosslinked polymer chains in each individual particle, while the secondary network is a system of crosslinked nanoparticles. The covalent bonding contributes to the structural stability of the nanostructured gels, while self-assembly provides them with crystal structures that diffract light, resulting in colors. By using N-isopropylacrylamide copolymer hydrogel nanoparticles, we have synthesized nanoparticle networks that display a striking iridescence like precious opal but are soft and flexible like gelatin. This is in contrast to previous colored hydrogels, which were created either by adding dyes or fluorescent, or by organic solvent or by embedding a colloidal crystal array of polymer solid spheres . Creating such periodic 3D structures in materials allows us to obtain useful functionality not only from the constituent building blocks but also from the long-range ordering that characterizes these structures. Hydroxypropyl cellulose (HPC) and poly (acrylic acid ) (PAA) complexes were studied using turbidity measurement and laser light scattering. The phase transition temperature of the complexes is found to depend on pH and molecular weights of PAA and HPC. The driving force for this phenomenon is due to the hydrogen bonding and hydrophobic interaction of the macromolecules. Based on the principle of the PAA/HPC complexes, the PAA nanoparticles were synthesized in 0.1wt % HPC aqueous solution at room temperature.

This study combined concentration-discharge analyses (filtration at 0.45 m), cascade filtrations (at 1.2, 0.4, and 0.025 m) and asymmetrical flow field flow fractionation (AF4) to probe the influence of colloidal carriers (dissolved organic matter and inorganic nanoparticles) on observed concentration-discharge relationships for trace metals in a 155 ha forested catchment of the Santa Catalina Mountains Critical Zone Observatory (SCM CZO), Arizona. Many major elements (Na, Mg, Si, K, Ca) show no colloidal influence, and concentration-discharge relationships for these species are explained by previous work. However, the majority of trace metals (Al, Ti, V, Mn, Fe, Cu, Y, REE, U) show at least some influence of colloids on chemistry when filtered at the standard 0.45 m cutoff. Concentration-discharge slopes of trace metals with modest colloidal influence are shallow (approximate to 0.3) similar to that measured for dissolved organic carbon (DOC, 0.24), whereas elements with greater colloidal influence have steeper concentration-discharge slopes approaching that of Al (0.76), the element with the largest colloidal influence in this study (on average 68%). These findings are further supported by AF4 measurements that show distinct and resolvable pools of low hydrodynamic diameter DOC-sized material coexistent with larger diameter inorganic colloids, and the ratio of these carriers changes systematically with discharge because the DOC pool has a concentration-discharge relationship with shallower slope than the inorganic colloidal pool. Together these data sets illustrate that positive concentration-discharge slopes of trace metals in stream waters may be explained as the relative partitioning of trace metals between DOC and inorganic colloids, with contributions of the latter likely increasing as a result of increased prevalence of macropore flow.

Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) and PNIPAM-co-acrylic acid (AA) have been synthesized and used as building blocks for creating three-dimensional networks. The close-packed PNIPAM-co-allylamine and PNIPAM-co-AA nanoparticles were stabilized by covalently bonding neighboring particles at room temperature and at neutral pH; factors which make these networks amicable for drug loading and release. Controlled release studies have been performed on the networks using dextran markers of various molecular weights as model macromolecular drugs. Drug release was quantified under various physical conditions including a range of temperature and molecular weight. These nanoparticle networks have several advantages over the conventional bulk gels for controlling the release of biomolecules with large molecular weights. Monodispersed nanoparticles of poly-N-isopropylacrylamide-co-allylamine (PNIPAM-co-allylamine) can self-assemble into crystals with a lattice spacing on the order of the wavelength of visible light. By initiating the crystallization process near the colloidal crystal melting temperature, while subsequently bonding the PNIPAM-co-allylamine particles below the glass transition temperature, a nanostructured hydrogel has been created. The crystalline hydrogels exhibit iridescent patterns that are tunable by the change of temperature, pH value or even protein concentration. This kind of soft and wet hydrogel with periodic structures may lead to new sensors, devices, and displays operating in aqueous solutions, where most biological and biomedical systems reside. The volume-transition equilibrium and the interaction potential between neutral PINPAM particles dispersed in pure water were investigated by using static and dynamic light-scattering experiments. From the temperature-dependent size and energy parameters, the Sutherland-like potential provides a reasonable representation of the inter-particle potential for PNIPAM particles in swollen and in collapsed phases. An aqueous dispersion of PNIPAM particles can freeze at both high and low temperatures. At low temperatures, the freezing occurs at a large particle volume fraction, similar to that in a hard-sphere system; while at high temperature, the freezing occurs at low particle concentrations, driven by the strong van der Waals attraction due to the collapsed microgel particles. The calculated phase diagram has been confirmed semi-quantitatively by experiments.

Addition of nanopacticles in a base solvent leads to suspensions with enhanced physiochemical properties, compared to base solvent. This new type of suspensions is called nanofluids, with applications ranging from biomedicine to automotives. As a consequence extensive research is being conducted in the field, in particular, on the evaporation of these fluids as it leads to well-defined and highly ordered coffee-rings. However, the exact physics governing this phenomenon remain elusive. The goal of this experimental investigation is to elucidate how various parameters affect the progression of nanofluid coffee-stain formation. Examination of the coffee-ring structuring, produced by the free evaporation of sessile droplets containing nanoparticles, revealed an unexpected, disordered region at the exterior edge of the ring. A self-assembly mechanism with two components, particle velocity and wedge constraints, was proposed to describe the deposition of particles at contact lines of evaporating drops. Environmental pressure was used as a method to control particle crystallinity in the coffee-rings. Essentially, evaporation rate and pressure were found to be inversely proportional. Macroscopically, lowering pressure led to a transition from “stick-slip” to constant pinning. Nanoscopically, lowering pressure promoted crystallinity. Findings supported the proposed, in this thesis, particle self-assembly mechanism. Particle aspect ratio and flexibility were subsequently examined. Pinning strength was found to be a function of particle aspect ratio and rigidity, leading to constant pinning. The proposed, in this thesis, particle self-assembly mechanism was found to be applicable to a variety of aspect ratios and flexibilities. Lastly, particulate crystals grew following different pathways depending on particle flexibility.

Peng Shufu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

by Lam King Shun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [40-41]). / by Lam King Shun. / Acknowledgement --- p.i / Biographical Sketch --- p.ii / Abstract --- p.iii / Table of Contents --- p.iv / Chapter Chapter One --- Introduction --- p.1 / Chapter Chapter Two --- The Sol-Gel Derived Silica / Chapter 2.1 --- Introduction to the so-gel science --- p.3 / Chapter 2.2 --- The procedure of the silica formation --- p.5 / Chapter 2.3 --- During the sol-gel process --- p.7 / Chapter 2.4 --- The silica characterization --- p.12 / Chapter 2.4.1 --- Physical properties --- p.12 / Chapter 2.4.2 --- Optical properties --- p.13 / Chapter 2.5 --- Sample preparation --- p.15 / Chapter Chapter Three --- Laser Experiments / Chapter 3.1 --- Basic principle of dye laser --- p.16 / Chapter 3.2 --- Experimental procedure --- p.20 / Chapter 3.3 --- Data and discussion --- p.23 / Chapter 3.3.1 --- Spectral and temporal behaviour --- p.2 3 / Chapter 3.3.2 --- The performance of the sol-gel silica laser --- p.37 / Chapter Chapter Four --- Conclusions and Suggestions for Further Work --- p.39 / References

by Shui-Qin Zhou. / Publication date from spine. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 152-157). / Acknowledgments --- p.i / Abstract --- p.ii / Contents --- p.vi / Abbreviation --- p.viii / List of Figures --- p.xi / List of Tables --- p.xvi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Project's Significance --- p.1 / Chapter 1.2. --- Research background.....................................: --- p.1 / Chapter 1.2.1. --- Linear PNIPAM chains in aqueous solution --- p.2 / Chapter 1.2.1.1. --- Origins of the LCST --- p.2 / Chapter 1.2.1.2. --- Experimental studies --- p.4 / Chapter 1.2.2. --- PNIPAM gels --- p.9 / Chapter 1.2.2.1. --- Origins of the volume phase transition --- p.10 / Chapter 1.2.2.2. --- Experimental studies --- p.11 / Chapter 1.2.3. --- Surfactant effects --- p.13 / Chapter 1.3. --- The objective of the project --- p.15 / Chapter 1.4. --- Experimental difficulties --- p.17 / Chapter 2. --- Basic Theory --- p.20 / Chapter 2.1. --- Laser light scattering (LLS) --- p.20 / Chapter 2.2. --- Polymer chains in solution --- p.23 / Chapter 2.3. --- Swollen polymer gels --- p.27 / Chapter 3. --- Results and Discussion --- p.32 / Chapter 3.1. --- Linear PNIPAM chains --- p.32 / Chapter 3.1.1. --- D = kDM-αD for PNIPAM in THF and water --- p.32 / Chapter 3.1.2. --- Coil-to-globule transition of single PNIPAM chains in water --- p.46 / Chapter 3.1.3. --- Additional chain-conformation broadening of the line-width distribution in dynamic LLS --- p.64 / Chapter 3.1.4. --- Internal motions of long linear PNIPAM chains --- p.72 / Chapter 3.1.5. --- Structural model of spherical water/AOT/n-hexane microemulsion --- p.80 / Chapter 3.2. --- Spherical PNIPAM microgels --- p.94 / Chapter 3.2.1. --- Volume phase transition of PNIPAM microgels --- p.94 / Chapter 3.2.2. --- Internal motions of short PNIPAM subchains inside the gel networks --- p.107 / Chapter 3.2.3. --- Surfactant effects on the volume phase transition --- p.113 / Chapter 3.2.4. --- Swelling and drying kinetics of a very thin PNIPAM gel film --- p.129 / Chapter 4. --- Conclusions --- p.141 / Chapter 5. --- Experimental --- p.145 / Chapter 5.1 --- Sample preparation --- p.145 / Chapter 5.2 --- Physical measurement --- p.149 / Chapter 6. --- References --- p.152

Colloid detachment and mobilization can be of significant interest to those studying colloid behavior in the environment. The transport of pathogens such as viruses, bacteria, and protozoa can cause health problems in animals and humans. The transport of organics, radionuclides, and other hydrophobic contaminants can be enhanced by adsorption to mobilized colloid surfaces. Research has been done by others quantifying the detachment of colloids from smooth porous media. Real surfaces in the environment and engineered systems are rough. Glass beads were chemically roughened by procedures similar to those from Shellenberger and Logan (2002) and It et al. (2001) using chromic acid and a citric acid/ammonium fluoride solution. Surface asperities were measured using Atomic Force Microscopy (AFM), and the roughness was defined by three parameters: Root Mean Square (RMS) roughness, peak to valley height (P/V height), and peak to peak distance (λ). Detachment from the chemically etched porous media was measured in column tests. The controlling roughness parameter between the two batches of beads was found to be λ. A theoretical model to predict the effect of roughness on detachment was developed. Using a moment balance around the downstream point of contact, the parameters incorporated into the model were particle diameter, P/V height, and λ. The model predicted the shear required for colloid detachment in column tests. Surface roughness was found to significantly inhibit colloid detachment.

by Gao Yibing. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.