Homopolymer / Surfactant Or A Random Copolymer Of The Aqueous Phase From The Assembly And Micro-reactor Applications

Self-assembly of small-molecular surfactants into micelles with various morphologies and sizes has been one of the core subjects in colloid and interface science. However, in recent years complexation of surfactants and water-soluble homopolymers and their co-self-assembly has drawn much attention of the researchers in the field of colloid as well as polymer sciences. The interaction between homopolymers and surfactants changes the assembly performance of surfactants, and offers some new co-self-assembly architectures. In fact, these co-self-assemblies have been applied in life science, food and medicine, enhanced oil recovery, personal care products and nanomaterials, etc.So far. studies on co-self-assemblies of water-soluble nonionic homopolymers and surfactants mainly focus on the discovery and verification of the dual-critical concentrations of surfactants, the sites of the interaction, and their miscellaneous applications. Nevertheless, it lacks of quantitative understanding of the processes of the complexation and co-self-asembly of the homopolymers and surfactant molecules. Therefore, one of the concerns in this dissertation is, can we investigate the co-self-assembly of surfactants and homopolymers leading to some quantitative results and clearly observe the microstructures and macrostructures of the co-self-assemblies?It is reported that wet-chemical method is one of the main strategies to synthesize inorganic nanoparticles. Surfactants or water-soluble polymers have been used separately as capping agents in many wet-chemical methods while polymer/surfactant complexes have been tried as well. However, there still remains unclear in the functions of the polymer/surfactant complexes, which makes it difficult to control effectively the sizes and morphologies of the synthesized inorganic nanoparticles. Therefore, another concern in this dissertation is, could we use the homopolymer/surfactant complexes as microreactors to control the sizes and morphologies of the target metal micro/nano-particles based on our understanding of the microstructures and macrostructures of the polymer/surfactant co-self-assemblies?Amphiphilic random copolymers demonstrate more potential in applications due to their low-cost and facile preparation. But much less attention has been paid to their self-assembly since their inherent feature of the "short hydrophilic/hydrophobic segment" makes it difficult to form clear core-shell structures as in block/graft copolymer micelles or noncovalently connected micelles. Thus, the third concern in this dissertation is, wether the simple amphiphilic random copolymers could assemble in aqueous solution into new aggregate architectures and if the assemblies have potential to apply as microreactors for metal micro/nano-particles?Aiming at the aforementioned three concerns, this dissertation mainly focuses on the following:1. The quantitative study on co-self-assembly between PVP or PEG and SDSThe aqueous solutions of PVP (polyvinylpyrrolidone)/SDS (sodium dodecyl sulfate) complex and PEG (polyethyleneglycol)/SDS complex were investigated with several methods including surface tension, electric conductivity, ultra filtration, solubilization and fluorescence molecular probe. Thus the characteristic parameters of the water-soluble nonionic homopolymer/SDS aggregates were obtained such as the first critical concentration of surfactant (c1), the second critical concentration of surfactant (C2) and N, the bound-micellar aggregation number of SDS. Three other novel characteristic parameters were inferred from the above experimental results, which describe the quantity ratios and the thresholds of the co-self-assemblies. That is. (1) Specific saturated bound capacity [B], the maximum number of homopolymer chain units bounded by each aggregated surfactant. (2) Critical bound-micellar aggregation number [N], the minimum bound-micellar aggregation number of SDS at c1.(3) Threshold molecular weight of polymer [M], the minimum polymer molecular weight required by co-self-assembly. The experimental results showed that the above three characteristic parameters are constants for given molecular structures of both surfactants and polymers, and independent of the molecular weights and concentrations of the homopolymers. The architecture of PVP/SDS co-self-assembly is deduced basically from NMR proofs, the critical concentrations, the above three characteristic parameters and some other supporting information got from cloud point, Krafft point and rheology data. Thus, PVP/SDS co-self-assembly was proposed to have a pseudo-polyelectrolyte microstructure and a necklace-like macro structure.2. Application of PVP/SDS co-self-assemblies as microreactorsPVP/SDS co-self-assemblies could be used as microreactors for metal micro/nano-particles. It was found out that the pseudo-polyelectrolyte microstructure of the assemblies has the function to accumulate the precursor metal counterions, and its necklace-like macrostructure has the function to direct morphologies and sizes of the target metal micro/nano-particles. Various metal micro/nano-particles in quasi-3-D, 2-D,1-D as well as 0-D including gold, silver, nickel and copper were synthesized in PVP/SDS microreactor; and a synergistic morphology control strategy was developed depending on competition among crystal growth, direction by microreactor and infinitesimal disturbance by influence factors. These results make the homopolymer/surfactant microreactors effective and practical in regulating the target metal micro/nano-particles, and thus shade some light on the practicability of wet-chemical methods to synthesize metal micro/nano-particles.3. pH responsive self-assembly of HPAM and their application as microreactorspH responsive self-assembly of HPAM (partially hydrolyzed polyacrylamide) alone or assisted by HEC (hydroxyethylcellulose) in aqueous solution was investigated, which led to aggregate sheets in a size around 500 nm at pH 1.3. A new contrast enhancing strategy for clear TEM observation of the microstructure of the sheets was established and adopted. In this strategy, the added HAuCl4 was easy to be reduced by weakly reductive polymers in situ and then the resultant metal particles were doped on the external surface as well as the possible porous internal surface of the aggregate sheets leading to apparent increase of the contrast. The in situ reduction gold-doping TEM images announced that the pH responsive HPAM or HPAM/HEC aggregate sheets have nano-porous microstructures. Furthermore, the TEM observation disclosed that at a lower pH 0.9, the HPAM or HPAM/HEC aggregate sheets actually fall apart into nanoparticles about 10 nm. This in situ reduction gold-doping TEM observation strategy provides an efficient technique to directly detect low contrast microstructure or morphology of tiny organic assembly. In addition, the experiment results illustrated that the nature of "short hydrophilic/hydrophobic segment" in amphiphilic random copolymers induces short-range and dispersive hydrophilic/hydrophobic domains in the aggregates. In the resultant large complex aggregates, the hydrophobic and hydrophilic micro-domains enriched inside and on the surface of the aggregates, respectovely. Some interesting morphologies of the composites made of gold particles and the random copolymer such as hollow or flower-like ones, were obtained using the above amphiphilic random copolymer aggregates as microreactors.